ALBERT

Description: This paper presents the field validation of a method to estimate the local wind speed on different sectors of a turbine rotor disk. Each rotating blade is used as a scanning sensor that, traveling across the rotor disk, samples the inflow. From the local speed estimates, the method can reconstruct the vertical wind shear and detect the presence and location on an impinging wake shed by an upstream wind turbine. Shear and wake awareness have multiple uses, from turbine and farm control to monitoring and forecasting. This validation study is conducted with an experimental data set obtained with two multi-megawatt wind turbines and a hub-tall met mast. Practical and simple procedures are presented and demonstrated to correct for the possible miscalibration of sensors. Results indicate a very good correlation between the estimated vertical shear and the one measured by the met mast. Additionally, the proposed method exhibits a remarkable ability to locate and track the motion of an impinging wake on an affected rotor.

Description: Nanofiltration for water and wastewater treatment – a mini review Drinking Water Engineering and Science, 6, 47-53, 2013 Author(s): H. K. Shon, S. Phuntsho, D. S. Chaudhary, S. Vigneswaran, and J. Cho The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals, mechanisms, fouling challenges and their controls.

Description: Application of DVC-FISH method in tracking Escherichia coli in drinking water distribution networks Drinking Water Engineering and Science, 6, 25-31, 2013 Author(s): L. Mezule, S. Larsson, and T. Juhna Sporadic detection of live (viable) Escherichia coli in drinking water and biofilm with molecular methods but not with standard plate counts has raised concerns about the reliability of this indicator in the surveillance of drinking water safety. The aim of this study was to determine spatial distribution of different viability forms of E. coli in a drinking water distribution system which complies with European Drinking Water Directive (98/83/EC). For two years coupons (two week old) and pre-concentrated (100 times with ultrafilters) water samples were collected after treatment plants and from four sites in the distribution network at several distances. The samples were analyzed for total, viable (able to divide as DVC-FISH positive) and cultivable E. coli . The results showed that low numbers of E. coli enters the distribution sytem from the treatment plants and tend to accumulate in the biofilm of water distribution system. Almost all of the samples contained metabolically active E. coli in the range of 1 to 50 cells per litre or cm 2 which represented approximately 53% of all E. coli detected. The amount of viable E. coli significantly increased into the network irrespective of the season. The study has shown that DVC-FISH method in combination with water pre-concentration and biofilm sampling allows to better understand the behaviour of E. coli in water distribution networks, thus, it provides new evidences for water safety control.

Description: Stored-heat assessments: a review in the light of field experience Geothermal Energy Science, 2, 49-54, 2014 Author(s): M. A. Grant Stored-heat or volumetric assessments of geothermal resources are appealingly simple: the resource being exploited is heat. A stored-heat calculation simply computes the amount of heat in the resource, similarly to computing the amount of ore in an ore body. The method has theoretical support in numerical simulations of resource production. While there are significant unknowns in any resource, some of these can be covered by probabilistic approaches, notably a Monte Carlo method. The Australian Geothermal Reporting Code represents one specification of such stored-heat assessments. However the experience of recent decades, with the development of significant numbers of geothermal resources, has shown that the method is highly unreliable and usually biased high. The tendency to overestimates, in particular, has led to the reduced credibility of the method. An example is quoted where simple application of the apparently simple rules gives a ridiculous result. Much of the problem lies in the "recovery factor", the proportion of the resource that can actually be exploited, where comparison with actual performance shows past values have been in all cases too high, as is the current version of the Australian code. There are further problems, usually overlooked, in the way that the reservoir volume and "cutoff temperature" are defined. Differing approaches mean that results between different reports are not comparable. The different approaches also imply unrecognised assumptions about the physical processes controlling reservoir depletion. The failure of Monte Carlo methods is similarly due to unrecognised violation of logical consistency in the use of probabilities. The net effect of these problems is that the method is not a simple means to generate a rough resource estimate, and it often generates faulty results. Usually, such results are overestimates. Monte Carlo methods do not provide a protection against these errors. The Australian Geothermal Reporting Code should be used for hydrothermal systems with an average recovery factor of 10%. With this average, results are subject to an error of ±70%. For enhanced geothermal systems (EGS), the recovery factor should be a few percent.

Description: Application of optical tomography in the study of discolouration in drinking water distribution systems Drinking Water Engineering and Science Discussions, 4, 39-59, 2011 Author(s): P. van Thienen, R. Floris, and S. Meijering Theories describing the turbulent deposition of particles from aerosols have recently been applied to drinking water distribution. In order to allow the study of these processes in a quantitative way and internally observe a cloud of suspended particles in a pipe, we have developed an optical tomography technique and measuring device using low cost electronic components specifically for this application. The mathematical methodology and the electronic device are described in this paper, and tests of both the mathematical approach and the actual device are presented. We conclude that the described methodology may provide a valuable tool for the study of processes related to drinking water discolouration in the lab.

Description: Status of organochlorine pesticides in the drinking water well-field located in the Delhi region of the flood plains of river Yamuna Drinking Water Engineering and Science, 4, 51-60, 2011 Author(s): P. K. Mutiyar, A. K. Mittal, and A. Pekdeger This study presents the occurrence of pesticides in a well-field located in Yamuna flood plain of Delhi region. Ground water sampling campaigns were carried out during pre-monsoon and post-monsoon periods covering 21 borewells and 5 Ranney wells. Major 17 organochlorine pesticides (OCP's) along with other water quality parameters were monitored during this period. Pesticide concentrations were determined using GC-ECD, while GC-MS was used for confirmatory purposes. OCP's groups like ∑HCH, ∑DDT, endosulfan and aldrin were observed in this well-field. Concentration of OCPs from Ranney well exceeded the limit (1 μg l −1 ) prescribed by the Bureau of Indian Standards (BIS) in pre-monsoon season, though OCP levels in borewells were within BIS limits. However, these levels were very close to the World Health Organisation (WHO) and European Union (EU) limit of for pesticides (0.5 μg l −1 ) in many samples. Borewell produced better quality water compared to the water from Ranney wells. Although, the level of OCP's was slightly lower than prescribed limit of national regulatory agency but such low doses may cause long-term damage to human populations if such water is consumed for longer durations. At low doses OCP's acts as endocrine disrupting agent and cause metabolic disorders in local population.

Description: Application of optical tomography in the study of discolouration in drinking water distribution systems Drinking Water Engineering and Science, 4, 61-69, 2011 Author(s): P. van Thienen, R. Floris, and S. Meijering Theories describing the turbulent deposition of particles from aerosols have recently been applied to drinking water distribution. In order to allow the study of these processes in a quantitative way and internally observe a cloud of suspended particles in a pipe, we have developed an optical tomography technique and measuring device using low cost electronic components specifically for this application. The mathematical methodology and the electronic device are described in this paper, and tests of both the mathematical approach and the actual device are presented. We conclude that the mathematical framework presented is suitable and that the technical implementation works in a test setting. The described methodology may provide a valuable tool for the study of processes related to drinking water discolouration in the lab.

Description: A new model for the simplification of particle counting data Drinking Water Engineering and Science Discussions, 4, 151-172, 2011 Author(s): M. F. Fadal, J. Haarhoff, and S. Marais This paper proposes a three-parameter mathematical model to describe the particle size distribution in a water sample. The proposed model offers some conceptual advantages over two other models reported on previously, and also provides a better fit to the particle counting data obtained from 321 water samples taken over three years at a large South Africa water utility. By using the data from raw water samples taken from a moderately turbid, large surface impoundment, as well as samples from the same water after treatment, typical ranges of the model parameters are presented for both raw and treated water. Once calibrated, the model allows the calculation of total particle number and volumes over any randomly selected size interval of interest.

Description: Assessing variable speed pump efficiency in water distribution systems Drinking Water Engineering and Science Discussions, 5, 47-65, 2012 Author(s): A. Marchi, A. R. Simpson, and N. Ertugrul Energy savings and greenhouse gas emission reductions are increasingly becoming important design targets in many industrial systems where fossil fuel based electrical energy is heavily utilised. In water distribution systems (WDSs) a significant portion of operational cost is related to pumping. Recent studies have considered variable speed pumps (VSPs) which aim to vary the operating point of the pump to match demand to pumping rate. Depending on the system characteristics, this approach can lead to considerable savings in operational costs. In particular, cost reductions can take advantage of the demand variability and can decrease energy consumption significantly. One of the issues in using variable speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper aims to provide a comprehensive discussion about the components of WDS that incorporate variable speed pumps (including electric motors, inverters and the pumps themselves) to provide an insight of ways of increasing the system efficiency and hence to reduce energy consumption. In addition, specific attention is given to selection of motor types, sizing, duty cycle of pump (ratio of on-time and time period), losses due to installation and motor faults. All these factors affect the efficiency of motor drive/pump system.

Description: Fluoride in the drinking water of Pakistan and the possible risk of crippling fluorosis Drinking Water Engineering and Science, 6, 17-23, 2013 Author(s): M. A. Tahir and H. Rasheed To explore the possibility of fluoride toxicity, 747 water samples were collected from surface water and groundwater sources of 16 major cities of Pakistan, adopting a uniform sampling design with distribution of samples: Lahore (79), Kasur (46), Faisalabad (30), Khushab (50), Chakwal (51), Mianwali (30), Jhelum (53), Bahawalpur (60), Karachi (60), Mirpur Khas (55), Peshawar (38), Risalpur (35), Quetta (81), Ziarat (21), Loralai (21), and Mastung (37). Comparison of analytical findings with WHO Guidelines of Drinking Water for Fluoride (i.e., 1.5 ppm) has concluded that 16% of the monitored water sources have fluoride concentration beyond the permissible safe limit of 1.5 mg L −1 falling in the concentration range of 1.6–25 mg L −1 . The highest fluoride contamination (22%) is detected in the Balochistan province followed by 19% in Punjab province. Comparatively higher fluoride levels of 〉 20% in the groundwater sources like hand pumps supported the possibility of increased groundwater contamination as excessive fluoride concentrations are expected to come from calcium-poor aquifers and in areas where fluoride-bearing minerals are common or where cation exchange of sodium for calcium occurs. Field observations have also indicated the prevalence of fluoride-associated health implications in the study areas with excessive fluoride in water sources. Findings of this study have provided bidirectional vision for the epidemiological investigations as well as to mitigate the issues in the affected vicinities of fluoride-rich areas.

Description: Accumulation and modeling of particles in drinking water pipe fittings Drinking Water Engineering and Science Discussions, 5, 139-171, 2012 Author(s): K. Neilands, M. Bernats, and J. Rubulis The effect of pipe fittings – mainly T-pieces – on particle accumulation in drinking water distribution networks is shown in this work. The online measurements of flow and turbidity for cast iron, polyethylene and polyvinylchloride pipe sections have been linked with the analysis of pipe geometry. Up to 0.29 kg of the total mass of particles was found to be accumulated in T-pieces ranging from DN 100/100–DN 250/250. The accumulated amount of particles in the fittings was defined as J and introduced into the existing turbidity model PODDS (Prediction of Discolouration in Distribution Systems) proposed by Boxall et al. (2001), which describes the erosion of particles leading to discoloration events in drinking water networks, viz. sections, of straight pipes. It does not interpret the mobilization of particles in pipe fittings, however, which have been considered in this article. T-pieces were the object of this study and depending on the diameter or daily flow velocity, the coefficient J varied from 1.16 to 8.02.

Description: Dynamic hydraulic models to study sedimentation in drinking water networks in detail Drinking Water Engineering and Science Discussions, 5, 121-137, 2012 Author(s): I. W. M. Pothof and E. J. M. Blokker Sedimentation in drinking water networks can lead to discolouration complaints. A sufficient criterion to prevent sedimentation in drinking water networks is a daily maximum velocity of 0.25 m s −1 . Flushing experiments have shown that this criterion is a sufficient condition for a clean network, but not a necessary condition. Drinking water networks include many locations with a maximum velocity well below 0.25 m s −1 without sediment. Other criteria need to be developed to predict which locations are susceptible to sedimentation and to prevent sedimentation in future networks. More distinctive criteria are helpful to prioritise flushing operations and to prevent water quality complaints. The authors use three different numerical modelling approaches – quasi-steady, rigid column and water hammer – with a temporal discretisation of 1 s in order to assess the influence of unsteady flows on the wall shear stress, causing resuspension of sediment particles. The model predictions are combined with results from flushing experiments in the drinking water distribution system of Purmerend, the Netherlands. The waterhammer model does not result in essentially different flow distribution patterns, compared to the rigid column and quasi-steady modelling approach. The extra information from the waterhammer model is a velocity oscillation of approximately 0.02 m s −1 around the quasi-steady solution. The presence of stagnation zones and multiple flow direction reversals seem to be interesting new parameters to predict sediment accumulation, which are consistent with the observed turbidity data and theoretical considerations on critical shear stresses.

Description: Technical Note: Wet validation of optical tomography for drinking water discolouration studies Drinking Water Engineering and Science Discussions, 6, 27-38, 2013 Author(s): R. Floris, P. van Thienen, and H. Beverloo This paper presents a set of validation experiments for the reconstruction of a cross-sectional particle concentration field in a transparent pipe filled with a fluid using optical tomography.

Description: Numerical and experimental investigation of leaks in viscoelastic pressurized pipe flow Drinking Water Engineering and Science, 6, 11-16, 2013 Author(s): S. Meniconi, B. Brunone, M. Ferrante, and C. Massari This paper extends the analysis concerning the importance in numerical models of unsteady friction and viscoelasticity to transients in plastic pipes with an external flow due to a leak. In fact recently such a benchmarking analysis has been executed for the cases of a constant diameter pipe (Duan et al., 2010), a pipe with a partially closed in-line valve (Meniconi et al., 2012a), and a pipe with cross-section changes in series (Meniconi et al., 2012b). Tests are based on laboratory experiments carried out at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy, and the use of different numerical models. The results show that it is crucial to take into account the viscoelasticity to simulate the main characteristics of the examined transients.

Description: Non-residential water demand model validated with extensive measurements Drinking Water Engineering and Science Discussions, 5, 455-471, 2012 Author(s): E. J. Pieterse-Quirijns, E. J. M. Blokker, E. van der Blom, and J. H. G. Vreeburg Existing guidelines related to the water demand of non-residential buildings are outdated and do not cover hot water demand for the appropriate selection of hot water devices. Moreover, they generally overestimate peak demand values required for the design of an efficient and reliable water system. Recently, a procedure was developed based on the end-use model SIMDEUM ® to derive design rules for peak demand values of both cold and hot water during various time steps for several types and sizes of non-residential buildings, i.e. offices, hotels and nursing homes. In this paper, the design rules are validated with measurements of cold and hot water patterns on a per second base. The good correlation between the simulated patterns and the measured patterns indicates that the basis of the design rules, the SIMDEUM simulated standardised buildings, is solid. Moreover, the SIMDEUM based rules give a better prediction of the measured peak values for cold water flow than the existing guidelines. Furthermore, the new design rules can predict hot water use well. In this paper it is illustrated that the new design rules lead to reliable and improved designs of building installations and water heater capacity, resulting in more hygienic and economical installations.

Description: Numerical and experimental investigation of leaks in viscoelastic pressurized pipes Drinking Water Engineering and Science Discussions, 5, 473-494, 2012 Author(s): S. Meniconi, B. Brunone, M. Ferrante, and C. Massari This paper extends the analysis concerning the importance in numerical models of unsteady friction and viscoelasticity to transients in plastic pipes with an external flow due to a leak. In fact recently such a benchmarking analysis has been executed for the cases of a constant diameter pipe (Duan et al., 2010), a pipe with a partially closed in-line valve (Meniconi et al., 2012a), and a pipe with cross-section changes in series (Meniconi et al., 2012b). The analysis is based on laboratory tests carried out at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy, and numerical experiments by means of different 1-D numerical models. The results show that it is crucial to take into account the viscoelasticity to simulate the main characteristics of the transients, also in the case of a damaged pipes.

Description: Accumulation and modeling of particles in drinking water pipe fittings Drinking Water Engineering and Science, 5, 47-57, 2012 Author(s): K. Neilands, M. Bernats, and J. Rubulis The effect of pipe fittings (mainly T-pieces) on particle accumulation in drinking water distribution networks were shown in this work. The online measurements of flow and turbidity for cast iron, polyethylene and polyvinyl chloride pipe sections were linked with analysis of pipe geometry. Up to 0.29 kg of the total amount mobilized in T-pieces ranging from DN 100/100–DN 250/250. The accumulated amount of particles in fittings was defined as J and introduced into the existing turbidity model PODDS (prediction of discoloration in distribution systems) proposed by Boxall et al. (2001) which describes the erosion of particles leading to discoloration events in drinking water network viz sections of straight pipes. However, this work does not interpret mobilization of particles in pipe fittings which have been considered in this article. T-pieces were the object of this study and depending of the diameter or daily flow velocity, the coefficient J varied from 1.16 to 8.02. The study showed that pipe fittings act as catchment areas for particle accumulation in drinking water networks.

Description: Leakages and pressure relations: an experimental research Drinking Water Engineering and Science Discussions, 5, 403-419, 2012 Author(s): F. De Paola and M. Giugni Leaks in water systems are presently a frequent and increasing event that involves cost increase and poor service, not compliant to quality standards and modern management criteria. The most recent data available in Italy, resumed into the report issued by Control Committee for Water Resources Use (CONVIRI), shows leakages with an average value of 37%. It is important, for maintenance perspective, to investigate occurrence and evolution of water leaks and the analytical links between leaks Q p and network pressure P , for a reliable calibration of water networks quali-quantitative simulation models. The present work reports the results of an experimental campaign started at Laboratory of Hydraulic of Department of Hydraulic, Geotechnical and Environmental Engineering of University of Naples Federico II in order to analyze the features of Q p ( P ) relation, which are compared with principal results issued in literature.

Description: Fluoride in the drinking water of Pakistan and the possible risk of crippling fluorosis Drinking Water Engineering and Science Discussions, 5, 495-514, 2012 Author(s): M. A. Tahir and H. Rasheed To explore the possibility of fluoride toxicity, seven hundred and forty seven (747) water samples were collected from surface and ground water sources of sixteen major cities of Pakistan, adopting a uniform sampling design with distribution of samples as: Lahore (79), Kasur (46), Faisalabad (30), Khushab (50), Chakwal (51), Mianwali (30), Jhelum (53), Bahawalpur (60), Karachi (60), Mirpur Khas (55), Peshawar (38), Risalpur (35), Quetta (81), Ziarat (21), Loralai (21), Mastung (37). The comparison of analytical findings with WHO Guidelines of Drinking Water for Fluoride (i.e. 1.5 ppm) has concluded that 16% of the monitored water sources have fluoride concentration beyond the permissible, safe limit of 1.5 mg l −1 , falling in the concentration range of 1.6–25 mg l −1 . The highest fluoride contamination (22%) has been detected in the Balochistan province followed by 19% in Punjab province. Comparatively higher fluoride levels of 〉20% in groundwater sources such as hand pumps has supported the possibility of increased ground water contamination, as excessive fluoride concentrations are expected to come from calcium-poor aquifers and from areas where fluoride-bearing minerals are common or where cation exchange of sodium for calcium occurs. Field observations have also indicated the prevalence of fluoride-associated health implications in the study areas with excessive fluoride in water sources. The findings in this study have provided a bidirectional vision for epidemiological investigations as well as for mitigating the issues in the affected vicinities of fluoride-rich areas.

Description: Modelling water quality in drinking water distribution networks from real-time direction data Drinking Water Engineering and Science, 5, 39-45, 2012 Author(s): S. Nazarovs, S. Dejus, and T. Juhna Modelling of contamination spread and location of a contamination source in a water distribution network is an important task. There are several simulation tools developed, however the significant part of them is based on hydraulic models that need node demands as input data that sometimes may result in false negative results and put users at risk. The paper considers applicability of a real-time flow direction data based model for contaminant transport in a distribution network of a city and evaluates the optimal number of flow direction sensors. Simulation data suggest that the model is applicable for the distribution network of the city of Riga and that the optimal number of sensors in this case is around 200.

Description: The large-scale impact of climate change to Mississippi flood hazard in New Orleans Drinking Water Engineering and Science Discussions, 5, 333-349, 2012 Author(s): T. L. A. Driessen and M. van Ledden The objective of this paper is to describe the impact of climate change on the Mississippi River flood hazard in the New Orleans area. This city has a unique flood risk management challenge, heavily influenced by climate change, since it faces flood hazards from multiple geographical locations (e.g. Lake Pontchartrain and Mississippi River) and multiple sources (hurricane, river, rainfall). Also the low elevation and significant subsidence rate of the Greater New Orleans area poses a high risk and challenges the water management of this urban area. Its vulnerability to flooding became dramatically apparent during Hurricane Katrina in 2005 with huge economic losses and a large number of casualties. A SOBEK Rural 1DFLOW model was set up to simulate the general hydrodynamics. This improved model includes two important spillways that are operated during high flow conditions. Subsequently, a weighted multi-criteria calibration procedure was performed to calibrate the model for high flows. Validation for floods in 2011 indicates a very reasonable performance for high flows and clearly demonstrates the necessity of the spillways. 32 different scenarios are defined which includes the relatively large sea level rise and the changing discharge regime that is expected due to climate change. The impact of these scenarios is analysed by the hydrodynamic model. Results show that during high flows New Orleans will not be affected by varying discharge regimes, since the presence of the spillways ensures a constant discharge through the city. In contrary, sea level rise is expected to push water levels upwards. The effect of sea level rise will be noticeable even more than 470 km upstream. Climate change impacts necessitate a more frequent use of the spillways and opening strategies that are based on stages. Potential alternatives on how to cope with the flood hazard of this river in the long term, such as river widening and large-scale redistribution of the flow through diversions, are proposed.

Description: Effect of biostimulation on biodegradation of dissolved organic carbon in biological filters Drinking Water Engineering and Science, 5, 23-29, 2012 Author(s): K. Tihomirova, A. Briedis, J. Rubulis, and T. Juhna The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and Luria Bertrani (LB) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 26 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration.

Description: Natural organic matter removal by ion exchange at different positions in the drinking water treatment lane Drinking Water Engineering and Science Discussions, 5, 375-401, 2012 Author(s): A. Grefte, M. Dignum, E. R. Cornelissen, and L. C. Rietveld To guarantee a good water quality at the customers tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research was to improve the drinking water quality, including biological stability, by incorporating anion exchange (IEX) for NOM removal. Different placement positions of IEX in the treatment lane (IEX positioned before coagulation, before ozonation or after slow sand filtration) are compared on water quality as well as costs. For this purpose the pre-treatment plant at Loenderveen and production plant Weesperkarspel of Waternet were used as a case study. NOM removal can be done efficiently before ozonation and after slow sand filtration; it was found that the position in the treatment lane did not influence the NOM removal capacity. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The operational costs for IEX positioned before coagulation were higher than for IEX positioned after slow sand filtration, however the savings on following treatment processes caused a cost reduction compared to IEX positioned after slow sand filtration. IEX positioned before coagulation or ozonation were most cost effective and produced the highest water quality.

Description: Assessing variable speed pump efficiency in water distribution systems Drinking Water Engineering and Science, 5, 15-21, 2012 Author(s): A. Marchi, A. R. Simpson, and N. Ertugrul Energy savings and greenhouse gas emission reductions are increasingly becoming important design targets in many industrial systems where fossil fuel based electrical energy is heavily utilised. In water distribution systems (WDSs) a significant portion of operational cost is related to pumping. Recent studies have considered variable speed pumps (VSPs) which aim to vary the operating point of the pump to match demand to pumping rate. Depending on the system characteristics, this approach can lead to considerable savings in operational costs. In particular, cost reductions can take advantage of the demand variability and can decrease energy consumption significantly. One of the issues in using variable speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper aims to provide a comprehensive discussion about the components of WDS that incorporate variable speed pumps (including electric motors, variable frequency drives and the pumps themselves) to provide an insight of ways of increasing the system efficiency and hence to reduce energy consumption. In addition, specific attention is given to selection of motor types, sizing, duty cycle of pump (ratio of on-time and time period), losses due to installation and motor faults. All these factors affect the efficiency of motor drive/pump system.

Description: Reliability of water distribution networks due to pumps failure: comparison of VSP and SSP application Drinking Water Engineering and Science Discussions, 5, 351-373, 2012 Author(s): N. Mehzad, M. Tabesh, S. S. Hashemi, and B. Ataee Kia Reliability is an important indicator to ensure the operation of Water Distribution Networks (WDNs). To optimize the operation of WDN, it is necessary to incorporate the reliability of active components (such as pumps and tanks) besides the reliability of pipes. In this research, a concept is suggested to calculate the reliability of WDNs' pumping stations. A computer code is provided in Visual Basic and is linked to EPANET2.0. To evaluate the proposed methodology a real WDN near the city of Tehran is considered. According to the obtained results, it is concluded that by increasing the demand of the WDN during a day, the reliability of pumps decrease. Therefore, it seems that decision-making is necessary if high demand hours are considered, in order to increase the reliability of the system. On the other hand, it is observed in this research that using variable speed pumps not only reduces the energy cost of the network, but also the reliability of the pumping stations with variable speed pumps is higher than single speed pumps. Therefore, using VSP is highly recommended in WDNs.

Description: Predicting the residual aluminum level in water treatment process Drinking Water Engineering and Science Discussions, 5, 243-264, 2012 Author(s): J. Tomperi, M. Pelo, and K. Leiviskä In water treatment processes, aluminum salts are widely used as coagulation chemical. High dose of aluminum has been proved to be at least a minor health risk and some evidence points out that aluminum could increase the risk of Alzheimer's disease thus it is important to minimize the amount of residual aluminum in drinking water and water used at food industry. In this study, the data of a water treatment plant (WTP) was analyzed and the residual aluminum in drinking water was predicted using Multiple Linear Regression (MLR) and Artificial Neural Network (ANN) models. The purpose was to find out which variables affect the amount of residual aluminum and create simple and reliable prediction models which can be used in an early warning system (EWS). Accuracy of ANN and MLR models were compared. The new nonlinear scaling method based on generalized norms and skewness was used to scale all measurement variables to range [−2...+2] before data-analysis and modeling. The effect of data pre-processing was studied by comparing prediction results to ones achieved in an earlier study. Results showed that it is possible to predict the baseline level of residual aluminum in drinking water with a simple model. Variables that affected the most the amount of residual aluminum were among others: raw water temperature, raw water KMnO 4 and PAC / KMnO 4 -ratio. The accuracies of MLR and ANN models were found to be almost equal. Study also showed that data pre-processing affects to the final prediction result.

Description: How much are households willing to contribute to the cost recovery of drinking water supply? Results from a household survey Drinking Water Engineering and Science Discussions, 5, 225-241, 2012 Author(s): S. Tarfasa Improving existing drinking water supply services in developing countries depends crucially on available financial resources. Cost recovery rates of these services are typically low, while demand for more reliable services is high and rapidly growing. Most stated preference based demand studies in the developing world apply the contingent valuation method and focus on rural areas. This study examines the willingness of households to pay for improved water supply services employing a choice model (CM) in an urban area in Ethiopia, a country with the lowest water supply coverage in Sub-Saharan Africa. The design of the choice model allows the estimation of the values of both drinking water reliability and safety. The estimated economic values can be used in policy appraisals of investment decisions. Despite significant income constraints, households are willing to pay up to 60% extra for improved levels of water supply over and above their current water bill, especially households living in the poorest part of the city with the lowest service levels. Women value the improvement of water quality most, while a significant effect is found for averting behavior and expenditures.

Description: Subsurface arsenic removal column tests: from the laboratory to the field Drinking Water Engineering and Science Discussions, 5, 193-207, 2012 Author(s): D. H. Moed, D. van Halem, J. Q. J. C. Verberk, J. A. M. van Paassen, and L. C. Rietveld Previous laboratory column experiments have given evidence of competitive effects between different groundwater constituents in the process of subsurface arsenic removal, a process in which arsenic is removed from groundwater by injecting water with oxygen into the subsurface. The presence of phosphate and other anions significantly limited arsenic removal. To investigate the influence of phosphate in natural groundwater, pumping stations in Loosdrecht (the Netherlands) and Subotica (Serbia) both with low phosphate concentrations (

Description: A new model for the simplification of particle counting data Drinking Water Engineering and Science, 5, 9-14, 2012 Author(s): M. F. Fadal, J. Haarhoff, and S. Marais This paper proposes a three-parameter mathematical model to describe the particle size distribution in a water sample. The proposed model offers some conceptual advantages over two other models reported on previously, and also provides a better fit to the particle counting data obtained from 321 water samples taken over three years at a large South African drinking water supplier. Using the data from raw water samples taken from a moderately turbid, large surface impoundment, as well as samples from the same water after treatment, typical ranges of the model parameters are presented for both raw and treated water. Once calibrated, the model allows the calculation and comparison of total particle number and volumes over any randomly selected size interval of interest.

Description: Water investment in Mexico City: contradictory elements preventing investment efficiency Drinking Water Engineering and Science Discussions, 5, 209-223, 2012 Author(s): M. J. Marquez-Dorantes The complex connections between environmental and socio-economic variables in the water sector system involve not only ecological changes such as climate change but also a need for changes in socio-economic arenas to reduce the impacts of climate change. It is necessary not only to acknowledge the elements of change but also to understand the constraints preventing change in specific cases. The challenges faced by the water sector in Mexico City, as the world's second largest urban agglomeration with its fast growing population, limited external water sources, depleted aquifers and increased disaster risks, call for urgent measures to resolve the inefficiencies found in the traditional approach to water investment. This paper explores how far the multiple objectives of different actors involved in water projects are balanced to attain integrated water management. The Santa Catarina Water Supply Project, which is in a highly contentious area because of the limited availability of drinking water, is presented as a case study. The analysis shows that the multiple objectives of the different actors involved, together with an institutional structure that perpetuates a traditional engineering approach, constrain the effective and efficient delivery of water projects. The institutional analysis development framework (Ostrom, 2006) is used to analyse the arena of investment decision-making in water for Mexico City. Following the notion of institutional arrangements as " incentives and deterrents " (Ostrom, 1976), eight contradictory elements are proposed to illustrate the process by which institutional arrangements, implemented by specific actors with the intention of producing specific outcomes, are inefficient in delivering the expected outcomes, and can even produce negative ones when interacting with other existing formal and informal arrangements determined by other actors. These elements explain both the resilience of the system, which has so far prevented its collapse, and the magnitude of a growing problem that demands change.

Description: Robust optimization methodologies for water supply systems design Drinking Water Engineering and Science Discussions, 5, 173-192, 2012 Author(s): J. Marques, M. C. Cunha, J. Sousa, and D. Savić Water supply systems (WSSs) are vital infrastructures for the well-being of people today. To achieve good customer satisfaction the water supply service must always be able to meet people's needs, in terms of both quantity and quality. But unpredictable extreme conditions can cause severe damage to WSSs and lead to poorer levels of service or even to their failure. Operators dealing with a system's day-to-day operation know that events like burst water mains can compromise the functioning of all or part of a system. To increase a system's reliability, therefore, designs should take into account operating conditions other than normal ones. Recent methods based on robust optimization can be used to solve optimization problems which involve uncertainty and can find designs which are able to cope with a range of operating conditions. This paper presents a robust optimization model for the optimal design of water supply systems operating under different circumstances. The method presented here uses a hydraulic simulator linked to an optimizer based on a simulated annealing heuristic. The results show that robustness can be included in several ways for varying levels reliability and that it leads to more reliable designs for only small cost increases.

Description: Modelling water quality in drinking water distribution networks from real-time direction data Drinking Water Engineering and Science Discussions, 5, 31-46, 2012 Author(s): S. Nazarovs, S. Dejus, and T. Juhna Modelling of contamination spread and location of contamination source in a water distribution network is an important task. The paper considers applicability of real-time flow direction data based model for contaminant transport for a distribution network of a city. Simulations of several contamination scenarios are made to evaluate necessary number of flow direction sensors. It is found that for a model, containing major pipes of Riga distribution system, sensor number decrease from 927 to 207 results in average 20% increase of simulated contaminated length of pipes. Simulation data suggest that optimal number of sensors for Riga model is around 200.

Description: CLIPS based decision support system for water distribution networks Drinking Water Engineering and Science, 4, 37-50, 2011 Author(s): K. Sandeep and K. Rakesh The difficulty in knowledge representation of a water distribution network (WDN) problem has contributed to the limited use of artificial intelligence (AI) based expert systems (ES) in the management of these networks. This paper presents a design of a Decision Support System (DSS) that facilitates "on-demand'' knowledge generation by utilizing results of simulation runs of a suitably calibrated and validated hydraulic model of an existing aged WDN corresponding to emergent or even hypothetical but likely scenarios. The DSS augments the capability of a conventional expert system by integrating together the hydraulic modelling features with heuristics based knowledge of experts under a common, rules based, expert shell named CLIPS (C Language Integrated Production System). In contrast to previous ES, the knowledge base of the DSS has been designed to be dynamic by superimposing CLIPS on Structured Query Language (SQL). The proposed ES has an inbuilt calibration module that enables calibration of an existing (aged) WDN for the unknown, and unobservable, Hazen-Williams C-values. In addition, the daily run and simulation modules of the proposed ES further enable the CLIPS inference engine to evaluate the network performance for any emergent or suggested test scenarios. An additional feature of the proposed design is that the DSS integrates computational platforms such as MATLAB, open source Geographical Information System (GIS), and a relational database management system (RDBMS) working under the umbrella of the Microsoft Visual Studio based common user interface. The paper also discusses implementation of the proposed framework on a case study and clearly demonstrates the utility of the application as an able aide for effective management of the study network.

Description: Effects of ozonation and temperature on the biodegradation of natural organic matter in biological granular activated carbon filters Drinking Water Engineering and Science, 4, 25-35, 2011 Author(s): L. T. J. van der Aa, L. C. Rietveld, and J. C. van Dijk Four pilot (biological) granular activated carbon ((B)GAC) filters were operated to quantify the effects of ozonation and water temperature on the biodegradation of natural organic matter (NOM) in (B)GAC filters. The removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and oxygen and the production of carbon dioxide were taken as indicators for NOM biodegradation. Ozonation stimulated DOC and AOC removal in the BGAC filters, but had no significant effect on oxygen consumption or carbon dioxide production. The temperature had no significant effect on DOC and AOC removal, while it had a positive effect on oxygen consumption and carbon dioxide production. Multivariate linear regression was used to quantify these relationships. In summer, the ratio between oxygen consumption and DOC removal was approximately 2 times the theoretical maximum of 2.6 g O 2 g C −1 and the ratio between carbon dioxide production and DOC removal was approximately 1.5 times the theoretical maximum of 3.7 g CO 2 g C −1 . The production and loss of biomass, the degassing of (B)GAC filters, the decrease in the NOM reduction degree and the temperature effects on NOM adsorption could only partly explain these excesses and the non-correlation between DOC and AOC removal and oxygen consumption and carbon dioxide production. It was demonstrated that bioregeneration of NOM could explain the excesses and the non-correlation. Therefore, it was likely that bioregeneration of NOM did occur in the (B)GAC pilot filters.

Description: Metals releases and disinfection byproduct formation in domestic wells following shock chlorination Drinking Water Engineering and Science, 4, 1-8, 2011 Author(s): M. Walker and J. Newman Shock chlorination is used for rapid disinfection to control pathogens and nuisance bacteria in domestic wells. A typical shock chlorination procedure involves adding sodium hypochlorite in liquid bleach solutions to achieve concentrations of free chlorine of up to 200 mg L −1 in the standing water of a well. The change in pH and oxidation potential may bring trace metals from aquifer materials into solution and chlorine may react with dissolved organic carbon to form disinfection byproducts. We carried out experiments with four wells to observe and determine the persistence of increased concentrations of metals and disinfection byproducts. Water samples from shock chlorinated wells were analyzed for Pb, Cu, As, radionuclides and disinfection byproducts (haloacetic acids and trihalomethanes), immediately prior to treatment, after sufficient treatment time with chlorine had elapsed, and at intervals determined by the number of casing volumes purged, for up to four times the well casing volume. Elevated concentrations of lead and copper dissipated in proportion to free chlorine (measured semi-quantitatively) during the purging process. Trihalomethanes and haloacetic acids were formed in wells during disinfection. In one of two wells tested, disinfection byproducts dissipated in proportion to free chlorine during purging. However, one well retained disinfection byproducts and free chlorine after 4 WV had been purged. Although metals returned to background concentrations in this well, disinfection byproducts remained elevated, though below the MCL. This may have been due to well construction characteristics and interactions with aquifer materials. Simple chlorine test strips may be a useful method for indicating when purging is adequate to remove metals and disinfection by-products mobilized and formed by shock chlorination.

Description: Water supply project feasibilities in fringe areas of Kolkata, India Drinking Water Engineering and Science, 4, 9-23, 2011 Author(s): K. Dutta Roy, B. Thakur, T. S. Konar, and S. N. Chakrabarty Water supply management to the peri-urban areas of the developing world is a complex task due to migration, infrastructure and paucity of fund. A cost-benefit methodology particularly suitable for the peri-urban areas has been developed for the city of Kolkata, India. The costs are estimated based on a neural network estimate. The water quality of the area is estimated from samples and a water quality index has been prepared. A questionnaire survey in the area has been conducted for relevant information like income, awareness and willingness to pay for safe drinking water. A factor analysis has been conducted for distinguishing the important factors of the survey and subsequent multiple regressions have been conducted for finding the relationships for the willingness to pay. A system dynamics model has been conducted to estimate the trend of increase of willingness to pay with the urbanizations in the peri-urban areas. A cost benefit analysis with the impact of time value of money has been executed. The risk and uncertainty of the project is investigated by Monte Carlos simulation and tornado diagrams. It has been found that the projects that are normally rejected in standard cost benefit analysis would be accepted if the impacts of urbanizations in the peri-urban areas are considered.

Description: Development of a predictive model to determine micropollutant removal using granular activated carbon Drinking Water Engineering and Science, 2, 57-62, 2009 Author(s): D. J. de Ridder, M. McConville, A. R. D. Verliefde, L. T. J. van der Aa, S. G. J. Heijman, J. Q. J. C. Verberk, L. C. Rietveld, and J. C. van Dijk The occurrence of organic micropollutants in drinking water and its sources has opened up a field of study related to monitoring concentration levels in water sources, evaluating their toxicity and estimating their removal in drinking water treatment processes. Because a large number of organic micropollutants is currently present (although in relatively low concentrations) in drinking water sources, a method should be developed to select which micropollutants has to be evaluated with priority. In this paper, a screening model is presented that can predict solute removal by activated carbon, in ultrapure water and in natural water. Solute removal prediction is based on a combination of solute hydrophobicity (expressed as log D , the pH corrected log K ow ), solute charge and the carbon dose. Solute molecular weight was also considered as model input parameter, but this solute property appeared to relate insufficiently to solute removal. Removal of negatively charged solutes by preloaded activated carbon was reduced while the removal of positively charged solutes was increased, compared with freshly regenerated activated carbon. Differences in charged solute removal by freshly regenerated activated carbon were small, indicating that charge interactions are an important mechanism in adsorption onto preloaded carbon. The predicted solute removal was within 20 removal-% deviation of experimentally measured values for most solutes.

Description: Online modelling of water distribution systems: a UK case study Drinking Water Engineering and Science Discussions, 2, 279-294, 2009 Author(s): J. Machell, S. R. Mounce, and J. B. Boxall Hydraulic simulation models of water distribution networks are routinely used for operational investigations and network design purposes. However, their full potential is often never realised because, in the majority of cases, they have been calibrated with data collected manually from the field during a single historic time period and, as such, reflect the network operational conditions that were prevalent at that time, and they are then applied as part of a reactive, desktop investigation. In order to use a hydraulic model to assist proactive distribution network management its element asset information must be up to date and it should be able to access current network information to drive simulations. Historically this advance has been restricted by the high cost of collecting and transferring the necessary field measurements. However, recent innovation and cost reductions associated with data transfer is resulting in collection of data from increasing numbers of sensors in water supply systems, and automatic transfer of the data to point of use. This means engineers potentially have access to a constant stream of current network data that enables a new era of "online" modelling that can be used to continually assess standards of service compliance for pressure and reduce the impact of network events, such as mains bursts, on customers. A case study is presented here that shows how an online modelling system can give timely warning of changes from normal network operation, providing capacity to minimise customer impact.

Description: NOM removal technologies – Norwegian experiences Drinking Water Engineering and Science Discussions, 2, 161-187, 2009 Author(s): H. Ødegaard, S. Østerhus, E. Melin, and B. Eikebrokk The paper gives an overview of the methods for removal of natural organic matter (NOM), particularly humic substances (HS), in water with focus on the Norwegian experiences. It is demonstrated that humic substances may be removed by a variety of methods, such as; molecular sieving through nanofiltration membranes, coagulation with subsequent floc separation (including granular media or membrane filtration), oxidation followed by biofiltration and sorption processes including chemisorption (ion exchange) and physical adsorption (activated carbon). All these processes are in use in Norway and the paper gives an overview of the operational experiences.

Description: NOM characterization and removal at six Southern African water treatment plants Drinking Water Engineering and Science Discussions, 2, 231-257, 2009 Author(s): J. Haarhoff, M. Kubare, B. Mamba, R. Krause, T. Nkambule, B. Matsebula, and J. Menge Organic pollution is a major concern during drinking water treatment. Major challenges attributed to organic pollution include the proliferation of pathogenic micro-organisms, prevalence of toxic and physiologically disruptive organic micropollutants, and quality deterioration in water distribution systems. A major component of organic pollution is natural organic matter (NOM). The operational mechanisms of most unit processes are well understood. However, their interaction with NOM is still the subject of scientific research. This paper takes the form of a metastudy to capture some of the experiences with NOM monitoring and analysis at a number of Southern African Water Treatment Plants. It is written from the perspective of practical process selection, to try and coax some pointers from the available data for the design of more detailed pilot work. NOM was tracked at six water treatment plants using dissolved organic carbon (DOC) measurements. Fractionation of the DOC based on biodegradability and molecular weight distribution was done at a water treatment plant in Namibia. A third fractionation technique using ion exchange resins was used to assess the impact of ozonation on DOC. DOC measurements alone did not give much insight into NOM evolution through the treatment train. The more detailed characterization techniques showed that different unit processes preferentially remove different NOM fractions. Therefore these techniques provide better information for process design and optimisation than the DOC measurement which is routinely done during full scale operation at these water treatment plants. Further work will focus on streamlining and improving the reproducibility of selected fractionation techniques, characterization of NOM from different water sources, and synthesis of the results into a systematic, practical guideline for process design and optimisation.

Description: Removal of radio N -nitrosodimethylamine (NDMA) from drinking water by coagulation and Powdered Activated Carbon (PAC) adsorption Drinking Water Engineering and Science, 2, 49-55, 2009 Author(s): J. Chung, Y. Yoon, M. Kim, S.-B. Lee, H.-J. Kim, and C.-K. Choi The presence of N -nitrosodimethylamine (NDMA) in drinking water supplies has raised concern over its removal by common drinking water treatment processes. However, only limited studies have been examined to evaluate the potential removal of NDMA by numerous water treatment technologies within a realistic range (i.e., sub μg/L) of NDMA levels in natural water due to analytical availability. In this study, a simple detection method based on scintillation spectroscopy has been used to quantify the concentration of 14 C-labeled NDMA at various ratios of sample to scintillation liquid. Without sample pretreatment, the method detection limits are 0.91, 0.98, 1.23, and 1.45 ng/L of NDMA at scintillation intensity ratios of 10:10, 5:15, 15:5, and 2.5:17.5 (sample: scintillation liquid), respectively. The scintillation intensity in all cases is linear ( R 2 〉0.99) and is in the range of 0 to 100 ng/L of NDMA. In addition, because scintillation intensity is independent of solution pH, conductivity, and background electrolyte ion types, a separate calibration curve is unnecessary for NDMA samples at different solution conditions. Bench-scale experiments were performed to simulate individual treatment processes, which include coagulation and adsorption by powdered activated carbon (PAC), as used in a drinking water treatment plant, and biosorption, a technique used in biological treatment of waste water. The results show that coagulation and biosorption may not be appropriate mechanisms to remove NDMA (i.e., hydrophilic based on its low octanol-water partitioning coefficient, Log K ow =0.57). However, relatively high removal of NDMA (approximately 50%) was obtained by PAC at high PAC dosages and longer contact times.

Description: Technical Note: Community of bacteria attached on the PVDF MF membrane surface fouled from drinking water treatment, in Seoul, Korea Drinking Water Engineering and Science, 2, 35-39, 2009 Author(s): K. Chon, K. Chon, J.-S. Chang, H. Oh, E. Lee, and J. Cho Alpha, beta, and gamma proteobacteria comprise approximately 68, 16, and 7% of all identified bacteria. In this study, bacterial communities that had fouled polyvinylidene fluoride microfiltration membranes, which are used for drinking water treatment, over an 18 month period were analyzed using the 16s rRNA gene clone library method. The alpha, beta, and gamma proteobacteria were composed of mainly Bradyrhizobium and Rhodopseudomonas , Ralstonia , and Legionella , respectively. The presence of a relatively high amount of alpha proteobacteria was due to the oligotrophic condition of the drinking water source, the Han River, tested in this specific case study. The second most prominent bacteria community was the beta proteobacteria, which are typically found in a freshwater environment. This finding supports the notion that the drinking water source was relatively clean. Analyses of the organic foulants indicated that they were most likely from extra cellular polymers and/or cell fractured chemicals from bacteria or micro-organisms, as identified using organic characterizing tools, including 3-D fluorescence excitation-emission matrix and Fourier transform IR analyses.

Description: Development of a predictive model to determine micropollutant removal using granular activated carbon Drinking Water Engineering and Science Discussions, 2, 189-204, 2009 Author(s): D. J. de Ridder, M. McConville, A. R. D. Verliefde, L. T. J. van der Aa, S. G. J. Heijman, J. Q. J. C. Verberk, L. C. Rietveld, and J. C. van Dijk The occurrence of organic micropollutants in drinking water and its sources has opened up a field of study related to monitoring concentration levels in water sources, evaluating their toxicity and estimating their removal in drinking water treatment processes. Because a large number of organic micropollutants is currently present (although in relatively low concentrations) in drinking water sources, a method should be developed to select which micropollutants has to be evaluated with priority. In this paper, a screening model is presented that can predict solute removal by activated carbon, in ultrapure water and in natural water. Solute removal prediction is based on a combination of solute hydrophobicity (expressed as log D, the pH corrected log K ow ), solute charge and the carbon dose. Solute molecular weight was also considered as model input parameter, but this solute property appeared to relate insufficiently to solute removal. Removal of negatively charged solutes by preloaded activated carbon was reduced while the removal of positively charged solutes was increased, compared with freshly regenerated activated carbon. Differences in charged solute removal by freshly regenerated activated carbon were small, indicating that charge interactions are an important mechanism in adsorption onto preloaded carbon. The predicted solute removal was within 20 removal-% deviation of experimentally measured values.

Description: Optimized conditions for application of organic flocculant aids in water purification Drinking Water Engineering and Science Discussions, 2, 205-229, 2009 Author(s): P. Polasek The application of organic flocculant aid (OFA) to a system undergoing aggregation has a direct effect on the quality of purified water as well as the settleability of resultant agglomerates. The optimum conditions for OFA application exist when the formation of aggregates by means of destabilisation (aggregation – CPE) reagent reaches flocculation optimum, i.e. the measure of flocculation γ=1, prior to OFA addition. Such method of OFA application is called the Post-Orthokinetic Agglomeration (POA) process. The POA process results in the formation of the fastest settleable agglomerates and the best quality of purified water matching that attainable without the use of OFA. Recirculation of the sludge conditioned by OFA back to the process of particle aggregation was found undesirable as it adversely affects the purified water quality as well as the settleability of produced agglomerates.

Description: Fluorescence spectroscopy as a tool for determination of organic matter removal efficiency at water treatment works Drinking Water Engineering and Science Discussions, 2, 259-278, 2009 Author(s): M. Z. Bieroza, J. Bridgeman, and A. Baker Organic matter (OM) in drinking water treatment is a common impediment responsible for increased coagulant and disinfectant dosages, formation of carcinogenic disinfection-by products, and microbial re-growth in distribution system. The inherent heterogeneity of OM implies the utilization of advanced analytical techniques for its characterization and assessment of removal efficiency. Here, the application of simple fluorescence excitation-emission technique to OM characterization in drinking water treatment is presented. The fluorescence data of raw and clarified water was obtained from 16 drinking water treatment works. The reduction in fulvic-like fluorescence was found to significantly correlate with OM removal measured with total organic carbon (TOC). Fluorescence properties, fulvic- and tryptophan-like regions, were found to discriminate OM fractions of different removal efficiencies. The results obtained in the study show that fluorescence spectroscopy provides a rapid and accurate characterization and quantification of OM fractions and indication of their treatability in conventional water treatment.

Description: Water quality and treatment of river bank filtrate Drinking Water Engineering and Science Discussions, 2, 127-159, 2009 Author(s): W. W. J. M. de Vet, C. C. A. van Genuchten, M. C. M. van Loosdrecht, and J. C. van Dijk In drinking water production, river bank filtration has the advantages of dampening peak concentrations of many dissolved components, substantially removing many micropollutants and removing, virtually completely, the pathogens and suspended solids. The production aquifer is not only fed by the river bank infiltrate but also by water percolating through covering layers. In the polder areas, these top layers consist of peat and deposits from river sediments and sea intrusions. This paper discusses the origin and fate of macro pollutants in river bank filtrate, based on extensive full-scale measurements in well fields and treatment systems of the Drinking Water Company Oasen in the Netherlands. First, it clarifies and illustrates redox reactions and the mixing of river bank filtrate and polder water as the dominant processes determining the raw water quality for drinking water production. Next, full-scale results are elaborated on to evaluate trickling filtration as an efficient and proven one-step process to remove methane, iron, ammonium and manganese. The interaction of methane and manganese removal with nitrification in these systems is further analyzed. Methane is mostly stripped during trickling filtration and its removal hardly interferes with nitrification. Under specific conditions, microbial manganese removal may play a dominant role.

Description: An innovative treatment concept for future drinking water production: fluidized ion exchange – ultrafiltration – nanofiltration – granular activated carbon filtration Drinking Water Engineering and Science, 2, 41-47, 2009 Author(s): Sheng Li, S. G. J. Heijman, J. Q. J. C. Verberk, and J. C. van Dijk A new treatment concept for drinking water production from surface water has been investigated on a pilot scale. The treatment concept consists of fluidized ion exchange (FIEX), ultrafiltration (UF), nanofiltration (NF), and granular activated carbon filtration (GAC). The FIEX process removed calcium and other divalent cations; the UF membrane removed particles and micro-organisms; and the NF membrane and GAC removed natural organic matter (NOM) and micro-pollutants. This study focused on the prevention of fouling of the UF and scaling of the NF and investigated the overall removal of micro-pollutants by the treatment concept. The results of the experiments showed that in 14 days of continuous operation at a flux of 65 l/h m 2 the UF performance was stable with the FIEX pre-treated feed water without the aid of a coagulant. The scaling of the NF was also not observed even at 97% recovery. Different micro-pollutants were spiked in the NF feed water and their concentrations in the effluent of NF and GAC were measured. The combination of NF and GAC removed most of the micro-pollutants successfully, except for the very polar substances with a molecular weight lower than 100 Daltons.

Description: CLIPS based decision support system for Water Distribution Networks Drinking Water Engineering and Science Discussions, 4, 1-38, 2011 Author(s): S. Kulshrestha and R. Khosa The Water Distribution Networks (WDN) are managed by experts, who, over the years of their association and responsibility, acquire an empirical knowledge of the system and, characteristically, this knowledge remains largely confined to their respective personal domains. In the event of any new information and/or emergence of a new problem, these experts apply simple heuristics to design corrective measures and cognitively seek to predict network performance. The human interference leads to inefficient utilization of resources and unfair distribution. Researchers over the past, have tried to address to the problem and they have applied Artificial Intelligence (AI) tool to automate the decision process and encode the heuristic rules. The application of AI tool in the field of WDN management is meager. This paper describes a component of an ongoing research initiative to investigate the potential application of artificial intelligence package CLIPS (short for C Language Integrated Production System, developed at NASA/Johnson Space Center) in the development of an expert decision support system for management of a water distribution network. The system aims to meet several concerns of modern water utility managers as it attempts to formalize operational and management experiences, and provides a frame work for assisting water utility managers even in the absence of expert personnel.

Description: Development and evaluation of new behavioral indexes for a biological early warning system using Daphnia magna Drinking Water Engineering and Science, 7, 1-9, 2014 Author(s): T. Y. Jeong, J. Jeon, and S. D. Kim New behavioral indexes including combined index (CI), distribution index (DI), toxic index (TI), and altitude index (AI) for a biological early warning system (BEWS) were developed and evaluated using Daphnia magna in this study. The sensitivity and stability of each index were compared to evaluate the performance of the indexes through a real-time exposure test with a synthetic copper solution. The applicability of the CI to the field sample was evaluated through an effluent exposure test. The proportional relationship between toxicity level and magnitude of response was much lower in the effluent due to the complexity of water than in the copper solution. The results showed that the CI was most sensitive among the three indexes, while the DI was confirmed as the most useful index among the individual indexes. The combined index (CI) shows not only sensitivity but also stability in normal conditions below the statistically significant threshold ( p 〈 0.01), whereas the individual indexes displayed unstable index values in normal conditions ( p 〉 0.01). The CI improved performance of the BEWS in terms of sensitivity and stability, and it was confirmed as the higher correlation coefficient between the magnitude of the index and the toxicity level of the water sample.

Description: WaterMet 2 : a tool for integrated analysis of sustainability-based performance of urban water systems Drinking Water Engineering and Science Discussions, 7, 1-26, 2014 Author(s): K. Behzadian, Z. Kapelan, G. Venkatesh, H. Brattebø, and S. Sægrov This paper presents the new "WaterMet 2 " model for long-term assessment of urban water system (UWS) performance which will be used for strategic planning of the integrated UWS. WaterMet 2 quantifies the principal water-related flows and other metabolism-based fluxes in the UWS such as materials, chemicals, energy, greenhouse gas emissions. The suggested model is demonstrated through sustainability-based assessment of an integrated UWS of Oslo city for daily time step over a 30 yr planning horizon. The integrated UWS modelled by WaterMet 2 includes both water supply and wastewater systems. Given a fast population growth, WaterMet 2 calculates six quantitative sustainability-based indicators of the UWS. The result of the water supply reliability (94%) shows the need for appropriate intervention options over the planning horizon. Five intervention strategies are analysed in WaterMet 2 and their quantified performance are compared with respect to the criteria. Multi-criteria decision analysis is then used to rank the intervention strategies based on different weights from the involved stakeholders' perspectives. The results demonstrate the best and robust strategies are those which improve the performance of both water supply and wastewater systems.

Description: A pipe network simulation model with dynamic transition between free surface and pressurized flow Drinking Water Engineering and Science Discussions, 7, 27-57, 2014 Author(s): J. Fernández-Pato and P. García-Navarro Water flow numerical simulation in urban pipe systems is one of the topics that shows the need for surface flows and pressurized flows in steady and transient situations. The governing equations for both flow types are different and this must be taken into account in order to get a complete numerical model for solving transients. A numerical simulation model is developed in this work, capable of solving pipe networks mainly unpressurized, with isolated peaks of pressurization. For this purpose, a reformulation of the mathematical model through the Preissmann slot method is proposed. By means of this technique, a reasonable estimation of the water pressure is calculated in cases of pressurization. The numerical model is based on the first order Roe's scheme, in the frame of finite volume methods. It is adapted to abrupt transient situations, with subcritial and supercritical flows. The validation has been done by means of several cases with analytic solutions or empirical laboratory data. It has also been applied to some more complex and realistic cases, like junctions or pipe networks.

Description: Online data processing for proactive UK water distribution network operation Drinking Water Engineering and Science, 7, 23-33, 2014 Author(s): J. Machell, S. R. Mounce, B. Farley, and J. B. Boxall Operational benefits and efficiencies generated using prevalent water industry methods and techniques are becoming more difficult to achieve; as demonstrated by English and Welsh water companies' static position with regards the economic level of leakage. Water companies are often unaware of network incidents such as burst pipes or low pressure events until they are reported by customers; and therefore use reactive strategies to manage the effects of these events. It is apparent that new approaches need to be identified and applied to promote proactive network management if potential operational productivity and standards of service improvements are to be realised. This paper describes how measured flow and pressure data from instrumentation deployed in a UK water distribution network was automatically gathered, checked, analysed and presented using recently developed techniques to generate apposite information about network performance. The work demonstrated that these technologies can provide early warning, and hence additional time to that previously available, thereby creating opportunity to proactively manage a network; for example to minimise the negative impact on standards of customer service caused by unplanned events such as burst pipes. Each method, applied individually, demonstrated improvement on current industry processes. Combined application resulted in further improvements; including quicker and more localised burst main location. Future possibilities are explored, from which a vision of seamless integration between such technologies emerges to enable proactive management of distribution network events.

Description: Effect of biostimulation on biodegradation of dissolved organic carbon in biological granular activated carbon filters Drinking Water Engineering and Science Discussions, 5, 67-83, 2012 Author(s): K. Tihomirova, A. Briedis, J. Rubulis, and T. Juhna The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and LB (Luria Bertrani) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 8 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration.

Description: Development of a iron pipe corrosion simulation model for a water supply network Drinking Water Engineering and Science Discussions, 5, 85-120, 2012 Author(s): M. Bernats, S. W. Osterhus, K. Dzelzitis, and T. Juhna Corrosion in water supply networks is unwanted process that causes pipe material loss and subsequent pipe failures. Nowadays pipe replacing strategy most often is based on pipe age, which is not always the most important factor in pipe burst rate. In this study a methodology for developing a mathematical model to predict the decrease of pipe thickness in a large cast iron networks is presented. The quality of water, the temperature and the water flow regime were the main factors taken into account in the corrosion model. The water quality and flow rate effect were determined by measuring corrosion rate of metals coupons over the period of one year at different flow regimes. The obtained constants were then introduced in a calibrated hydraulic model (Epanet) and the corrosion model was validated by measuring the decrease of wall thickness in the samples that were removed during the regular pipe replacing event. The validated model was run for 30 yr to simulate the water distribution system of Riga (Latvia). Corrosion rate in the first year was 8.0–9.5 times greater than in all the forthcoming years, an average decrease of pipe wall depth being 0.013/0.016 mm per year in long term. The optimal iron pipe exploitation period was concluded to be 30–35 yr (for pipe wall depth 5.50 mm and metal density 7.5 m 3 t −1 ). The initial corrosion model and measurement error was 33%. After the validation of the model the error was reduced to below 15%.

Description: Experimental investigation of turbulent particle radial transport processes in DWDS using optical tomography Drinking Water Engineering and Science Discussions, 4, 61-83, 2011 Author(s): R. Floris and P. van Thienen Several transport mechanisms govern the cross-sectional particle distribution in fully developed turbulent flow in a pipe. These transport mechanisms affect particle load deposition as well as particle resuspension, which are identified as principal protagonists in the build-up of potential discolouration risk in drinking water distribution systems (DWDS). Both are to a large degree controlled by particle size and flow conditions. However, so far, these relationships are not completely understood in the context of DWDS. In this research we have attempted to identify under which conditions particles suspended in water are transported towards the pipe wall, which generate favourable conditions for deposition. Experimental results are reported and then compared, qualitatively and quantitatively, to the theoretical predictions in the regime transport map for turbulent flow proposed by van Thienen et al. (2011a). The research was conducted by completing a series of experiments in a laboratory test facility with different hydraulic regimes and different particle size ranges. A newly developed optical tomography measurement system was used in order to produce cross-sectional images of particle concentration in water flowing inside a pipe. The experimental results allowed us to identify flow conditions and particles sizes under which gravitational settling and turbophoresis dominated the radial particle transport. These findings show a good correspondence between experimental data and theoretical predictions on the occurrence of turbophoresis and lead to a better understanding of the processes that increase the potential discolouration risk in DWDS.

Description: Effect of fouling on removal of trace organic compounds by nanofiltration Drinking Water Engineering and Science Discussions, 4, 117-149, 2011 Author(s): S. Hajibabania, A. Verliefde, J. E. Drewes, L. D. Nghiem, J. McDonald, S. Khan, and P. Le-Clech The fate of chemical of concern is not yet fully understood during treatment of impaired waters. The aim of this paper is to assess the impact of different organic-based fouling layers on the removal of a large range of trace organics. Both model and real water samples (mixed with trace organic contaminants at environmental concentration of 2 μg l −1 ) were used to simulate fouling in NF under controlled environment. The new and fouled membranes were systematically characterised for surface charge, hydrophobicity and roughness. It was observed that fouling generally reduced the membrane surface charge; however, the alterations of the membrane hydrophobicity and surface roughness were dependent on the foulants composition. The rejection of charged trace organics was observed to be improved due to the increased electrostatic repulsion by fouled membranes and the adsorption of the trace organic chemicals onto organic matters. On the other hand, the removal of nonionic compounds decreased when fouling occurred, due to the presence of cake enhanced concentration polarization. The fouling layer structure was found to play an important role in the rejection of the trace organic compounds.

Description: Effect of fouling on removal of trace organic compounds by nanofiltration Drinking Water Engineering and Science, 4, 71-82, 2011 Author(s): S. Hajibabania, A. Verliefde, J. E. Drewes, L. D. Nghiem, J. McDonald, S. Khan, and P. Le-Clech The fate of chemical of concern is not yet fully understood during treatment of impaired waters. The aim of this paper is to assess the impact of different organic-based fouling layers on the removal of a large range of trace organics. Both model and real water samples (mixed with trace organic contaminants at environmental concentration of 2 μg l −1 ) were used to simulate fouling in nanofiltration under controlled environment. The new and fouled membranes were systematically characterised for surface charge, hydrophobicity and roughness. It was observed that fouling generally reduced the membrane surface charge; however, the alterations of the membrane hydrophobicity and surface roughness were dependent on the foulants composition. The rejection of charged trace organics was observed to be improved due to the increased electrostatic repulsion by fouled membranes and the adsorption of the trace organic chemicals onto organic matters. On the other hand, the removal of nonionic compounds decreased when fouling occurred, due to the presence of cake enhanced concentration polarization. The fouling layer structure was found to play an important role in the rejection of the trace organic compounds.

Description: Status of organochlorine pesticides in Ganga river basin: anthropogenic or glacial? Drinking Water Engineering and Science Discussions, 5, 1-30, 2012 Author(s): P. K. Mutiyar and A. K. Mittal This study reports the occurrences of organochlorine pesticides (OCPs) in Ganga river basin covering 3 states, i.e. Uttarakhand, Uttar Pradesh and Bihar covering 72% of total river stretch consisting of 82 sampling points covered through 3 sampling campaigns. Samples were monitored for 16 major OCPs, including HCHs, Endosulfan group, Aldrin group, DDTs and Heptachlor group pesticides. The results showed the ng l −1 levels contamination of OCPs in all the stretches sampled during these campaigns. The results also revealed that different type of OCPs were dominating in different stretches in accordance to the land use practices and agricultural runoff generated from those stretches. HCHs were most frequently detected (detection rate = 75%) in mountainous stretch; Endosulfans were prominent in UP (detection rate = 75%) stretch while BR stretch Aldrin group pesticides were paramount (detection rate = 34%). Source apportionment of the OCP's revealed that in the upper reaches of the Ganges i.e. in the state of Uttarakhand, the glacial melt may be responsible for the presence of OCP's. In the lower reaches, intensive agriculture and industrial activities may be significantly contributing these pesticides. The sample from tributaries of Ganga river were found to contain higher number of pesticides as well as higher concentrations. The maximum total pesticide in an individual sample from these sampling campaigns was found in Son river sample (0.17 μg l −1 , Location: Koilwar, Bhojpur, Bihar).

Description: Preface: CCWI 2013 Drinking Water Engineering and Science, 7, 99-100, 2014 Author(s): B. Brunone, M. Ferrante, S. Meniconi, and L. Berardi

Description: Empirical relations of rock properties of outcrop and core samples from the Northwest German Basin for geothermal drilling Geothermal Energy Science, 2, 21-37, 2014 Author(s): D. Reyer and S. L. Philipp Information about geomechanical and physical rock properties, particularly uniaxial compressive strength (UCS), are needed for geomechanical model development and updating with logging-while-drilling methods to minimise costs and risks of the drilling process. The following parameters with importance at different stages of geothermal exploitation and drilling are presented for typical sedimentary and volcanic rocks of the Northwest German Basin (NWGB): physical ( P wave velocities, porosity, and bulk and grain density) and geomechanical parameters (UCS, static Young's modulus, destruction work and indirect tensile strength both perpendicular and parallel to bedding) for 35 rock samples from quarries and 14 core samples of sandstones and carbonate rocks. With regression analyses (linear- and non-linear) empirical relations are developed to predict UCS values from all other parameters. Analyses focus on sedimentary rocks and were repeated separately for clastic rock samples or carbonate rock samples as well as for outcrop samples or core samples. Empirical relations have high statistical significance for Young's modulus, tensile strength and destruction work; for physical properties, there is a wider scatter of data and prediction of UCS is less precise. For most relations, properties of core samples plot within the scatter of outcrop samples and lie within the 90% prediction bands of developed regression functions. The results indicate the applicability of empirical relations that are based on outcrop data on questions related to drilling operations when the database contains a sufficient number of samples with varying rock properties. The presented equations may help to predict UCS values for sedimentary rocks at depth, and thus develop suitable geomechanical models for the adaptation of the drilling strategy on rock mechanical conditions in the NWGB.

Description: Rearrangement of stresses in fault zones – detecting major issues of coupled hydraulic–mechanical processes with relevance to geothermal applications Geothermal Energy Science, 2, 39-48, 2014 Author(s): G. Ziefle The South German Molasse Basin provides favourable conditions for geothermal plants. Nevertheless, micro-seismic events occur in the vicinity of the geothermal Unterhaching Gt2 well and seem to be caused by the geothermal plant. The injection and production are located in an existing fault system. The majority of seismic events takes place at a horizontal distance of 500 m or less of the borehole. However, none of the seismic events are located in the injection reservoir but in fact at a significantly greater depth. A deeper process understanding of the interacting thermal–hydraulic–mechanical effects in the vicinity of the well is desired. This article presents a significantly simplified 2-D model, investigating interactions of the stress field in the vicinity of the geothermal well and movements in the fault system. This might be of special interest, as the operation of the geothermal plant might lead to changes in the material and fracture properties on the one hand and in the equilibrium state on the other. A detailed description of the model, as well as various parameter studies, is presented. It can be seen that boundary conditions such as direction of the stress field in relation to the fault system, geometry of the fault system and parameters of the fractures have a significant influence on stresses in the proximity of the geothermal well. A variation in the spatial stress field in some parts of the fault system is to be expected. For the chosen assumptions the dimension of this variation is about 25% of the assumed stresses. Future work on this model might focus on the characteristics of the fault system, as well as on the influence of the coupled thermal–hydraulic–mechanical effects.

Description: Assessing the prospective resource base for enhanced geothermal systems in Europe Geothermal Energy Science, 2, 55-71, 2014 Author(s): J. Limberger, P. Calcagno, A. Manzella, E. Trumpy, T. Boxem, M. P. D. Pluymaekers, and J.-D. van Wees In this study the resource base for EGS (enhanced geothermal systems) in Europe was quantified and economically constrained, applying a discounted cash-flow model to different techno-economic scenarios for future EGS in 2020, 2030, and 2050. Temperature is a critical parameter that controls the amount of thermal energy available in the subsurface. Therefore, the first step in assessing the European resource base for EGS is the construction of a subsurface temperature model of onshore Europe. Subsurface temperatures were computed to a depth of 10 km below ground level for a regular 3-D hexahedral grid with a horizontal resolution of 10 km and a vertical resolution of 250 m. Vertical conductive heat transport was considered as the main heat transfer mechanism. Surface temperature and basal heat flow were used as boundary conditions for the top and bottom of the model, respectively. If publicly available, the most recent and comprehensive regional temperature models, based on data from wells, were incorporated. With the modeled subsurface temperatures and future technical and economic scenarios, the technical potential and minimum levelized cost of energy (LCOE) were calculated for each grid cell of the temperature model. Calculations for a typical EGS scenario yield costs of EUR 215 MWh −1 in 2020, EUR 127 MWh −1 in 2030, and EUR 70 MWh −1 in 2050. Cutoff values of EUR 200 MWh −1 in 2020, EUR 150 MWh −1 in 2030, and EUR 100 MWh −1 in 2050 are imposed to the calculated LCOE values in each grid cell to limit the technical potential, resulting in an economic potential for Europe of 19 GW e in 2020, 22 GW e in 2030, and 522 GW e in 2050. The results of our approach do not only provide an indication of prospective areas for future EGS in Europe, but also show a more realistic cost determined and depth-dependent distribution of the technical potential by applying different well cost models for 2020, 2030, and 2050.

Description: Status of organochlorine pesticides in the drinking water well-field located in the Delhi region of the flood plains of river Yamuna Drinking Water Engineering and Science Discussions, 4, 85-115, 2011 Author(s): P. K. Mutiyar, A. K. Mittal, and A. Pekdeger This study presents the occurrence of pesticides in a well-field located in Yamuna flood plain of Delhi region. Ground water sampling campaigns were carried out during pre-monsoon and post-monsoon periods covering 21 bore-wells and 5 Ranney wells. Major 17 organochlorine pesticides (OCP's) along with other water quality parameters were monitored during this period. Pesticide concentrations were determined using GC- ECD, while GC-MS was used for confirmatory purposes. OCP's groups like ∑HCH, ∑DDT, endosulfan and aldrin were observed in this well-field. Concentration of OCPs from Ranney wells exceeded the limit (1 μg l −1 ) prescribed by the Bureau of Indian Standards (BIS) in pre-monsoon season, though OCP levels in bore wells were within BIS limits. However, these levels were very close to the World Health Organisation (WHO) and European Union (EU) limit of for pesticides (0.5 μg l −1 ) in many samples. Bore well produced better quality water compared to the water from Ranney wells. Although, the level of OCP's was slightly lower than prescribed limit of national regulatory agency but such low doses may cause long-term damage to human populations if such water is consumed for longer durations. At low doses OCP's acts as endocrine disrupting agent and cause metabolic disorders in local population.

Description: Method development for arsenic analysis by modification in spectrophotometric technique Drinking Water Engineering and Science, 5, 1-8, 2012 Author(s): M. A. Tahir, H. Rasheed, and A. Malana Arsenic is a non-metallic constituent, present naturally in groundwater due to some minerals and rocks. Arsenic is not geologically uncommon and occurs in natural water as arsenate and arsenite. Additionally, arsenic may occur from industrial discharges or insecticide application. World Health Organization (WHO) and Pakistan Standard Quality Control Authority have recommended a permissible limit of 10 ppb for arsenic in drinking water. Arsenic at lower concentrations can be determined in water by using high tech instruments like the Atomic Absorption Spectrometer (hydride generation). Because arsenic concentration at low limits of 1 ppb can not be determined easily with simple spectrophotometric technique, the spectrophotometric technique using silver diethyldithiocarbamate was modified to achieve better results, up to the extent of 1 ppb arsenic concentration.

Description: Removal of paraquat pesticide with Fenton reaction in a pilot scale water system Drinking Water Engineering and Science, 7, 11-21, 2014 Author(s): C. Oliveira, K. Gruskevica, T. Juhna, K. Tihomirova, A. Alves, and L. M. Madeira Advanced oxidation processes, such as the Fenton's reagent, are powerful methods for decontamination of different environments from recalcitrant organics. In this work, the degradation of paraquat (PQ) pesticide was assessed (employing the commercial product gramoxone) directly inside the pipes of a pilot scale loop system; the effect of corroded cast iron pipe and loose deposits for catalysing the process was also evaluated. Results showed that complete degradation of paraquat ([PQ] 0 = 3.9 × 10 −4 M, T = 20–30 °C, pH 0 = 3, [H 2 O 2 ] 0 = 1.5 × 10 −2 M and [Fe (II)] = 5.0 × 10 −4 M,) was achieved within 8 h, either in lab scale or in the pilot loop. Complete PQ degradation was obtained at pH 3 whereas only 30% of PQ was degraded at pH 5 during 24 h. The installation of old cast iron segments with length from 0.5 to 14 m into PVC pipe loop system had a significant positive effect on degradation rate of PQ, even without addition of iron salt; the longer the iron pipes section, the faster was the pesticide degradation. Addition of loose deposits (mostly corrosion products composed of goethite, magnetite and a hydrated phase of FeO) also catalysed the Fenton reaction due to presence of iron in the deposits. Moreover, gradual addition of hydrogen peroxide improved gramoxone degradation and mineralization. This study showed for the first time that is possible to achieve complete degradation of pesticides in situ pipe water system and that deposits and corroded pipes catalyse oxidation of pesticides.

Description: Optimization of coagulation-flocculation parameters using a photometric dispersion analyser Drinking Water Engineering and Science Discussions, 7, 95-120, 2014 Author(s): S. Ramphal and M. Sibiya The size and structural characteristics of floc particles are important design and control parameters in water treatment and should be rapidly monitored with a reasonable amount of accuracy. In this study, a photometric dispersion analyser (PDA) coupled to standard jar test experiments was used to optimize coagulation-flocculation parameters while monitoring floc size and structure as well as the rate of floc formation during coagulation using alum. The optimal coagulation conditions were as follows: sample pH 8; alum dosage, 6 mg L −1 as Al 3+ ; G value, 116 s −1 ; rapid mixing time, 20 s. These conditions resulted in unstable treated water having a calcium carbonate precipitation potential of −15 mg L −1 as CaCO 3 and required a slaked lime dosage of 17 mg L −1 to equilibrate CCPP to acceptable levels. PDA data revealed that aggregation rate and steady-state variance are primary parameters as both have significant influence on coagulation-flocculation efficiency. However, the average steady state ratio, although an important parameter, had a lessened impact on coagulation-flocculation efficiency. The results of this study showed that the PDA instrument is an important tool in coagulation kinetic studies and can be employed as an additional tool in the optimization of coagulation conditions.

Description: Assessment of calculation methods for calcium carbonate saturation in drinking water for DIN 38404-10 compliance Drinking Water Engineering and Science Discussions, 6, 167-198, 2013 Author(s): P. J. de Moel, A. W. C. van der Helm, M. van Rijn, J. C. van Dijk, and W. G. J. van der Meer The new German standard for calcium carbonate saturation in drinking water, DIN 38404-10, 2012 (DIN), marks a change in drinking water standardization from using simplified equations applicable for nomographs and simple calculators to using extensive chemical modeling requiring computer programs. The standard specifies the chemical outlines for the modeling and presents a dataset with 10 water samples for validating used computer programs. The DIN standard, as well as the Standard Methods 2330 (SM) and NEN 6533 (NEN) for calculation of calcium carbonate saturation in drinking water were translated into chemical databases for use in PHREEQC (USGS, 2013). This novel approach gave the possibility to compare the calculations as defined in the standards and internationally accepted chemical databases provided with PHREEQC. From the research it is concluded that the computer program PHREEQC with the developed chemical database din38404-10_2012.dat complies with the DIN standard for calculating Saturation Index (SI) and Calcite Dissolution Capacity (Calcitlösekapazität) or Calcium Carbonate Precipitation Potential (CCPP). This compliance is achieved by assuming equal values for molarity as used in DIN (obsolete) and molality as used in PHREEQC. From comparison with internationally accepted chemical databases it is concluded that the use of molarity limits the use of DIN to a maximum temperature of 45 °C. For current practical applications in water treatment and drinking water applications, the PHREEQC database stimela.dat was developed within the Stimela platform of Delft University of Technology. This database is an extension of the internationally accepted chemical database phreeqc.dat and thus in compliance with Standard Methods 2330. The database stimela.dat is also applicable for hot and boiling water, which is important in drinking water supply with regard to scaling of calcium carbonate in in-house drinking water practices. The SM and NEN proved to be not accurate enough to comply with DIN, because of their simplifications. The differences in calculation results for DIN, SM and NEN illustrate the need for international unification of the standard for calcium carbonate saturation in drinking water.

Description: Present challenges for future water sustainable cities: a case study from Italy Drinking Water Engineering and Science, 7, 35-40, 2014 Author(s): L. Bonzanigo and G. Sinnona The global population is increasingly concentrated in cities. Cities and urban areas face many challenges – economic, social, health and environmental – which are often exacerbated by an increase in the frequency of natural disasters. Together, these challenges call for a shift towards sustainable cities which reduce their impact on the surrounding environment, whilst at the same time succeeding to make resources available to their increasing number of inhabitants. This study explores the state of the art of water management practices of the highly urbanised Northern Italian region and plans and scope for the future development of water management. Although the region is at present not under severe water stress, recently some cities faced water scarcity problems and were forced to implement water rationing. We assessed the vulnerability of Parma and Ferrara to a water crisis, together with the regular and emergency adaptation measures already in place, and the forecast for the near future. In two workshops, the authors adapted the Australian concept of water sensitive urban design for the Italian context. Although the population remains generally unaware of the impact of the two latest severe drought events (2003 and 2006/7), many adaptation measures towards a more sustainable use of the water resource are already in place – technically, institutionally, and individually. Water managers consider however that the drastic and definite changes needed to integrate the urban water management cycle, and which minimise the ecological footprint of urban spaces, lay far in the future.

Description: Functioning conditions of the Casale pumping station in Mantova, Italy Drinking Water Engineering and Science, 7, 93-97, 2014 Author(s): C. Capponi, M. Ferrante, M. Pedroni, B. Brunone, S. Meniconi, M. Zaghini, and F. Leoni Pump speed, input power, pressure and discharge data are analyzed for evaluating functioning conditions of Casale pumping station in Mantova, Italy, managed by TeaAcque. A model based on the affinity laws is used to simulate the behavior of the installed variable speed pumps. Quadratic and cubic polynomial curves are used to fit the pump data given by the affinity laws. Such curves allow predicting the efficiency when the functioning conditions change. The relationship between the rotation speed and the efficiency is also derived.

Description: Finite volume simulation of unsteady water pipe flow Drinking Water Engineering and Science, 7, 83-92, 2014 Author(s): J. Fernández-Pato and P. García-Navarro The most commonly used hydraulic network models used in the drinking water community exclusively consider fully filled pipes. However, water flow numerical simulation in urban pipe systems may require to model transitions between surface flow and pressurized flow in steady and transient situations. The governing equations for both flow types are different and this must be taken into account in order to get a complete numerical model for solving dynamically transients. In this work, a numerical simulation tool is developed, capable of simulating pipe networks mainly unpressurized, with isolated points of pressurization. For this purpose, the mathematical model is reformulated by means of the Preissmann slot method. This technique provides a reasonable estimation of the water pressure in cases of pressurization. The numerical model is based on the first order Roe's scheme, in the frame of finite volume methods. The novelty of the method is that it is adapted to abrupt transient situations, with subcritical and supercritical flows. The validation has been done by means of several cases with analytic solutions or empirical laboratory data. It has also been applied to some more complex and realistic cases, like junctions or pipe networks.

Description: 〈b〉Empirical relations of rock properties of outcrop and core samples from the Northwest German Basin for geothermal drilling〈/b〉〈br〉 D. Reyer and S. L. Philipp〈br〉 Geoth. Energ. Sci., 2, 21-37, https://doi.org/10.5194/gtes-2-21-2014, 2014〈br〉 Information about geomechanical and physical rock properties, particularly uniaxial compressive strength (UCS), are needed for geomechanical model development and updating with logging-while-drilling methods to minimise costs and risks of the drilling process. The following parameters with importance at different stages of geothermal exploitation and drilling are presented for typical sedimentary and volcanic rocks of the Northwest German Basin (NWGB): physical (〈i〉P〈/i〉 wave velocities, porosity, and bulk and grain density) and geomechanical parameters (UCS, static Young's modulus, destruction work and indirect tensile strength both perpendicular and parallel to bedding) for 35 rock samples from quarries and 14 core samples of sandstones and carbonate rocks. 〈br〉〈br〉 With regression analyses (linear- and non-linear) empirical relations are developed to predict UCS values from all other parameters. Analyses focus on sedimentary rocks and were repeated separately for clastic rock samples or carbonate rock samples as well as for outcrop samples or core samples. Empirical relations have high statistical significance for Young's modulus, tensile strength and destruction work; for physical properties, there is a wider scatter of data and prediction of UCS is less precise. For most relations, properties of core samples plot within the scatter of outcrop samples and lie within the 90% prediction bands of developed regression functions. The results indicate the applicability of empirical relations that are based on outcrop data on questions related to drilling operations when the database contains a sufficient number of samples with varying rock properties. The presented equations may help to predict UCS values for sedimentary rocks at depth, and thus develop suitable geomechanical models for the adaptation of the drilling strategy on rock mechanical conditions in the NWGB.

Description: 〈b〉Influence of major fault zones on 3-D coupled fluid and heat transport for the Brandenburg region (NE German Basin)〈/b〉〈br〉 Y. Cherubini, M. Cacace, M. Scheck-Wenderoth, and V. Noack〈br〉 Geoth. Energ. Sci., 2, 1-20, https://doi.org/10.5194/gtes-2-1-2014, 2014〈br〉 To quantify the influence of major fault zones on the groundwater and thermal field, 3-D finite-element simulations are carried out. Two fault zones – the Gardelegen and Lausitz escarpments – have been integrated into an existing 3-D structure of the Brandenburg region in northeastern Germany. Different geological scenarios in terms of modelled fault permeability have been considered, of which two end-member models are discussed in detail. In addition, results from these end-member simulations are compared to a reference case in which no faults are considered. 〈br〉〈br〉 The study provides interesting results with respect to the interaction between faults and surrounding sediments and how it affects the regional groundwater circulation system and thermal field. 〈br〉〈br〉 Impermeable fault zones seem to induce no remarkable effects on the temperature distribution; that is, the thermal field is similar to the no-fault model. In addition, tight faults have only a local impact on the fluid circulation within a domain of limited spatial extent centred on the fault zone. Fluid flow from the surrounding aquifers is deviated in close proximity of the fault zones acting as hydraulic barriers that prevent lateral fluid inflow into the fault zones. 〈br〉〈br〉 Permeable fault zones induce a pronounced thermal signature with alternating up- and downward flow along the same structures. Fluid flow along the plane of the faults is principally driven by existing hydraulic head gradients, but may be further enhanced by buoyancy forces. Within recharge domains, fluid advection induces a strong cooling in the fault zones. Discharge domains at shallow depth levels (~〈br〉 This study is the first attempt to investigate the impact of major fault zones on a 3-D basin scale for the coupled fluid and heat transport in the Brandenburg region. The approach enables a quantification of mechanisms controlling fluid flow and temperature distribution both within surrounding sediments and fault zones as well as how they dynamically interact. Therefore, the results from the modelling provide useful indications for geothermal energy exploration.

Description: 〈b〉Rearrangement of stresses in fault zones – detecting major issues of coupled hydraulic–mechanical processes with relevance to geothermal applications〈/b〉〈br〉 G. Ziefle〈br〉 Geoth. Energ. Sci., 2, 39-48, https://doi.org/10.5194/gtes-2-39-2014, 2014〈br〉 The South German Molasse Basin provides favourable conditions for geothermal plants. Nevertheless, micro-seismic events occur in the vicinity of the geothermal Unterhaching Gt2 well and seem to be caused by the geothermal plant. 〈br〉〈br〉 The injection and production are located in an existing fault system. The majority of seismic events takes place at a horizontal distance of 500 m or less of the borehole. However, none of the seismic events are located in the injection reservoir but in fact at a significantly greater depth. A deeper process understanding of the interacting thermal–hydraulic–mechanical effects in the vicinity of the well is desired. 〈br〉〈br〉 This article presents a significantly simplified 2-D model, investigating interactions of the stress field in the vicinity of the geothermal well and movements in the fault system. This might be of special interest, as the operation of the geothermal plant might lead to changes in the material and fracture properties on the one hand and in the equilibrium state on the other. A detailed description of the model, as well as various parameter studies, is presented. It can be seen that boundary conditions such as direction of the stress field in relation to the fault system, geometry of the fault system and parameters of the fractures have a significant influence on stresses in the proximity of the geothermal well. A variation in the spatial stress field in some parts of the fault system is to be expected. For the chosen assumptions the dimension of this variation is about 25% of the assumed stresses. Future work on this model might focus on the characteristics of the fault system, as well as on the influence of the coupled thermal–hydraulic–mechanical effects.

Description: 〈b〉Effectiveness of acidizing geothermal wells in the South German Molasse Basin〈/b〉〈br〉 S. Schumacher and R. Schulz〈br〉 Geoth. Energ. Sci., 1, 1-11, https://doi.org/10.5194/gtes-1-1-2013, 2013〈br〉 In Germany, many hydro-geothermal plants have been constructed in recent years, primarily in the region of Munich. As the host formation here mainly consists of carbonates, nearly all recently drilled wells have been acidized in order to improve the well yield. In this study, the effectiveness of these acid treatments is analyzed with respect to the amount of acid used and the number of acid treatments carried out per well. The results show that the first acid treatment has the largest effect, while subsequent acidizing improves the well only marginally. Data also indicate that continued acidizing can lead to degradation of the well. These findings may not only be important for geothermal installations in Germany but also for projects, for example, in Austria, France or China where geothermal energy is produced from carbonate formations as well.

Description: Dynamic hydraulic models to study sedimentation in drinking water networks in detail Drinking Water Engineering and Science, 5, 87-92, 2012 Author(s): I. W. M. Pothof and E. J. M. Blokker Sedimentation in drinking water networks can lead to discolouration complaints. A sufficient criterion to prevent sedimentation in the Dutch drinking water networks is a daily maximum velocity of 0.25 m s −1 . Flushing experiments have shown that this criterion is a sufficient condition for a clean network, but not a necessary condition. Drinking water networks include many locations with a maximum velocity well below 0.25 m s −1 without accumulated sediments. Other criteria need to be developed to predict which locations are susceptible to sedimentation and to prevent sedimentation in future networks. More distinctive criteria are helpful to prioritise flushing operations and to prevent water quality complaints. The authors use three different numerical modelling approaches – quasi-steady, rigid column and water hammer – with a temporal discretisation of 1 s in order to assess the influence of unsteady flows on the wall shear stress, causing resuspension of sediment particles. The model predictions are combined with results from flushing experiments in the drinking water distribution system of Purmerend, the Netherlands. The waterhammer model does not result in essentially different flow distribution patterns, compared to the rigid column and quasi-steady modelling approach. The extra information from the waterhammer model is a velocity oscillation of approximately 0.02 m s −1 around the quasi-steady solution. The presence of stagnation zones and multiple flow direction reversals seem to be interesting new parameters to predict sediment accumulation, which are consistent with the observed turbidity data and theoretical considerations on critical shear stresses.

Description: Water use scenarios as a tool for adaptation to climate change of a water supply company Drinking Water Engineering and Science Discussions, 5, 265-289, 2012 Author(s): R. Jacinto, M. J. Cruz, and F. D. Santos The project ADAPTACLIMA, promoted by EPAL, the largest Portuguese Water Supply Utility, aims to provide the company with an adaptation strategy in the medium and long term to reduce the vulnerabilities of its activities to climate change. We used the special report emissions scenarios (SRES) of the IPCC (Intergovernmental Panel on Climate Change) to produce local scenarios of water use. Available population SRES for Portugal were downscaled to the study area using a linear approach. Local land use scenarios were produced using the following steps: (1) characterization of the present land use for each municipality of the study area using Corine Land Cover and adapt the CLC classes to those used in the SRES; (2) identification of recent tendencies in land use change for the study area; (3) identification of SRES tendencies for land use change in Europe; and (4) production of local scenarios of land use. Water use scenarios were derived considering both population and land use scenarios as well as scenarios of change in other parameters (technological developments, increases in efficiency, climate changes, or political and behavioural changes). The A2 scenario forecasts an increase in population (+16%) in the study area while the other scenarios show a reduction of resident population (−6 to 8%). All scenarios, but especially A1, show a significant reduction in agricultural area and an increase in urban area. Regardless of the scenario, water use will progressively be reduced until 2100. These reductions are mainly due to increased water use efficiency and reduction of irrigated land. The results concord with several projects modelling water use at regional and global level.

Description: Low-cost multi-stage filtration enhanced by coagulation-flocculation in upflow gravel filtration Drinking Water Engineering and Science Discussions, 5, 291-332, 2012 Author(s): L. D. Sánchez, L. M. Marin, J. T. Visscher, and L. C. Rietveld This paper assesses the operational and design aspects of coagulation and flocculation in upflow gravel filters (CF-UGF) in a multi-stage filtration (MSF) plant. This study shows that CF-UGF units improve the performance of MSF considerably, when the system operates with turbidity above 30 NTU. It strongly reduces the load of particulate material before the water enters in the slow sand filters (SSF) and therewith avoids short filter runs and prevents early interruption in SSF operations. The removal efficiency of turbidity in the CF-UGF with coagulant was between 85 and 96%, whereas the average efficiency without coagulant dosing was 46% (range: 21–76%). Operating with coagulant also improves the removal efficiency for total coliforms, E-coli and HPC. No reduction was observed in the microbial activity of the SSF, no obstruction of the SSF bed was demonstrated and SSF runs were maintained between 50 and 70 days for a maximum head loss of 0.70 m. The most important advantage is the flexibility of the system to operate with and without coagulant according to the influent turbidity. It was only necessary for 20% of the time to operate with the coagulant. The CF-UGF unit represented 7% of total construction costs and the O&M cost for the use of coagulant represented only 0.3%.

Description: Nanofiltration for water and wastewater treatment – a mini review Drinking Water Engineering and Science Discussions, 6, 59-77, 2013 Author(s): H. K. Shon, S. Phuntsho, D. S. Chaudhary, S. Vigneswaran, and J. Cho The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals of membrane process in general, mechanisms of NF process including few basic models. fouling challenges and their control mechanisms adopted.

Description: How much are households willing to contribute to the cost recovery of drinking water supply? Results from a household survey Drinking Water Engineering and Science, 6, 33-38, 2013 Author(s): S. Tarfasa Financial resources are crucial to improve existing urban drinking water supply in developing countries typically characterized by low cost recovery rates and high and rapidly growing demand for more reliable services. This study examines the willingness to pay for improved urban drinking water supply employing a choice model (CM) in an urban context in Ethiopia, Hawassa, with a household survey of 170 respondents. The design of the choice model allows the estimation of the values of two attributes of urban drinking water service (extra day water delivery per week and safer water). The findings indicate that households are willing to pay up to 60% extra for improved levels of water supply over and above their current water bill. Especially those households living in the poorest part of the city with the lowest service levels demonstrate that they are willing to pay more despite significant income constraints they are facing. Women value the improvement of water quality most, while a significant effect is found for averting behavior and expenditures. The estimated economic values can be used in policy appraisals of investment decisions.

Description: Removal and transformation of pharmaceuticals in wastewater treatment plants and constructed wetlands Drinking Water Engineering and Science Discussions, 6, 97-117, 2013 Author(s): E. Lee, S. Lee, J. Park, Y. Kim, and J. Cho Since trace organic compounds such as pharmaceuticals in surface water have been a relevant threat to drinking water supplies, in this study the removal of pharmaceuticals and transformation of pharmaceuticals into metabolites were investigated in the main sources of micropollutants such as wastewater treatment plants (WWTPs) and engineered constructed wetlands. Pharmaceuticals were effectively removed by different WWTP processes and wetlands. Pharmaceutical metabolites with relatively low log D value resulted in the low removal efficiencies compared to parent compounds with relatively high log D value, indicating the stability of metabolites. And the constructed wetlands fed with wastewater effluent were encouraged to prevent direct release of micropollutants into surface waters. Among various pharmaceuticals, different transformation pattern of ibuprofen was observed with significant formation of 1-hydroxy-ibuprofen during biological treatment in WWTP, indicating preferential biotransformation of ibuprofen. Lastly, transformation of pharmaceuticals depending on their structural position was investigated in terms of electron density, and the electron rich C 1 = C 2 bond of carbamazepine was revealed as an initial transformation position.

Description: Effects of network pressure on water meter under-registration: an experimental analysis Drinking Water Engineering and Science Discussions, 6, 119-149, 2013 Author(s): C. M. Fontanazza, V. Notaro, V. Puleo, and G. Freni In water supply systems, a considerable amount of apparent loss is caused by meter under-registration. Water meters are subject to intrinsic systemic error depending on the actual flow rates passing through them. Furthermore, the moving parts of the meter are subject to wear and tear that progressively reduce meter accuracy. The increase in systemic error is especially evident at low flow rates because of growing friction in the rotating mechanism, which requires a higher flow to start the meter (starting flow). The aim of this paper is to experimentally investigate metering error in an attempt to find a direct link between meter age, network pressure and apparent losses caused by the inability of the meter to accurately register the volume passing though it at low flow rates. The study was performed through laboratory experiments in which worn-out water meters were tested using a test bench. The results of the laboratory experiments show that ageing and pressure are both relevant parameters for determining meter starting flow. These results were then applied to assess the effects on apparent losses of the age of the meter, varying pressure values upstream of the meter (the pressure in the network where the meter is installed) and different patterns of flow rates passing through the device (the consumption pattern of the user). The presented results are useful for understanding the effects of operating conditions on water meter under-registration, which can aid water managers in implementing effective replacement campaigns.

Description: Present challenges for future water sustainable cities: a case study from Italy Drinking Water Engineering and Science Discussions, 6, 151-166, 2013 Author(s): L. Bonzanigo and G. Sinnona The global population is increasingly concentrated in cities. Cities and urban areas face many challenges – economic, social, health and environmental – which are often exacerbated by an increase in the frequency of natural disasters. Together, these challenges call for a shift towards sustainable cities which reduce their impact on the surrounding environment, whilst at the same time succeeding to make resources available to their increasing number of inhabitants. This article explores the state of the art of water management practices of the highly urbanised Northern Italian region and plans and scope for the future development of water management. Although the region is at present not under severe water stress, recently some cities faced water scarcity problems and were forced to implement water rationing. We assessed the vulnerability of Parma and Ferrara to a water crisis, together with the regular and emergency adaptation measures already in place, and the forecast for the near future. In two workshops, the authors adapted the Australian concept of Water Sensitive Urban Design for the Italian context. Although the population remains generally unaware of the impact of the two latest severe drought events (2003 and 2006/7), many adaptation measures towards a more sustainable use of the water resource are already in place – technically, institutionally, and individually. Water managers consider however that the drastic and definite changes needed to integrate the urban water management cycle, and which minimise the ecological footprint of urban spaces, lay far in the future.

Description: Status of organochlorine pesticides in Ganga river basin: anthropogenic or glacial? Drinking Water Engineering and Science, 6, 69-80, 2013 Author(s): P. K. Mutiyar and A. K. Mittal This study reports the occurrences of organochlorine pesticides (OCPs) in the Ganga river basin covering 3 states, i.e., Uttarakhand, Uttar Pradesh and Bihar comprising 72% of total river stretch consisting of 82 sampling points covered through 3 sampling campaigns. Samples were monitored for 16 major OCPs, including hexachlorocyclohexanes (HCHs), Endosulfan group, Aldrin group, DDTs and Heptachlor group pesticides. The results showed the ng L −1 levels contamination of OCPs in all the stretches sampled during these campaigns. The results also revealed that different types of OCPs were dominating in different stretches in accordance with the land use practices and agricultural runoff generated from those stretches. HCHs were most frequently detected (detection rate = 75%) in mountainous stretch; Endosulfans were prominent in UP (detection rate = 75%) stretch while in BR stretch Aldrin group pesticides were paramount (detection rate = 34%). Source apportionment of the OCP's revealed that in the upper reaches of the Ganges i.e., in the state of Uttarakhand, the glacial melt may be responsible for the presence of OCP's. In the lower reaches, intensive agriculture and industrial activities may be significantly contributing these pesticides. The samples from tributaries of Ganga river were found to contain higher numbers of pesticides as well as higher concentrations. The maximum total pesticide concentration in an individual sample during these sampling campaigns was found in the Son river sample (0.17 μg L −1 , Location: Koilwar, Bhojpur, Bihar).

Description: The large-scale impact of climate change to Mississippi flood hazard in New Orleans Drinking Water Engineering and Science, 6, 81-87, 2013 Author(s): T. L. A. Driessen and M. van Ledden The objective of this paper was to describe the impact of climate change on the Mississippi River flood hazard in the New Orleans area. This city has a unique flood risk management challenge, heavily influenced by climate change, since it faces flood hazards from multiple geographical locations (e.g. Lake Pontchartrain and Mississippi River) and multiple sources (hurricane, river, rainfall). Also the low elevation and significant subsidence rate of the Greater New Orleans area poses a high risk and challenges the water management of this urban area. Its vulnerability to flooding became dramatically apparent during Hurricane Katrina in 2005 with huge economic losses and a large number of casualties. A SOBEK Rural 1DFLOW model was set up to simulate the general hydrodynamics. This model included the two important spillways that are operated during high flow conditions. A weighted multi-criteria calibration procedure was performed to calibrate the model for high flows. Validation for floods in 2011 indicated a reasonable performance for high flows and clearly demonstrated the influence of the spillways. 32 different scenarios were defined which included the relatively large sea level rise and the changing discharge regime that is expected due to climate change. The impact of these scenarios on the water levels near New Orleans were analysed by the hydrodynamic model. Results showed that during high flows New Orleans will not be affected by varying discharge regimes, since the presence of the spillways ensures a constant discharge through the city. In contrary, sea level rise is expected to push water levels upwards. The effect of sea level rise will be noticeable even more than 470 km upstream. Climate change impacts necessitate a more frequent use of the spillways and opening strategies that are based on stages.

Description: Assessment of calculation methods for calcium carbonate saturation in drinking water for DIN 38404-10 compliance Drinking Water Engineering and Science, 6, 115-124, 2013 Author(s): P. J. de Moel, A. W. C. van der Helm, M. van Rijn, J. C. van Dijk, and W. G. J. van der Meer The new German standard on the calculation of calcite saturation in drinking water, DIN 38404-10, 2012 (DIN), marks a change in drinking water standardization from using simplified equations applicable for nomographs and simple calculators to using extensive chemical modeling requiring computer programs. The standard outlines the chemical modeling and presents a dataset with 10 water samples for validating used computer programs. The DIN standard, as well as the Standard Methods 2330 (SM) and NEN 6533 (NEN) for calculation of calcium carbonate saturation in drinking water were translated into chemical databases for use in PHREEQC (USGS, 2013). This novel approach gave the possibility to compare the calculations as defined in the standards with calculations using widely used chemical databases provided with PHREEQC. From this research it is concluded that the computer program PHREEQC with the developed chemical database din38404-10_2012.dat complies with the DIN standard for calculating Saturation Index (SI) and Calcite Dissolution Capacity (Calcitlösekapazität) or Calcium Carbonate Precipitation Potential (CCPP). This compliance is achieved by assuming equal values for molarity as used in DIN (obsolete) and molality as used in PHREEQC. From comparison with widely used chemical databases it is concluded that the use of molarity limits the use of DIN to a maximum temperature of 45 °C. For current practical applications in water treatment and drinking water applications, the PHREEQC database stimela.dat was developed within the Stimela platform of Delft University of Technology. This database is an extension of the chemical database phreeqc.dat and thus in compliance with SM. The database stimela.dat is also applicable for hot and boiling water, which is important in drinking water supply with regard to scaling of calcium carbonate in in-house drinking water practices. SM and NEN proved to be not accurate enough to comply with DIN, because of their simplifications. The differences in calculation results for DIN, SM and NEN illustrate the need for international unification of the standard for calcium carbonate saturation in drinking water.

Description: Pump schedules optimisation with pressure aspects in complex large-scale water distribution systems Drinking Water Engineering and Science, 7, 53-62, 2014 Author(s): P. Skworcow, D. Paluszczyszyn, and B. Ulanicki This paper considers optimisation of pump and valve schedules in complex large-scale water distribution networks (WDN), taking into account pressure aspects such as minimum service pressure and pressure-dependent leakage. An optimisation model is automatically generated in the GAMS language from a hydraulic model in the EPANET format and from additional files describing operational constraints, electricity tariffs and pump station configurations. The paper describes in details how each hydraulic component is modelled. To reduce the size of the optimisation problem the full hydraulic model is simplified using module reduction algorithm, while retaining the nonlinear characteristics of the model. Subsequently, a nonlinear programming solver CONOPT is used to solve the optimisation model, which is in the form of Nonlinear Programming with Discontinuous Derivatives (DNLP). The results produced by CONOPT are processed further by heuristic algorithms to generate integer solution. The proposed approached was tested on a large-scale WDN model provided in the EPANET format. The considered WDN included complex structures and interactions between pump stations. Solving of several scenarios considering different horizons, time steps, operational constraints, demand levels and topological changes demonstrated ability of the approach to automatically generate and solve optimisation problems for a variety of requirements.

Description: Functioning conditions of the Casale pumping station in Mantova, Italy Drinking Water Engineering and Science Discussions, 7, 151-168, 2014 Author(s): C. Capponi, M. Ferrante, M. Pedroni, B. Brunone, S. Meniconi, M. Zaghini, and F. Leoni This paper aims to analyze data provided by TeaAcque for Casale pumping station in Mantova, Italy. A~model based on the affinity laws is used to simulate the behavior of the Casale pumping station where variable speed pumps (VSPs) are installed. Quadratic and cubic polynomial curves are used to fit the pump data given by the affinity laws. Such curves can be used to predict the efficiency when the functioning conditions change. The relationship between the variation in the rotation speed and the efficiency is also derived.

Description: WaterMet 2 : a tool for integrated analysis of sustainability-based performance of urban water systems Drinking Water Engineering and Science, 7, 63-72, 2014 Author(s): K. Behzadian, Z. Kapelan, G. Venkatesh, H. Brattebø, and S. Sægrov This paper presents the "WaterMet 2 " model for long-term assessment of urban water system (UWS) performance which will be used for strategic planning of the integrated UWS. WaterMet 2 quantifies the principal water-related flows and other metabolism-based fluxes in the UWS such as materials, chemicals, energy and greenhouse gas emissions. The suggested model is demonstrated through sustainability-based assessment of an integrated real-life UWS for a daily time-step over a 30-year planning horizon. The integrated UWS modelled by WaterMet 2 includes both water supply and wastewater systems. Given a rapid population growth, WaterMet 2 calculates six quantitative sustainability-based indicators of the UWS. The result of the water supply reliability (94%) shows the need for appropriate intervention options over the planning horizon. Five intervention strategies are analysed in WaterMet 2 and their quantified performance is compared with respect to the criteria. Multi-criteria decision analysis is then used to rank the intervention strategies based on different weights from the involved stakeholders' perspectives. The results demonstrate that the best and robust strategies are those which improve the performance of both water supply and wastewater systems.

Description: Water Expert: a conceptualized framework for development of a rule-based decision support system for distribution system decontamination Drinking Water Engineering and Science Discussions, 7, 169-211, 2014 Author(s): J. L. Gutenson, A. N. S. Ernest, J. R. Fattic, L. E. Ormsbee, A. A. Oubeidillah, and X. Zhang Significant drinking water contamination events pose a serious threat to public and environmental health. Water utilities often must make timely, critical decisions without evaluating all facets of the incident, as the data needed to enact informed decisions are inevitably dispersant and disparate, originating from policy, science, and heuristic contributors. Water Expert is a functioning hybrid decision support system (DSS) and expert system framework, with emphases on meshing parallel data structures to expedite and optimize the decision pathway. Delivered as a thin-client application through the user's web browser, Water Expert 's extensive knowledgebase is a product of inter-university collaboration that methodically pieced together system decontamination procedures through consultation with subject matter experts, literature review, and prototyping with stakeholders. This paper discusses development of Water Expert , analyzing the development process underlying the DSS and the system's existing architecture specifications.

Description: Immobilized photocatalyst on stainless steel woven meshes assuring efficient light distribution in a solar reactor Drinking Water Engineering and Science, 7, 41-52, 2014 Author(s): A. S. El-Kalliny, S. F. Ahmed, L. C. Rietveld, and P. W. Appel An immobilized TiO 2 photocatalyst with a high specific surface area was prepared on stainless steel woven meshes in order to be used packed in layers for water purification. Immobilization of such a complex shape needs a special coating technique. For this purpose, dip coating and electrophoretic deposition (EPD) techniques were used. The EPD technique gave the TiO 2 coating films a better homogeneity and adhesion, fewer cracks, and a higher · OH formation than the dip coating technique. The woven mesh structure packed in layers guaranteed an efficient light-penetration in water treatment reactor. A simple equation model was used to describe the distribution of light through the mesh layers in the presence of absorbing medium (e.g., colored water with humic acids). Maximum three or four coated meshes were enough to harvest the solar UV light from 300 nm to 400 nm with a high penetration efficiency. The separation distance between the mesh layers played an important role in the efficiency of solar light penetration through the coated mesh layers, especially in case of colored water contaminated with high concentrations of humic acid.

Description: Optimization of coagulation-flocculation parameters using a photometric dispersion analyser Drinking Water Engineering and Science, 7, 73-82, 2014 Author(s): S. R. Ramphal and M. S. Sibiya The size and structural characteristics of floc particles are important design and control parameters in water treatment and should be rapidly monitored with a reasonable amount of accuracy. In this study, a photometric dispersion analyser (PDA) coupled to standard jar test experiments was used to optimize coagulation-flocculation parameters while monitoring floc size and structure as well as the rate of floc formation during coagulation using alum. The optimal coagulation conditions were as follows: sample pH 8; alum dosage, 3 mg L −1 as Al 3+ ; G value, 172 s −1 ; rapid mixing time, 20 s. These conditions resulted in unstable treated water having a calcium carbonate precipitation potential (CCPP) of −15 mg L −1 as CaCO 3 and required a slaked lime dosage of 17 mg L −1 as CaCO 3 to equilibrate CCPP to acceptable levels. PDA data revealed that aggregation rate and steady-state variance are primary parameters as both have substantial influence on coagulation-flocculation efficiency. However, the average steady state ratio, although an important parameter, had a lessened impact on coagulation-flocculation efficiency. The results of this study showed that the PDA instrument is an important tool in coagulation kinetic studies and can be employed as an additional tool in the optimization of coagulation conditions.

Description: Preventive strategy in response to climate change and infrastructural failures for Jakarta slum dwellers Drinking Water Engineering and Science Discussions, 5, 421-434, 2012 Author(s): V. Pooroe and I. Prabaharyaka Jakarta is a city with unpredictable yet annual water shortages, both during the dry and wet season, which disproportionately affect the urban poor. One possible solution is to redevelop the existing water supply system which is now working in one of the largest slum area in Penjaringan, North Jakarta. This system is equipped with a large meter, the Master Meter, to record the communal water consumption and individual meters to record household consumptions. The Community Based Organization uses, operates, and maintains the system based on agreement with water users. Improvement of the Master Meter is achieved by harvesting uncollected rain water during the wet season with its high rainfall intensity, modifying the water storage system and improving the influent water quality. This paper aims to provide a preventive strategy in response to climate change and infrastructural failures based on a case study of community-based water supply project in Penjaringan, Jakarta.

Description: Abnormal quality detection and isolation in water distribution networks using simulation models Drinking Water Engineering and Science Discussions, 5, 435-453, 2012 Author(s): F. Nejjari, R. Pérez, V. Puig, J. Quevedo, R. Sarrate, M. A. Cugueró, G. Sanz, and J. M. Mirats This paper proposes a model based detection and localisation method to deal with abnormal quality levels based on the chlorine measurements and chlorine sensitivity analysis in a water distribution network. A fault isolation algorithm which correlates on line the residuals (generated by comparing the available chlorine measurements with their estimations using a model) with the fault sensitivity matrix is used. The proposed methodology has been applied to a District Metered Area (DMA) in the Barcelona network.

Description: Robust optimization methodologies for water supply systems design Drinking Water Engineering and Science, 5, 31-37, 2012 Author(s): J. Marques, M. C. Cunha, J. Sousa, and D. Savić Water supply systems (WSSs) are vital infrastructures for the well-being of people today. To achieve good customer satisfaction the water supply service must always be able to meet people's needs, in terms of both quantity and quality. But unpredictable extreme conditions can cause severe damage to WSSs and lead to poorer levels of service or even to their failure. Operators dealing with a system's day-to-day operation know that events like burst water mains can compromise the functioning of all or part of a system. To increase a system's reliability, therefore, designs should take into account operating conditions other than normal ones. Recent approaches based on robust optimization can be used to solve optimization problems which involve uncertainty and can find designs which are able to cope with a range of operating conditions. This paper presents a robust optimization model for the optimal design of water supply systems operating under different circumstances. The model presented here uses a hydraulic simulator linked to an optimizer based on a simulated annealing heuristic. The results show that robustness can be included in several ways for varying levels reliability and that it leads to more reliable designs for only small cost increases.

Description: Cost and impact analysis of preventive and remedial measures for safe drinking water Drinking Water Engineering and Science Discussions, 6, 1-26, 2013 Author(s): M. A. Tahir and H. Rasheed Preventive measures yield much higher cost effective benefits as compared to remedial measures. To verify this hypothesis, a survey was conducted in two different regions of Rawalpindi district of Pakistan by comparing the cost on medication and mitigation expenditures for reduction in the burden of water borne diseases. Water Quality monitoring of the study areas in comparison to WHO Drinking Water Guidelines revealed the satisfactory level of physico-chemical parameters, however; significant bacteriological contamination was found at 86% of the monitored sites in Gujar Khan and 87% in Murree region. A field questionnaire was used to estimate the expenditures on disinfection and sanitation and concluded that 8.09% of total income of each family were spent by the inhabitants of the study area on medication for water borne diseases. Correlation was worked out between the rate of water related diseases ( V WRD ), unsafe drinking water ( C DW ), poor sanitation ( P S ), unhealthy personal hygiene and environment (UH PHE ). A simulation model "Victim's Rate Calculator" was developed to forecast the estimated number of victims within a population. Findings of the study verified the hypothesis that preventive measures are better choice than remedial measures due to cost benefit ratio (1 : 1.6) with a clear advantage of 60%.

Description: Application of DVC-FISH method in tracking Escherichia coli in drinking water distribution networks Drinking Water Engineering and Science Discussions, 5, 515-532, 2012 Author(s): L. Mezule, S. Larsson, and T. Juhna Sporadic detection of live (viable) Escherichia coli in drinking water with molecular methods but not with standard plate counts has raised concerns about the reliability of this indicator in the surveillance of drinking water safety. Previous studies have shown that in low numbers metabolically active E. coli can be found in the biofilm of drinking water. The aim of this study was to analyse the distribution of non-cultivable E. coli in the drinking water distribution system meeting microbiological quality standards and evaluate the importance of the biofilm as its harbour. In total 24 biofilm samplings and 40 at least 100 times pre-concentrated water samples were taken over a period of two years from two water treatment plants (surface water and groundwater) and four locations in water distribution network of a large city. Cultivable, total and able to divide (viable) E. coli concentration was measured in all samples. The results showed that none of the network biofilm samples contained cultivable E. coli and less than two cells per 10 l were detected in the pre-concentrated water samples. However, almost all of the samples contained viable E. coli in the range of 1–50 cells per litre or cm 2 which represented approximately 53% of all E. coli detected. The amount of viable E. coli was higher in the biofilm after surface water treatment when compared to the outlet from the groundwater plant and the number tended to increase from both treatment plants further into the network irrespective of the season. In conclusion, E. coli in the water supply is not necessarily directly linked to recent faecal contamination and tends to accumulate in the networks where it is less exposed to disinfectants. Thus it can be accepted that biofilm formation in the drinking water distribution networks increases the risk of accumulation of viable but not cultivable E. coli in the system.

Description: Leakages and pressure relation: an experimental research Drinking Water Engineering and Science, 5, 59-65, 2012 Author(s): F. De Paola and M. Giugni Leaks in water systems are presently a frequent and increasing event that involves cost increase and poor service, not compliant to quality standards and modern management criteria. The most recent data available in Italy, resumed into the report issued by Control Committee for Water Resources Use (CONVIRI), shows leakages with an average value of 37%. It is therefore important, for maintenance perspective, to investigate occurrence and evolution of water leaks and the analytical link between leaks Q p and network pressure P , for a reliable calibration of water networks quali-quantitative simulation models. The present work reports the first results of an experimental campaign started at Laboratory of Hydraulics of Department of Hydraulics, Geotechnical and Environmental Engineering of University of Naples Federico II in order to analyze the features of Q p (P) relation, which are compared with other results issued in literature.

Description: Method of evaluation of efficiency improvement potential for water supply systems with focus on variable speed centrifugal pumps Drinking Water Engineering and Science Discussions, 5, 533-553, 2012 Author(s): D. Pilscikovs and E. Dzelzitis The goal of this research is the derivation of the method for evaluation of efficiency improvement potential for public water supply systems with a focus on centrifugal network pumps. The efficiency of proportional pressure control usage has been analyzed for variable speed pumps. It has been done if proportional pressure control is used in comparison with constant pressure control mode. For this reason, energy calculation analyses have been realized for variable speed centrifugal pumps, and the theoretical tool of estimation of the efficiency improvement potential for public water supply systems has been derived. The conclusions are as follows: (1) it has been found that 1110 MWh of annually consumed electrical energy can be saved up, if the control mode of variable speed network pumps will be changed from constant pressure to proportional pressure control mode with the deviation of 20% from head value of duty point at zero flow; (2) about 13 MWh of annually consumed electrical energy can be saved up, if the proportional pressure control mode with the deviation of 15% will be changed to the deviation of 20%; (3) totally about 1123 MWh or 1.12 GWh (14% of the annually consumed electrical energy by variable speed network pumps) can be saved up in small public water supply systems in Latvia.

Description: Low-cost multi-stage filtration enhanced by coagulation-flocculation in upflow gravel filtration Drinking Water Engineering and Science, 5, 73-85, 2012 Author(s): L. D. Sánchez, L. M. Marin, J. T. Visscher, and L. C. Rietveld This paper assesses the operational and design aspects of coagulation and flocculation in upflow gravel filters (CF-UGF) in a multi-stage filtration (MSF) plant. This study shows that CF-UGF units improve the performance of MSF considerably, when the system operates with turbidity above 30 NTU. It strongly reduces the load of particulate material before the water enters in the slow sand filters (SSF) and therewith avoids short filter runs and prevents early interruption in SSF operations. The removal efficiency of turbidity in the CF-UGF with coagulant was between 85 and 96%, whereas the average efficiency without coagulant dosing was 46% (range: 21–76%). Operating with coagulant also improves the removal efficiency for total coliforms, E-coli and HPC. No reduction was observed in the microbial activity of the SSF, no obstruction of the SSF bed was demonstrated and SSF runs were maintained between 50 and 70 days for a maximum head loss of 0.70 m. The most important advantage is the flexibility of the system to operate with and without coagulant according to the influent turbidity. It was only necessary for 20% of the time to operate with the coagulant. The CF-UGF unit represented 7% of total construction costs and the O&M cost for the use of coagulant represented only 0.3%.

Description: Natural organic matter removal by ion exchange at different positions in the drinking water treatment lane Drinking Water Engineering and Science, 6, 1-10, 2013 Author(s): A. Grefte, M. Dignum, E. R. Cornelissen, and L. C. Rietveld To guarantee a good water quality at the customers tap, natural organic matter (NOM) should be (partly) removed during drinking water treatment. The objective of this research was to improve the biological stability of the produced water by incorporating anion exchange (IEX) for NOM removal. Different placement positions of IEX in the treatment lane (IEX positioned before coagulation, before ozonation or after slow sand filtration) and two IEX configurations (MIEX ® and fluidized IEX (FIX)) were compared on water quality as well as costs. For this purpose the pre-treatment plant at Loenderveen and production plant Weesperkarspel of Waternet were used as a case study. Both, MIEX ® and FIX were able to remove NOM (mainly the HS fraction) to a high extent. NOM removal can be done efficiently before ozonation and after slow sand filtration. The biological stability, in terms of assimilable organic carbon, biofilm formation rate and dissolved organic carbon, was improved by incorporating IEX for NOM removal. The operational costs were assumed to be directly dependent of the NOM removal rate and determined the difference between the IEX positions. The total costs for IEX for the three positions were approximately equal (0.0631 € m −3 ), however the savings on following treatment processes caused a cost reduction for the IEX positions before coagulation and before ozonation compared to IEX positioned after slow sand filtration. IEX positioned before ozonation was most cost effective and improved the biological stability of the treated water.