ALBERT

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 (

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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%.

Beschreibung: 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).

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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%.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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%.

Beschreibung: Abnormal quality detection and isolation in water distribution networks using simulation models Drinking Water Engineering and Science, 5, 67-72, 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 cm2 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 m3 t−1). The initial corrosion model and measurement error was 33%. After the validation of the model the error was reduced to below 15%.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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 (〈0.1 mg l−1) and considerable arsenic concentrations (30 and 110 μg l−1) were chosen, to perform experiments identical to the previous laboratory work. Despite of the absence of phosphate, the subsurface arsenic removal process performed poorly in Subotica, with 50% arsenic breakthrough occurring after 2 to 4 column pore volumes of abstracted water. In Loosdrecht subsurface arsenic removal showed more promising results, 50% breakthrough after 6 to 7 pore volumes, while having a lower pH than Subotica and similar silicate concentrations. The water composition of both locations gives reason to suggest that natural organic matter has a limiting effect on subsurface arsenic removal as well. The presented results have shown the complexity of factors influencing subsurface arsenic removal, making it very challenging to select appropriate sites.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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%.

Beschreibung: 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 Qp 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 Qp(P) relation, which are compared with other results issued in literature.

Beschreibung: 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.