ALBERT

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: 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: 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 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: 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: 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: 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: 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: 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 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: 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: 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 O2 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 CO2 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.