bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing a strategy for leakage management in water distribution systems
Authors: Trow S. , Farley M.
Published: May 2018

Much that has been written about leakage economics and strategy, has been aimed at either the leakage specialist or the economic regulator. This paper aims to make the practitioner aware of the key messages from the theory, and the issues which have to be taken into account, when developing appropriate policies and practices.

The most important aspect of any leakage strategy is the leakage target. What level of leakage should the water supplier aim for, and what level should be maintained in the longer term? In an ideal world, every water supplier would like to eliminate leakage from water distribution systems. However, there will always be a level of leakage which has to be tolerated, and which has to be managed. The paper gives an overview of the prime techniques for leakage management, which have been referred to as the four “pillars”. Each of these follows a similar law of diminishing returns on investment to make savings in leakage. The key issues for introducing these four elements are discussed, together with the steps required to calculate the economic level of leakage.
Evaluation of water losses in distribution networks: Rammallah as a case study
Authors: Mimi Z. , Abuhalaweh O. , Wakileh V. , Jerusalem Water Undertaking Staff
Published: May 2018

Water is one of the most valuable natural resources in Palestine. Therefore, it is very crucial for the Palestinians to achieve proper planning and management of their water resources to ensure proper usage of their water in the different sectors. Moreover, many of the Palestinian localities still lack the existence of water networks while many others suffer from the poor conditions and high losses in their networks that reach up to 50% of the input into the supply system. The paper will present a method to determine water losses from distribution networks and procedures of reducing it in a practical way. The method is based on three main steps: (1) tracing leaks of the supply districts or pipe sections by means of tightness tests and measuring minimum night flow; (2) pinpointing the leaks using the electro-acoustic techniques by DF Junior device and (3) repairing leaks. Consequently, the amount of leakage for the study area was largely reduced (from 5.6 L/sec to 0.16 L/sec).
NOM increase in Northern European source waters: discussion of possible causes and impacts on coagulation/contact filtration processes
Authors: Eikebrokk B. , Vogt R.D. , Liltved H.
Published: May 2018

A significant increase in the content of natural organic matter (NOM) has been observed in several surface water sources in Norway during the past 10–12 years. Similar observations are reported also from est sites in Europe and North America. Water works in the southern part of Norway have experienced a doubling and in some cases even a tripling of source water color levels during the last decade. Other important characteristics of NOM, e.g. the specific UV absorption (SUVA), have changed as well. The change in raw water quality increases the required NOM removal capacity in water treatment, and significantly affects treatment process selection, design and operation. However, the operational impacts on water treatment processes are poorly quantified. This paper addresses the observed NOM increase in parts of Europe and North America. Although the reasons are not fully understood or identified, possible causes are presented and discussed. Factors like climate change or variability, especially alteration in precipitation patterns and land-use, as well as reductions in anthropogenic sulfur loadings seem relevant. From pilot testing on relevant raw waters, major operational impacts of increasing NOM and SUVA levels on coagulation-contact filtration processes are identified and quantified. As an illustration, an increase in raw water color from 20 to 35 mg Pt L−1 increased the required coagulant dose, sludge production, number of backwashes per day and residual TOC by 64%, 64%, 87%, and 26%, respectively. In addition, hydraulic capacity and filter run time decreased by 10% and 47%, respectively.
NOM increase in drinking water reservoirs - relevance for drinking water production
Authors: Korth A. , Fiebiger C. , Bornmann K. , Schmidt W.
Published: May 2018

In the last 10–15 years in some German drinking water reservoirs an increase in the NOM (natural organic matter) content has occurred. The impact of such a change on the drinking water quality was almost unknown. A research project was carried out at several drinking water reservoirs and water works concerning the change in the NOM quality and the nutrient situation. The results indicate that the NOM increase in the reservoir is predominately caused by an increasing input of high and intermediate molecular weight humic substances from the catchment area into the reservoir. The fractions of the polysaccharides and the high molecular weight humic substances are significantly reduced in the treatment process. In contrast, the elimination rate for the substances with an intermediate and low molecular weight was low. Due to the low elimination rate particularly of the intermediate humic fraction, the NOM content of the treated water increased with the change in the raw water. Furthermore, the BDOC of the treated water increased with the NOM content. For the AOC of the treated water no relationship was found with the NOM content. However, the change of this parameter was affected by the snowmelt and the circulation in the reservoir.
Fouling of a polyethersulfone ultrafiltration membrane by natural organic matter
Authors: Makdissy G. , Croué J.-P. , Amy G. , Buisson H.
Published: May 2018

This research focused on membrane flux decline trends observed during ultrafiltration (UF) of solutions of NOM fractions isolated from surface waters. All filtration experiments were performed with a non-stirred dead-end cell unit equipped with flat sheet polyethersulfone PES UF membrane coupons under a constant transmembrane pressure of 1 bar. Results showed that the most significant flux decline was due to the organic colloid fraction, a hydrophilic fraction consisting mostly of bacterial cell wall residues. This research demonstrated that these colloids which incorporate 2/3 of dissolved organic structures (<0.45 μm) and 1/3 of particulate organics exert strong fouling properties due to both rejection phenomena and the adsorption mechanism. The fouling contribution by humic-like materials depends on their origin and nature. Aromaticity appears to be a secondary parameter which influences membrane fouling. Polysaccharides, proteins and amino sugars also largely present in humic-like structures (supramolecular structure) play an important role in UF membrane fouling. The perspective of NOM as a biopolymer mixture can contribute to an understanding of membrane fouling.
Can we predict the removal of MIB and geosmin with PAC by using water quality parameters?
Authors: Cook D. , Newcombe G.
Published: May 2018

Cyanobacterial blooms in source waters are of concern as they can produce some compounds that are aesthetically unpleasant in potable water. Musty–earthy taste and odour compounds 2-methylisoborneol (MIB) and geosmin are produced by some species of cyanobacteria and actinomycetes. These compounds are low molecular weight volatile tertiary alcohols whose presence in treated water even at low ng L‒1 levels can result in consumer complaints. Adsorption onto powdered activated carbon (PAC) is often used to remove these compounds during the treatment process. PAC is very efficient at removing these compounds but the presence of natural organic matter (NOM) reduces the efficiency of the PAC. For effective application of PAC the impact of NOM must be taken into account when determining the required dose. In this study the adsorption of MIB and geosmin from several waters was related to water quality parameters of dissolved organic carbon (DOC), UV absorbance at 254 nm and colour to determine if these could be used to predict adsorption. Results obtained showed that the water quality parameters of DOC and UV absorbance at 254 nm could be useful indicators for MIB and geosmin adsorption, although the relationship appears to be specific to the water source in question.
Coagulation of natural organic material: effects on speciation of halogenated disinfection by-products
Authors: Singer P.C. , Liang L.
Published: May 2018

A recent paper by Liang and Singer showed that haloacetic acid (HAA) precursors were removed by coagulation to a greater degree than trihalomethane (THM) precursors. Furthermore, they showed that coagulation generally removed more trihaloacetic acid precursors than THM precursors but removed dihaloacetic acid precursors and THM precursors to a similar degree. The objectives of this current study were to compare the findings by Liang and Singer to those of three other investigations conducted in the senior author's laboratory to demonstrate the extent to which coagulation removes THM and HAA precursors, and to contrast the removal of dihaloacetic acid and trihaloacetic precursors by coagulation. These other studies were conducted on seventeen other waters from across the US.
Impact of pore size on competitive adsorption of phenolic compounds
Authors: Lu Q. , Sorial G.
Published: May 2018

Single and binary solute adsorption of phenol and o-cresol at 23°C on three activated carbons with different pore size were conducted in this study. One granular activated carbon (GAC) F400 and two activated carbon fibers (ACFs) were considered. Anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) conditions were evaluated. For the single solute system, the three adsorbents studied have shown higher adsorptive capacities under oxic conditions as compared to anoxic conditions. The degree of adsorption enhancement was related to the pore size of the adsorbent. For binary adsorption on ACC-10, which has the least average pore size (1.76 nm), the oxic and anoxic adsorption isotherms overlapped, indicating no impact of the presence of molecular oxygen on the adsorptive capacity. Significant differences on adsorptive capacities were noticed for the binary solute adsorption on ACC-15 (2.10 nm) and F400 (2.48 nm). The Ideal Adsorbed Solution Theory (IAST) predicted well all binary systems for ACC-10 and anoxic isotherms on ACC-15 and F400. Poor model predictions for GAC and ACC-15 under oxic conditions were attributed to the oligomerization of the adsorbates on the surface of activated carbon. The unique pore size of ACFs has been shown to be a limiting factor in hampering the oligomerization under oxic conditions.
Application of charge measurement to water treatment processes
Authors: Jefferson Bruce , Sharp Emma L. , Goslan Emma , Henderson Rita , Parsons Simon A.
Published: May 2018

The measurement of surface charge has long been proposed a convenient way to optimise coagulant dosage in water treatment processes. In the UK there has been a renewed interest in the use of charge measurement in the form of both zeta potential and streaming current for controlling coagulation and filtration processes. This paper review current knowledge on the factors effecting charge measurement and using data collected from a sampling survey of 12 UK water treatment works identified windows of optimum charge for sedimentation, flotation and filtration processes.
Affinity isolation of algal organic matters able to form complex with aluminium coagulant
Authors: Takaara T. , Sano D. , Konno H. , Omura T.
Published: May 2018

Mass propagation of algae in drinking water source affects the coagulation process in water treatment systems. Many researchers indicated that some kinds of algal organic matters (AOMs) interacted with coagulants by coordinate bonds and brought about several disorders due to the increase in both the coagulant demand and the residual coagulant in treated water. However, the inhibitory mechanism on the coagulation by AOMs has not been fully elucidated. In this study, AOMs able to form complex with aluminium coagulant were isolated and analyzed. The results of the gel chromatography showed that extracellular organic matters (EOMs) from Microcystis aeruginosa (NIES-91) have molecular weight of between 10 and 20 kDa, around 40 kDa and more than 600 kDa. The amount and diversity of EOMs increased as the algal growth. AOMs able to form complex with aluminium coagulant were successfully isolated with the affinity chromatography. SDS-PAGE analysis revealed that these AOMs included proteins that have molecular weight between 43 and 67 kDa. Since several kinds of proteins such as metallothionein are known for strongly adsorbing multivalent cations, the isolated algal proteins able to form complex with aluminium might have a high capacity of capturing coagulants and inhibit the coagulation in the drinking water treatment.
Water Quality 21 research programme for water supplies in The Netherlands
Authors: van Dijk J.C. , van der Kooij D.
Published: May 2018

The Dutch water companies have commissioned an ambitious 4 year research programme in pursuit of an impeccable drinking water quality, called Quality 21 (Quality for the 21st century). The Dutch approach has always been to safeguard drinking water quality from source to tap by excellent design, operation and research. This drinking water is generally distributed without a disinfectant residual. The Dutch consumers appreciate this concept and have a high confidence in the quality of tap water. The new research programme aims at providing the scientific foundation for future decisions on quality goals and the advantages and limitations of modern water treatment technology, such as membrane filtration and UV/AOP. The goals are to achieve a robust and reliable drinking water infrastructure that will guarantee an impeccable water quality at the tap at all times, also in the future when new threats may emerge. The programme includes studies on water quality goals and total system approach, and experimental research into water treatment, biological stability and (the prevention of) quality deterioration in the distribution network. Important focal points in the research will be the prevention of microbiological problems (including Legionella) in the network and in building installations, the prevention of problems with organic micropollutants such as NDMA, EDCs and pharmaceuticals and the advantages of reducing particles and sediment in the distribution network. The programme will be coordinated by Kiwa Water Research and will be carried out with the water supply companies and in cooperation with universities and other research institutes including the partners of the Global Water Research Coalition.
Removal of natural organic matter using iron oxide-coated membrane systems
Authors: Choo K.-H. , Park I.-H. , Choi S.-J.
Published: May 2018

Natural organic matter (NOM) removal and membrane fouling were investigated using iron oxide-coated microfiltration (MF) systems for drinking water treatment. Addition of iron oxide particle (IOP) adsorbents into MF always improved NOM removal and reduced fouling, but IOP dosing methods did affect the membrane performance. The IOP coating layer formed on the membrane surface played a major role in preventing membrane fouling by residual NOM in water. Pre-mixing of IOP with raw water followed by continuous injection into the MF system controlled membrane fouling better than pre- and intermittent loadings of IOP. This could be in close association with the distribution of IOPs across the hollow fiber MF surfaces and the effectiveness of contact of IOP with feedwater. The turbidity of water influenced the MF system with intermittent IOP loads more greatly than that with IOP in suspension. There existed an optimal IOP dose where membrane fouling can be minimized achieving maximal NOM removal.
Coagulation/flocculation/ultrafiltration for natural organic matter removal in drinking water production
Authors: Costa A.R. , de Pinho M.N.
Published: May 2018

Membrane fouling by natural organic matter (NOM), namely by humic substances (HS), is a major problem in water treatment for drinking water production using membrane processes. Membrane fouling is dependent on membrane morphology like pore size and on water characteristics namely NOM nature. This work addresses the evaluation of the efficiency of ultrafiltration (UF) and Coagulation/Flocculation/UF performance in terms of permeation fluxes and HS removal, of the water from Tagus River (Valada). The operation of coagulation with chitosan was evaluated as a pretreatment for minimization of membrane fouling. UF experiments were carried out in flat cells of 13.2×10−4 m2 of membrane surface area and at transmembrane pressures from 1 to 4 bar. Five cellulose acetate membranes were laboratory made to cover a wide range of molecular weight cut-off (MWCO): 2,300, 11,000, 28,000, 60,000 and 75,000 Da. Severe fouling is observed for the membranes with the highest cut-off. In the permeation experiments of raw water, coagulation prior to membrane filtration led to a significant improvement of the permeation performance of the membranes with the highest MWCO due to the particles and colloidal matter removal.
Two new approaches for the stochastic least cost design of water distribution systems
Authors: Kapelan Z. , Babayan A.V. , Savic D.A. , Walters G.A. , Khu S.T.
Published: May 2018

The problem of stochastic (i.e. robust) water distribution system (WDS) design is formulated and solved here as an optimisation problem under uncertainty. The objective is to minimise total design costs subject to a target level of system robustness. System robustness is defined as the probability of simultaneously satisfying minimum pressure head constraints at all nodes in the network. The decision variables are the alternative design options available for each pipe in the WDS. The only source of uncertainty analysed is the future water consumption uncertainty. Uncertain nodal demands are assumed to be independent random variables following some pre-specified probability density function (PDF). Two new methods are developed to solve the aforementioned problem. In the Integration method, the stochastic problem formulation is replaced with a deterministic one. After some simplifications, a fast numerical integration method is used to quantify the uncertainties. The optimisation problem is solved using the standard genetic algorithm (GA). The Sampling method solves the stochastic optimisation problem directly by using the newly developed robust chance constrained GA. In this approach, a small number of Latin Hypercube (LH) samples are used to evaluate each solution's fitness. The fitness values obtained this way are then averaged over the chromosome age. Both robust design methods are applied to a New York Tunnels rehabilitation case study. The optimal solutions are identified for different levels of robustness. The best solutions obtained are also compared to the previously identified optimal deterministic solution. The results obtained lead to the following conclusions: (1) Neglecting demand uncertainty in WDS design may lead to serious under-design of such systems; (2) Both methods shown here are capable of identifying (near) optimal robust least cost designs achieving significant computational savings.
Influence of phosphorus on biofilm accumulation in drinking water distribution systems
Authors: Kasahara S. , Maeda K. , Ishikawa M.
Published: May 2018

Continuous reactor tests using rotating reactors with polyvinyl chloride (PVC) coupons were conducted. Laboratory tap waters with and without 50 μg P/L KH2PO4 (phosphorus water and non-phosphorus water) were supplied to the reactors in the absence of residual chlorine. Numbers of cells attached on the surface of the coupons (biofilm cells) and numbers of cells suspended in the influent and effluent waters (planktonic cells) were enumerated, and then specific growth rates of biofilm cells and planktonic cells were estimated.

Concentrations of assimilable organic carbon (AOC) in both feed waters were comparable, whereas numbers of biofilm cells in phosphorus reactors were 1 order of magnitude larger than those in non-phosphorus reactors at the steady state of the continuous reactor test. Total planktonic cell concentrations in phosphorus reactors were also 1 order of magnitude higher than those in non-phosphorus reactors. Specific growth rate of biofilm cells estimated from heterotrophic plate count in non-phosphorus reactors was 1 order of magnitude higher than that in phosphorus reactors.

This study concluded that phosphorus would increase amounts of biofilm cells on distribution pipe walls because phosphorus lengthened the generation time of biofilm cells. The concentration of AOC could not represent the potential of biofilm accumulation sufficiently.
Assessment of public perception regarding wastewater reuse
Authors: Robinson K.G. , Robinson C.H. , Hawkins S.A.
Published: May 2018

A descriptive-correlational study was recently conducted in a four county metropolitan area in the southeast United States (US) as part of a collaborative effort between nursing and environmental engineering researchers. The purpose of the study was to assess attitudes, knowledge and information sources concerning wastewater reuse and evaluate the results with respect to population demographics. The study indicated that both men and women unfavorably view the use of wastewater for possible consumption (released into potable surface or groundwater supplies) or applications involving close, personal contact (laundry). Women were especially concerned about pumping wastewater into the groundwater for subsequent potable use. Both genders felt that wastewater reuse for applications not involving close personal contact (such as firefighting, car washing, lawn irrigation and agricultural uses) was acceptable. General knowledge concerning wastewater reuse was mixed. Those with lower incomes, less education, and 65 years of age or older had significantly less knowledge of this issue than younger, more educated, higher income individuals. Primary sources of information for most demographic groups included newspaper and television, although the Internet was identified as a frequent source for selected groups.
Wastewater reclamation and reuse in Europe: a model-based potential estimation
Authors: Hochstrat R. , Wintgens T. , Melin T. , Jeffrey P.
Published: May 2018

The basic aim of this paper is to present an approach to quantitatively assess the potential of municipal wastewater reclamation and reuse in a European context. The model developed is based on the analysis and interrelation of water management data like water availability, water demand and treated effluent. In conjunction with information about the current status of wastewater reuse simple key figures are deduced, which allow future projection of wastewater reclamation and reuse. The simulation points out that there is a significant potential for an increased utilisation of reclaimed wastewater in many European countries, specifically in the Mediterranean region driven by different factors like increased wastewater treatment capacity and higher demand for irrigation and groundwater recharge.
Treatment matrix for reuse of upgraded wastewater
Authors: van der Graaf J.H.J.M. , de Koning J. , Ravazzini A. , Miska V.
Published: May 2018

In 2003 the Aquarec project sponsored by the European Commission under the 5th Framework Programme was started, aiming at “integrated concepts for reuse of upgraded wastewater with special focus on the European countries”. One of the key elements is the development of a treatment matrix, in which wastewater treatment processes are categorised as a function of the raw wastewater quality and the reuse application and are further characterised with respect to costs, operational critical control points and environmental aspects. The construction of the treatment matrix is based on the reuse options (industrial, domestic, natural and agricultural applications), the water quality requirements, the treatment requirements and the extensive description of the various treatment processes and schemes. In the process of constructing the matrix it can be concluded that the actual knowledge on municipal wastewater treatment is definitely well consolidated until the so-called secondary treatment including biological or physical/chemical nutrients removal; the treatment of this effluent should be accomplished by more advanced techniques. As a consequence of the actual EU rules on water discharges, it makes sense to focus the Aquarec project on the possible refinements of secondary effluent. Great attention must be given to the advanced or tertiary wastewater treatment processes, as a mean to upgrade the effluent to water suitable for reuse.
Food and water insecurity: re-assessing the value of rainfed agriculture
Authors: Ahmad M. , Rodríguez A. , Braslavskaya A.
Published: May 2018

Rainfed agriculture has potential to produce needed cereals for the growing populations of West and Central Asia even though rainfed agriculture is perceived as risky. The value of rainfed agriculture to produce competitively should be re-assessed. This requires the concerted efforts of farmers, researchers, and policy makers to work on the technical factors that determine agricultural production as well as to address the economic policy environment. Syria is a small country with a diversified rainfed and irrigated agriculture. Rainfed and supplemental irrigation technology has improved Syria's food self-reliance, however, the policy environment is not conducive to the sustainable use of natural resources. Supplemental irrigation technology to produce wheat is used to illustrate the need to address both the technical issues as well as the economic incentives to make agricultural production competitive. Kazakhstan is a large country with a predominantly rainfed agriculture. Farmers could benefit from rainfall probabilities to use fertilizer and improved wheat varieties under rainfed agriculture as Syria did during the eighties and nineties. Implicit taxation of farmers needs to be removed and access to markets must be ensured for farmers in Kazakhstan to benefit from international wheat prices. While it is important to improve production technology, the economic policy environment needs to be addressed first to create incentives for farmers to produce commodities competitively in water-scarce regions.
Application of MIEX® pre-treatment for ultrafiltration membrane process for NOM removal and fouling reduction
Authors: Son H.J. , Hwang Y.D. , Roh J.S. , Ji K.W. , Sin P.S. , Jung C.W. , Kang L.S.
Published: May 2018

In this study, pretreatment of organic matters with MIEX® was evaluated using bench-scale experimental procedures on three organic matters to determine its effect on subsequent UF or MF membrane filtration. For comparison, a coagulation process was also used as a pretreatment of UF or MF membrane filtration. Moreover, the membrane fouling potential was identified using different fractions and molecular weights (MW) of organic matter. From the removal property of MW organic matter by the coagulation process for the sample water NOM and AOM, the removal efficiencies of high MW organic matter were much higher than those of low MW organic matter. It was shown that the removal efficiency of high MW organic matter (more than 10 kDa) was lower than that of low MW organic matter for the MIEX® process. For the change of permeate flux by the pretreatment process, the MIEX®-UF process showed high removal efficiency of organic matter compared with the coagulation-UF processes, but a high reduction rate of permeate flux was presented through the reduction of removal efficiency of high MW organic matter. From sequential filtration test results to examine the effect of MW of organic matter on membrane fouling, we found that the membrane fouling occurred with high MW organic matter, and the DOC of organic matter less than 0.5 mg/L was acting as the membrane foulant. In sample water composed of low MW organic matter (less than 10 kDa), because the low MW organic matter of less than 10 kDa has a high removal efficiency by MIEX®, a low reduction rate of permeate flux is obtained compared with the coagulation-UF processes. In summary, research on the physical/chemical characteristics of original water is needed before a membrane pretreatment process is selected, and a pertinent pretreatment process should be used based on the physical/chemical characteristics of the original water.
Bank filtration and groundwater recharge for treatment of polluted surface waters
Authors: Jekel M. , Gruenheid S.
Published: May 2018

Investigations on the behavior of different bulk organics and trace organic compounds at a bank filtration site at Lake Tegel in Berlin, Germany, and in a long retention soil column system are reported. The objective of the research was to assess important factors of influence for the degradation of bulk and trace organics. More than two years of monitoring for the bulk parameter DOC proved that the redox conditions significantly influence the DOC-degradation rates but not necessarily the residual concentration. LC-OCD measurements confirmed that the change in character is comparable for aerobic and anoxic/anaerobic infiltration. Only the fraction of polysaccharides shows a better removal under aerobic conditions.

Furthermore, adsorbable organic iodine (AOI) measurements revealed a more efficient degradation of AOI and AOBr under anoxic/anaerobic conditions. The moznitoring of the single organic pollutants Iopromide, Sulfamethoxazole and naphthalenedisulfonic acids showed that the redox conditions have an influence on the degradation behavior of some of the monitored compounds. Iopromide was efficiently removed at all times, but no evidence for a dehalogenation under oxic conditions was found. Sulfamethoxazole showed a better removal under anoxic/anaerobic conditions. The very stable 1.5-naphthalenesulfonic acid was not removed under either redox condition.
Decentralised wastewater treatment technologies from a national perspective: at what cost are they competitive?
Authors: Maurer M. , Rothenberger D. , Larsen T.A.
Published: May 2018

In this paper we estimate at what cost decentralised wastewater treatment can be competitive compared with conventional centralised technologies. For the current wastewater infrastructure in Western Europe and North America, typical replacement costs are 2,600 US$/cap for large countries and 4,800 US$/cap for small ones. In the same literature, average annual operating costs are reported to be 3.8% of replacement costs. However, if a long-term interest rate of 3% is consistently applied, this value increases to 4.7% for small countries and 5.5% for large ones. Assuming that alternative wastewater systems will only be accepted if their costs are similar to existing ones, the possible investments for alternative wastewater treatment technologies are calculated. Between 640 and 2,170 US$/cap can be invested in new technologies for scenarios without a sewer system. The corresponding figures for scenarios with sewer systems are between 260 and 680 US$/cap. Acceptable maintenance requirements are calculated on the basis of unit size. Transition periods are not accounted for.
Charging to enter the water shop? The costs of urban water connections for the poor
Authors: Franceys R.W.A.
Published: May 2018

The cost of new water connections for poor urban dwellers in middle and low-income economies, that is the official fees, costs of pipework and additional costs, is reported from a global survey of water utilities and a four country, two city questionnaire of newly connected households. The objective is to investigate whether directly ‘charging to enter the water shop’ is the most effective means of recovering costs for the water utility whilst ensuring maximum access to the urban poor who benefit most from convenient access to clean, affordable water.
Theory matters! Efficiency measurement and water utilities
Authors: Sauer J.
Published: May 2018

As is the case of other infrastructure sectors the availability of efficiency estimation software based on statistical inference – freely distributed via the internet and relatively easy to use – recently inflated the number of corresponding applications in the water sector. The robustness of regulatory measures based on inferences from efficiency measures nevertheless crucially depends on theoretically well-founded estimates. This is illustrated by using an empirical example of an inconsistent technical efficiency frontier for water utilities in Germany.
Recent advances in calculating economic intervention frequency for active leakage control, and implications for calculation of economic leakage levels
Authors: Lambert A.O. , Fantozzi M.
Published: May 2018

During the last decade, IWA Water Losses Task Force members have developed a systematic practical approach to the technical management of non-revenue water and its components, with (since 2002) increasing use of 95% confidence limits in these calculations. The current Water Losses Task Force has recently set itself an objective to develop a quick and practical method for calculating economic intervention (for active leakage control to locate unreported leaks and bursts), and short-run economic leakage level. This paper outlines a quick and practical method for assessing economic intervention frequency (and associated budgetary and volumetric parameters) for an active leakage control policy based on regular survey. Calculations are based on three key parameters: natural rate of rise of unreported leakage, marginal cost of water, and cost of intervention. It is hoped this will encourage Utilities that do not currently undertake active leakage control to adopt an ongoing basic active leakage control policy which can be simply demonstrated as being economic for their own situation.
Detection of changes in streamflow series in western Europe over 1901–2000
Authors: Wang W. , Van Gelder P.H.A.J.M. , Vrijling J.K.
Published: May 2018

Streamflow processes of 12 rivers in western Europe are investigated for trend and nonstationarity in the full 100-year period in the 20th century. Trend analyses with Mann–Kendall test show that there is no trend in annual mean discharges. Only three annual maximum flow series exhibit significant trends (Rhine and Moselle, upward; Rhone, downward). There are two minimum flow series exhibiting significant downward trend (Maas and Thames) and five exhibiting upward trend (Danube, Elbe, Weser, Reuss and Rhone). Monthly flow series are examined with seasonal Kendall test. A significant downward trend is observed in the monthly flow series of Maas, whereas a significant upward trend is observed in the monthly flow series of Rhone. Meanwhile, significant heterogeneity in trends among different months is observed in three Alpine rivers (Inn, Reuss and Rhone). ADF and KPSS tests which originate from econometrics are introduced to test for nonstationarity in streamflow series at three characteristic timescales. All annual mean discharge series and most monthly mean discharge series appear to be stationary. But only 2 out of the 12 daily series are statistically stationary.
Burst detection and location in water distribution networks
Authors: Misiunas D. , Lambert M. , Simpson A. , Olsson G.
Published: May 2018

An algorithm for the detection and location of sudden bursts in water distribution networks combining both continuous monitoring of pressure and hydraulic transient computation is presented. The approach is designed for medium and large bursts that are the result of the sudden rupture of the pipe wall or other physical element in the network and are accompanied by the transient pressure wave that propagates throughout the network. The burst-induced transient wave arrival times and magnitudes measured at two or more points are used to find the location of a burst. The wave arrival times and magnitudes are detected using the modified cumulative sum (CUSUM) change detection test. Results of validation on a real network show the potential of the proposed burst detection and location technique to be used in water distribution systems.
Predicting water pipe breaks using neural network
Authors: Ahn J.C. , Lee S.W. , Lee G.S. , Koo J.Y.
Published: May 2018

The relationships between pipe breaks of service pipes and mains and several factors were examined. Historical pipe breaks, and water and soil temperatures were also modeled by an artificial neural network to predict pipe breaks for efficient management and maintenance of the pipe networks. It was observed that the breaks of pipes increased after the temperatures of water and soil crossed in spring and fall. The pipe breaks were closely related to water and soil temperature, especially mains were affected more than service pipes. The fittings and valves were susceptible to the temperatures and needed to take measures for preventing breaks. The prediction of the pipe breaks by the ANN model built had a good performance except that the sensitivity was not good when the pipe breaks rapidly increased or decreased. The ANN model gave a good performance and was to be useful to predict the patterns of pipe breaks on a seasonal basis.
Raingardens for stormwater infiltration and focused groundwater recharge: simulations for different world climates
Authors: Dussaillant A.R. , Cuevas A. , Potter K.W.
Published: May 2018

Traditional stormwater management does not mitigate groundwater depletion resulting from pumping and loss of recharge. There has been an increasing interest in the use of alternative practices, such as raingardens, that enhance infiltration of stormwater. We develop a simple numerical model for their design and evaluation. Water flow through the soil is modelled over three layers: a root zone; a middle storage layer; and the site subsoil. To continuously simulate recharge, runoff and evapotranspiration, a Green-Ampt equation coupled with a surface water balance is used. For the humid climate of Madison, Wisconsin, USA, results show very high recharge rates in the rainy season, where a raingarden with an area of 10–20% of the contributing impervious area maximizes recharge. For the semiarid climate of Santiago, Chile, the optimum ratio was 10–20%, and for the arid climate of Reno, Nevada, USA, it was closer to 5%.
Use competition and water exchange in Marina Baja district, Alicante, Spain
Authors: Martí T.T.
Published: May 2018

The water problems in Marina Baja district, located in the north of Alicante Province, southeast Spain, gives rise to very interesting practices in the management of this scarce resource. The key issue in water use both in the Júcar Catchment and in Marina Baja district is the growing demand for water in inland areas for intensive crop irrigation (principally fruit, medlars and citrus fruit) and the growth in demand for water for urban use, as well as for use in the tourist industry and its related services mainly in the towns in the coastal areas, due to strong growth in tourism. This trend of increasing demand has created a tense situation as well as conflict between existing water uses and the need for integrated water management in the area. This step implies that procedures for water exchange contracts have to be developed, that are significantly different from emerging water markets.
Nature and Origin of Micropollutants
Authors: Mackay D
Published: May 2018

The origins of “micropollutants” are discussed and classified. It is suggested that assessing the risk and ensuring an acceptably low level of adverse effects from these substances requires information or control of three factors (exposure, toxicity and characteristics of the victim or organism) which combine to generate the toxic event. Methods of estimating exposure are discussed, especially environmental models. Ultimately, it should be possible to couple these models to toxicity data in a rational, rigorous manner to elucidate the extent of risk and control it to acceptable levels.
New Trends in Water Quality Management
Authors: Benedek P
Published: May 2018

In the present water quality management practice the ambient water quality is determined on the basis of classification of recipients. This system disregards, however, the fact that the majority of hazardous micropollutants is tending to accumulate in suspended solids and may contaminate the bottom sediment.

The proposed water quality management system is aiming at providing potable water of good quality without any regards to classification of surface waters. The tasks are outlined on the basis of morphological, hydrological, hydraulic and technological conditions of drinking water production. In this approach both the previous events i.e. deposition or scouring of polluted bottom silt and the transport of suspended solids with coupled micropollutants are involved.

The new system is focused on Danube river, since the water supply or rather the bank-filtered water resources along it is endangered at many locations by accumulated pollutants in bed load.
Experience from 10 Years Advanced Wastewater Treatment – Technology and Results
Authors: Forsberg C , Hawerman B , Hultman B
Published: May 2018

Experience from advanced municipal wastewater treatment plants and recovery of polluted waters are described for the last ten years in Sweden. Except in municipalities with large recipients, the urban population is served by treatment plants with combined biological and chemical treatment. Most of these plants are post-precipitation plants. Several modified operational modes have been developed in order to improve the removal efficiencies of pollutants and to reduce the costs. Results are presented on the recovery of specially investigated lakes with a lowered supply of total phosphorus and organic matter.
Criteria for Nitrification in Fixed Film Reactors
Authors: Harremoës P
Published: May 2018

It is postulated that nitrification in fixed films can be achieved only when nitrifiers embedded in the surface of a growing biofilm of mineralizing bacteria get sufficient time in the aerobic zone of the biofilm to multiply and reach such concentrations that ammonia conversion becomes significant. This phenomenon is modelled analytically under simplified assumptions. The developed criterion is compared with data from the literature and found qualitatively adequate -though the investigations often lack data on parameters, like the oxygen concentration, which theoretically has been found to be the rate limiting substrate.
Environmental Aspects of Multi-Purpose Reservoir Projects in Developing Countries*
Authors: Ludwig H F
Published: May 2018

Planning and implementation of dam/reservoir projects has traditionally been prompted by the need for furnishing sufficient quantities of water to meet specific needs such as hydropower generation, irrigation, and flood control, and has generally involved little attention to associated environmental aspects such as effects on water quality and regional ecology. Experience in the developing countries over the past two decades points out the need for marked reorientation in thinking on the appropriate role of such projects and hence in their planning and implementation, to make them truly multipurpose. Because of accelerating population growth, food and energy are emerging as critical parameters in many developing countries. Together with shortage of water in the dry season periods of monsoon climate regions, this makes it mandatory to plan such projects to accommodate all water-oriented needs, including promotion of a gamut of human development values as well as protection of natural resources for sustaining continuing development. By such “total multipurpose” planning, as contrasted to the limited multipurpose planning accomplished to date, the major investments in projects for utilizing scarce water resources can be far more useful in helping solve the critical problems ahead. This will require strict coordination of the existing agencies of most government agencies concerned with water resource development, most of which still function with limited purpose objectives and capabilities.
Electrochemical Processes for Wastewater Treatment
Authors: Mendia L
Published: May 2018

Many electrochemical processes for watewater treatment have been developed over the years. In the field of sewage purification attention has focused on clarification, disinfection and phosphate removal with the aim of reducing costs compared to traditional processes. The on-site production of necessary chemicals is a step towards reducing operating costs. Electrochemical treatment is very efficient and reduces process detention times thereby allowing smaller plants.

Sea water or brine is mixed with the screened sewage in an appropriate ratio, then passed through an electrolysis cell rather similar to that used for hypochlorite production. Depending on the material of the electrodes, their arrangement (vertical or horizontal) and the applied potential difference, the reactions which occur produce the chemicals required for the purification processes.

Downstream the electrolysis, the mixture flows into a clarification basin which acts as a contact tank for disinfection. The detention time of this process depends on the type of basin used.

I report results of electrochemical treatment performed on a semiindustrial scale, using horizontal electrodes: anode of graphite or silicon-iron and stretch-iron cathodes; followed by a sludge recirculation clarification basin. The removal of suspended solids and the abatement of B.O.D. and phosphates were much better than those reached by traditional physical-chemical treatment. The energy consumption is approximately 0.5 kWh/m of raw sewage.
The Mechanism of Ozone Inactivation of Water Borne Viruses
Authors: Sproul O J , Pfister R M , Kim C K
Published: May 2018

Ozone was used to study the inactivation of the DNA bacteriophage, T4. Ozone attacks the protein capsid, liberating the nucleic acid and inactivates the DNA. The DNA inactivation rate was about the same rate as the intact phage. The general ozone inactivation mechanism for RNA or DNA viruses is an initial attack on the capsid with apparent concurrent inactivation of the nucleic acid. The liberated nucleic acid is then further attacked by ozone.
Predicted Changes in Water Quality after Elimination of Storm Runoff into the Urban Lake and Canals of Hamburg
Authors: Caspers H
Published: May 2018

Storm-water overflows from the combined sewer system into the Alster Lake in Hamburg and its canals have resulted in heavy eutrophication. Predictions were made, based on the Water Quality Index, concerning the degree of improvement to be expected from various restoration measures. Elimination of sewage input alone should not have a noticeable effect because much nutrient material is deposited on the bottom of the lake and canals. Calculations indicate that reduction of sewage overflow together with sediment removal would improve the appearance of the Alster system, eliminate the danger of fish kills, and prevent algal “blooms” in summer.
Fate of Heavy Metals and Potential for Clinker Formation during Pilot Scale Incineration of Municipal Sludge
Authors: Campbell H W , Crescuolo P J , Bridle T R
Published: May 2018

This study describes multiple-hearth incineration investigations conducted at the Water Pollution Control Plant (WPCP) in Hamilton, Ontario. The objectives of the study were to determine, under controlled conditions, the fate of selected heavy metals present in the sludge and to determine optimal operating conditions to minimize clinker formation and residual organic content of the ash. A factorial experimental design which included four levels of temperature, three levels of throughput rate and three levels of centre shaft speed was conducted.

Within the constraints of the experiment, zinc, iron, magnesium, aluminum, nickel, copper, calcium, chromium, lead, silica and phosphorus proved to be conservative and remained in the ash. Varying proportions of cadmium, mercury and arsenic were classified to the gas stream. The destruction of total carbon was essentially complete under all test conditions, with the minimum level being 98.7%. Clinker formation was observed only under conditions of high temperature combined with a long furnace residence time.