bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative assessment of the removal of indicator bacteria in full-scale treatment plants
Authors: Hijnen W.A.M. , Medema G.J. , van der Kooij D.
Published: May 2018

The elimination of thermotolerant coliforms (Coli44) and spores of sulphite-reducing clostridia (SSRC) in full-scale water treatment was determined by large volume sampling. The objective was to determine the elimination capacity of full-scale treatment processes for micro-organisms, both vegetative bacteria and bacterial spores. In two short-periods in winter and summer, information was collected about the elimination of Coli44 and SSRC by the overall treatment, the contribution of the unit processes and the variability in elimination. Coli44 concentrations in the source waters were reduced by 3.2 to 6.3 log to an average concentration sufficiently low to achieve more than 99% compliance with the drinking water standard. The elimination of SSRC was lower (1.4 to 4.2) and SSRC were observed occasionally (>1%) in finished water by the routine weekly sampling of 100 ml samples. The study also yielded much information about the elimination efficacy of unit processes at the different locations, which enables process optimization and improved process control. Moreover, it is demonstrated that this quantitative information on removal of indicator bacteria by full-scale treatment systems can be used as input for quantitative microbial risk assessment. Further research will be focussed on comparative studies on the removal of faecal indicators and pathogens by unit processes and the improvement of the enumeration methods of pathogens in the source water (recovery efficiencies, specificity).
A scenario approach to demand forecasting
Authors: Westcott R.
Published: May 2018

The Environment Agency's 2001 national water resources strategy, Water resources for the future, provides a secure framework for the management of water that protects the long-term future of the water environment while encouraging sustainable development. Underpinning the strategy are a suite of scenario based forecasts developed to explore the impact of key drivers of demand within different sectors of water use across England and Wales. This paper explains the approach used to produce these forecasts, summarises how the individual components of demand were considered and highlights opportunities for future application and development of this approach. Using the premise that total water demand can mask conflicting trends between sectors, it is essential to consider each sector and its micro-components independently to understand the specific drivers of demand and consequently determine how these might best be managed. Four scenarios reflecting different possible futures of socio-economic and governmental structure were created to test “how”, “why” and “where” these water demands may change by 2025. Such an approach provides an opportunity to test the implications of macro drivers of demand, such as, economic growth and regulatory reform, on the micro-components of water use, linking disparate sectors to a common set of assumptions about the future.
Using multivariate principal component analysis of injected water flows to detect anomalous behaviors in a water supply system - a case study
Authors: Palau C.V. , Arregui F. , Ferrer A.
Published: May 2018

The amount of data collected by the SCADA (supervisory control and data acquisition) of an urban water supply system is sometimes difficult to process. A multivariate statistical technique, Principal Component Analysis (PCA) is presented in this paper, which processes this data, simplifying and synthesizing the most significant information. This technique extracts new variables, principal components (PC), that explain the behaviour of injected flow. Multivariate control charts to detect outliers show higher sensitivity than those generated with traditional univariate statistical methods.
Removal of humic acid by biofiltration
Authors: Basu O.D. , Huck P.M.
Published: May 2018

Biofiltration was found to be a possible process for humic acid removal once filters had been acclimated to a synthetic feedwater for 12–16 months. The biofilters were exposed to a synthetic feedwater with influent TOC concentrations ranging from 1.6–4.5 mg L‒1 and a composition of 65% humic acid, 15% formate, 10% acetate and 10% formaldehyde on a carbon mass basis. TOC removals improved from 19 ± 13% (n = 15) to 49 ± 10% (n = 20) in one biofilter and from −11 ± 25% (15) to 51 ± 7% (n = 20) in another biofilter. These increases were found to be statistically significant at the 5% level. The increase in removal was due to an increase in removal of both the readily biodegradable carbons and humics in the biofilters. The humic removal increased from 10 to 36% in biofilter #1 and from 0 to 35% in biofilter #2. At the end of the experiments, formate removals were between 91–94%, acetate removals ranged from 83–87%, and formaldehyde was completely removed in the biofilters. SUVA was not found to be a good indicator of humic removal in the biofilters.
Decolorisation of natural organic matter by Phanerochaete chrysosporium: the effect of environmental conditions
Authors: Rojek K. , Roddick F.A. , Parkinson A.
Published: May 2018

Phanerochaete chrysosporium was shown to rapidly decolorise a solution of natural organic matter (NOM). The effect of various parameters such as carbon and nitrogen content, pH, ionic strength, NOM concentration and addition of Mn2+ on the colour removal process was investigated. The rapid decolorisation was related to fungal growth and biosorption rather than biodegradation as neither carbon nor nitrogen limitation, nor Mn2+ addition, triggered the decolorisation process. Low pH (pH 3) and increased ionic strength (up to 50 g L‒1 added NaCl) led to greater specific removal (NOM/unit biomass), probably due to increased electrostatic bonding between the humic material and the biomass. Adsorption of NOM with viable and inactivated (autoclaved or by sodium azide) fungal pellets occurred within 24 hours and the colour removal depended on the viability, method of inactivation and pH. Colour removal by viable pellets was higher under the same conditions, and this, combined with desorption data, confirmed that fungal metabolic activity was important in the decolorisation process. Overall, removals of up to 40–50% NOM from solution were obtained. Of this, removal by adsorption was estimated as 60–70%, half of which was physicochemical, the other half metabolically-dependent biosorption and bioaccumulation. The remainder was considered to be removed by biodegradation, although some of this may be ascribed to bioaccumulation and metabolically-dependent biosorption.
Effect of fractionated NOM on low-pressure membrane flux declines
Authors: Gray S.R. , Ritchie C.B. , Bolto B.A.
Published: May 2018

The membrane fouling characteristics of natural organic matter (NOM) were assessed using single polypropylene hollow fibre membranes of pore size 0.2 μm. The membranes were liquid backwashed every 30 minutes and filtration runs of up to 48 hours (≤8 litres) were conducted. The NOM samples were fractionated into different chemical classes based on their adsorption properties. For the two waters investigated, the hydrophobic components were the major foulant for one water, and the hydrophilics were the major foulant for the other. Interaction between the strongly hydrophobic and weakly hydrophobic fractions was significant for one water, but the extent of interaction between these fractions was minor for the other. The long term membrane fouling characteristics could not always be deduced from short term fouling trials.
Tuning the enhanced coagulation process to obtain best chlorine and THM profiles in the distribution system
Authors: Fisher I. , Kastl G. , Sathasivan A. , Chen P. , van Leeuwen J. , Daly R. , Holmes M.
Published: May 2018

Water treatment processes produce water with low turbidity and colour. It is also now becoming necessary to reduce DOC (Dissolved Organic Carbon) so that less chlorine is lost in a distribution system and less THMs (trihalomethanes) are formed. Enhanced coagulation (exceeding other requirements) at pH of about 5-6 is known to significantly reduce DOC so that acceptable water quality can be achieved at the tap. In this paper, models are integrated to project the impact of water treatment on water quality through the entire distribution system. A DOC removal model, which predicts DOC resulting from a given coagulant, its dose and the coagulation pH, is used to simulate the treatment. By linking this model of DOC removal with models of chlorine decay and THM formation, the impact of treatment on chlorine and THM concentrations in a distribution system can be simulated. This method was applied in a case study with relatively high initial DOC. It was shown that more DOC can be removed by using ferric coagulant than the current practice achieves. This would result in an improved chlorine profile and a substantial reduction in THM concentrations.
NOM removal for extension of chlorine dioxide residuals and lower biological regrowth potentials
Authors: Ring E. , Samblebe M. , Leak M. , Gray S.
Published: May 2018

Techniques to decrease the rate of chlorine dioxide (ClO2) decay in a treated water from Whitfield, Australia were investigated. Biofiltration, microfiltration (MF) and ultrafiltration (UF) were considered as possible means of removing organic compounds which react with the ClO2. Membrane filtration removed more organic material than biofiltration, but biofiltration led to greater ClO2 durations and lower biological regrowth potentials than MF or UF. The results indicated that biofiltration was able to preferentially remove the fast reacting component of organic material that led to rapid ClO2 decay and also lowered the biological regrowth potential of the water.
Neural networks modelling of pesticides removal by activated carbon for water treatment
Authors: Cougnaud A. , Faur-Brasquet C. , Le Cloirec P.
Published: May 2018

The adsorption equilibrium of pesticides (atrazin, atrazin-desethyl and triflusulfuron-methyl) onto activated carbon (AC) carried out in batch reactors has been determined for a large range of concentrations (from 5 μg/L to 21.4 mg/L) to characterise adsorption mechanisms. Single-solute isotherms tend to confirm the decisive role of the adsorbent's microporosity in the adsorption capacity of the AC. These adsorption capacities are high and range between 63 and 509 mg/g. The adsorption of the three pesticides is also studied in a dynamic reactor. The influence of operating conditions (initial concentration Co, flow velocity Uo) and adsorbent's characteristics is investigated. All dynamic experimental results are modelled by a neural network to establish the link between the characteristics of activated carbon materials and the adsorption's results. Parameters related to the adsorbate–adsorbent affinity in a batch reactor are consequently introduced in the input layer of the neural network added to operating conditions whose influence was shown (Co and Uo) and time t. The statistical quality of the neural network modelling is high (R2=0.985 for the static neural network and R2=0.993 for the dynamic neural network between experimental and predicted values for the test data set).
Biodegradation of gasoline compounds (BTEX) in a water works sand filter
Authors: Arvin E. , Engelsen P. , Sebber U.
Published: May 2018

Various chemical compounds including aromatic gasoline compounds frequently contaminate drinking water wells in urban areas. Because ground water treatment is simple, usually consisting of aeration/stripping and sand-filtration, it is of significant interest to know the ability of the conventional treatment to remove the chemical contaminants. The removal of gasoline compounds was investigated in a two-stage pilot scale sand filter, each with a filter depth of 0.8–1 m and with a filtration rate of 7.6 m/h. The concentrations of aromatic compounds were in the range 7–15 μg/L, which are realistically low concentrations. The experiments demonstrated a surprisingly high removal efficiency of the filter system. Most of the hydrocarbons were removed already in the primary filter (3 mm sand grains) and the concentrations were in the range 0.05–0.1 μg/L at the outlet from the secondary filter (1 mm sand grains). Influent iron concentrations in the range 0–4 mg/L and backwashing did not adversely affect the biodegradation of hydrocarbons. This study has shown that a conventional biological active sand filter can act as an efficient barrier against gasoline compounds, thereby saving the consumer capital costs and operational costs from installation of supplementary treatment.
The treatment of algae-laden raw water with compact flofilter of dissolved air flotation and GAC deep bed filtration
Authors: Zhang X. , Zhang S. , Liu Y.
Published: May 2018

Compact flofilter of dissolved air flotation and GAC deep bed filtration is a good integrated procedure, having the following characteristics: flotation and filtration are integrated in one tank, the flotation unit is above the filtration unit, filtration is GAC deep bed, and conventional and advanced treatments are integrated in one tank. During the treatment of algae-laden raw water with compact flofilter of dissolved air flotation and GAC deep bed filtration, the general performance was good: the outlet algae-count was 1.21×105–1.26×106 cell/l, the average removal of algae was 95.4%, the outlet chl-a was 0.68 μg/l, the removal of chl-a was 92.2%, the outlet turbidity was 0.16–0.20 NTU, the outlet had no odor, the outlet color was 3, the removal of color was 86.4%, the outlet Al-residual was 0.011 mg/l. Good removal of organics can be achieved: the average removal of UV254 was 54.3%, the outlet UV254 was 0.016–0.018 cm−1, the removal of DOC was 29.6%, the outlet DOC was 1.608 mg/l, the removal of BDOC was 42.6%, the outlet BDOC was 0.120 mg/l, the removal of AOC was 72.2%, the outlet AOC was 52 μg/l. Filter run period and UFRV were 36 h and 504 m3/m2. The results show that flofilter is a good alternative process for conventional treatment plus GAC adsorption.
Colour removal by ion exchange and reuse of regenerant by means of nanofiltration
Authors: Schippers D. , Kooi M. , Sjoerdsma P. , de Bruijn F.
Published: May 2018

In the past year Vitens, The Netherlands' largest water supply company, and Witteveen+Bos, have prepared the preliminary, basic and detailed design for a full-scale ion exchange plant reducing colour in drinking water to a value of less than 10 mg/l PtCo. Current pilot study shows that the results are even better than expected. The plant will be built in 2004 and start-up is scheduled for mid 2005. The introduction of ion exchange at WTP (Water Treatment Plant) Oldeholtpade is part of a larger project, also including softening in pellet reactors, preceded by counter-current aeration and renovation of the existing treatment plant.

The colour content present in groundwater is caused by peat layers. In contrast with conventional ion exchange processes, previous pilot studies showed that the exchange capacity of the resin for organics is much larger than expected. The excellent results can be explained by assuming the simultaneous occurrence of adsorption and ion exchange processes on the resin. It can be concluded that optimising operating conditions, such as higher exchange capacity (as KMnO4/liter resin), higher superficial velocity, shorter contact time and longer filter run cycle clearly affect resin volume as well as the required amount of regenerant.

Vitens has started additional experiments at WTP Spannenburg to confirm the innovative design parameters. Aim of the research is the relation between adsorption and ion exchange during filtration, in order to clarify the achieved results. Furthermore the relationship between the specific water type (characterisation of organic compounds) and the operational results of ion exchange will be studied.

In order to minimise the waste regenerant, treatment towards recycling is studied by dead end nanofiltration. With nanofiltration it is possible to concentrate the waste stream to a maximum of 10% of the original waste stream. The recovered regenerant can be recycled for regeneration of the resin.
Neural networks: an efficient approach to predict on-line the optimal coagulant dose
Authors: Deveughèle S. , Do-Quang Z.
Published: May 2018

The problem under study was the on-line prediction of the optimal coagulant dose from raw water parameters; it has been tackled by using powerful modeling tools: Artificial Neural Networks (ANNs). Such tools do not rely on physico-chemical relationships; the model is built by using an historical dataset available on the plant (raw water parameters and Jar-tests data). A prototype has been implemented on a full-scale water treatment plant in France. The approach is explained, some relevant results are shown and the industrial benefits are discussed. The expected OPEX reduction (coagulant) is about 10%.
Natural organic matter fractionation: XAD resins versus UF membranes. An investigation into THM formation
Authors: Goslan Emma H. , Wilson Derek , Banks Jenny , Hillis Peter , Campbell Andrew , Parsons Simon A.
Published: May 2018

An increase in reservoir water colour over the last 10 years has been impacting on the ability of water treatment works (WTWs) in the UK to meet THM regulations. The problem is exacerbated in autumn particularly after heavy rainfall. It appears that residual organics are labile precursors to disinfection by-products (DBPs). One WTW was investigated to determine a link between raw water characteristics and reactivity with chlorine. Bulk water parameters were measured but the information obtained was limited. To further characterise the water, samples of reservoir water were fractionated using XAD resins and UF membranes. The resulting fractions were subjected to analysis of dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), specific UV absorbance (SUVA) defined as the ratio of UV254 to DOC and trihalomethane formation potential (THM-FP). The samples were also characterised using high performance size exclusion chromatography (HPSEC). Both methods of fractionation described here have limitations in explaining the bulk water behaviour. The relationship between SUVA and THM-FP was discussed. HPSEC showed that the size distribution of the resin separated and membrane separated fractions was similar indicating that the molecular weight cut-off (MWCO) of the membranes is not sharp.
A monitoring study for the impact evaluation of water treatment sludge discharge on Ribeira de Iguape River, São Paulo, Brazil
Authors: Reis E.L.T. , Cotrim M. , Filho O.B. , Badiru A.I. , Pires M.F.
Published: May 2018

Brazilian urban centers have been supplied by water from some basins, which are facing several negative interventions that are endangering their properties as water quality resources. Such effects have recently been observed at Ribeira de Iguape basin, located on the south coast of São Paulo State, due to the growth of unconformities in the environmental water quality tests control. Much of this area constitutes an environmental preservation system, with just a reasonable sanitation support. All the water treatment plants (WTPs) in this basin usually discharge large quantities of water treatment sludge to nearby rivers and streams. Few studies have reported the impact of these residues. However, some cities in the basin continue to use river waters for provisioning. On the other hand, high rainfall and wide flow variation of streams due to the tropical weather may minimize potential sludge deposition effects. This work discusses a monitoring study of a WTP on Ribeira de Iguape River, to evaluate the possibility of this continuous discharge, and search for new alternatives of disposal and treatment of water works residuals, according to environmental patterns.
Natural organic matter fouling and chemical cleaning of nanofiltration membranes
Authors: Li Q. , Elimelech M.
Published: May 2018

Fouling and subsequent chemical cleaning are two important issues for sustainable operation of nanofiltration (NF) membranes in water quality control applications. Because fouling strongly depends on the feed water quality, especially the ionic composition, chemical cleaning solutions should be chosen to target the solution chemistry that is most responsible for the formation of a compact, high resistance fouling layer. In this study, the effect of solution chemistry on natural organic matter (NOM) fouling of two NF membranes with different surface properties was investigated. Compared to monovalent cations, divalent cations were found to greatly enhance NOM fouling by complexation. Moreover, calcium ions caused a much greater fouling rate than magnesium ions, presumably due to the intermolecular bridging formed among NOM molecules through the calcium ions. Various chemical cleaning solutions were evaluated for water flux recovery efficiency. Although both deionized water and dilute NaOH solution were found effective in cleaning membranes fouled in the absence of calcium ions, efficient chemical cleaning in presence of calcium was achieved only when the calcium ion bridging was eliminated. The cleaning efficiency was shown to be highly dependent on solution pH and the concentration of the chemical cleaning agent.
Improving water quality by reducing coagulant dose? A case study at the Sidi Said Maachou Water Treatment Plant (Morocco)
Authors: Codiasse D. , Caudron Ch. , Baudin I. , Chouhou M. , Campos C.
Published: May 2018

Many water treatment plants are currently facing the challenge of removing both turbidity and organic matter at a reasonable cost. This double objective often requires high coagulant doses, resulting in high operating costs due to the increase in both reagents use and sludge production. An attractive approach to reducing operating costs while maintaining the finished water quality is to add the coagulant in a double step sequence, which is referred to as double step coagulation. In this article, bench-scale experiments were conducted to assess the impact of a double step addition of coagulant on both turbidity and organic matter removal in clarification processes. The results showed that coagulant dose required for a given turbidity target can be significantly reduced. For example, for a final turbidity of 1 NTU, the coagulant dose can be reduced by 20% with respect to the Coagulant Reference Dose (CRD), which represents 200,000 Euros per year without any additional investment on infrastructure. Following these bench scale demonstrative tests, the double step coagulation strategy was adopted at full scale by the Sidi Said Maachou Water Treatment Plant in Morocco. Operated by the Société des Eaux de l'Oum Er-rbia, this plant treats 200,000 m3/day to supply the city of Casablanca. The double step coagulation was implemented to achieve a double objective: turbidity and organic matter removal at the lowest chemical cost.
Monitoring of hazardous substances at Alcantarilha's water treatment plant, Portugal
Authors: Rosa M.J. , Cecílio T. , Ribau Teixeira M. , Viriato M. , Coelho R. , Lucas H.
Published: May 2018

A monitoring programme of hazardous substances was implemented in Alcantarilha's water treatment plant (Algarve, Portugal) since 2002, in addition to the legally established monitoring of standard physical, chemical and microbiological parameters. The objective of this programme was to ensure the drinking water quality regarding the waterborne disease organisms Cryptosporidium, Giardia, Salmonella, Pseudomonas aeruginosa, enterovirus and cyanobacteria, and the potentially harmful chemicals aluminium, cyanotoxins, and disinfection by-products (THM) and their precursors (TOC, DOC, UV254 nm, SUVA). Most of these parameters are new and still not regulated by the Portuguese and the European legislation. Data presented in this study refer to the period of August 2002 to October 2003. Results show that, despite the seasonal variations of the raw water quality, concentrations of the hazardous substances in the supplied drinking water were far below the legal standards and the WHO's and EPA guideline values, demonstrating the high removal efficiencies of this treatment plant.
WaterScope: an innovative water quality information management system
Authors: Howard J.R. , Lucas J. , Maitland J. , Tarrant P. , Watson T.
Published: May 2018

SA Water is a State owned organisation that owns and manages South Australia's water supplies, providing reliable drinking water to nearly 1.4 million South Australians. A major issue affecting SA Water's ability to manage water quality effectively has been the difficulty accessing water quality information which has been stored in separate, generally inaccessible databases with poor reporting and decision support capability. To improve SA Water's ability to make timely and effective decisions regarding water quality, an integrated business system has been developed which provides water managers with direct access to comprehensive water quality information. The system includes improved field data collection units which incorporate a barcode system; sample point images and workflow support tools; an integrated water quality data warehouse with automated standard and ad hoc reporting capabilities; a geographical information system containing comprehensive coverages of natural resources and system infrastructure information; and water incident exception reporting and incident management support through a corporate incident management system. Major benefits of the system will include improved management of public health risk through quicker and more accurate reporting of incidents; improved customer confidence in SA Water; improved knowledge capture and visibility of water quality information; increased efficiency of capital utilisation and better understanding of system performance through spatial representation of data and trending of results. WaterScope can also be used and shared by data partners and regulators, making optimal use of the State's limited water quality data sets. It can also be made available commercially to other water management organisations. Future challenges include the integration of wastewater and recycled water data, linking of continuous (on-line) water quality data and links to water demand management systems.
Hydroponic cultivation of lettuce (Lactuca sativa) using effluents from primary, secondary and tertiary +UV treatments
Authors: Keller R. , Perim K. , Semionato S. , Zandonade E. , Cassini S. , Gonçalves R.F.
Published: May 2018

The aim of this study was to evaluate the potential cultivation of lettuce (Lactuca sativa) with domestic wastewater effluents with different levels of treatment from a compact WWTP in Brazil. Vegetables were grown in five treatments: nutrient solution (control), secondary effluent diluted 50%, secondary effluent not diluted, tertiary effluent UV irradiated, and UASB effluent. Microbiological analyses from leaves showed low levels of contamination with E. coli, thermotolerant coliforms and total coliforms. Salmonella spp. and helminth eggs were not detected. However, roots showed hardly any concentration of these microorganisms. These results shows that it is possible to cultivate leafy vegetables in a hydroponic system with treated effluents, taking care at the moment of harvesting vegetables.
Strategic planning in today's dynamic world
Authors: Brueck Terrance M.
Published: May 2018

Utilities today must adapt quickly to complex changes in workforce, infrastructure, technology, and regulations, as well as outside factors of the economy, security issues, and societal trends. Linear, cause-and-effect strategic planning does not work well in today's world. Given these uncertainties, how can utilities develop meaningful and useful strategic plans? Faced with these challenges, a group of 18 leading international utilities, assisted through IWA, has developed new ways of strategic planning. This project, sponsored by AwwaRF and conducted by EMA, has created a dynamic and flexible strategic planning framework. A new framework, coupled with many of these utilities' experiences in strategic planning, is the subject of this paper.
Effective asset management maximizes your return on investment (ROI) and customer satisfaction
Authors: Johnson K. , Mortada M.M.
Published: May 2018

Asset management is a critical link in balancing overall product or service delivery cost of ownership to achieve and sustain customer satisfaction. Current drivers for asset management make it one of the most critical issues on the minds of leaders today. Many are overwhelmed by the enormity of the task they face and they are concerned about their company's ability to design, implement and sustain an effective asset management program. This paper provides practical guidance on the asset management concept, how it fits into the overall business model, benefits to be achieved once a program is implemented, suggested performance measures and an approach to implementation.
Sanitation for all in periurban areas? Only if we use simplified sewerage
Authors: Mara D.D.
Published: May 2018

Simplified sewerage is considered the only periurban sanitation technology that has a chance of ensuring that the WHO/UNICEF target of Sanitation for All by the end of 2025 is achieved. On-site sanitation technologies, such as ventilated improved pit (VIP) latrines, pour-flush toilets and ecological sanitation toilets, are either technically infeasible in high-density areas or more expensive than simplified sewerage. Simplified sewerage is often institutionally and professionally acceptable to sewerage authorities simply because it is a sewerage system, albeit different from conventional sewerage in that it uses small-diameter sewers laid at shallow gradients (e.g., 100-mm sewers at 1 in ∼200). The success of simplified sewerage in Latin America, principally Brazil, has to be replicated on a truly huge scale in Africa and Asia where most of those without adequate sanitation live. In areas where even simplified sewerage is unaffordable, the only option is to install communal sanitation blocks of the type implemented in India by Sulabh International.
Residential price elasticity of demand for water
Authors: Metaxas S. , Charalambous E.
Published: May 2018

This paper presents an analysis on price elasticity of demand for water as a consequence of price increases. The objective of this research study is to estimate the residential price elasticities of demand for water for different regions, which may have different income levels. The general conclusion is that price elasticity for residential water use is inelastic (i.e. a given percentage of price increase results in a proportionally smaller decrease in quantity demanded) and it varies by consumer class and type of water use. The elasticity is not significantly affected by demographic and other factors.
Design of water allocation model: efficiency and risk aspects
Authors: Kim C. , Han D.
Published: May 2018

The primary objective of this study is to improve the methodology for water allocation focused on efficiency and risk aspects. To attain the primary objective, this study sets up an objective function to maximize social expected benefits, and considers three types of allocation methods. Three types of allocation methods are optimal, proportional, and fixed allocation between regions and service sectors. The results of case study area shows that the fixed allocation method is preferred to the proportional allocation in most cases except that the variance of flow is small with respect to efficiency. Also, efficient and less-risky allocation is simultaneously obtained in some cases, while efficiency and risk show the relation of trade-off in other cases.
Building sustainable wastewater reuse in Jordan
Authors: Pasch J. , Macy P.
Published: May 2018

Jordan's population is projected to reach 6.5 million by 2010. Limited water does not meet present or projected demands, groundwater levels are dropping, and industrialization is increasing pressure on water resources and the environment. The agricultural sector alone uses approximately 70% of total water resources. Wastewater represents a resource that can help fill Jordan's gap between supply and demand. While approximately 80% of the over 80 MCM of wastewater/yr is currently reused, only a fraction is formalized with permitting and adherence to reuse guidelines. The Jordanian government seeks to embrace reclaimed resources in national water resources planning through recognized/regulated reuse implementation activities. A multi-sectoral project is being performed to help reach this goal in Jordan and worldwide, sharing lessons learned in increasing access to reused water, and involving performance of four demonstration projects with an aim toward developing replicable operational conditions that support sustainability/enhance expansion of treated wastewater reuse in Jordan.
Contingent valuation by the community of indirect benefits of using recycled water: an Australian case study
Authors: Hurlimann A. , McKay J.
Published: May 2018

Contingent valuation (CV) was used to survey an Australian community who will soon be using recycled water for non-potable purposes. Willingness to pay (WTP) for four indirect, non-market utilities of recycled water were investigated: a decreased amount of sewage going into the ocean; exemption form water restrictions; a continuously green appearance of public open space; and wetlands located in close proximity to dwellings. WTP trends were found across demographic variables (gender, age, income and education), with some significant differences between groups. Strong concern for the environment was found to influence WTP. An improved methodology for further research is suggested.
Social interaction in water demand management implementation
Authors: Buckle J.S.
Published: May 2018

This article describes a successful awareness and education project undertaken in an East Rand township by the Water Cycle Management Section of Rand Water. The Project's focus was to create awareness in the community of the broad concept of water cycle management within an environment and to transfer skills to community members (facilitators) who could then assist in ensuring effective and efficient water use.
Mathematical Model Investigation of Far-Field Transport of Ocean-Dumped Sewage Sludge Related to Remote Sensing
Authors: Kuo C Y
Published: May 2018

An existing, three-dimensional, Eulerian-Lagrangian finite-difference model was modified and used to examine the far-field transport processes of dumped sewage sludge in the New York Bight. Both in situ and laboratory data were utilized in an attempt to approximate model inputs such as mean current speed, vertical and horizontal diffusion coefficients, particle size distributions, and specific gravities. Concentrations of the sludge near the sea surface predicted from the computer model were compared qualitatively with those remotely sensed.
Disposal of Sewage Sludge to Sea – Research Needs
Authors: Agg A R
Published: May 2018

The need for further research on the environmental effects of sewage sludge disposed of at sea is examined with particular reference to conditions in the UK. Additional expenditure on monitoring and research appears to be justitied Dy comparison with the cost to dischargers of adopting alternative means of disposal. Research should be directed to improving methods of predicting the effects of increased discharges at selected sites and to understanding the behaviour of specific components of sludge which are not degraded in the sea. It is concluded that improved information should be obtained about (a) relative inputs of pollutants from land-based sources in some areas, (b) the physical processes controlling dispersion, sedimentation, and degradation of sludge particulates, (c) the mobilisation of conservative substances from sludge, and (d) the role of nutrients and other substances in sludge in the development of certain algal blooms.
Sludge Disposal Strategy: A UK Viewpoint
Authors: Walker D L
Published: May 2018

The paper considers the world perspective affecting sewage sludge disposal and describes the UK background. It summarises factors affecting sludge disposal to land, to sea, and by incineration. It considers the possible influence of international restraints, outlines present research priorities and concludes with the author's views on the choice between sludge disposal methods.
Effects on the Ecosystem of Sewage Sludge Disposal by Dumping from Ships
Authors: McIntyre A D
Published: May 2018

Information on the environmental consequences of discharging sewage sludge from ships at sea is reviewed. Effects on the water column and on the seabed are summarised. The major impact is related to the nutrient and organic content of the sludge and is found in areas where sludge accumulates on the bottom, producing changes in the sediments and in the benthic communities. There is no clear evidence of adverse effects from potentially toxic substances in the sludge. Careful selection of dumping grounds is important to prevent public health and amenity effects and to ensure there is no interference with fisheries.
Influence of Micropollutants on Vegetation
Authors: Davis R D
Published: May 2018

Potentially phytotoxic inorganic and organic micropollutants are listed and some of their effects are described. The use of plant analysis for assessing phytotoxicity in terms of relative pollution hazard is discussed. The discharge of sludges and effluents are facets of the water cycle which result in exposure of plants to micropollutants. When sewage sludge is applied to agricultural land, determination of ‘total' concentrations of micropollutants in soils indicates only the extent of contamination. Its significance in terms of phytotoxicity and transfer to foodchains depends on soil conditions and crop type. Biological toxicity tests can be used both to screen for phytotoxicity in sludges and effluents before their discharge, and to trace sources of phytotoxic pollutants.
Control of Activated Sludge Filamentous Bulking – IV. Effect of Sludge Regeneration
Authors: Chudoba J , Dohányos M , Grau P
Published: May 2018

In addition to the previously published growth theory based on the relation of μ^ to ks , the paper deals with an accumulation-regeneration theory of microorganisms selection. The accumulation-regeneration phenomenon can play a role in population dynamics only in the systems where the accumulated substrate can be subsequently oxidized and thus the accumulation capacity restored in one feeding cycle. This condition can be realized in properly designed systems with the substrate concentration gradient along the reactor. As a criterion of accumulation capacity restoration it is suggested to use the oxidized proportion of the substrate removed in one feeding cycle. Extensive laboratory experiments have shown a significant relation between the SVI and the percentage of the substrate oxidized. Practical consequences of these findings for the control of filamentous activated sludge bulking are also discussed in the present paper.
Water-Pollution Research and Its Application in Developing Countries
Authors: Isaac P , Pescod W
Published: May 2018

Much research into the control of water pollution is of little practical application in developing countries, being too concerned with abstract science. Research to be applied in the Third World must not only lead to inexpensive solutions, that can be developed as finances allow, but must take account of the social, political, religious and financial factors in the poorer rural areas of the world.

This paper draws the attention of research-workers in this field to the wider realities of developing countries, and emphasizes that success in the field, as opposed to success in the laboratory, will demand a multidisciplinary approach. Research must be prepared to take full account of non-technical and non-scientific factors.
Control of Bulking Sludge – Practical Experiences in Austria
Authors: Matsché N F
Published: May 2018

Practical experiences with the control of bulking sludge are reported. The control methods include: increase of the specific weight of the floc, damage of filamentous organisms, removal of factors causing growth of filamentous organisms and generation of process conditions that adversely affect the growth of filamentous organisms. Plug flow conditions that cause a time varying substrate concentration profile turned out to be a successful tool in the prevention of bulking, however, in some cases a combination with other methods including chlorination was necessary.
Wastewater Technologies in South Africa: Research and Application
Authors: Stander G J , Cillie G G , Hall E J , Henzen M R
Published: May 2018

South Africa's water economy has necessitated concerted research on aspects contributing to water and wastewater management and water reuse. This paper deals briefly with highlights of research and application in these areas. Development of advanced wastewater treatment technology has led to its application in the reclamation of potable water in Windhoek, and of process water for the pulp and paper industry. Reverse osmosis shows great promise as an alternative water reclamation process to abate the build-up of inorganic salts within the cycle of use, reclamation and reuse. Ion exchange and ultrafiltration have been successfully applied in the recycling of water and chemicals in the textile industry. Studies on biological nutrient removal have resulted in the development of the novel Bardenpho process and its modification, the Phoredox process. Particular attention has been devoted to water quality control and to health aspects. Of special significance has been the postulation of pollution indices based on chromatograms of a series of potentially harmful organic pollutants and the finding that routine, expensive enteric virus monitoring can be replaced with simpler, equivalent bacterial tests. The Ames test and a mammalian cell bioassay have been adopted for the detection of potential carcinogens in water. Biological monitoring systems using fish and another assay using a protozoan have been developed, primarily for quality control of industrial effluents. However, continual development and application of new knowledge is a necessity for further growth.
Design and Operation Interaction – An Example: Main Treatment Plant Vienna
Authors: von der Emde W
Published: May 2018

The development of the Main Treatment Plant Vienna-Simmering for 2,5 million population equivalent, which was recently put into operation, is described. The biological stage is a high rate activated sludge process at 1,2 days sludge age and 1,5 h average nominal hydraulic detention time. In a pilot Scale study, the design criteria for the biological stage were fully confirmed and indicated that the required purification efficiency (70 %) could readily be achieved (88 %) . Sludge disposal is undertaken by gravity thickening, centrifugation and incineration. A comprehensive analysis of the present operation of the process has showed that the plant has fully met expectations.
The Distribution and Significance of Toxic Metals in Sharks from the Natal Coast, South Africa
Authors: Watling R J , Watling H R , Stanton R C , McClurg T P , Engelbrecht E M
Published: May 2018

The concentrations of ten metals in the tissues of three commercial shark species have been determined. Mercury concentrations increase with size and are a predictable but limiting factor which must be considered when sharks intended for human consumption are exported from South Africa. Apparently high concentrations of some metals have been found in the livers of these sharks but, as the Southern African coastal marine environment is relatively unpolluted with respect to metals, it is concluded that these concentrations are “normal”. Some interesting differences in the concentrations of the other study elements in these sharks have also been observed.
Examination of a Drinking-Water Supply for Mutagenicity
Authors: van Rossum P G , Willemse J M , Hilner C , Alexander L
Published: May 2018

The results of an Ames test survey of the drinking-water of the administrative capital of South Africa showed the widespread presence of at least one unidentified, frameshift, weakly polar mutagen, which needed no activation by rat liver enzymes. This mutagenicity was found to be perpetual in the water from at least one sampling point and probably originated from the same source. Extraction of the mutagen(s) from the water was achieved by adsorption onto XAD-2 resin, followed by desorption with acetone. No base-pair substitution mutagen could be detected. Optical density, pH and electrical conductivity determinations showed that the relative contribution of surface and groundwater to the drinking-water at the different sampling points remained fairly constant during the survey. No correlation could be found between mutagenicity and the volatile halogenated organic compounds as well as the polynuclear aromatic hydrocarbons in the waters. The survey was organized as part of an identification process, so that the results could be used not only to establish whether there was a need for further identification of the mutagen(s), but to furnish some of the information needed for their successful isolation.
Virus Removal by Filtration
Authors: Sriramula N , Chaudhuri M
Published: May 2018

An investigation was undertaken on the removal of a model virus, bacterial virus MS2 against Escherichia coli, by sand filtration using untreated, and alum or cationic polyelectrolyte treated media, and uncoagulated as well as alum coagulated influent. Data on discrete virus removal were satisfactorily accounted for by electrokinetic phenomena and diffusion. For virus in association with turbidity, filter coefficients computed from experimental data were in good agreement with those predicted by mechanical straining and gravity settling which were the dominant mechanisms for removal of the turbidity particles to which the viruses attached.
A New Configuration of the High-Lime Process with Sludge Recirculation for Magnesium Recycling
Authors: Idelovitch E , Wachs A M
Published: May 2018

Laboratory experiments carried out with lime-algae sludge and low-magnesium effluent showed that Mg can be recycled in the high-lime process by sludge recirculation. By mixing of sludge with effluent, a pH of about 9 is achieved, which ensures partial dissolution of Mg (OH)2 to MgCO3 and Mg(HCO3)2. After settling of the sludge, the effluent enriched with Mg can be conveyed to lime treatment (without external Mg addition), whereas the new sludge can be dewatered more economically than the original sludge. The clarification results obtained with recycled Mg by sludge recirculation are similar to those obtained with MgCl2 and with recycled Mg by means of CO2, but lime consumption is lower, since part of the effluent alkalinity is consumed in the process of Mg dissolution. No dissolution of boron or heavy metals occurs, but part of the colloidal organic matter and phosphorus are released from the sludge. By means of simple computer programs that were prepared, it is possible to determine the total Mg concentration that can be reached by recycling, as well as to forecast the increase in the concentration of the dissolved and suspended fractions of any substance, at steady-state conditions. In spite of the increase in the concentration of some substances in the secondary effluent, there is no danger of their accumulation to undesirable levels in the final effluent. An economic evaluation carried out showed that the new configuration of the high-lime process with sludge recirculation facilitates the solution of the sludge problem, eliminates the need for Mg addition from external sources, and reduces considerably the process cost.
Inhibition Modelling in Anaerobic Digestion
Authors: Duarte A C , Anderson G K
Published: May 2018

The effects of volatile acids and pH on anaerobic digestion were studied in laboratory and pilot-scale digesters. The wall growth was shown to be an important parameter when operating digesters at low solid concentrations.

The role of propionic acid inhibition is emphasized.

Mathematical models to predict digester performance are discussed and are used to fit available inhibition data.