bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a health information telephone line, Info-Santé CLSC, for the surveillance of waterborne gastroenteritis
Authors: Gilbert Marie-Line , Levallois Patrick , Rodriguez Manuel J.
Published: May 2018

The increasing frequency of waterborne outbreaks demonstrates that classic indicators used for the surveillance of the microbiological quality of drinking water have several gaps and that routine public health surveillance seems insufficient to allow for the rapid detection of these outbreaks. The main objective of this study was to evaluate the possibility of using a regional health information telephone line, ‘Info-Santé CLSC’ (Info-Health Local Community Health Centre), for the surveillance of waterborne gastroenteritis. This study measured the incidence rate of calls for acute gastrointestinal illness (AGI) placed to the Info-Santé CLSC line, investigated the relationship between the frequency of calls for AGI placed to the Info-Santé CLSC line and the turbidity of the treated water in the Quebec City drinking water plant and evaluated the relevance and the conditions of use of the Info-Santé CLSC system for the surveillance of waterborne enteric illness. A relationship between the turbidity and the calls for AGI placed to Info-Santé CLSC line was observed. Significant time lags (11, 15 and 17 days prior to the outcome) were identified in the final model derived from a Poisson model using generalized additive models (GAM) as a time series analysis. Some recommendations to improve the system were formulated even though the system already seems to be useful for the surveillance of waterborne enteric diseases.
Application of microbial risk assessment on a residentially-operated Bio-toilet
Authors: Nakagawa Naoko , Oe Hana , Otaki Masahiro , Ishizaki Katsuyoshi
Published: May 2018

The Sustainable Sanitation System is a new wastewater treatment system that incorporates a non-flushing toilet (Bio-toilet) that converts excreta into a reusable resource (as fertilizer or humus for organic agriculture) and reduces the pollution load to environments of the rivers, the lakes, and the sea. However, the risk of exposure to pathogens should be considered, because excrement is stored in the Bio-toilet. The aim of the present work is to analyze the health risk of dealing with the matrix (excreta and urine mixed with sawdust) of the Bio-toilet. Therefore, the fate of pathogenic viruses was investigated using coliphages as a virus index, and the modeling of the die-off rate in matrix was introduced. Then the microbial risk assessment was applied to a Bio-toilet that was actually used in a residential house; the infection risks of rotavirus and enterovirus as reference pathogens were calculated. According to the lab-scale experiment using coliphages for investing the die-off rate of viruses in the Bio-toilet, Qβ had a higher die-off, which was greatly influenced by the water content and temperature. On the other hand, T4 showed a lower rate and was independent of water content. Therefore, these two phages' data were used as critical examples, such as viruses having high or low possibilities of remaining in the Bio-toilet during the risk assessment analysis. As the result of the risk assessment, the storage time required for an acceptable infectious risk level has wide variations in both rotavirus and enterovirus cases depending on the phage that was used. These were 0–260 days' and 0–160 days' difference, respectively.
Reevaluation of the toxicity of chlorinated water and the usefulness of MX as an index
Authors: Itoh Sadahiko , Nakano Atsushi , Araki Toshiaki
Published: May 2018

Changes in the toxicity in chlorinated water after chlorine addition were examined. For toxicity evaluation, the chromosomal aberration test and the transformation test were conducted as indexes of initiation activity and promotion activity, respectively, in the carcinogenesis process. Activity inducing chromosomal aberrations in chlorinated Lake Biwa water gradually decreased over time after chlorination. In contrast, activity inducing transformations determined by the two-stage assay gradually increased. Thus, toxicity that decreases or increases is present in chlorinated water. Furthermore, activity inducing transformations determined by the non-two-stage assay gradually decreased over time. This direction of change is opposite to that of activity inducing transformations determined by the two-stage assay and is consistent with that of activity inducing chromosomal aberrations. The drastic decrease in initiation activity detected as activity inducing chromosomal aberrations could be the main cause for the decrease in activity inducing transformations determined by the non-two-stage assay (an index of the sum of initiation and promotion activity). MX change was quantitatively consistent with those of activity inducing chromosomal aberrations and transformations determined by the non-two-stage assay. On the other hand, directions of changes in concentrations of typical by-products such as chloroform were consistent only with that of activity inducing transformations determined by the two-stage assay. Findings of this study suggest that MX is appropriate as an index for comparing the carcinogenicity of tap water near and far from a water purification plant.
Improving Cryptosporidium testing methods: a public health perspective
Authors: Weintraub June M.
Published: May 2018

Cryptosporidium is a protozoan parasite found in surface waters throughout the United States. Waterborne cryptosporidiosis outbreaks may be associated with contaminated drinking water supplies. The approved method, USEPA (United States Environmental Protection Agency) Method 1623, for testing for the presence of Cryptosporidium in United States surface waters has several limitations. Firstly, recovery efficiency varies widely. Secondly, Method 1623 does not specify a mechanism for assessing the viability and infectivity of oocysts detected, or the Cryptosporidium species of the oocysts. Lastly, there are logistical limitations which are relevant to Method 1623 in particular, and to the state of the science of Cryptosporidium testing in general. Methods that give specific results more quickly, with higher recoveries and better consistency must be developed and made accessible for utilities to use. Improved Cryptosporidium testing methods can minimize uncertainty; this, in turn, will simplify the risk communication task, and the level of trust which the public has in the water utility can be maintained and improved. This paper reviews the current and ongoing research on analytical, monitoring, and sampling methods for Cryptosporidium, and identifies the needs that should be considered in future research.
Access and competition in the water industry
Authors: Wills-Johnson Nick , Lowdon Alan , Bell Hudson
Published: May 2018

Access regimes, coupled with entry in the contestable sectors of the relevant industries, have facilitated substantial competition in the electricity and gas industries in many countries, but water has yet to benefit from such competition. In the UK, access codes in the water industry have been in place since September 2000, and a bill is currently before the UK Parliament to open the retailing and abstraction sectors of the water industry to competition. Will the UK, and other countries which subsequently follow it in reform, be likely to see substantial increases in competition in the water industry as a result of these reforms? This paper argues that it will not, as water is an economically different product to electricity and gas, with few of the attributes inherent in electricity and gas which have attracted entry to the competitive sectors of these industries. Moreover, potential environmental externalities associated with access regimes in water, but not in electricity and gas, suggest caution before establishing comprehensive access regimes in water.
Has widening participation in decision-making influenced water policy in the UK?
Authors: Page Ben
Published: May 2018

This paper addresses public participation in debates over service quality in the water sector in England and Wales. It is argued that just at the moment when the British Government claims to be interested in getting stakeholders to participate in policy debates there are important questions arising about the future of the UK water industry in relation to commercial restructuring and increasing competition. The paper looks at two strategies for fostering public participation. First, it analyzes the structures established in 1989 and reformed in 2002 to represent consumers within the regulatory framework. It is argued that, as the institutions of consumer regulation have evolved, they have adopted fairly traditional strategies for influencing the Government's policy decisions that do not really accord to current theoretical models of stakeholder participation. Second, it analyzes the public consultation exercises run by the Water Services Regulator Ofwat (The Office of Water Services). The conclusions are based on a study of 35 recent consultation exercises carried out by Ofwat. The study analyzed 1250 responses to see which stakeholders were participating in consultation and then used questionnaires to identify how they perceived the consultation process. Most stakeholders were skeptical about the impact of consultation on Ofwat policy. Instead they regarded consultation as one strategy amongst the many which they used to try and steer policy in their own interest.
Efficiency effects of “privatization” in Argentina’s water and sanitation services
Authors: Estache Antonio , Trujillo Lourdes
Published: May 2018

This paper provides a “back-of-the-envelope” assessment of the efficiency effects of the reforms of the water sector in Argentina. Private operators are now key players in 15 of Argentina's provinces. While all have adopted incentive based regulatory regimes which require estimates of economic efficiency changes, none have actually issued any estimate yet. This paper provides upper bounds estimates of efficiency gains achieved for four operators. The paper concludes with a discussion of the implication of the results for regulatory accounting and data collection processes by regulators in developing countries relying on incentive based regulatory systems.
Shared watercourses in the Southern African development community: challenges and opportunities
Authors: Salman Salman M. A.
Published: May 2018

The countries of the Southern African Development Community (SADC) are characterized by sharp variations in size, population, economic development, as well as water availability. The SADC region is, by and large, arid or semi-arid, and as a result faces tremendous challenges in its water sector. The challenges stem from a number of factors, including the high rate of population growth, urbanization and environmental degradation. Those problems are compounded by periodic floods and droughts. Moreover, the region depends, to a considerable extent, on river waters, most of which are shared by two or more states. As such, those shared rivers could be a source of conflict as well as a catalyst for cooperation. This article examines the water resources problems of SADC, with particular emphasis on its shared watercourses, and analyzes the problems therein and the attempts to deal with them.
Lack of influence of climate on present cost of water supply in the USA
Authors: Kirshen Paul H. , Larsen Andrea L. , Vogel Richard M. , Moomaw William
Published: May 2018

Previous studies have sought to develop econometric models of water supply systems, which can be used to predict future water supply costs; none, however, have investigated the influence of climatic factors. In this paper, climatic and other regional influences on the costs of water supply in the USA are explored using multivariate analysis of water supply costs from water supply utilities located throughout the USA. Results showed that over 90% of the variation in present water supply capital and operating costs for surface and ground water systems can be explained by variations in quantity of water delivered, with other variables, particularly regional climate, playing a negligible role. An analysis of the historic development of water supply in the USA showed that capital expenses for water supply systems are a relatively small component of the present total annual costs because: (1) the original capital expenditures were reduced for utilities due to large public subsidization; (2) repayment of capital expenditures is now complete owing to the long time period since the original investments; and (3) new policies encourage demand management instead of supply expansion. Therefore, the present costs of water supply are not related to climate and thus are not a useful guide to future costs in studies that evaluate climate change impacts.
Challenges for water sector reform in transition economies
Authors: Davis Jennifer , Whittington Dale
Published: May 2018

This paper discusses the practical problems of implementing water policy and pricing reforms in transition economies by looking at the case of Odessa, Ukraine. Chief among the policy advice for the water and sanitation (W&S) sector in less developed countries is greater cost-sharing by customers through increased service prices, with the goals of encouraging more efficient water use by users, promoting a greater perceived stake among customers in the health of their W&S systems and enabling service providers to maintain and expand their networks as needed. While appropriate for much of the developing world, this policy advice has had limited applicability for many communities in transition economies. The complex existing water supply infrastructure in much of Central and Eastern Europe, along with residents' low effective demand for high-quality service, create an environment in which typical price reform strategies will initially be a minor component in sector reform efforts. We use the case of Odessa, Ukraine, to discuss the reasons why traditional advice on water pricing has been of limited use in the region.
Performance of a rural multi-stage filtration plant after its handover
Authors: Dorea C. C. , Clarke B. A. , Bertrand S.
Published: May 2018

This paper reports on the performance of a multi-stage filtration (MSF) system and associated operational details two years after its handover to the local water association (Regie) in Nyabwishongwezi, Rwanda. During a shortterm study period the Nyabwishongwezi Water Treatment Plant (WTP) was monitored for turbidity, suspended solids and faecal coliform removals. Results indicated that although the quality of the product water did not comply with WHO guidelines, it was still aesthetically much more acceptable than the source water (River Umuvumba). Despite operational difficulties, the Regie continues to run the system and serve local communities in this rural area of Africa. The relative success of the Nyabwishongwezi Regie contrasts dramatically with the experiences of the nearby communities served by the Ntoma WTP that reportedly only worked for two days. Two years after the Nyabwishongwezi plant handover several problems have been identified and discussed with the Regie.
Water institutional reforms in Namibia
Authors: Heyns Piet
Published: May 2018

After years of colonial rule and a long struggle to end external administration, Namibia became independent in 1990. The realization of political reform within a modern democratic framework has called for wide-ranging reforms in all sectors of the economy to which the water sector is not an exception. Institutional reforms in the water sector were undertaken with an overall aim of introducing integrated water resources management as a durable solution to the water challenges of the arid environment prevailing in Namibia. The reforms included the development of a new national water policy, the preparation of draft legislation, and new organizational changes to develop, manage and regulate activities in the water sector. Although institutional reforms in the water sector are necessary to meet the demands of a new nation, they cannot succeed without the required level of skill and capacity both within and outside water administration. While it is relatively easier to formulate new policies, promulgate legislation and create new organizations, it is very difficult for an emerging country to develop quickly the human capacity necessary to handle the reforms, especially when inadequate funding constraints create a conflict between resource development and capacity building.
Water resources management in the Nile basin: the economic value of cooperation
Authors: Whittington Dale , Wu Xun , Sadoff Claudia
Published: May 2018

Since 1999 a multilateral effort termed the Nile Basin Initiative has been underway among the Nile riparians to explore opportunities for maximizing the benefits of the river's waters through cooperative development and management of the basin. However, to date there has been virtually no explicit discussion of the economic value of cooperative water resources development. We believe that a serious discourse among Nile riparians about the economics of Nile cooperation is both inevitable and desirable, and that this discourse will not diminish the importance of environmental, social, or cultural issues that new infrastructure on the Nile will entail. To initiate such a discussion, in this paper we present the results of the first economic model designed to optimize the water resources of the entire Nile basin. Total (potential) annual direct gross economic benefits of Nile water utilization in irrigation and hydroelectric power generation are estimated to be on the order of US$7–11 billion. This does not account for the costs of building or operating the infrastructure.
What water managers need to know about public participation: one US practitioner's perspective
Authors: Creighton James L.
Published: May 2018

Increasingly, public participation is a precondition for water management decision making. In the USA, water management agencies have been utilizing public participation since the early 1970s, with varying degrees of success and commitment to the process. Some of the US experience may not be transferable to other countries or other cultures. But the author describes basic lessons he believes are fundamental to effective public participation in virtually all countries and situations.
Water in the Middle East revisited: conflict management alternatives
Authors: El-Fadel M. , El-Fadl K.
Published: May 2018

Water resources have been the source of political tension across continents including the Middle East – the region located in southwestern Asia renowned for its arid climate and water scarcity. A multitude of economic, social, cultural, environmental and political issues govern current water sharing policies in this region where politics appears to be the most prominent and influential factor for water allocation. In fact, water allocation along international rivers in the region is largely determined by political power. Past and recent experiences indicate that the complex and politically sensitive issues of international watersheds cannot be resolved unilaterally, but rather require a genuine cooperation and commitment between countries, in addition to an understanding and acknowledgement of each others' needs. This paper revisits adjustments at the national and international levels geared towards the resolution of water disputes in the Middle East with the ultimate goal of promoting regional consensus for the integrated development of various watersheds.
Free basic water in Msunduzi, KwaZulu-Natal: is it making a difference to the lives of low-income households?
Authors: Smith Julie A. , Green J. Maryann
Published: May 2018

South Africa's past apartheid inequities create unique challenges in achieving water delivery goals. The South African government implemented the free basic water (FBW) policy in July 2001 to ensure all South Africans had access to a basic amount of safe water by 2004. The FBW policy entitles all people to a free lifeline supply of 6000 ls/6 kilolitres (kl) (1 kl = 1000 l) of water per household per month. Despite being heralded as a way of ensuring access of lifeline water services to low-income households, fundamental policy flaws exist. The FBW allocation does not meet the basic water requirements and special water requirements of the majority of low-income households. Low-income households require more than the 6 kl allocation and are thereby expected to pay the full cost for their water service. The affordability crisis has not been addressed as tariff structures and cross-subsidisation mechanisms remain inadequate. The financial sustainability of the FBW policy is reliant on the equitable share, an unconditional grant from national government and user-fees, which the extensive low-income sector cannot afford to pay. The FBW policy is analysed, via a case study, conducted in Pietermaritzburg, KwaZulu-Natal, within the Msunduzi municipal jurisdiction, which draws on low-income household experience of the policy.
Analysing industrial water demand in India: An input distance function approach
Authors: Kumar Surender
Published: May 2018

This study investigates the water demand of Indian manufacturing plants. It adopts an input distance function approach and approximates it by a translog form. Duality between cost function and input distance function is exploited to retrieve information concerning substitutability and the shadow price of water. The model is estimated using a linear programming approach on a sample of 92 firms over three years. The results show that the average shadow price of water is 7.21 Rupees per kilolitre (Rupees/kl) and the price elasticity of derived demand for water is high, −1.11 on average, a value similar to that found by other researchers working in developing countries (for example, China and Brazil). This indicates that water charges may be an effective instrument for water conservation.
The role of solution chemistry in the stability and detachment of cohesive kaolinite particles
Authors: Ravisangar V. , Brouckaert B.M. , Amirtharajah A. , Sturm T.W.
Published: May 2018

The effect of solution chemistry on the behavior of kaolinite in three different situations was investigated: (1) the detachment of kaolinite from glass beads in a fluidized bed, (2) the erosion of kaolinite deposits in a laboratory flume and (3) the determination of the stress-strain rate relationship of concentrated suspensions in a rheometer. The experimental results from these three different approaches could be explained in terms of changes in mode of particle associations which in turn could be characterized in terms of a micromechanical force model which predicts the effect of solution chemistry on the interaction force between adjacent particle surfaces. Understanding the relationship between solution and surface chemistry on the structure, mechanical strength and mechanism of erosion of cohesive sediment deposits is an important step towards developing predictive models of a number of processes including erosion of cohesive sediments in streams and estuaries, and detachment of particles from granular media during filtration and filter backwashing.
Enhanced coagulation of surface waters with high organic content by permangante preoxidation
Authors: Ma J. , Li G.B. , Chen Z.L. , Xu G.R. , Cai G.Q.
Published: May 2018

Laboratory and full-scale experiments were conducted for enhancing the coagulation of stabilised surface waters with high organic content by permanganate preoxidation. It was indicated that permanganate preoxidation enhanced both the processes of coagulation and filtration of selected surface waters, River Songhua water, Qitaihe Reservoir water and Ba Reservoir water. Permanganate preoxidation is especially effective for enhancing the coagulation of very stable surface waters with relatively high organic content. Experimental results showed that the manganese dioxide produced in situ during permanganate preoxidation played an important role in enhancing the coagulation and filtration processes. The experimental results suggested that manganese dioxide may adsorb naturally occurring organic materials through surface bonding to form bigger particulates, thus increasing the floc density and improving the removal of organic particulates and possibly the inorganic fine particles. Manganese dioxide was shown to adsorb humic acid and enhance its removal by filtration.
Mathematical simulation on accumulation process of a blooming plankton Peridinium bipes (Dinophyceae) in a dam reservoir
Authors: Kishimoto N. , Somiya I. , Ohnishi Y. , Nakamura T.
Published: May 2018

The accumulation process of the blooming plankton Peridinium bipes was studied in this paper using a mathematical model based on a horizontal one-dimensional multi-layered flow model coupled with a vertical migration model of the Peridinium bipes community. The estimated accumulation process consisted of three processes: upward swimming and dispersion of Peridinium bipes cells, advection of the cells with the countercurrent of surface water, and entrainment and effluent of the cells with the plunging flow of inflow river water. The numerical analysis has revealed that the accumulation process helps Peridinium bipes to avoid hydraulic washout and it contributes to a contributes to a concentration of Peridinium bipes cells on the upper side of the reservoir.
Field measurement and modelling of two-dimensional river mixing
Authors: Putz G. , Smith D.W.
Published: May 2018

Wastewater treatment facilities commonly discharge effluent to large receiving streams. An effluent plume may easily extend for many tens of kilometres downstream of a discharge point. A characteristic of the effluent plume is the existence of significant transverse concentration gradients in the river as the discharged effluent slowly mixes with the river water. Within this two-dimensional, transverse mixing zone accurate delineation of the effluent plume is essential for water quality monitoring and for management of the receiving stream. The capability to mathematically model two-dimensional river mixing and to predict effluent plume concentrations is a valuable tool for water quality management. An overview of two-dimensional river mixing theory is presented. Tracer methods for delineating effluent plumes resulting from continuous or transient input to rivers are described, and the results of tracer studies conducted on the Athabasca River in western Canada are presented. A computer modelling procedure for simulating two-dimensional river mixing is described. Application of the model is explained and comparison of model output to measured tracer concentrations is presented.
Development of an on-line chlorine sensor for water quality monitoring in public distribution networks
Authors: Gobet J. , Rychen P. , Madore C. , Skinner N. , van Buel H. , Jaggi F.
Published: May 2018

A new on-line free chlorine sensor based on a microdisc electrode array is presented. The sensor is microfabricated using microelectronic-based processes. Sensor characteristics include a good linearity in the 0-1 mg/l range, a sensitivity of 13 nA/(mgCl2/l) with a detection limit of 0.02 mg/l of free chlorine. The sensor response has a low pH and flow dependence. A very good stability over 4 weeks of continuous use in drinking water is demonstrated. Mounted on an automatic control valve the sensor will offer the possibility to monitor and control the water quality in a distribution network.
Toxic cyanobacterial blooms in a drinking water reservoir - causes, consequences and management strategy
Authors: Tarczyńska M. , Romanowska-Duda Z. , Jurczak T. , Zalewski M.
Published: May 2018

Eutrophication of reservoirs used for drinking water supplies is a very common problem, particularly in lowland reservoirs. Long water retention time (60-120 days) favours cyanobacterial bloom occurrence in Sulejów Reservoir, Poland. The localisation of the water intake in a bay exposed to north-east winds favoured the Microcystis bloom accumulation, which formed a 0.5 m thick dense scum for the first time in September 1999. Cyanobacterial hepatotoxins can pose a potential health problem because the presence of about 0.8 μg/l microcystins was detected in drinking water during three series of analysis. An investigation of the efficiency of each stage of water treatment processes in the elimination of microcystins showed that pre-chlorination, coagulation, and rapid sand filtration were ineffective in removing microcystins from water. Significant elimination was observed after ozonation and chlorination. The concentration of microcystins in bloom material was between 12 to 860 μg/g dry weight of phytoplankton biomass. Management strategies for reservoirs should consider the important role of ecohydrological processes, which are often very easy to regulate, and which can be useful for bio-manipulation of the water ecosystem.
Trichloroanisole kinetics and musty tastes in drinking water distribution systems
Authors: Piriou P. , Malleret L. , Bruchet A. , Kiéné L.
Published: May 2018

Trichloroanisoles (TCA) might contribute to several unsolved earthy-musty taste episodes, because their taste threshold concentrations are lower than the CLSA GC-MS detection limit. The relative importance of such taste-causing compounds in earthy-musty taste episodes in distribution systems was investigated by combining lab-scale and water aging experiments in a pipe loop pilot. Experiments showed that earthy-musty taste associated with TCA formation can easily occur in distribution systems and is linked mainly to fungi metabolism. By maintaining chlorine residual, a control of such tastes can be achieved. The masking effect of these earthy-musty tasters induced by TCA by chlorine is not very effective.
Assimilable organic carbon and biodegradable organic carbon removal by nanofiltration: full and bench-scale evaluation
Authors: Escobar I.C. , Randall A.A. , Hong S.K.
Published: May 2018

The main objective of this research was to evaluate the effectiveness of nanofiltration (NF) at full and bench scale for controlling AOC and BDOC, which are the main indicators of biological stability of the finished potable water. One of the major observations from full-scale operation was that nanofiltration was a very effective means to reduce BDOC, but conversely, did not reject a significant fraction of AOC. The high BDOC rejection by nanofiltration (NF) membranes at full scale can be explained by size exclusion, since a significant fraction of BDOC consists of compounds, such as humic and fulvic acids, which are larger than the pores of NF membranes (molecular-weight cutoff ≈200 daltons). The insignificant AOC rejection observed in full-scale systems was probably due to the low pH, high hardness, and high ionic strength (TDS) of the raw water. Bench scale tests using simulated waters clearly demonstrated that AOC removal by NF membranes decreases markedly with decreasing pH, and increasing hardness and ionic strength, implying that electrostatic repulsion plays a significant role in AOC removal mechanisms. These solution environments repress the electrostatic interaction between charged organic compounds and membranes, allowing passage of small molecular weight compounds and thus reducing AOC rejection.
Fouling mechanism of hollow fiber ultrafiltration membrane with pretreatment by coagulation/sedimentation process
Authors: Minegishi S. , Jang N.-Y. , Watanabe Y. , Hirata S. , Ozawa G.
Published: May 2018

The fouling mechanism of the hollow fiber UF membrane with a pretreatment by coagulation/sedimentation process was investigated. The experiments were carried out in three different feed water conditions: river surface water, coagulated water containing micro flocs and clarified water from the coagulation/sedimentation process. The river water contained a lot of suspended particles (high turbidity) and natural organic matter (NOM) such as humic substances. From analysis of the data obtained in the three membrane processes, the mathematical model expressing the change of the filtration resistance is proposed and proved, which includes the pore size distribution of the membrane. The effect of DOC and DOC/E260 on the membrane fouling was also discussed. The analysis of the pore size distribution change with increasing filtration time suggests that the primary mechanism of the fouling is the decrease in the pore number by the high molecular weight humic substances. As a result of experiments and mathematical model analysis, it could be concluded that the coagulation/sedimentation pretreatment process was very effective for expanding ultrafiltration membrane life, because the coagulation/sedimentation process could remove the primary foulants such as high molecular weight humic substances.
Applying CFD modelling in order to enhance water treatment reactors efficiency: example of the ozonation process
Authors: Do-Quang Z. , Cockx A. , Laîne J.M. , Roustan M.
Published: May 2018

Disinfection/oxidation processes are a major step in the water treatment train. As high levels of inactivation or removal of pathogens and micropolluants are aimed at the design and optimized operating conditions are crucial issues for the reliability of the treatment and cost control. In this context, using computational fluid dynamics allows better evaluation of the efficiency of the treatment and guarantees its performance prior to full-scale design. Examples are given in this paper of the capability of the numerical tool in order to propose an optimized solution for a refurbishment or a new plant design. The full-scale realization confirmed the predicted quality benefit.
Chemical aspects and by-products of electrolyser
Authors: Cho J. , Choi H. , Kim I.S. , Amy G.
Published: May 2018

The electrolyser is a disinfection device consisting of a series of porous graphite plates through which water flows while low voltage and current are applied. This electrolyser had been demonstrated successfully for efficient microbial (coliform bacteria, bacteriophage, Giardia, and Cryptosporidium) inactivation before this study. In this study, chemical aspects were evaluated in terms of the formation of disinfectants and/or oxidants as well as disinfection by-products (DBPs) during the disinfection by the electrolyser. Experiments were performed under constant electrolyser conditions but variable water quality conditions (electrolyte type and concentration, dissolved organic carbon, bromide ion (Br-) and, to an extent, pH). It was shown that disinfectants and (chlorinated or ozonated) DBPs could be measured successfully for the effluent samples from the electrolyser. Chlorination by-products did not pose any problem in compliance to drinking water regulations, while bromate and chlorate (ozonation by-products) were shown to be formed at levels near their respective regulation levels, but only under extreme water quality conditions.
Combination of coagulation and ultrafiltration for drinking water production: impact of process configuration and module design
Authors: Guigui C. , Bonnelye V. , Durand-Bourlier L. , Rouch J. C. , Aptel P.
Published: May 2018

The in-line coagulation/ultrafiltration (UF) combined process has been studied in order to improve membrane performance for the treatment of surface water with high organic content. Ultrafiltration experiments were performed using cellulose derivative hollow-fibre membranes with ferric chloride as coagulant. The efficacy of adding coagulant just before the membrane module depends on the filtration mode, the process configuration and the module design. In dead-end mode, permeation flux of 70 l/hm2 can be maintained, but high backwash frequency (low recovery) is necessary to prevent plugging. Cross-flow filtration was effective in reducing fouling and allows operation at higher permeation flux. In cross-flow filtration, the feed-and-bleed configuration (single stage continuous process) appears promising to reduce backwash frequencies: for a recovery of 95% and at a permeation flux of 120 l/h.m2, quasi-steady transmembrane pressure can be maintained with a low fouling rate (10 kPa in 400 min.). In cross-flow filtration, the use of curved modules with Dean vortices reduces the fouling rate by a factor of 2 compared with a conventional straight module.
Enhanced pre-coat engineering (EPCE) for micro- and ultrafiltration: the solution for fouling?
Authors: Galjaard G. , van Paassen J. , Buijs P. , Schoonenberg F.
Published: May 2018

The feasibility of ultra- and microfiltration depends strongly on the achieved net flux. Direct treatment of surface water frequently results in low net fluxes and high cleaning frequencies. Experiments have been conducted at constant flux on surface water with an ultrafiltration pilot plant with direct filtration, in-line coagulation and pre-coating (EPCE) with ferric hydroxide flocs. The aim was to control and reduce the rate of fouling. With the use of a pre-coat at the beginning of the filtration cycle a stable ultrafiltration process was obtained. This is contrary to the use of in-line coagulation and direct filtration which resulted, due to a very high fouling potential of the feed water, in high fouling rates at low fluxes. The result of this exploratory research is an important step towards a higher feasibility of micro- and ultrafiltration.
A novel biofilm-membrane reactor for advanced drinking water treatment - pilot scale study
Authors: Kimura K. , Watanabe Y. , Ohkuma N.
Published: May 2018

The authors have proposed a novel biofilm-membrane reactor (BMR) in which nitrifying biofilm is fixed on the surface of the rotating membrane disk. With this reactor, both strict solid-liquid separation and oxidation of ammonia nitrogen can be simultaneously performed. Based on the knowledge obtained in the previous experiments with the bench-scale equipment, a pilot scale study was conducted using river water at a water purification plant. The results obtained in the pilot study can be summarized as follows: (1) A pilot scale BMR worked successfully even with the water from an actual drinking water source. By implementation of pre-treatment (coagulation and sedimentation), the filter run could be continued for more than 8 months without any chemical washing. (2) The sponge cleaning developed in this study was found to be very effective. This indicates that the accumulated cake resistance is dominant in the practical situation. (3) Sufficient nitrification was observed when water temperature was high. (4) In addition to the nitrification, biological oxidation of AOC and manganese can be expected with the BMR. In this study, both AOC and manganese concentration in the permeate decreased to a level less than 10 μg/L.
A study on the PP hollow fiber membrane contactor and its performances for removing ammonia from wastewater or mixed gas: I. Removal and recovery of ammonia from wastewater
Authors: Xu Y. , Wang J. , Xu Z. , Xu H.
Published: May 2018

Recent research indicated that hydrophobic microporous hollow fiber membrane Contactor could be used to separate volatile contaminants from wastewater efficiently. The factors that influence the effect of separation of NH3/H2O are investigated carefully. It is found that the average diameter of micropores, porosity and gas penetration rate of polypropylene (PP) hollow fiber membrane are maximized synchronously at draw elongation 260%. The modules assembled with this PP hollow fiber membrane have good performance for separation of NH3/H2O. It is found that the overall mass transfer coefficient (K) only is dependent on the temperature and flux of ammonia solution and independent of the pressure and concentration of ammonia solution. Concentration of absorbing acid influences slightly the overall transfer coefficients K while the absorbent supply is sufficient. Under this condition, the relationship between transfer coefficient and raw ammonia water flow rate can be described using the Sieder and Tate equation. K is directly proportional to v1/3 (v stands for the flow rate of ammonia solution). The removal rate of NH3 was about 96-98% in the lab. Further industrial tests have been carried out individually in catalyst and chemical fertilizer factories to treat wastewater containing ammonium, whose concentration ranged from 1000-10,000g/m3. Wastewater treatment amount was 9.6 m3/day and 24 m3/day in catalyst and chemical fertilizer factories respectively. Average removal rate of NH3 was 93.5% during 5 months of continuous operation in the catalyst factory. The fouling is not heavy because the wastewater containing ammonia did not pass through the membrane wall. It is efficient to get rid of membrane fouling by washing the membrane with dilute acid and the cleanout period was 3 days. PP hollow fiber membrane can be produced by the melt-spinning and drawing method. This paper also investigates the relationship between processing condition of PP hollow fiber membrane and its structure and performance.
Iron and manganese removal by a membrane filtration system
Authors: Jimbo Y. , Goto K.
Published: May 2018

The design standards of the iron and manganese removal system by membrane filtration were investigated. The membrane filtration after pre-chlorination could remove iron completely and could remove around 70% of manganese. In the case of manganese concentration being more than 0.05 mg/l, the membrane filtration could remove them completely after the deposition in the oxidation tank. The concentrations of iron and manganese were reduced more than 90% by the oxidation tank and were reduced until under the detection limit after the membrane filtration. The economic comparisons between the rapid sand filtration system and this membrane filtration system in a small capacity and a middle capacity were investigated. The 15 years total costs of the membrane filtration system were estimated to be smaller than or around equal to the rapid sand filtration system in both capacities.
The dewatering of a mining sludge containing hexavalent chromium using a tubular filter press - a South African development
Authors: Coopmans E.J.A. , Schwarz H.P. , Pryor M.J.
Published: May 2018

A chromium smelting process can result, under oxidising conditions, in the production of a dust which when slurried and pumped to a waste dump heap is likely to pollute the environment. South Africa is a large producer of chromium metal and the problem of the release of hexavalent chromium (Cr6+) to the environment is a serious concern. The department of Water Affairs and Forestry in South Africa monitors all environmental discharges and regulate the levels of toxic chemicals and pollutants. The ‘Tubular Filter Press’ a South African developed sludge dewatering system was proposed for the recovery of dust in this effluent. The filter press was operated for the dewatering of waterworks sludges and promises to be successful for this application. A single tube pilot study shows that chromium discharge to the environment can be eliminated. Feed solids concentrations of between 40 and 50 g/l were fed to the tubular filter resulting in cake solids concentrations in excess of 50%. The operating pressure of the system was between 200 and 300 kPa and the flux reduced to 200 L/m2.h during the filtration cycle. The filtration was modelled using a variable pressure, internal cylindrical compressible cake filtration model and operating parameters for a full scale plant were proposed.
Removal of natural organic matter - a fresh approach
Authors: Drikas M. , Morran J.Y. , Pelekani C. , Hepplewhite C. , Bursill D.B.
Published: May 2018

Natural organic matter (NOM) has been shown to be one of the major parameters that affects water quality and treatment processes. NOM reduces the effectiveness of water treatment by interfering with the flocculation process, makes treatment with activated carbon and membrane filtration less efficient and is a precursor to the formation of disinfectant by-products (DBP). Furthermore, NOM acts as a food source for micro-organisms resulting in bacterial regrowth in distribution systems. These concerns have resulted in the removal of NOM from raw water being of prime concern for water authorities. The elevated levels of NOM in Australian water supplies have resulted in priority being given to research into methods of removing NOM by the Australian Water Quality Centre (AWQC). Early work showed that some types of anion exchange resins were very effective for NOM removal and that while resin column systems were rapidly fouled by waters with high concentration of suspended matter, a stirred system had no such limitation. This lead to the development of a resin with a high adsorptive capacity for NOM by the Commonwealth Scientific & Industrial Research Organisation (CSIRO) in collaboration with the AWQC which will be manufactured under licence by Orica Australia Pty Ltd. This resin then formed the basis for a novel process for NOM removal developed by the AWQC in collaboration with Orica Australia Pty Ltd. Both the MIEX® resin and process have been patented internationally. This paper outlines the process, gives examples of some of the benefits and provides recent results from an operating pilot plant with a capacity 160 kL/day.
Modelling of drinking water treatment processes within the Stimela environment
Authors: van der Helm A.W.C. , Rietveld L.C.
Published: May 2018

Drinking water production plants (in The Netherlands) are normally controlled by effluent quality. When the effluent quality does not meet the guidelines, the treatment process is manipulated. This is mainly done using the experience of the operators. Water quality models can be used to support the operators' task by off-line process evaluation and model predictive control (MPC).

Stimela is a modelling environment that is developed by DHV Water BV and the Delft University of Technology. It is especially designed for water quality modelling. An example of off-line use of Stimela for operation and design is given by a model of a counter-current packed tower aerator.

In the near future Stimela will be used for MPC. Therefore DHV Water BV and the Delft University of Technology are starting a project with water companies in which MPC with Stimela will be applied. In this project internet technology will be used to access water quality data from online measurements and form the model calculations. The data can be used by operators when they are at other locations, by drinking water technologists at the office to analyse specific problems, and by the management for weekly, monthly and yearly reports. In this way all the data are available for everyone in the organisation, from the operator to the managing director.
Spores of sulphite-reducing clostridia (SSRC) as surrogate for verification of the inactivation capacity of full-scale ozonation for Cryptosporidium
Authors: Hijnen W.A.M. , van der Veer A.J. , van Beveren J. , Medema G.J.
Published: May 2018

The inactivation of C. parvum and spores of Cl. perfringens by ozone treatment in natural water in a lab-scale continuous-flow system was compared. In addition the inactivation of the natural occurring spores of sulphite-reducing clostridia (SSRC) in this water was monitored in one of the lab-scale systems as well as in a full-scale ozonation process. The survival ratio of C. parvum oocysts was determined using the CD-1 neonatal mouse infectivity test and for Cl. perfringens and SSRC the survival ratio was assessed with the standard anaerobic colony count on the iron-sulphite medium.

The results of the lab-scale experiments revealed an inactivation rate constant k (Chick-Watson modelling) at 10°C for C. parvum of 0.14 (SD=0.014; P<0.001) and for Cl. perfringens of 0.25 (SD=0.01; P<0.001). Moreover, first results of monitoring the SSRC inactivation in full-scale ozonation processes indicated that the inactivation rate constant for these wild strains was in the same order of magnitude as determined for Cl. perfringens. Further research is needed to compare inactivation ozone kinetics for Cl. perfringens D10 and SSRC at different temperatures and in other natural waters. Results of additional lab-scale experiments with Cl. perfringens strain D10 indicated that the CT of the gas-feed chamber should be incorporated in the design of a full-scale ozonation. Moreover, setting theCT with the contact time was not as effective for the inactivation capacity as setting the CT with the ozone dosage.