bluuebunny/crossref_metadata_2025 huggingface dataset:
A methodology to determine the effectiveness of water demand management measures in South Africa
Authors: Johnson E. , Bhagwan J.
Published: May 2018

The aim of this project was to develop a methodology to determine the effectiveness of Water Demand Management (WDM) and Water Conservation (WC) measures in developing regions and countries. The project, which was sponsored by South Africa's Water Research Commission, involved a critical examination of those applicable local (South African) conditions that guide the development of the methodology. Some of the specific challenges identified included the practical definition of linkage between the principle of increasing the supply of water through the implementation of WDM/WC measures and the unlimited needs of users, a strong culture of non-payment for water which limits the impact of economic measures, the overall lack of programmes for the repair and maintenance of water infrastructure as well as the increasing shortage of skilled human resources. Several existing related methodologies were examined in order to provide a historic and conceptual framework for the research. Selected WDM/WC case studies, both locally in South Africa and internationally, have provided useful insight during the development of the methodology. A pragmatic and easy to understand consolidated methodology has been developed that takes cognisance of the objectives of Integrated Water Resource Management (IWRM). The methodology is a consultative and consensus based approach assisted by numerous graphic based techniques, tools and examples.
Ultrasonic disinfection of wastewater effluents for high-quality reuse
Authors: Neis U. , Blume T.
Published: May 2018

Cavitation, induced by ultrasound at low frequencies, is an effective means for the disintegration of bacterial cells. Two effects can be observed: at low ultrasound doses bacteria flocs can be declumped by mechanical shear stresses, and at increased doses ultrasound cavitation has an impact on the cell walls such that they are broken. In lab scale experiments a horn sonotrode operated at 20 kHz was run in combination with a low-pressure mercury arc lamp to treat wastewater samples taken from the effluent of a municipal treatment plant. At low ultrasound intensities a drastic change in samples' particle size distribution was observed. Consequently, subsequent UV irradiation was far more efficient as the number of large particles which impede disinfection processes was minimised by the sonication. Hence, applied UV doses could be reduced notably to obtain the same or even better disinfection effects.
Secondary effluent disinfection by peracetic acid (PAA): microrganism inactivation and regrowth, preliminary results
Authors: Mezzanotte V. , Antonelli M. , Azzellino A. , Citterio S. , Nurizzo C.
Published: May 2018

The paper summarises - in terms of bacterial removal and re-growth - the results of a pilot scale study performed on a continuous flow pilot plant, using peracetic acid (PAA) as disinfecting agent. Trials were carried out with increasing doses and contact times (6, 12, 18, 36, 42, 54 min). The paper reports data deriving from the only doses (15 and 25 mg L-1) which were able to ensure the respect of the limits for agricultural re-use, according to Italian law. Disinfection efficiency was comparable for E. coli, TC and FC, and lower for total heterotrophic bacteria (THB), and clearly grew with increasing Cát values. The effect of contact time was greater at the lower doses. Microbial counts, performed by both traditional methods and flow cytometry, immediately and 6 hours after the sample collection (PAA was previously inactivated by sodium thiosulphate and bovine catalase), showed that no appreciable re-growth took place after 6 hours for coliform group bacteria. THB formed a slightly lower number of colonies immediately after collection than after 6 hours. The slight variations observed after 6 hours were the result of the recovered ability of forming colonies and of the lysis of some of the residual bacteria, as it was shown by flow cytometry.
UV disinfection of water: the need for UV reactor validation
Authors: Lawryshyn Y.A. , Cairns B.
Published: May 2018

Disinfection by ultraviolet light (UV) has received wide endorsement as an important contribution to the multiple barrier approach for protection of public health. UV can be used both to disinfect wastewater discharged to the environment, and to disinfect that water when it is picked up again for human consumption. UV readily blocks infectivity by such chlorine-resistant pathogens as Cryptosporidium parvum, Giardia lamblia and Legionella pneumophila. Multiple disinfectant use is now being discussed to broaden the spectrum of pathogens that can be inactivated by using disinfectants in their most strategically advantageous dose and function. Optimizing multiple barrier strategies requires attention to validation of the concepts and technologies involved. UV technology validation ensures that the equipment can deliver the target UV design dose, and that the monitoring/control technology modulates the dose appropriately with changes in water quality or operating conditions. The bioassay approach for UV reactor validation is recommended over analytical and numerical models. Analytical models, which provide an average dose estimate, have been shown to be inadequate. Numerical models, which utilize Computational Fluid Dynamics (CFD) and UV light intensity models to predict reactor performance, can be accurate when used by skilled professionals but require significant validation and/or calibration against bioassay data.
Reliability-based optimal design of water distribution networks
Authors: Aklog D. , Hosoi Y.
Published: May 2018

Maintaining network loops, and hence attaining acceptable system reliability, has been a challenge in the optimal design of water distribution networks. Aimed at a possible solution to the problem, this paper has two objectives: to introduce a new reliability-based optimal design formulation and a model, and to examine the effect of specifying minimum allowable pipe sizes during least-cost designs on system reliability. System reliability is estimated using the minimum cut-set method, but instead of using the mechanical failure probabilities of pipes, weighted failure probabilities are calculated by considering the ratio of the actual supply to demand. One of the salient features of this study and the new reliability-based design model in particular, is that a pressure-driven network simulation model is used to determine the actual supply at each demand point when a component fails. A simplified two-loop network is used to illustrate the performance of the new model and to study the effect of specifying minimum allowable pipe sizes. The results obtained show that the new model preserves loops and results in a system with better reliability; and, if appropriate, minimum allowable pipe sizes are specified in the least-cost design, a required reliability can be attained with a reasonably low cost.
Security and redundancy in trunk main distribution networks
Authors: Wallen A. , Woodward T. , Powell R.
Published: May 2018

A methodology is being developed that may be incorporated in a hydraulic network modelling tool to analyse redundancy in the trunk main network of a water distribution system. A rigorous definition of the terms redundancy and security are given in this paper. Redundancy in the trunk main infrastructure is assessed in terms of supply security, which is the probability of water of adequate pressure, quality and appearance reaching the demand nodes. Supply security is increased by providing multiple supply routes to demand nodes so that there is minimal supply interruption in the case of failure of a network component.

This paper presents a method that evaluates supply security under network conditions caused by trunk main failures. The supply security level ensured by multiple pipe routes is compared with the costs of maintaining additional routes. Three indices are used as measures of the cost of additional infrastructure: network condition, water age and link failure probability. The fitness of a trunk main system is evaluated in terms of supply security and infrastructure costs. The system may then be modified using a genetic algorithm to create a population of reduced networks, from which infrastructure which may be redundant has been removed. The fitness of each reduced network is assessed, compared with the fittest network, and progressive generations are developed using the algorithm, until an improved network is selected.
Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model
Authors: Nagaoka H. , Nakano T. , Akimoto D.
Published: May 2018

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.
Prediction of chlorine and trihalomethanes concentration profile in bulk drinking water distribution systems from laboratory data
Authors: Kastl G. , Fisher I. , Jegatheesan V. , Chandy J. , Clarkson K.
Published: May 2018

Nearly all drinking water distribution systems experience a “natural” reduction of disinfection residuals. The most frequently used disinfectant is chlorine, which can decay due to reactions with organic and inorganic compounds in the water and by liquid/solids reaction with the biofilm, pipe walls and sediments. Usually levels of 0.2-0.5 mg/L of free chlorine are required at the point of consumption to maintain bacteriological safety. Higher concentrations are not desirable as they present the problems of taste and odour and increase formation of disinfection by-products. It is usually a considerable concern for the operators of drinking water distribution systems to manage chlorine residuals at the “optimum level”, considering all these issues.

This paper describes how the chlorine profile in a drinking water distribution system can be modelled and optimised on the basis of readily and inexpensively available laboratory data. Methods are presented for deriving the laboratory data, fitting a chlorine decay model of bulk water to the data and applying the model, in conjunction with a simplified hydraulic model, to obtain the chlorine profile in a distribution system at steady flow conditions.

Two case studies are used to demonstrate the utility of the technique. Melbourne’s Greenvale-Sydenham distribution system is unfiltered and uses chlorination as its only treatment. The chlorine model developed from laboratory data was applied to the whole system and the chlorine profile was shown to be accurately simulated. Biofilm was not found to critically affect chlorine decay. In the other case study, Sydney Water’s Nepean system was modelled from limited hydraulic data. Chlorine decay and trihalomethane (THM) formation in raw and treated water were measured in a laboratory, and a chlorine decay and THM model was derived on the basis of these data. Simulated chlorine and THM profiles agree well with the measured values available. Various applications of this modelling approach are also briefly discussed.
A methodology for assessing the operational potential of the urban wastewater system using integrated modelling
Authors: Zacharof A.I. , Schütze M. , Butler D.
Published: May 2018

Application of real-time control (RTC) is one possible measure to increase the performance of the urban wastewater system. However, the potential and the benefits of control depend strongly on the characteristics of the individual site under question. Conventionally, RTC potential is evaluated by performing a detailed feasibility study, which in some cases may conclude that for the given site real-time control does not have any significant potential. This can result in spending considerable precious resources for a detailed feasibility study only to identify the non-feasibility of RTC in the system.

It would therefore be desirable to have a methodology that allows simple, and cost-effective, screening of sites for which the analysis of real-time control may be beneficial. Earlier research has led to the provision of an easy-to-apply scoring system allowing a quick assessment of the RTC potential of controlling flow in sewer systems. However, as this procedure does not take into account water quality aspects, nor the treatment plant or the receiving water body, it cannot be used for assessing the potential of RTC of the complete system.

This paper describes the work of an on-going project aimed at establishing an enhanced procedure for assessing the real-time control potential for the entire urban wastewater system. This entails simulating many (partly hypothetical) case studies (varying several key parameters of the wastewater system) using the simulation tool SYNOPSIS. For each of these sites, several real-time control algorithms are developed and optimised, following a general procedure, which allows for local, global and integrated scenarios to be considered. Analysis of the results reveals those system parameters which are of particular significance to the RTC potential of urban wastewater systems. Furthermore, it is recognised that there is considerable uncertainty associated with modelling of such a large and diverse system and a framework is developed for incorporating this in the RTC potential screening tool. Finally, further work is currently underway in broadening the number of case study simulations and developing more complex approaches to quantifying and propagating uncertainty in the model.
Heavy metal tracers for the analysis of groundwater contamination: case study in Hanoi City, Vietnam
Authors: Nga T.T.V. , Inoue M. , Khatiwada N.R. , Takizawa S.
Published: May 2018

Groundwater quality data taken in August and December 2000 revealed that the groundwaters in Hanoi are contaminated by arsenic (up to 110 μg/l), iron (up to 32 mg Fe/l), organic matter (DOC up to 12 mg/l), and ammonia (up to 29 mg-N/l). Data on trace metals, as well as conventional water quality parameters such as pH, ORP, major cations and anions, were used to analyse groundwater flow and the mechanisms of groundwater contamination using multivariate data analysis methods. The results of Cluster Analysis (CA) demonstrated that the groundwater flow and characteristics were separated into three different zones, namely the Riverain zone, the Northwest zone, and the South zone where the highest levels of arsenic, iron, organic matter and ammonia were detected. Principal Component Analysis (PCA) showed strong correlation among two groups of trace metals: the first group includes Cd, Co, Mg, Mn, and Sr and these metals are considered to be leached out from rock minerals under moderately oxidizing conditions. The second group contains As, B, Ba, Cr, Cs, FeII, Mo, P, Pb, Rb, Ti, DOC and bicarbonate, and these are negatively correlated with SO42- and ORP, which indicates that these elements are eluted from organic matter and/or iron oxyhydroxide under anaerobic conditions. Further analyses of data obtained in the contaminated groundwaters by PCA and correlation between As and DOC suggest that there may be two possible mechanisms of arsenic release: reduction of iron oxyhydroxide and anaerobic degradation of organic matter in the peat layers.
Impact of a new legislation on the water market and competition in France
Authors: Brunet E. , Guérin-Schneider L. , Bonnet F.
Published: May 2018

In France, watr services are under municipal responsibility. They can be managed, either by municipalities themselves, or by private companies through delegation contracts. Whatever the situation is, water management remain under state control. The law of 29 January 1993 known as “Sapin Act” limits the duration of the contracts of delegation and imposes a procedure of publicity and consultation preliminary to their conclusion or their renewal. A study has been led from 1998 by our laboratory on the impact of this competition between private companies on the delegation contracts and their price. The main conclusions are the following:Including water and wastewater contracts, the procedure of competition led to an average fall of 10% of the price paid to the contractor. The most significant falls concern services of more than 20 000 inhabitants;If the global distribution of the contracts between the three major companies in this sector is not basically modified, one notes an increasingly marked presence of independent private operators;The duration of the contracts is in reduction, on average, from 17 to 11 years.

Then, it appears that the procedure instituted by the law of 29 January 1993 allowed a better exercise of competition between the private companies. The municipalities, mainly the smallest, encounter difficulties in the course of the procedure, and this is the reason why they expressed strong expectations in regard to the services of consulting. The progressive development of associations of municipalities makes it possible for the municipalities to obtain more favourable contractual conditions. This study makes it possible to follow the evolution of the number of procedures initiated pursuant to the law of 29 January 1993: nearly 300 in 1997, 582 in 1998 and 684 in 1999. In 2005, most of the 12,000 French contracts would have been renegotiated, a figure which shows the economical impact on water services.
Experiences in integrity testing ultrafiltration membranes at a large potable water treatment works
Authors: Oxtoby S.
Published: May 2018

The Clay Lane Water treatment works of Three Valleys Water, in the south east of England, is currently the world’s largest ultrafiltration works with a capacity of 160 Ml/d. It utilises ultrafiltration membranes constructed as hollow fibres with a number of membrane elements in a pressure housing. The plant has been operating since spring 2001. The decision to install the system was made in anticipation of the introduction of tighter regulations on Cryptosporidium in water supplies in the UK. Once a decision was made to proceed with a membrane system the ability to monitor the integrity of the system and to repair problems became a crucial design parameter that was a critical part of membrane selection. The need to include a system affected the design of the filtration units offered by manufacturers. The available systems for integrity testing are reviewed and the reasons for selecting the system adopted are discussed. These include particle counting and the dosing of test particulate loads. The different forms of air passage integrity tests are discussed and the displaced air flow system used is described. Once a failure has been detected it must be traced so that the fault can be repaired. This procedure is described together with the techniques of pin repair of damaged fibres. At Clay Lane and other membrane filtration sites the backwash water from membrane cleaning is recovered using a secondary membrane system. Currently the secondary system operates in the same integrity testing regime as the primary system and the secondary filtrate is returned ahead of the primary membrane system. The relative merits of this system, or the alternative of adding the recovered water to the filtrate are discussed.
Nanofiltration of colored surface water: Quebec's experience
Authors: Kouadio P. , Tétrault M.
Published: May 2018

Three colored surface water nanofiltration pilot-scale projects were conducted in the province of Quebec (eastern Canada), between November 2000 and March 2002, by the company H2O Innovation (2000) inc., for the municipalities of Lac Bouchette, Latulipe-et-Gaboury and Charlesbourg (now part of Quebec City). Results indicated that nanofiltration permeate quality has an advance on present drinking water regulation standard in Quebec, but important membrane fouling occurred. Fouling can be controlled by pretreatment and optimization of the operating conditions.
Application of ScaleGuard® at reverse osmosis and nanofiltration installations
Authors: Heijman S.G.J. , Folmer H. , Donker F. , Rietman B.M. , Schippers J.C.
Published: May 2018

ScaleGuard® is a continuous on-line monitor that detects scaling at an early stage when fed with the concentrate of a pilot- or full-scale plant. Scaling is observed in the ScaleGuard before it occurs in the full-scale installation. The ScaleGuard is used to optimize the recovery of two full-scale plants: one reverse osmosis plant treating pretreated surface water and one nanofiltration plant treating anaerobic groundwater. Based on the results of the ScaleGuard the conversion of both the reverse osmosis plant and the nanofiltration plant has been increased from 80% to 82%. The interpretation of the results of the ScaleGuard which was connected with the reverse osmosis plant was not unambiguous. This was due to the mass transfer coefficient decline in the ScaleGuard which could not be attributed to scaling. Results in the nanofiltration plant did not give room for any doubt. In addition, safe supersaturation ratios were derived from experience in pilot- and full-scale plants using anti-scalants for seven sparingly soluble inorganic compounds.
Minimization of membrane organic fouling and haloacetic acids formation by controlling amino sugars and/or polysaccharide-like substances included in colloidal NOM
Authors: Kwon B. , Lee S. , Gu M.B. , Cho J.
Published: May 2018

The objective of this study was to evaluate the effect of colloidal natural organic matter (NOM) on the disinfection by-products (DBPs) formation potentials and membrane organic fouling. From various analyses of a NOM-fouled ultrafiltration membrane surface, large amounts of colloidal NOM were found in the analyzed foulants. From FTIR spectra and pyrolysis analyses, colloidal NOMs were found to include amino sugars and polysaccharides, as indicated by N-acetyl groups in the FTIR spectra and from pyrolysis GC-mass analyses. Colloidal NOMs have two problematic aspects for membrane applications, which may induce bio-fouling due to their low biostabilities, and relatively high DBPs reactivities. The amino sugars and polysaccharides can be utilized by heterotrophic bacteria, and are identified as colloidal NOM with high fractions of biodegradable dissolved organic carbon (approximately 39%), so, their removal is expected to involve some form of biological pre-treatment process. Colloidal NOM also exhibit relatively high formation potentials of DBPs, especially haloacetic acids.
Membrane bioreactor configurations for enhanced biological phosphorus removal
Authors: Adam C. , Kraume M. , Gnirss R. , Lesjean B.
Published: May 2018

A membrane bioreactor (MBR) bench-scale plant (210 L) was operated under two different enhanced biological phosphorus removal (EBPR) configurations, characterised by pre- and postdenitrification mode. Both configurations were operated at 15 d SRT in parallel to a conventional WWTP and fed with degritted raw water. Effluent PT-concentrations were very stable and low between 0.05-0.15 mg/L for both configurations at sludge P-contents of 2-3%P/TS. In contrast to aerobic P-uptake with postdenitrification anoxic P-uptake clearly dominated in the pre-denitrification configuration. N-removal was surprisingly high with up to 96% in the post-denitrification system without resorting to any carbon addition. During P-spiking (influent: -­40 mgP/L) the P-content increased up to 6-7.5%P/TS. However, a significant amount of P-removal was due to adsorption and precipitation.
Aerated thermophilic biological treatment with membrane ultrafiltration: alternative to conventional technologies treating paper mill effluents
Authors: Lopetegui J. , Sancho L.
Published: May 2018

The European paper industry produces 70 million tons of paper annually, being one of the most water consuming industrial processes. The reduction in water use leads to partially recirculated water into industrial processes. This results in quality deterioration and a drop in productivity. Because of this, the socalled zero effluent operation has only been applied in a few papermills around Europe. Existing technologies usually operate within the mesophilic range. However, most of the mills work at a 50-70°C water circuit temperature range due to the positive effects on productivity and energy consumption. In this paper, a thermophilic aerobic treatment (55°C) combined with ultrafiltration is tested, this combination reaches mesophilic COD removal rates. Moreover, problems with water settleability under high temperatures are now avoided and the suspended solids free effluent gives water more possibilities of being reused.
Biological treatment of wastewater from fruit juice production using a membrane bioreactor: parameters limiting membrane performance
Authors: Blöcher C. , Britz T. , Janke H.D. , Chmiel H.
Published: May 2018

The application of a membrane bioreactor (MBR) was investigated to treat polluted process water from fruit juice processing. The aim was either direct discharge or further treatment by nanofiltration/low pressure reverse osmosis to produce water of drinking quality. The results of a one-year test operation of the process in industrial scale at a fruit juice production plant are presented. Focus was centred on the influence of activated sludge characteristics on membrane performance. Under the operating conditions in place, neither solids content, particle size distribution nor addition of nutrient significantly affected the permeate flux which was considerably lower than expected (based on municipal wastewater treatment with MBRs). Instead, evidence was obtained that the insufficient permeate flux was most likely due to the high content of extracellular polymeric substances. However, it was impossible to relate in detail the substantial flux variations during the test run to AS characteristics or changes in microbial population.
Arsenic removal by MF membrane with chemical sludge adsorption and NF membrane equipped with vibratory shear enhanced process
Authors: Yi S.-H. , Ahmed S. , Watanabe Y. , Watari K.
Published: May 2018

Conventional arsenic removal processes have difficulty removing low concentrations of arsenic ion from water. Therefore, it is very hard to comply with stringent low levels of arsenic, such as below 10 μg/L. So, we have developed two arsenic removal processes which are able to comply with more stringent arsenic regulations. They are the MF membrane process combined with chemical sludge adsorption and NF membrane process equipped with the vibratory shear enhanced process (VSEP). In this paper, we examine the performance of these new processes for the removal of arsenic ion of a low concentration from water. We found that chemical sludge produced in the conventional rapid sand filtration plants can effectively remove As (V) ions of H2AsO4- and HAsO42- through anion exchange reaction. The removal efficiency of MF membrane process combined with chemical sludge adsorption increased to about 36%, compared to MF membrane alone. The strong shear force on the NF membrane surface produced by vibration on the VSEP causes the concentration polarization layer to thin through increased back transport velocity of particles. So, it can remove even dissolved constituents effectively. Therefore, As (V) ions such as H2AsO4- and HAsO42- can be removed. The concentration of As (V) ions decreased from 50 μg/L to below 10 μg/L and condensation factor in recirculating water increased up to 7 times by using NF membrane equipped with VSEP.
Data envelopment analysis for assessing optimal operation of ultra-filtration systems for effluent polishing
Authors: Bick A. , Oron G. , Gillerman L. , Manor Y.
Published: May 2018

The scarcity of fresh water in most of the countries in the Mediterranean Basin makes treated wastewater a valuable alternative water source. The improved technology for the removal of particles, turbidity, bacteria and cysts from effluent, without the use of disinfectants is based on the use of membranes, mainly on micro-filtration (MF) and ultra-filtration (UF). Membrane treatment of secondary effluent sounds attractive since it is a stable water source. Pathogens, soluble organic matters, turbidity, color, parasites and viruses can be removed by UF membrane technology. Experiments are in progress in the commercial fields of Gadash Har Hebron Enterprise (GHHE), located near the City of Arad, Israel. Field data collected from a two-stage UF pilot plant (240 m3/day) enable us to provide performance estimate efficiencies based on the data envelopment analysis method. The research focused on individual UF experiments allowing us to determine the UF performance efficiency in terms of information quality for adequate decision-making. Field results are presented in order to support the theory and related pricing decisions.
Optimal uses of advanced technologies for water and wastewater treatment in urban environments
Authors: Weber W.J.
Published: May 2018

Steadily increasing requirements for recycle and reuse of water in urban societies present global challenges to our abilities to meet ongoing needs for water suitable for human consumption. Current practices of subjecting the total water demands of urban communities to the levels of treatment required for drinking water are not sustainable indefinitely, and viable alternative strategies for ensuring adequate supplies of potable water are essential. Given the inherent advantages of flexibility and responsiveness associated with decentralization of complex functions and operations, one logical alternative might be the strategic dispersal of flexible advanced treatment and control technologies throughout urban water transport and storage networks. Integration of multiple satellite systems of this type with the critical components of existing systems and infrastructures in densely populated urban environments would facilitate optimal cost-effective applications of highly sophisticated advanced technologies. It would, moreover, do so entirely within the context of water and waste treatment and distribution/collection systems and infrastructures already in place in most densely populated urban regions. Finally, it would provide markedly enhanced “personal water” quality and significant potential for energy recovery.
Compact high-rate treatment of wastewater
Authors: Ødegaard H. , Liao Z. , Melin E. , Helness H.
Published: May 2018

Many cities need to build compact wastewater treatment plants because of lack of land. This paper discusses compact treatment methods. An enhanced primary treatment process based on coarse media filtration is analysed. A high-rate secondary wastewater treatment process has specifically been investigated, consisting of a highly loaded moving bed biofilm reactor directly followed by a coagulation and floc separation step. The objective with this high-rate process is to meet secondary treatment effluent standards at a minimum use of chemicals, minimum sludge production and minimum footprint. It is demonstrated that the biofilm in the bioreactor mainly deals with the soluble organic matter while coagulation deals with the colloidal matter. The bioreactor may, therefore, be designed based on the soluble COD loading only, resulting in a very compact plant when a compact biomass/floc separation reactor (i.e. flotation or direct filtration) is used. The paper reports specifically on the coagulant choice in flotation and filter run time in direct filtration.
A new wastewater treatment system recovering magnetically immobilized microorganisms under strong magnetic field
Authors: Ozaki H. , Kurinobu S. , Watanabe T. , Nishijima S. , Sumino T.
Published: May 2018

A new generation of high gradient magnetic separation (HGMS) has recently received attention again, especially for its applications in the field of water and wastewater treatment. The reason for this attention is that a newly developed superconducting magnet can be used to easily generate a high magnetic field, under which even weakly paramagnetic materials can be separated at high efficiency. We have developed a new wastewater treatment process using magnetic gel particles containing immobilized microorganisms and magnetic particles. The magnetic gel particles are separated and recovered from the effluent in water and wastewater treatment processes, and are then recycled to a bioreactor directly or reused after storing. In this research, a novel type of magnetic separator without a filter matrix was designed for the separation and recovery of magnetic gel particles with different magnetic characteristics. No backwashing is required for this new type of separator. By using the separator, polyethylene glycol (PEG) gel particles with 2% magnetite were continuously separated and recovered from the PEG gel particles with 0.04% magnetite at an efficiency of around 90%. The PEG gel particles containing nitrifying bacteria and magnetic particles were available for the oxidation of ammonia solution at a slightly lower nitrification rate than the PEG gel particles with nitrifying bacteria but without magnetite.
Pressure dependent stochastic reliability analysis of water distribution networks
Authors: Tabesh M. , Tanyimboh T.T. , Burrows R.
Published: May 2018

Any reliability analysis based on just deterministic values of daily average or peak demands, cannot represent the overall system reliability realistically. Using a stochastic model in this paper variations of the system and nodal reliability values are investigated through a period of time. Considering probabilistic nature of demands, this paper combines the extended period simulation of water distribution networks with the head driven simulation based reliability analysis that presents the nodal and system reliabilities more realistically than conventional demand driven simulation based analysis. A sample network with possibility of one link failure is examined and diurnal profile of reliability values due to mechanical and hydraulic failures and known probabilities of demands is presented. It is seen that considering the probabilistic nature of demands the severity of mechanical and hydraulic failures on the hydraulic performance of the system are illustrated properly and realistically, especially at the critical times or nodes, in comparison with the deterministic values.
Accuracy in water losses estimation in the distribution network - the Paris case
Authors: Nguyen B.
Published: May 2018

The yield of a distribution network represents one of the indicators most commonly used by water distributors to account for the state of the volumes of losses over a given period or to measure the evolution of these losses from one year to the next, generally speaking. However, contrary to what might be thought, complex situations and very differing interpretations are to be found on the back of the result of the calculation of the volumes of water lost in the distribution network. A study of drinking water network yield was carried out in Paris in 2001 so as to get a better grasp of the developments recorded since 1987. The consequences of the changes that have taken place during this period have each been measured: alterations to the organisation of the water system, developments affecting the structure of the supply system, technical improvements in the wholesale water metering systems and overall reduction in volumes consumed.
Comparison of MIEX® treatment and coagulation on NOM character
Authors: Morran J.Y. , Drikas M. , Cook D. , Bursill D.B.
Published: May 2018

The MIEX® DOC Process was developed specifically for the removal of problematic natural organic matter (NOM) in drinking water production. The Mt Pleasant plant in South Australia was constructed to assess the MIEX® DOC Process in likely operating scenarios including retrofit into existing conventional water treatment plants and installation into new plants combined with microfiltration. The plant has been operating since 2001. In conjunction with this has been an extensive laboratory investigation into the factors impacting on the effectiveness of the process for dissolved organic carbon (DOC) removal and water quality improvement, particularly for MIEX® treatment combined with coagulation. Both plant monitoring and laboratory studies indicate that changes in the character of the NOM and water quality have had a significant impact on DOC removal by the MIEX® resin. MIEX® and coagulation have been very effective in combination and consistently reduced turbidity to <0.5 NTU from an average of 60 NTU. The target is now to achieve higher DOC removal rates. To achieve this, it is important that the influence of water quality changes on the MIEX® and coagulation processes, particularly the impact of changes in NOM character are fully understood.
Influence of ionic composition on NOM size and removal by ultrafiltration
Authors: Xi W. , Rong W. , Fane A.G. , Fook-Sin W.
Published: May 2018

In this study, the effects of Na+ and Ca2+ on the apparent MWt distribution and removal efficiency of NOM by deadend ultrafiltration were investigated. NOM samples from Singapore (reservoir-based), IHSS (river-based standard) and Biohumic (soil-based) were used. The effective particle sizes and MWt distributions of the NOM, with and without ions, were analyzed by light scattering and HPSEC, respectively. The effective size of the NOM was significantly reduced by increasing the Na+ concentration. This was robably due to coil-to-globule conversion and polyelectrolyte interaction, changing the NOM conformation from linear to spherical. However, increasing the concentration of Ca2+ showed competing effects. At relatively low concentrations of Ca2+, the size of the NOM was reduced, presumably by the mechanism attributed to Na+. As the concentration of Ca2+ was further increased the NOM size increased, due to aggregation or chelation between humic acid in the NOM and Ca2+ becoming the dominant factor. Ion interactions with NOM also had a significant impact on removal by ultrafiltration. With addition of Na+, the Singapore NOM retention decreased from 52% to 29%. In contrast, the retention of Biohumic NOM increased from 45% to around 70% with an increase in Ca2+ concentration.
Comparison between biological and chemical–physical treatment for colour removal
Authors: Farabegoli G. , Pietrelli L. , Rolle E. , Sabene A.
Published: May 2018

The main aim of this research is to compare the efficiency of biological and chemical–physical treatments for the removal of organic azo dyes in the textile wastewater. Regarding the biological reduction of the wastewater colour the anaerobic/aerobic (ANA/AER) sequential step-treatment provides the best reductions in colour and COD. A lab-scale Sequencing Batch Reactor (SBR) fed with synthetic wastewater and mono-azo dye (at the initial concentration of 25 mg/l) was used achieving 84% colour reduction and 82% COD removal. Chemical–physical treatments were performed using the oxidative method with Fenton's reagent and adsorption on the activated carbon achieving respectively colour reduction over 90% (from the initial concentration of 250 mg/l) and 155 mg col/g GAC total adsorption capacity (from the initial concentration of 1 g/l).
Novel technology for improving the treatability of turbidizing substances by coagulation and sedimentation
Authors: Ebie K. , Kawaguchi T. , Asano M.
Published: May 2018

Treatability in the coagulation and sedimentation of turbidizing substances varies greatly depending on the rapid stirring strength GR. It is demonstrated that when PACl coagulant is used, the optimum treatability is achieved at GR values of 450 for turbidity and 1,000 sec−1 for STR, a newly introduced evaluation parameter. These values are much higher than the values typical of many water purification plants where the GR values are set at 100~200 sec−1. The remarkable improvement of coagulation and sedimentation treatment is found to be related to the formation of denser, smaller-diameter microfloc with increasing GR, and an increase in the incorporation of coagulant-derived aluminium in the microfloc and zeta-potential of the microfloc, among other flock properties.
Prediction of filter expansion during backwashing
Authors: Akgiray Ö. , Soyer E. , Yüksel E.
Published: May 2018

The application of the Ergun equation to predict the expansion of filter media during backwashing is investigated. Fluidization data from the literature have been analyzed and the values k1=3.519 and k2=0.266 have been found to give a very good fit to the data in the range of Reynolds numbers of interest in filter backwashing. An empirical equation that is applicable over a wider range of Reynolds numbers than the Ergun equation is also developed. New experiments have been carried out with glass spheres, plastic spheres, silica sand, and crushed glass. The effect of particle shape on expansion behaviour is investigated. It is found that the influence of particle shape is larger than previously recognized. Furthermore, the shape effect depends on the Reynolds number based on the backwash velocity. The advantages, limitations, and range of applicability of each method of calculation are delineated.
Evaluating effective volume and hydrodynamic behavior in a full-scale ozone contactor with computational fluid dynamics simulation
Authors: Mizuno T. , Park N.-S. , Tsuno H. , Hidaka T.
Published: May 2018

An ozone reaction model combined with CFD (Computational Fluid Dynamics) technique was developed in this research. In the simulation of ozonation, hydrodynamic behavior caused by bubbling of ozone contacting-gas is important as well as reaction kinetics. CFD technique elucidated hydrodynamic behavior in the selected ozone contactor, which consisted of three main chambers. Back-mixing zone was found in each chamber. The higher velocities of water were observed in the second and third chambers than that in the first one. The flow of the opposite direction to the main flow was observed near the water surface. Based on the results of CFD simulation, each chamber was divided into small compartments, and hydrodynamic behavior and effective volume were discussed. Mass balance equations were also established in each compartment with reaction terms associated with DOC, odor compounds, bacteria, bromide ion and bromate ion. This reaction model was intended to predict dissolved ozone concentration, especially. We concluded that the model could predict favourably the mass balance of ozone, namely absorption efficiency of gaseous ozone, dissolved ozone concentration and ozone consumption. After establishing the model, we discussed the effects of hydrodynamic behavior on dissolved ozone concentration.
Estimating regional water demand in Seoul, South Korea, using principal component and cluster analysis
Authors: Koo J.Y. , Yu M.J. , Kim S.G. , Shim M.H. , Koizumi A.
Published: May 2018

In Seoul, the multiple regression models were used to estimate future water demand and to verify the ability of the water supply to cope with regional development. A regional development project extending over two districts was planned to stimulate the regional economy of Seoul in October 2003, and multiple regression models for each district were developed to verify the capacity of water facilities and the retention time of reservoirs. Two variables, the population and the area of the commercial district, were used to express domestic and commercial water usage. Coefficients for variables of models should be positive values; however, the coefficient for population was negative in Jung-gu. The prediction of water demand with one regression formula for each district may not be sufficient to characterize the water use pattern of a district. So, by characterizing each sub-district of the two districts, applying principal component and cluster analysis, they were divided into residential and commercial groups. Then, multiple regression models with the same variables were developed for each group. As a result, the models not only had positive coefficients for all variables, but also could provide reasonable sensitivity for the variables. For each group, the commercial area had nearly same sensitivity, but the population in the commercial area showed more sensitivity than in the residential area, because people living in the commercial area do not have to go to another district to work or sleep. Future water demands were estimated, depending on three scenarios of regional development, using the existing and newly developed models. The water demands estimated by the newly developed model are 3,416-11,372 ton/day less than those by existing model. Therefore, the model developed gave the correct water demand and prevented a wrong decision from being made.
Water quality dependence on the depth of the vadose zone in SAT-simulated soil columns
Authors: Cha W. , Choi H. , Kim J. , Cho J.
Published: May 2018

Three soil aquifer treatment (SAT) columns were operated for five months to investigate the dependence of the treated water quality upon the depth of unsaturated vadose zone in terms of its organics, nitrogen and phosphorus contents. It was found that DOC removal was independent of the unsaturated vadose zone depth except during the initial flooding period when the effluent was injected into each column. From tests to study the nitrate profile, it was found that the pattern of nitrification was dependent on the depth of the unsaturated zone during the initial periods of SAT flooding. However, no further nitrification occurred at the end of the flooding since the injection of the effluent continued to provide a high loading concentration to the SAT columns. The lack of phosphate removal in this study indicates that its removal is more dependent upon the soils and aquifer characteristics than on the depth of unsaturated zone.
Developing a non-revenue water reduction strategy: planning and implementing the strategy
Authors: Farley M. , Liemberger R.
Published: May 2018

A companion paper dealt with the tasks required to investigate and assess the components of non-revenue water (NRW). This is a necessary first step in a diagnostic approach to understanding the condition of the network, the way that it is operated, and the constraints acting upon it. This second part deals with the tasks and tools required to address the constraints, and to develop a strategy to reduce NRW which is practicable and achievable, and which can be adapted for any distribution network anywhere in the world. Not all utilities, particularly those in developing countries, have the luxury of a well-developed and efficiently managed network. The paper deals with the tasks required to upgrade the network, and to review and improve the operational policies and practices, before the tools and techniques to reduce NRW can be put in place. The paper discusses each step of the strategy and its development, from upgrading the network by improved infrastructure management and zoning, to the available techniques and equipment for monitoring and detecting real and apparent losses.