bluuebunny/crossref_metadata_2025 huggingface dataset:
Applying cast iron pipes aging prediction methodology to the Mendoza, Argentina drinking water network
Authors: Besson-Taboada S.E.
Published: May 2018

The drinking water network in the city of Mendoza, Argentina, is, for a great proportion of pipes, more than 40 years old. The network is confronted with a significant number of repairs and leakage is very important. The operator uses a methodology issued from experience in France, which consists of sampling representative lengths of pipes and analysing them for corrosion. Environmental influences are also taken into account for the calculation of corrosion speed. The objective is to obtain a program of replacement based upon the estimation of the remaining lifespan of each pipe in the network.
Comparative reliability analysis of the distribution areas of a water supply system and its application for an earthquake risk analysis
Authors: Hosoi Y. , Kido Y.
Published: May 2018

A methodology for comparative evaluation of the water supply reliability of distribution areas was presented. There are various factors which affect water supply reliability. As they cannot be quantified by the same standard, reliability of water distribution area was examined according to the value of each factor. These factors were organized into an index through the analytical hierarchy process. The reliability of each distribution area of the water supply system in the case study area was comparatively evaluated by the method. The problems and points necessary for improvement of the water supply reliability of each distribution area were indicated.
Transient permeate flux analysis: model validation
Authors: Tarabara V. , Hovinga R. , Wiesner M.R.
Published: May 2018

An extended model integrating several particle back-transport theories has been proposed by Sethi and Wiesner to predict transient permeate flux as a function of operational parameters for constant permeate flux (CF) and constant transmembrane pressure (CP) cross-flow regimes. Filtration experiments using monodisperse latex suspensions of particles 0.02 μm, 0.12 μm and 0.68 μm in diameter in a cross-flow flat slit membrane were carried out for model validation. In a separate set of filtration experiments with monodisperse latex particles 0.10 μm, 0.43 μm and 1.00 μm in diameter, the transient behavior of permeate flux in CP and CF modes of operation was compared. Significant differences between model calculations and experiments were observed. A slightly more complex structure at the cake-suspension interface was hypothesized to explain these differences. A representation of the cake with a gradually changing solids concentration allowed for better matching of the extended model and experimental results. The CP operation mode yielded a higher specific permeate flux resulting from a thinner cake or a cake with a lower average specific resistance. Experimentally observed differences between performance in CP and CF modes were less sensitive to the size of particles in the suspension than predicted by theory.
Nanofiltration for colour removal - 8 years' operational experience in Scotland
Authors: Irvine E. , Welch D. , Smith A. , Rachwal T.
Published: May 2018

The development of the ‘ Fyne’ Process, from an operator's perspective, for the removal of humic colour from water is described. The use of cellulose triacetate nanofiltration membranes in both tubular and spiral wound configurations has been a major advancement in the treatment of highly variable coloured upland water sources in Scotland. Membrane technology has enabled full compliance with all drinking water legislation even at the remote island sites. Operational and cost comparisons of nanofiltration with conventional treatment technologies for colour removal are discussed.
Comparison between rejection characteristics of natural organic matter and inorganic salts in ultra low pressure nanofiltration for drinking water production
Authors: Thanuttamavong M. , Oh J.I. , Yamamoto K. , Urase T.
Published: May 2018

Comparisons between rejection characteristics of natural organic matter and inorganic salts by nanofiltration in a very low operational pressure (<0.5 MPa) are demonstrated here. A nanofiltration pilot plant has been operated at the Tamagawa water purification plant, which is located downstream on the Tama River, Japan. The molecular weight distribution and concentration of natural organic matter that account for trihalomethane formation potential, and concentrations of various inorganic salts have been measured in the raw water from the Tama River, microfiltration pretreated effluent and nanofiltration production during 6-months operation of the pilot plant. This paper discusses the water quality and rejection mechanism of natural organic matter and inorganic salts. In addition, the steric-hindrance pore (SHP) model and the Nernst-Planck equation have been used to evaluate membrane pore structures and rejection of ionic solutes, respectively.
Heavy metals removal from wastewaters of phosphoric acid production: a comparison of hybrid liquid membrane (HLM) and aqueous hybrid liquid membrane (AHLM) technologies
Authors: Kislik V. , Eyal A.
Published: May 2018

Selective removal of heavy metal ions from industrial wet-process phosphoric acid (WPA) was studied, using the two liquid membrane systems: Hybrid Liquid Membrane (HLM) and Aqueous Hybrid Liquid Membrane (AHLM). Monothiophosphinic acid (Cyanex 302) in kerosene (for the HLM) and Polyvinylsulfonic acid (PVSA) aqueous solution (for the AHLM) were used as a liquid membrane (LM), separated from the feed and strip streams by neutral or cation-exchange membranes.

On application of the HLM separation system, the permeation from the feed to the strip phase followed the selectivity sequence: Zn >> Cd > Cu with all types of membranes used. Results show that the selective separation of Cd and Zn from the WPA may be achieved by the HLM with cation-exchange membranes, using a single set-up installation at continuous processing. Copper is accumulated in the Cyanex 302, poisoning the carrier. So, this carrier and HCl as a strip solution can not be recommended for the HLM processing of WPA.

Using the AHLM separation system, heavy metals such as cadmium and copper, were successfully recovered from the WPA: average fluxes (in mol/m2sec) to the strip phase were 3.7 × 10-7 and 6.7 × 10-7. Satisfactory dynamic selectivity to copper (≈16) was found. The transfer of iron and zinc species to the strip phase was below detection levels during the 144 hrs of the AHLM experiment. Contamination of the feed and strip solutions by PVSA was not observed during the 500 hrs of processing. The membranes were completely regenerable and used repeatedly.

In comparison with the HLM and other liquid membrane systems, the AHLM can potentially provide many operational, economic and environmental advantages, some of them being higher transport rates, low carrier losses and low contamination of the feed and strip solutions by water-soluble polymers, long membrane lifetime, ambient temperature, low energy requirements and chemical consumption, no special requirements for membrane resistance in organic solvents, and fewer limitations on the variability of membrane pore sizes, etc.
Monitoring membrane integrity using high sensitivity laser turbidimetry
Authors: Banerjee A. , Lambertson M. , Lozier J. , Colvin C.
Published: May 2018

Membrane filtration plants for drinking water typically use pressure decay testing in conjunction with particle counting and turbidity to monitor membrane integrity. Pilot plants offer the capability of monitoring permeate quality with both intact and intentionally compromised membranes. We compare data from a particle counter, a pressure decay test and a laser turbidimeter on pilot plants from two different manufacturers of microfiltration membranes.
Actual problems related to inorganic water compounds
Authors: Jekel M.
Published: May 2018

Some well known inorganic compounds have been subject to treatment for a century and to recent improvements and innovations. The occurrence, the environmental behaviour and the removal techniques of inorganic substances depend primarily on their aquatic chemistry, involving various reactions. The knowledge on speciation and its alteration is essential for process selection. Out of the more recent problems of some inorganic substances, natural, geogenic arsenic plays obviously a major role in a large number of countries. The relatively high chronic toxicity induced lower drinking water standards and activities on improved arsenic removal. Arsenic is a good example to demonstrate the chemistry principles and to derive new treatment techniques at affordable costs. A full-scale process comparison in Germany is presented, indicating the superior efficiency of a newly developed fixed-bed adsorption with a commercial granular ferric hydroxide, developed in the early 1990s. It is especially suitable for small-scale water supplies, for well-head treatment and even for decentralised removal of arsenic with low maintenance requirements.
Enhanced removal of herbicides by different in-site barrier-systems (GAC, FAC, anthracite, lignite coke) in slow sand filtration
Authors: Donner C. , Remmler F. , Zullei-Seibert N. , Schöttler U. , Grathwohl P.
Published: May 2018

Improvement of artificial groundwater recharge via slow sand filtration combined with different in-site barrier-layers (activated carbons, anthracite, lignite coke) was tested. The micropollutant control of the systems achieve significant different pesticides reductions. Operation time depends on the micropore structure and site properties of the activated carbons (Sorption reactor) and reaches a calculated slow sand filter operation time of nearly 6 years (GAC). No distinct improvement of pesticide removal was observed by anthracite (biological reactor). Lignite coke was not used in pilot plant, because of its high pH-value during first 100 bed volumes.
Filtration progress - more questions arising with fewer answers
Authors: Ives K.J.
Published: May 2018

About 50 years ago, Wilhelm Wiederhold wrote “Offene Fragen der Filtertechnik” (Open questions on filter technology) in the journal Gas und Wasserfach. His questions centred on 5 topics: the Boucher microstraining index and its application to sand filtration; the Michau pressure diagrams through the depth of a filter; the design and use of experimental filter columns; a multiple layer filter model comprising perforated bronze strainers; fluid flow regimes in porous media; backwashing with air scour followed by water fluidisation of a sand bed. This is reviewed in the light of the advances in the understanding of filter behaviour which have accrued over the past 50 years. Both theory and experimental techniques have enabled some of Wiederhold's questions to be answered, and for some of his ideas to be corrected. Nevertheless, our knowledge of filtration has raised more questions than have been answered. Wiederhold's ideas were a springboard for advances to be made, particularly experimentally. But new challenges face filtration technology, not least that granular bed filtration may disappear in favour of the progress of membrane technology.
Optimization of particle removal in drinking water treatment of reservoir water in a pressure filter plant
Authors: Bornmann K. , Wricke B. , Habel D.
Published: May 2018

Most surface water treatment plants use floc-filtration as the most important treatment step in drinking water production. This paper presents a new technological development which allows floc-filtration to be carried out in pressure filters. Experiments in pilot and full scale show its high efficiency. The technological development allows us to treat algal-rich and high turbid matter containing raw water efficiently at high filtration rates. Floc formation can be realised by means of a special reaction tank in front of the filter inlet. Efficient removal of particles and turbidity is achieved if filtration with filter inlet flow controller is used.
A systems analysis comparing drinking water systems - central physical-chemical treatment and local membrane filtration
Authors: Westrell T. , Bergstedt O. , Heinicke G. , Kärrman E.
Published: May 2018

This paper presents a first attempt at an integrated systems analysis of drinking water systems using Microbiological Risk Assessment (MRA) and Material Flow Analysis (MFA) with focus on the comparison of central physical-chemical treatment (conventional system) and local membrane filtration. The MFA shows that energy use is the most significant environmental impact of the three studied drinking water systems, but there are no considerable differences in energy use comparing central physical-chemical treatment and local membrane filtration. According to the MRA, the conventional system might not reduce the microbial risks sufficiently, but such a reduction can not confidently be achieved in a one-step ultrafiltration system either, since membrane filter integrity can hardly be guaranteed over the service life of the equipment. A quite costly two-step membrane filtration system, where water for all household purposes passes microfiltration and further reverse osmosis for drinking and cooking, seems to fulfil this criterion. On the other hand, this system does not reduce the microbial risks from ingestion of water from showers compared with the one-step ultrafiltration alternative. In order to achieve drinking water systems with sufficient microbial barriers and with reasonable costs for operation, a promising solution seems to be a combination of one-step membrane filtration and other methods e.g. biological treatment.
Sequential anaerobic/aerobic biodegradation of chlorinated hydrocarbons in activated carbon barriers
Authors: Tiehm A. , Gozan M. , Müller A. , Schell H. , Lorbeer H. , Werner P.
Published: May 2018

The aim of this study is to develop a long lasting, sequential anaerobic/aerobic biological activated carbon barrier. In the biobarrier, pollutant adsorption on granular activated carbon (GAC) and biodegradation occur simultaneously. Trichloroethene (TCE), chlorobenzene (CB), and benzene were used as model pollutants. In the first barrier, that was operated under anaerobic conditions with sucrose and ethanol as auxiliary substrates, TCE was completely converted to lower chlorinated metabolites, predominantly cis-dichloroethene (cis-DCE). The reductive dechlorination process was stable for about 300 d, although the concomitant sulphate-reducing and methanogenic processes varied considerably. In the second barrier, that was operated with addition of hydrogen peroxide and nitrate, dechlorination was limited by a lack of oxygen and restricted mainly to CB biodegradation. Additional aerobic batch tests revealed that the metabolites of anaerobic TCE dechlorination, i.e. cis-DCE and vinyl chloride, were oxidatively dechlorinated in the presence of suitable auxiliary substrates such as ethene, CB, benzene, or sucrose and ethanol. During periods of low biological activity, elimination of TCE and CB occurred by adsorption in the GAC barriers. The pre-sorbed pollutants were available for subsequent biodegradation resulting in a bioregeneration of the activated carbon barriers.
Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria
Authors: Winzenbacher R. , Schick R. , Stabel H.-H. , Jekel M.
Published: May 2018

Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.
Addressing the sustainability of small-user rural water treatment systems in South Africa
Authors: Mackintosh G.S. , de Souza P.F. , Delport E.
Published: May 2018

A crucial consideration when considering water treatment in rural communities is the sustainability thereof. This paper compares the financial and technological sustainability of a membrane based water treatment plant versus a conventional type plant at two small rural communities in South Africa, and brief observation is made as to the importance of socio-political sustainability. The membrane-based process is shown to provide consistently good water, whilst the conventional process only provides intermittently good water. The membrane-based plant was successfully operated for an extended period by a community member with no prior skills in water treatment, and showed superior technological sustainability. Using a Net Present Value based approach, financial comparison shows that contrary to conventional wisdom in South Africa, the membrane-based plant has superior financial sustainability. The principle advantage of the membrane based treatment process is that it provides consistently high quality drinking-water and it is not possible for the system to pass on partially treated water that fails bacteriological standards. This will ensure the socio-political sustainability of the membrane-based process. In comparison the regular failure of the conventional system is likely to lead to eventual rejection of the technology by the community.
Influence of gasoline hydrocarbons on methyl tert-butyl ether biotreatment in fluidized bed bioreactors
Authors: Stringfellow W.T. , Oh K.-C.
Published: May 2018

Fluidized bed bioreactors (FBRs) are frequently used for the treatment of gasoline contaminated groundwater. Due to changes in gasoline formulations in the last decade, gasoline contaminated groundwater may also contain significant quantities of methyl tert-butyl ether (MTBE), a recalcitrant gasoline additive. It has been shown that MTBE is biodegradable and there is interest in determining if MTBE contaminated groundwater can be biologically treated using FBR technology. We examined the biodegradation of MTBE in FBRs treating contaminated groundwater and establish that there was an inverse correlation between total petroleum hydrocarbon (TPH) loading and MTBE treatment efficiency. Follow-up laboratory studies demonstrated that toluene, a component of TPH, is a strong inhibitor of MTBE biotreatment in FBRs.
Hydraulic distribution of water and air over a membrane module using AirFlush®
Authors: Verberk J.Q.J.C. , Hoogeveen P.E. , Futselaar H. , van Dijk J.C.
Published: May 2018

Delft University of Technology, Department of Sanitary Engineering, is researching the fundamentals of air-water flushing (AirFlush®) for membrane cleaning. The research is focused on two topics: velocities of water and air for optimal cleaning and the distribution of water and air over the cross sectional area of the module. In an earlier study the velocities of water and air to achieve an optimal cleaning for tubular membranes have been investigated. In this article the distribution of water and air over the cross sectional area of a 3ʺ-membrane module will be discussed. Experiments have been performed and the fundamental processes that influence the distribution of air and water have been studied.
Effects of particle size distribution on the cake formation in crossflow microfiltration
Authors: Kim S. , Cho S.-H. , Park H.
Published: May 2018

In crossflow microfiltration, the tendency of particle deposition of polydisperse suspensions has been established experimentally and compared with that of monodisperse suspensions. The mass transfers of particles are different according to size in polydisperse suspensions. The most particles, which deposit to membrane surface without clogging pore in microfiltration, are much larger than 0.1 μm. Among these particles, smaller particles are easier to deposit than larger particles because of shear-induced diffusion and particle deposition depends on the size distribution of small particles. Effective particle diameter is introduced as a representative particle size which can reflect the diffusivity of each particle according to size and it describes the tendency of particle deposition very well in polydisperse suspensions. The effect of effective particle diameter is larger than that of feed concentration. The most important factor affecting particle deposition of polydisperse suspensions is effective particle diameter. The results of our research suggest that the effective particle diameter can be an important factor which can represent the potential for cake formation.
Enteric viruses in drinking water supplies
Authors: Wyn-Jones A.P. , Watkins J. , Francis C. , Laverick M. , Sellwood J.
Published: May 2018

Two rural spring drinking water supplies were studied for their enteric virus levels. In one, serving about 30 dwellings, the water was chlorinated before distribution; in the other, which served a dairy and six dwellings the water was not treated. Samples of treated (40 l) and untreated (20 l) water were taken under normal and heavy rainfall conditions over a six weeks period and concentrated by adsorption/elution and organic flocculation. Infectious enterovirus in concentrates was detected in liquid culture and enumerated by plaque assay, both in BGM cells, and concentrates were also analysed by RT-PCR. Viruses were found in both raw water supplies. Rural supplies need to be analysed for viruses as well as bacterial and protozoan pathogens if the full microbial hazard is to be determined.
Hygienic risk assessment by monitoring pathogens in municipal sewage
Authors: von Bonsdorff C.-H. , Maunula L. , Niemi R.M. , Rimhanen-Finne R. , Hänninen M.-L. , Lahti K.
Published: May 2018

The purpose of this study was to monitor the levels of human enteric viruses and enteric protozoa and to relate their presence to the microbes used as hygienic quality indicators in domestic sewage from a small community in Finland during a period of one year. Genome-based sensitive detection methods for the pathogens selected (astro- and Norwalk-like viruses, Giardia and Cryptosporidium) have become available only recently and thus no earlier data was available. The effluent sewage is delivered into a river that serves as raw water for a larger town and the pathogens therefore constitute a health risk. The results showed that all the monitored pathogens could be detected, and that enteric viruses were present at considerable concentrations in sewage. High concentrations of astrovirus in raw sewage were observed during a diarrhea epidemic in the local day-care centre. The presence of viruses did not correlate with the monitored bacterial indicators of faecal contamination (coliforms, E. coli and enterococci) or with bacteriophages (somatic coliphages, F-specific RNA phages and B. fragilis phages). Giardia cysts and Cryptosporidium oocysts were detected from one sample (1/10) each.
Sub-species typing among bovine C. parvum isolates by PCR-PAGE using a novel microsatellite + telomere primer scheme
Authors: Blasdall S.A. , Ongerth J.E. , Ashbolt N.J.
Published: May 2018

A PCR-PAGE procedure based on a novel primer set including a previously described microsatellite (M) plus a telomere anchor (+T) was used to biotype C. parvum isolated from bovine sources in three categories: geographically diverse, intra herd, and specifically defined. The PAGE patterns resulting from the procedure consisted of from 8 to 18 bands in the 300 to 3,000 bp size range. Application of the procedure revealed widely divergent PAGE banding among the geographically diverse samples. Consistent banding patterns were observed among multiple calf hosts from the same dairy herd sampled over 1 to 2 year periods. Some differences were observed in PAGE banding between samples in different time periods although all independent samples in each sampling period (up to 5 shown) were homogeneous. Analysis of DNA from samples of the Iowa defined strain of C. parvum isolated in 1998 and in 2000 from the same source (University of Arizona) resulted in PAGE banding that was homogeneous. The sub-type differentiation effectiveness of the M+T PAGE procedure was observed to be substantial. Reference to work being prepared for publication elsewhere indicates that it is similarly effective for Type 1 samples.
Evaluation of the ICR protozoan method and Method 1623 for detecting Giardia and Cryptosporidium in actual water samples
Authors: Hsu B.-M. , Huang C. , Yeh H.-H.
Published: May 2018

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern. This study examined both parasites in actual water samples, which were taken from Cheng-Ching Lake waterworks in southern Taiwan. The Method 1623 was characterized by a higher recovery rate and lower detection limit compared with the ICR protozoan method. It was discovered that water turbidity reduced the recovery efficiencies, and raised the detection limits for both parasites, regardless of the method used. The concentrations of both parasites showed inconsistency for different recovery rates and detection limits between the two methods. A significant correlation between water turbidity and Cryptosporidium oocysts in raw water samples were found in this study.
Depressed filtration ripening enhances removal of Cryptosporidium parvum
Authors: Gitis V. , Haught R.C. , Clark R.M. , Radha Krishnan E.
Published: May 2018

Pilot-scale experiments were conducted to investigate removal of Cryptosporidium parvum by contact granular filtration. The research demonstrated enhanced removal of Cryptosporidium parvum in the presence of kaolin particles. This is believed to be due electrostatic adhesion of Cryptosporidium parvum oocysts to the kaolin clay particles. The elementary physico-chemical interactions between filter granules and suspension particles will be discussed. This innovative concept was successfully implemented to reduce the ripening sequence of subsequent filtration experimental test runs by the addition of large surface area particles to slurry of kaolin and Cryptosporidium parvum in surface water.
A risk assessment case study in the suburbs of Paris: balancing health effects of Cryptosporidium parvum and bromate
Authors: Dilé-Mary V. , Galey C. , Gatel D. , Cavard J. , Havelaar A.
Published: May 2018

To meet newly proposed bromate standards, ozone doses should be decreased, thus also decreasing the risk of renal cell cancer, but the risk of infection with Cryptosporidium parvum will increase at the same time. The present study was designed to evaluate and balance these two risks, using a probabilistic risk assessment, which involves calculating the disease burden, expressed in the number of disability adjusted life-years (DALY) as developed by Havelaar et al. In the case of Neuilly-sur-Marne ozone contactors, four ozone doses were studied at 5°C and at 22°C. Results showed a sharp decrease of the disease burden with the application of ozone, and then a slight increase as the ozone dose was increased. Minimal DALYs were obtained with ozone doses of 1.5 mg/L at 22°C and 2.5 mg/L at 5°C. Nevertheless, these two ozone doses do not comply with the 10 μg/L bromate standard, as an average of 12 at 5°C and 11 at 22°C are produced.
EDP-supported development of economically optimized line renewal strategies by damage analyses
Authors: Ohmer R. , Dandl J.
Published: May 2018

The criterion for the replacement of lines in many water supply enterprises is still their age. Economically aligned strategies of the network renewal do still not exist in many places. In the context of a federal research project at the ESWE Supply PLC in Wiesbaden, a software for economical rehabilitation planning as well as the appropriate database are created. From damage data and the use of economical algorithms this program sets up damage prognoses for individual line sections of the supply network. By inclusion costs of renewal and sanitation measures the expected costs in the future can be calculated on the basis of these damage prognoses. The line sections can be sorted according to different criteria in the program. Thereby, the network planner has the possibility to quickly and efficiently finding the exact line sections of the network which must be renewed or sanitized. In parallel to the software development, investigations into the causes of damage like aggressive soils or earth movements were executed. They supply further important information for the specification of the decisions of the network planner. This information was integrated into the resource information system and can be recalled for planning purposes. Thus the combination of an economical rehabilitation program and resource information system, provides an optimal package for decision making to aid the network planner.
Biofouling and corrosion of stainless steels in natural waters
Authors: Lewandowski Z. , Avci R. , Geiser M. , Shi X. , Braughton K. , Yurt N.
Published: May 2018

The noble shift in corrosion potential to values between +300 and +400 mVSCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.
Biofilms in copper plumbing systems: sensitivity to copper and chlorine and implications for corrosion
Authors: Critchley M.M. , Cromar N.J. , McClure N. , Fallowfield H.J.
Published: May 2018

Microbial biofilms have been implicated as a major contributor to the corrosion of metals in drinking water distribution systems. This study investigated the sensitivity of biofilm bacteria with previously established cuprosolvency activity, isolated from domestic copper plumbing pipes, to chlorine and copper and assessed their potential to adsorb aqueous copper. Bacterial suspensions were exposed to free chlorine residuals of 0.1, 0.2 and 0.5 mg/L and viable bacteria enumerated at times 0, 1, 2, 5 and 10 minutes. Disinfection curves showed the isolated bacteria were more resistant to free chlorine in comparison to the indicator organism Escherichia coli. Disc diffusion assays demonstrated high resistance by all bacteria to copper, with a Corynebacteria sp. showing no growth inhibition at concentrations up to 4 gCu/L. The isolated bacteria showed the ability to bind aqueous copper ions from solution in adsorption experiments. Significantly higher adsorption of copper was shown by a species of Pseudomonas. The results of this research will provide a greater understanding of causes of biofilm accumulation and copper contamination of drinking water, aiding in health risk assessment and risk management.
The role of algae in causing coliform problems within the distribution system
Authors: Lake R. , Driver S.
Published: May 2018

Coliforms are used as indicators of faecal pollution in water. Therefore, the presence of coliforms in drinking water causes concern as it indicates the potential presence of other bacteria. Coliforms have been seen in water within the Vivendi Water UK area during the summer months and their presence has previously been explained by localised pipe renovation. In this study, the influence that the algal bloom has on the presence of coliforms has been assessed. It has been shown that there is a strong link between the end of the algal bloom and coliforms being found in the distribution system. The algal bloom does not allow coliforms to pass through the treatment works. However, the high level of total organic carbon (TOC) in the treated water, made up of algal breakdown products, provides a good nutritional source for regrowth in the distribution system. Where there are high TOC levels, coliforms can grow even with high chlorine concentrations. However, where there is little TOC, then even a very low chlorine residual is adequate to prevent coliform growth.
Measuring up: do you have a scorecard?
Authors: Johnson K.
Published: May 2018

Performance measurement can be an effective tool in driving organization improvement to enable your utility to become more competitive, or improve customer satisfaction. WERF Project #99-WWF-7, Developing and Implementing a Performance Measurement System, is developing performance measurement systems by investigating a number of “best practices” in other industries and implementing selected practices at various water/wastewater utilities nationwide to determine how these practices can be adapted and applied. This joint WERF/AWWARF research project has been underway since mid-1999 to provide methods and tools that enable the utility to develop and implement a performance measurement system based on a demonstrated, proven approach. The Volume I Report summarizes the secondary research and project approach.

Well designed, properly implemented performance measurement systems can enable utilities to achieve new levels of performance in terms of efficiency, quality, and effectiveness. Interest in performance measurement is increasing in all competitive businesses and industries today, and has been advanced through concepts such as the Balanced Scorecard. Utilities can employ these same concepts and learn “best practices” from other industries' experiences.

While a performance measurement system alone does not improve performance or make a utility competitive, when combined with an appropriate business strategy and performance improvement initiatives, it can drive a cycle of change. A successful performance measurement system combines a holistic approach around improved business practices and effective human/organizational strategies in addition to actual performance information for operational decision-making.
Assessing socio-cultural aspects of sustainable urban water systems - the case of Hammarby Sjöstad
Authors: Söderberg H. , Åberg H.
Published: May 2018

The Swedish national research programme “Sustainable Urban Water Management” aims to analyse and assess the sustainability of urban water systems (UWS) covering a range of perspectives. This paper will concentrate on development of tools to assess organisational and household related aspects, being an area with a particular need of development. Incorporated in our definition of UWS, is the condition that the functioning within the system is critical for sustainability as such and three sub-systems are distinguished: households, organisation and technical structure. A point of departure is that functional fit between the sub-systems needs to be high in order to create sustainable UWS.

Organisational capacity, adaptability, motivation, opportunity and ability are used as criteria for comparison of two different technical structures. We can conclude that no straight answer to the question which system to prefer emerge - which is most often the case in reality. The two systems are high on some sub-criteria and low on others. With a combination of internal systems analysis, like this, and impact assessments, it is possible to both increase the quality of the impact assessments and manage to make analysis of organisations and households within their own frames of logic.
Mathematical analysis of a batch electrocoagulation reactor
Authors: Holt P.K. , Barton G.W. , Mitchell C.A.
Published: May 2018

Electrocoagulation treats water by delivering coagulant from a sacrificial anode (aluminium) in an electrochemical cell. Hydrogen is evolved from the inert cathode. In the batch electrocoagulation reactor numerous interactions occur with settling and flotation identified as the dominant removal paths. Current determines both coagulant dosage and bubble production rate. The bubbles influence the mixing, and hence mass diffusion within the reactor. Rate of flotation and settling were experimentally determined for currents 0.25-2.0 A and pollutant loading 0.1-1.7 g/L. The performance of the electrocoagulation reactor was quantified by analysis of experimental results.

First-order ordinary differential equations were developed to describe the pollutant's settling and flotation behaviour. Kinetic rate constants were calculated considering this pair of irreversible reactions. At low current (0.25A), sedimentation dominates with slow release of coagulant and gentle agitation provided by low bubble production. Removal is slow and hence the low rate constants calculated were appropriate. At high currents (1.0 and 2.0 A) faster removal occurs due to greater bubble density. This resulted in greater mass floated to the surface and higher rate constants were observed. Thus the developed rate equations successfully quantified the reactor's performance over a variety of conditions.
Reducing turbidity and coagulant residue in treated water through optimization of rapid mix conditions
Authors: Ebie K. , Azuma Y.
Published: May 2018

This study reports basic research on the effectiveness of raising the rapid agitation strength (velocity gradient, or GR value) in improving the treatment efficacy of coagulation and sedimentation. Coagulation and sedimentation treatment with a normal velocity gradient of 100-200 s-1 reduces turbidity to less than 1 mg/L but leaves a significant amount of coagulant residue and thus does not reduce the suction time index (STI) to a desirable level. By contrast, higher GR values yield improvements in the turbidity of the treated water, as well as marked improvements in the STI. Good coagulation and sedimentation treatment is also related to reductions in filtration head loss.
Monitoring and maintaining the integrity of immersed ultrafiltration membranes used for pathogen protection
Authors: Côté P. , Cadera J. , Adams N. , Best G.
Published: May 2018

Membrane filtration has become the preferred alternative to conventional technology to remove water-borne pathogens in the preparation of drinking water. This paper presents the integrity monitoring and maintenance options for the ZeeWeed® immersed membrane. Results from two versions of air-based tests, a pressure decay test and a vacuum decay test are presented and shown to be conservative when compared to challenge results from independent studies.
Membrane fouling control through aggregate design and trans-membrane pressure selection
Authors: Lee S.A. , Waite T.D. , Fane A.G. , Amal R.
Published: May 2018

Treatment of waters and wastewaters by microfiltration (MF) requires the addition of chemical coagulants to enhance the removal of dissolved substances. Under these conditions the feed to the MF contains flocculated particulates which must be retained by the membrane. While an extensive knowledge base on the effect of dispersed particles on membrane cake formation and fouling exists, much less information is available on the impact of aggregates on cake characteristics. Results of impact of the size and structure (as characterized by the fractal dimension) of particulate aggregates on microfiltration membrane fouling are in qualitative agreement with a simple model based on the Carman-Kozeny equation. Larger flocs form a cake with large inter-floc porosity which results in a significantly higher permeate flux than achieved for smaller flocs. Concomitantly, looser flocs (of low fractal dimension) are likely to form a cake that has higher intra-floc voidage thus flux is higher than a cake made of compact flocs of similar size. Analysis of cake compression indicates that compressibility is strongly influenced by trans-membrane pressure (TMP). The placement of highly porous aggregates onto the membrane results in formation of a highly porous cake layer provided a low TMP is maintained. Rapid compression of the cake occurs at higher TMPs as shown by the significantly lower porosity of the cake. Under high TMP conditions, the cake porosity exhibits a strong size dependence with larger floc sizes yielding higher porosities. This result possibly indicates formation of relatively impermeable assemblages (as a result of significant compaction) with flux controlled by inter-aggregate flow, i.e. flow around compressed flocs. In comparison, the marked lack of size dependence of porosity at low TMP suggests that permeate flux is dominated by flow through (rather than around) the highly permeable flocs. These results suggest that it should be possible to control both operating conditions (such as TMP) and floc characteristics such that high permeate flux at a given TMP or low cake resistance at a fixed flux is achievable.
Method for evaluating antiscalants, as applied to the treatment of water from the River Oise
Authors: Plottu-Pecheux A. , Houssais B. , Democrate C. , Gatel D. , Parron C. , Cavard J.
Published: May 2018

Nanofiltration, used in the Méry-sur-Oise water treatment plant (90 MGD) provides a softened water with a low organic matter content from which micropollutants and microorganisms have been removed. The experience acquired on the site since 1992 has revealed that the use of a crystal formation inhibitor is essential to slow down the clogging of the nanofiltration membranes, essentially on the third stage. Given the complexity of the action of the antiscalants (threshold effect, metal ion sequestration capacity, particle dispersion capacity), it is difficult to theoretically define the type of product to be used and its optimal dosing level. In addition to laboratories or modelling studies, pilot experiments are needed to assess antiscalants and optimise their doses. Nanofiltration cycles being long (1-2 months), it is nevertheless difficult to compare results of cycles, and the objective of the project was to develop a methodology for sequestering agent testing.

To carry out strictly comparative studies of commercially available products as well as studies using the same product but at several different dosage levels, a pilot unit comprising three parallel nanofiltration trains was built. The pilot unit is fed with 2nd stage concentrate, produced without sequestering agent, and each trains has its own separate antiscalant injection point. The first cycle aimed to provide answers to the following: (i) choice of the antiscalant best adapted to the treatment of water from the river Oise, (ii) identification of the clogging agents, (iii) the efficiency of the chemical regeneration procedure.

A production cycle using the same antiscalant at three different doses (0, 1 and 3 g.m-3) demonstrated that this product acted through a threshold effect. Analysing the cleaning waters provided further information on the type of clogging agents deposited on the membrane. Although for all the cycles the overall nature of the clogging is identical, essentially composed of organic matter and mineral elements (calcium, phosphorus, aluminium, etc.). The similarity of the water permeability and salt rejection at the beginning of two consecutive cycles tends to demonstrate that the chemical regeneration procedure (caustic soda/citric acid) is efficient.
Transport characterizations of natural organic matter in ion-exchange membrane for water treatment
Authors: Kim D.H. , Moon S.-H. , Cho J.
Published: May 2018

A series of adsorption experiments were performed to investigate the factors affecting the transport of natural organic matter (NOM) in an ion-exchange (IX) membrane. In this study, the structure of the NOM was hypothesized to be an important factor in terms of the organic fouling of IX membrane. It was found that the adsorbed mass of hydrophobic NOM constituent on the membrane surface was higher than that of either the hydrophilic or transphilic NOM constituent. NOM adsorption was seriously affected by the apparent charge of the NOM. As the apparent charge increased, NOM adsorption also significantly increased. Moreover, the molecular mass of the hydrophobic NOM acids was too high to enable them to pass through the IX membrane, and this caused an accumulated adsorption of solutes on the membrane surface, i.e. NOM fouling. In addition, both pH and ionic strength affected NOM adsorption on the surface of the IX membrane. Lower NOM adsorption resulted from a lower pH and a higher ionic strength.
Excitation-emission fluorescence spectra and trihalomethane formation potential in the Tama River, Japan
Authors: Nakajima F. , Hanabusa M. , Furumai H.
Published: May 2018

Three-dimensional fluorescence spectroscopy was applied to investigate the water quality in the Tama River, Japan, and the variation of the excitation-emission matrix (EEM) profiles of the river water was discussed with particular reference to trihalomethane formation potential (THMFP). The EEMs of the water downstream of a lake exhibited a small but strong peak at 225 nm (excitation)/295 nm (emission) and a weak one at 270 nm/295 nm, which seemed to be derived from algae. The EEMs of the water receiving treated sewage had a distinctive, large and broad peak at around 345 nm/430 nm and also a strong fluorescence at 240 nm/330-450 nm. From the comparison with EEMs of human urine, humic acid and a laundry detergent with fluorescent whitening agents, the peak at around 345 nm/430 nm on the EEM of treated sewage was also found on the EEM of the laundry detergent. The fluorescence intensity had a good correlation with T-THMFP for a wide range of excitation/emission wavelengths considered. The fluorescence intensity at 255-295 nm/345-385 nm correlated with T-THMFP better than E260, and the maximum value of the determination coefficient was R2 = 0.90 at 260 nm/355 nm, where no distinctive peak was found on the EEMs of the river water samples. The highest correlation coefficient between the fluorescent intensity and DOC was R2 = 0.77 at 280 nm/335 nm. Multiple regression analysis revealed that the fluorescence emission from a unit concentration of THM precursors was 1,000 times or more higher than that of the overall DOC, particularly in the wavelength range of 250-265 nm/325-480 nm, and that the THM precursors in the river water contributed to a much larger degree to the fluorescence than the other DOMs not forming THM.