bluuebunny/crossref_metadata_2025 huggingface dataset:
Destruction of helminth eggs (Ascaris suum) by ozone: second stage
Authors: Orta-de Velásquez Ma. T. , Rojas-Valencia Ma. N. , Vaca-Mier M.
Published: May 2018

With the purpose of destroying helminth eggs, laboratory tests were carried out using a batch reactor of 1 L with 500 mL of eggs in suspension (1 × 105 eggs/L). In all the tests, a 36.8 mg O3/L concentration of gas-phase ozone was applied at the bottom of the reactor, with flows of 0.25 and 0.5 L/min to achieve rates of 9.2 and 18.4 mg O3/min, respectively. The results (first stage) showed that the eggs of Ascaris suum were destroyed at a pH of less than 5, with a dose of 18.4 mg O3/min., giving a 94% success rate; these results were improved when applying a pH 3 (second stage) with 18.4 mg O3/min for an hour, and 96.7% of the eggs showed damage to their external covers. In comparison with other species, total destruction was achieved in 1 hour and 45 minutes at pH 3 for the case of the Fasciola hepatica and the Strongiloides sp. The destruction of the Dypilidium caninum was completed after 3 hours. However, with regard to the Toxocara canis, eggs still remained, but they were observed to be seriously damaged. The degree of COD removal in the tests with the Ascaris suum was 75% after 2 hours. In the case of the other species, the COD removal was better since it varied from 85-94% after 2 hours of treatment. It can be concluded that during the process of oxidation in an acid environment, ozone hydrolyzes the amino acids that characterize the proteins of the layers covering the egg, and at the same time it breaks the cover of the egg and disperses the cytoplasm of the eggs into the solution, therefore making it impossible for the eggs to become reactivated.
Preventing bacterial regrowth in old distribution systems without disinfection
Authors: Uhl W. , Schaule G. , Gimbel R.
Published: May 2018

As a result of high-quality source water and consumer preference, more than half of the utilities supplying water in Germany have not needed to use disinfection to comply with German Drinking Water Regulations (GDWR). Changed conditions, such as decreased consumption levels and, consequent decreased flow rates and increased temperatures, bring the risk of sudden violations of GDWR1. This paper examines strategies to deal with such risks and how to monitor water quality for bacterial regrowth events. Particular attention is paid to the part played by the age and condition of decade-old distribution pipes. It is shown that careful management of such distribution systems can prevent bacterial regrowth without chlorination.
Evaluation of magnetic ion exchange resin (MIEX®) and alum treatment for formation of disinfection by-products and bacterial regrowth
Authors: Chow C. , Cook D. , Drikas M.
Published: May 2018

Four treatment options: (a) alum coagulation without pH adjustment; (b) alum coagulation at pH 6; (c) magnetic ion-exchange (MIEX®*) resin; and (d) combined alum/MIEX® treatment, were used to compare the removal of dissolved organic carbon (DOC) and treated water quality, particularly the formation of disinfection by-products and bacterial regrowth potential. Improved DOC removal was achieved with the inclusion of MIEX® treatment in the process. The DOC remaining after each treatment strategy was different in character. The molecular weight distribution results indicated that MIEX® treatment removed a broad range of compounds, whilst alum treatment targetted the removal of high molecular weight compounds. In addition, the DOC remaining after MIEX® treatment consisted of compounds with lower specific UV absorbance (SUVA). Including MIEX® in the treatment stream provided better DOC and bromide removal thus reducing chlorine decay and trihalomethane (THM) formation. The ability of the water to support bacterial growth as measured by bacterial regrowth potential (BRP) was the lowest after MIEX® treatment (option c) compared with the three other treatments (options a, b and d). In summary, laboratory tests show that including MIEX® in the treatment process can improve treated water quality. (*MIEX® is a registered trademark of Orica Australia Pty Ltd)
Performance target based non-revenue water reduction contracts: a new concept successfully implemented in southeast Asia
Authors: Liemberger R.
Published: May 2018

Non-revenue water (NRW), the difference between water produced and water sold, has reached unacceptable levels in the majority of water utilities all around the world. Outsourcing of NRW reduction activities is often the only feasible solution. The paper describes the concept of “performance target based non-revenue water reduction contracts” in general and provides detailed information on the world's largest NRW reduction contract - the Selangor NRW reduction project. The performance target of Phase 1 was to reduce NRW by 18,540 m3/day. The works were completed on time and the target has been over-achieved. Based on this success, Phase 2 of the project has commenced in April 2000 with the aim of reducing NRW across the entire state of Selangor, by 200,000 m3/day over a 9 year period. After the first 15 months of the project, all targets have been substantially over-achieved. The project cost is RM 398 M (equivalent to US$ 105 million) with a pay-back period of 6.7 years. The internal rate of return was calculated to be 33.2% based on the assumption that the value of water equals the average tariff of RM 1.27 (equivalent to US$ 0.33). It can be concluded that performance target based NRW reduction contracts are a feasible model for water utilities around the world.
Influence of corrosion scales on copper corrosion by-product release
Authors: Merkel T. , Groß H.-J. , Beuchle G. , Werner W. , Detscher E. , Eberle S.H.
Published: May 2018

Based on a literature study and experiments the copper corrosion mechanism is subdivided into three processes: copper oxidation, deposition of corrosion by-products, and establishment of a solubility equilibrium. This approach is applied to explain the results of a study on the influence of temperature on copper dissolution and deposition of copper corrosion by-products. Changes in water quality are monitored by regular sampling, qualitative and quantitative changes of surface layers are studied using computer-supported light microscopy and scanning electron microscopy.
The role of communication in the delivery of water services to communities
Authors: Schoeman G. , Pybus P.
Published: May 2018

The key to providing sustainable water and sanitation services to communities lies in the proper understanding by all the parties involved of their roles, responsibilities and what the outcomes will be. The extent to which engineers and communities were able to communicate and understand one another was investigated in a number of case studies in South Africa. The findings of the study showed the importance of understanding the nature of communication, the real needs of the community, the explanation of the roles of the participants, the identification of the appropriate level of service and the definition of capacity building.
Hydraulic study and optimisation of water treatment processes using numerical simulation
Authors: Craig K. , De Traversay C. , Bowen B. , Essemiani K. , Levecq C. , Naylor R.
Published: May 2018

Until recently, water treatment plants were frequently designed solely on the basis of the biological, chemical and physical constraints of processes. Nowadays, the use of Computational Fluid Dynamics (CFD) software enables the dimensioning of water treatment processes by taking into account the real hydraulic behaviour of processes. That has be done for the Coliban Water Aqua 2000 project, which consists of the construction of three water treatment plants. The disinfection performance of three ozone contactors were compared using the CFD software, Fluent. Moreover, the CFD application has been extended to a large range of water treatment processes in recent years. The paper presents several of these: flocculation tanks, UV reactors and secondary settling tanks.
Direct capillary nanofiltration for ground water and surface water treatment
Authors: Verberk J.Q.J.C. , Post J. , van der Meer W.G.J. , van Dijk J.C.
Published: May 2018

Capillary nanofiltration is a new concept in membrane filtration. This technique combines the advantages of the good water quality obtained from nanofiltration membranes with the easy hydraulic cleaning of capillary membranes. Direct capillary nanofiltration can be used to treat ground water or surface water without pre-treatment. At the Delft University of Technology several MSc-thesis projects have been carried out on this subject. This paper will describe some results of these studies. A model based on a mass balance to predict the flux of a capillary nanofiltration installation treating groundwater is proposed. In this model the only resistance taken into account is the concentration polarisation. Also a model to predict the flux when treating surface water has been developed. This model takes into account the resistance due to cake filtration.
Removal of particulates, natural organic matters, and microorganisms in a surface amended slow sand filter
Authors: Jun H.-B. , Lee Y.-J. , Shin S.-S.
Published: May 2018

Removal characteristics of particulates, natural organic matters, and microorganisms with six slow sand filter units were measured with a diameter of 50 mm and packed with sand to a depth of 50, 150, 300, 600, and two 700 mm, respectively. One of the 700 mm depth filters was amended by covering the surface of the filter bed with a prefilter. The raw water turbidity and pH was in the range of 1.5-2.0 NTU, and 7.0-7.7, respectively. Turbidity in each filter effluent was decreased as the depth of filter medium increased. However, a greater part of influent turbidity was removed within the top layer of the slow sand filters. Turbidity removal in the 700 mm depth filter with prefilter was similar to that without the prefilter, however, the removal of particles smaller than 2 mm was improved with the prefilter. The particles greater than 10 mm could be removed within the upper 50 mm depth in the slow sand filter. A greater fraction of the particles smaller than 2 mm was removed within the upper 50 mm, however, they were also removed in the deeper sand bed. The removal efficiency of DBP precursors represented by DOC and UV-254 absorbance was 9.2-31% and 2-31%, respectively. pH drop in the 50 mm depth filter was 0.12, while that in the 700 mm depth filter was 0.19. The effects of surface treatment with prefilter on UVA and DOC were not apparent.
Effect of several natural water constituents on bromate formation during ozonation
Authors: Hofmann R. , Larcher S. , Andrews R.
Published: May 2018

Synthetic water matrices containing ammonia, bicarbonate, hydrogen peroxide, and natural organic matter were studied to identify the effects of these compounds (individually and in combination) on bromate formation. Ammonia alone was observed to significantly reduce bromate formation through the sequestering of brominated intermediates as bromamines. Natural organic matter reacted quickly with bromamines, which could impair the ability of ammonia to block bromate formation. Bicarbonate was observed to generally promote bromate formation in otherwise pure water, but bicarbonate worked synergistically with ammonia to reduce bromate formation by a greater factor than ammonia alone, due to OH radical scavenging. Experiments showed that hydrogen peroxide lowered the effectiveness of ammonia to block bromate formation.
Biologically induced precipitation in urine-collecting systems
Authors: Udert K.M. , Larsen T.A. , Gujer W.
Published: May 2018

Precipitation in urine-separating toilets (NoMix toilets), waterless urinals, and conventional urinals causes severe maintenance problems. Additionally, the partial fixation of nutrients in precipitates may affect the later use and treatment of source-separated urine. The goal of this study was to characterise the mineral composition of the precipitates and to identify the main causes for precipitation. X-ray diffraction analysis showed that the main crystalline compounds are struvite, hydroxyapatite, and calcite. We measured concentrations in the solutions of the traps and of the urine collection tank for estimating saturation indices, extent of urea degradation, urine dilution, and elimination of solutes. Our results indicate that bacterial urea degradation triggers precipitation. The composition of the precipitates depends on the urine dilution with flushing water: in low diluted urine, struvite is the main compound, while calcite dominates in systems with high urine dilution. HAP occurs over a wide range of dilution factors. A high fraction of phosphate is incorporated into the precipitates. Dilution with tap water increases this fraction by providing the limiting calcium and magnesium ions. Currently, constructing exchangeable traps seems to be the best solution to deal with problematic precipitation.
Reverse osmosis desalination of QNI Yabulu Nickel Refinery wastewater for reuse
Authors: Milsom J. , Palmer N. , Smallwood M.
Published: May 2018

Queensland Nickel Pty Limited commissioned a water recycling facility incorporating micro-filtration and reverse osmosis to treat wastewater from its Yabulu Nickel Refinery in North Queensland. Used process waters are brackish and unsuitable for reuse in the refinery. They have traditionally been stored in tailings ponds for evaporation, or discharged to sea under environmental authority. The development has demonstrated the potential for large-scale industrial desalination plants by recycling wastewater for reuse in the plant. By recycling this 12 ML/day waste stream, the refinery's new water input has been reduced by 40%. The utilisation of electro-magnetic anti-scaling technology in the reverse osmosis system is also discussed. No anti-scalant chemicals are used in the process.
Membrane filtration in water recycling: removal of natural hormones
Authors: Nghiem L.D. , Schäfer A.I. , Waite T.D.
Published: May 2018

Recent detections of endocrine-disrupting chemicals (EDCs) in effluent are of great concern to sections of the community associated with the issue of water recycling. In vitro and in vivo studies by many researchers have confirmed the impacts of EDCs on trout at the common concentration encountered in sewage effluent. Amongst many types of EDCs the impacts of steroid estrogens such as estrone, estradiol (natural hormones) and ethinylestradiol (a synthetic hormone) are prominent as they have far higher endocrine-disrupting potency than other synthetic EDCs. Given the continuous developments in membrane technology, tertiary treatment using membrane processes has been identified as a promising technology to provide a safeguard to water recycling practice and to protect the environment. This paper investigates retention and adsorptive behavior of the natural hormones estrone and estradiol by two commercial low-pressure nanofiltration membranes TFC-SR2 and TFC-S, using dead end stirred cell systems. The removal phenomena of estradiol are similar to that of estrone. pH has been found to significantly influence the adsorption of estrone and estradiol by the membranes, presumably due to hydrogen bonding. This adsorption is critical in the risk of possible release of such hormones to the product waters. Total adsorbed amounts were calculated for standard membrane elements and are indeed important.
Meeting the challenge of climate variability in a major water supply system
Authors: Hughes G.J.
Published: May 2018

A continuing period of climate variability affecting the south west of Western Australia has seen a 12% decrease in rainfall reduce streamflow to Perth's water supply dams by 50% during the last 27 years. A change in organisational arrangements and an evaluation of risk exposure were key triggers for the implementation of plans to restore the public drinking water supply reliability. The Water Corporation mobilised the support of customers and regulators during the recovery period. Poor and extremely low inflow events during the last five years required additional planning, regulator support and implementation strategies to minimise the impact on the Perth Community.
How do consumers perceive water quality? Example of an anthropological study carried out in Paris
Authors: Euzen A.
Published: May 2018

Observation of quality standards is the prime concern of water producers, but are the quality criteria used by professionals the same as those of consumers? How do consumers perceive the quality of the water distributed to their homes? The main concern of SAGEP, water producer for the City of Paris, is to respond at all times to users' expectations. To answer that requirement, SAGEP launched a consumer study on the reaction to tap water.

Analysis of the perceptions of water quality is presented in this paper. It reveals multiple and singular responses, which themselves depend on personal history and development of the individual concerned. An anthropological approach enables one to gain a grasp of the degree to which the diversity of perception comes into play in the day-to-day practice in the domestic environment of tap water. The example of consumer practice in regard to the type of water drunk demonstrates how custom changes with the context and how each person builds up confidence in tap water.

The complexity of what are a priori trivial uses confirms the need for water producers and distributors to make this reality an integral part of their overall management. They should now take in to account, perhaps in a different way, the consumers' expectations.
A new planning method for selecting water supply alternatives in an urbanized watershed with a stochastic approach
Authors: Eom D. , Kusuda T.
Published: May 2018

Water supply alternatives to alleviate water shortage damages in urbanized watersheds are itemized and evaluated in terms of cost, life cycle energy (LCE), and damages. A newly developed stochastic model of precipitation and constructed GIS databases are applied to estimation of potential water resources in the Hakata bay watershed in Japan. Based on these results, water supply alternatives in the watershed are selected at several return periods on less annual precipitation in the order of minimizing cost, LCE, and damages. The water supply alternatives selected are cascade reuse in house, groundwater, two kinds of recycled water, and desalinated water. The storage water volume in the reservoirs at initial time, annual precipitation, and annual precipitation patterns are considered as three factors on water shortage from the water supply side. The unit values of cost, LCE, and damages are obtained to estimate damages of water shortage and to consider measures for water supply by applying the above three factors. Finally, based on statistical distribution of damages on water shortage, a new planning method to avoid water shortage is developed and how to decide a design precipitation level is proposed in terms of the return period of damages instead of that of precipitation.
The California Urban Water Conservation Council: a consensus partnership for water conservation
Authors: Dickinson M.A.
Published: May 2018

California, perhaps more than any other of the United States, has been a leader in water efficiency experiments. It adopted uniform efficient plumbing standards in 1978 for showerheads and faucets and the same for water closets in 1992. Comprehensive water management planning was adopted in 1983 for all water agencies serving more than 3,000 connections or 3,000 people, and in 1991, a Memorandum of Understanding was signed by major water utilities and environmental groups statewide - pledging to implement standardized water efficiency programs called “Best Management Practices” in an attempt to help save the dying Bay-Delta Estuary. The California Urban Water Conservation Council, created by this Memorandum, is a non-profit NGO formed to oversee the Best Management Practices and to enforce the terms of the Memorandum. Since the historic signing of this Memorandum ten years ago, the Council has become a national example of consensus partnership on water efficiency. Water utilities and environmental groups work together on defining programs for water conservation, not as adversaries fighting each other in the press or in the courtroom. Technical assistance provided by Council staff helps utilities plan and implement conservation projects. This paper will outline national programs and will focus specifically on the Council partnership, which has resulted in benefits to water utilities, environmental groups, and state governmental agencies alike.
Optimisation of water extraction considering water demands of water supply, agriculture and ecology
Authors: Emmert M. , Schneck A.
Published: May 2018

For drinking water supply in the Donauried area (52 km2) approximately 950 l/s groundwater are abstracted from 6 catchment plants with 220 wells. In the Donauried also intensive farming and several natural parks with valuable but drained lower moors are located so that many conflicts have arisen around the water. In a joint research project the goal is to manage the 6 plants' water demands, hydrology and season to achieve a water-optimum for each party. That is to have enough water for water supply, to guarantee farming without affecting groundwater quality and to rewet the lower moors. This task is solved by developing an optimisation algorithm that is based on a numerical groundwater flow model taking into account the water demands of all parties.
Evaluating alternative strategies for wastewater recycling and reuse in the Mediterranean area
Authors: Ganoulis J.
Published: May 2018

The concept of sustainability in wastewater reclamation and reuse in the Mediterranean area needs to be expressed in a realistic and practical way. This paper suggests a suitable methodology for sustainable wastewater reuse in the Mediterranean area by considering not only technical and economic, but also, environmental and social aspects of wastewater reuse. Alternative strategies based on different treatment and storage technologies are evaluated by using the Multicriterion Decision Analysis (MCDA) method. Alternative strategies are formulated by combining elements such as different treatments, different disposal sites, the type of irrigation scheme, crop pattern, water pricing and the use of fertilizers. The criteria used to evaluate the most sustainable strategy include firstly public health and environmental factors, that pose risks on human health, water pollution during and after irrigation, efficiency of water use, secondly economic factors, including the water cost, the initial cost of the irrigation system, maintenance costs and crop profitability, and thirdly social issues including the employment of rural labour. Various MCDA techniques, namely, ELECTRE-3, ELECTRE-4 and Compromise Programming (CP) may be employed to rank alternative strategies and find out the most sustainable alternative.
Wastewater recycling and reuse in the Near East Region: experience and issues
Authors: Bazza M.
Published: May 2018

Wastewater in most countries of the Near East Region (NER) is being more and more recognized as of vital importance to be treated and made safe for reuse. It contributes considerably to the water budget in several countries, particularly those suffering from water scarcity. Treated wastewater is used directly in irrigation of farms or landscape green areas. Limited indirect use includes recharge of groundwater aquifers to control over-draft and salt intrusion in coastal areas. A large share of wastewater is still not treated and part of it is used in an uncontrolled manner, including for the production of uncooked food crops the consumption of which poses health risks. Expansion of treated wastewater reuse in the region is linked to a number of issues and constraints. The high cost of treatment and management of reclaimed wastewater is one of the major limitations facing the week economy of most countries. Unclear polices, institutional conflicts and lack of regulatory frameworks constitute other important constraints that hinder implementation and proper operation of wastewater reuse projects. The manpower capacity is at varying levels between countries, but additional training and capacity strengthening are generally needed throughout the region. This paper gives an overview of the existing practices of wastewater reuse in the NER and of the constraints facing it. It concludes with recommendations and policy options that are likely to lift these constraints and to make a better use of the wastewater potential.
Removal of fecal coliforms, somatic coliphages and F-specific bacteriophages in a stabilization pond and reservoir system in arid regions
Authors: Alcalde L. , Oron G. , Gillerman L. , Salgot M. , Manor Y.
Published: May 2018

The contents of FC, somatic coliphages and F-specific bacteriophages were measured in the stabilization pond and stabilization reservoir system of the City of Arad (Israel) in order to determine the efficiency of the treatment process regarding the microorganisms removal. Monitoring was conducted close to one year. Physical and chemical parameters (temperature, pH, BOD5, COD, SS) were also analyzed with the aim of finding factors that affect the microorganisms removal. The field results prove a very good performance of this treatment system. FC, somatic coliphages and F-specific bacteriophages were removed between 4.16 and 5.76 log units, during winter and in between 6.02 and 6.47 log units during summer. The microbial quality of the final effluent complies with the WHO guidelines for unrestricted irrigation. The results also indicate that retention time and temperature seem to be the most important factors for microorganisms removal. F-specific bacteriophages were removed at higher rates than FC and somatic coliphages. Consequently, it is suggested that F-specific bacteriophages might be less adequate viral indicators for this treatment system.
The “go with what you know” approach to forecasting future asset replacement expenditure
Authors: D’Agata S.
Published: May 2018

A reliable predictive model for the deterioration of water mains and sewers has been the quest of water industry asset managers for several decades. No doubt driven by finance managers, asset managers have been searching for that mythical formula that will tell them exactly when an asset will fail and allow them to accurately forecast replacement and renewal expenditure into the future.

Although it is imperative that water authorities act to avoid and prevent the catastrophic failure of major infrastructure assets where the consequence of failure is high, for most authorities these assets form a relatively small part of the asset base. Therefore, the detailed predictive modelling and analysis of pipe material properties employed to plan the replacement of these critical assets is not appropriate or practical to apply to reticulation assets that represent over 95% of the total infrastructure for most Authorities.

The application of predictive models based upon pipe material performance to develop replacement programs for extensive reticulation systems, does not adequately take into consideration the variations in construction methods, ground conditions, consumption patterns, topography and climatic conditions that exist in many networks. These variations are, however, implicit in historical performance data which also provides information of the rate of failure of assets which is the main driver for the replacement of reticulation assets. It is only when the rate of failure of an asset becomes unacceptable that replacement is necessary and this adopted level of service will have a greater influence on future asset replacement expenditure than the assessment of the deterioration of pipe materials. All the more reason to base asset replacement programs around historical data and go with what you know.
Asset planning for water reticulation systems - the PARMS model
Authors: Burn S. , Tucker S. , Rahilly M. , Davis P. , Jarrett R. , Po M.
Published: May 2018

Traditionally water reticulation systems have been operated so that pipeline repair/renewal occurs on a reactive basis, based upon the number of failures, the consequence of failure and the cost. Planning for future replacements and the costs associated with these has been based upon a best guess of pipe lifetimes, which have generally been very conservative, when compared to the actual pipe life obtained. Factors such as the required level of customer service, trade-offs between repair and renewal, or operating practices such as pressure reduction or shut-off block reduction have not been widely considered, except when they are required under the water authorities operating licence. To allow long-term strategies to be implemented for the repair/renewal of water pipelines, a Pipeline Asset and Risk Management System (PARMS) is being developed. This planning model has been designed to allow a range of “what if” scenarios to be analysed to determine their effects on water authorities’ long-term costs. This model is based upon whole of life costing and includes data on externality and customer impact costs. It analyses the failures of individual pipe assets, rather than the traditional practice of predicting failure of pipe cohorts, currently used by many authorities. This paper discusses the application of the PARMS planning model to allow selection of pipeline repair/renewal, and briefly analyses the influences that a range of customer service or operating decisions can have on a water authority’s capital and operational expenditure.
Real-time optimization simulation software modules for water networks
Authors: Cioc D. , Anton A.
Published: May 2018

Several mathematical models and commercial computer codes are available to assess the behaviour of a hydraulic network both at peak demands and in 24 hour operation. Could a new model add some value to the prestigious existing ones? Are we really at the end of the research path in this field? These questions are to be answered in the present paper. A new concept of optimization is presented for water distribution modelling: a concept based on life-cycle cost analysis. Introducing a minimum number of parameters, technical and also economic, the authors were able to elaborate a mathematical model for optimization. The corresponding computer code’s capabilities are related both to the design of brand new networks and to the rehabilitation of old ones. The speed of the code allows, among others, a real-time optimization simulation for an existing network, making it a valuable operational tool. Finally the code has been tested on several networks and has been validated with very good results, being a simple tool that is easy to handle and capable of exchanging input and output data with practically any other similar software or graphic tool.
Monitoring of priority pesticides using SPME (solid phase microextraction) in river water from Greece
Authors: Albanis T.A. , Lambropoulou D.A. , Sakkas V.A. , Hela D.
Published: May 2018

A solid phase microextraction (SPME) method was applied for the extended monitoring survey of priority pesticides for the European Union, for 12 months, in Kalamas River water samples (Epirus region in northwestern Greece) to determine their concentration levels and seasonal variations. For this purpose, polydimethylsiloxane-coated fiber has been utilized. The samples were screened using gas chromatography with flame thermionic detection. Detections were confirmed by gas chromatography-mass spectroscopy (MS). The most frequently detected pesticides were some of the more commonly used herbicides such as EPTC, trifluralin, atrazine, desethylatrazine, terbuthylazine, alachlor and insecticides such as carbofuran, diazinon, disulfoton, methyl parathion, ethyl parathion, fenthion and ethion. Concentrations of individual compounds ranged from 0.050 to 0.3 μg/L. Greater pesticide concentrations occurred during application seasons. A comparison with a well established SPE (C18-disks) procedure was performed for the samples of high season application (May-September) to confirm the effectiveness of the SPME technique. The results demonstrate the suitability of the SPME method for routine screening multi-residue analysis in natural waters.
Optimisation meets the manager: a case study of the La Paz reservoir system
Authors: Bender M. , Stanic M. , Luketina D. , Hranisavljevic D.
Published: May 2018

Managers must usually apply operating rules to optimise the use of water resources in a sustainable manner. Ideally a manager needs a set of near-optimal dynamic operating rules that are consistent with the objectives and level of risk set by the manager. The traditional approach for a reservoir is to develop fixed (static) rule curves based upon a statistical analysis. However, improved dynamic rules can be derived using optimisation techniques such as genetic algorithms. Also, simulation methods can be used. Here we show how both methods can be applied to generate near-optimal dynamic operating rules for a reservoir system used for drinking water supply in La Paz, Bolivia. In particular, we show how simple practical operating rules can incorporate the level of risk set by the manager. Further, these rules advise how quickly water levels should be altered when they are too high or too low.
Effects of coagulation on filtration mechanisms in dead-end ultrafiltration
Authors: Kennedy M. , Zhizhong L. , Febrina E. , Van Hoof S. , Shippers J.
Published: May 2018

Filtration mechanisms occurring during ultrafiltration of coagulated and non-coagulated surface water were investigated using the general blocking filtration laws. The sharp decline in permeate flux in the first 10-20 minutes of filtration was largely due to a combination of the blocking filtration mechanisms. However, a distinction between “complete”, “standard” and “intermediate blocking” mechanisms was not possible as a large degree of overlap existed between the mechanisms and the transition from one type of blocking to another was very smooth. Coagulation appeared to retard blocking and consequently, the duration of the “blocking phase” was twice as long for coagulated water compared with non-coagulated water. The “transition phase”, where both blocking and cake filtration occurred simultaneously, was also extended in the case of coagulated water as continuous blocking of the membrane through the pores of the cake was observed. The modified fouling index-ultrafiltration (MFI-UF) was employed to examine the impact of coagulation on filter cake properties. Coagulation reduced the specific resistance of the filter cake by 50% at a TMP of 1.5 bar, and 35% at a TMP of 0.5 bar. Depth filtration was hardly evident at a TMP of 0.5 bar, but was very pronounced at a TMP of 1.5 bar as the specific resistance of the filter cake increased continuously, particularly in the absence of coagulant. The filter cake was sensitive to the applied TMP and the MFI-UF value increased by 130% for non-coagulated surface water and 55% for coagulated water due to compression of the cake, when the TMP increased from 0.5 to 1.5 bar.
Optimising dose of antiscalant in membrane filtration systems using a desupersaturation unit
Authors: Bremere I. , Kennedy M. , Johnson A. , Witkamp G.-J. , Schippers J.
Published: May 2018

The strategy behind the desupersaturation unit (DU) is rapid desupersaturation of the membrane concentrate stream by forced precipitation of sparingly soluble inorganic compounds on seed crystals. The efficiency of deposition will depend on the supersaturation and the condition of seeds, i.e. their reactivity. Poisoning of seeds by adsorption of natural organic matter and/or added commercial antiscalant will hinder the desupersaturation efficiency by blocking centres available for crystallisation. Barium sulphate precipitation in a laboratory scale DU was examined from natural reverse osmosis (RO) concentrates from surface water treatment pilot plant. Tests indicated similar effects on poisoning the barite seed grains by commercial antiscalant and natural organic matter from surface water (the Rhine River) treatment RO pilot plant (80% conversion) while no effect was observed from supersaturated synthetic (no organic matter) concentrate. An attempt was made to relate the effects of organic matter and the RO system conversion (50-85%). The rate of barite seed grain poisoning was attributed to the relative barium supersaturation in the concentrate. The efficiency of natural organic compounds started to decline above the supersaturation ratio of 3.3. Addition of commercial antiscalant enhanced the effect of natural organic matter. If the effects of organic matter in membrane systems are quantified and related to the RO system conversion, a laboratory DU can practically be used to control scaling.
Novel methods for characterizing algogenic organic matter and associated nanofiltration membrane fouling
Authors: Her N. , Amy G. , Yoon J. , Song M.
Published: May 2018

Algogenic organic matter (AOM) has been extracted from blue-green algae (cyanobacteria) by various means and analyzed by UV absorbance scanning, HPSEC-UV-fluorescence-DOC, FTIR, and fluorescence excitation emission matrix (EEM). AOM extracted in water as a solvent showed a high hydrophilic fraction (57.3%) with a low SUVA (1.0 L/m-mg). The molecular weight (MW) distribution showed a significant heterogeneity (high value of polydispersivity) and high protein content (as indicated by specific fluorescence). A significant amount of proteinaceous components such as mycosporine-like amino acids (MAAs, UV-screening components) and phycobilins (light-harvesting pigment) was detected by UV/visible absorption. The confirmation of proteins was proven by FTIR (at 1,661 cm-1 and 1,552 cm-1) and EEM spectra (EX: 278-282 nm and EM: 304-353 nm). A bench-scale cross-flow unit, employing a flat-sheet membrane specimen, was used to examine nanofiltration (NF) membrane fouling and removal of natural organic matter (NOM) derived from different blends of Suwannee River humic acid (SRHA) and AOM. The flux decline and organic matter rejection as a function of delivered DOC showed significantly different results depending on the organic matter composition of samples even though the test conditions were the same (organic matter concentration, pH, temperature, inorganic salt composition and concentration, and recovery). A higher flux decline was observed with increasing proportions of AOM. Organic matter rejections also decreased with higher AOM contributions to the samples, indicating that lower MW AOM components were not well rejected by the NF 200 membrane having a 360 dalton molecular weight cutoff (MWCO). However, SRHA that shows a relatively high MW (5,000-1,000 daltons) and high SUVA (7.4 L/m-mg) was preferentially rejected through electrostatic repulsion/size exclusion by the NF 200 membrane, having a high negative charge (zeta potential: -15.6 mV), low MWCO, and relatively low hydrophobicity. Even though the DOC concentration of feed water is a decisive factor for membrane fouling along with membrane properties and operating conditions, the characteristics of organic matter are more influential in fouling potential. Protein-like and polysaccharide-like substances were found as major foulants by FTIR.
Effects of characteristics of softening as a pretreatment for ultrafiltration
Authors: Kweon J.H. , Lawler D.F.
Published: May 2018

Softening was proposed as a pretreatment for ultrafiltration, which reduces foulants prior to membrane processes. The objectives of this research were to understand the nature of the fouling mechanisms for ultrafiltration when used for waters that either require softening or have been softened, and to use that understanding to determine promising options for the use of softening as a pretreatment before ultrafiltration (UF). Several characteristics of softening, including extent of softening, precipitation kinetics, and hydrophobicity of membrane materials, were investigated as independent variables. Because of softening, both the organic matter concentration and the particle concentration of feed water to ultrafiltration were reduced, thus reducing the degree of fouling. The slow kinetics of softening had little effect on membrane fouling although precipitation directly occurred on the membrane surface in the system during the operation. Detailed images of the membrane surface obtained by scanning electron microscopy confirmed substantial amounts of the precipitates on the surface. In contrast, the hydrophobicity of the membrane material showed a significant effect on the flux decline behavior. Overall, the integrated water treatment of softening and ultrafiltration is shown to be a promising option for hard waters.
Assessment of ultrafiltration as a pretreatment of reverse osmosis membranes for surface seawater desalination
Authors: Brehant A. , Bonnelye V. , Perez M.
Published: May 2018

Pre-treatment of seawater feeding reverse osmosis (RO) membranes is a key step in designing desalination plants, especially when treating surface seawater with highly variable quality. The objective of the study was to assess the potential of ultrafiltration (UF) pre-treatment prior to RO for desalting seawater with high-fouling tendency. A UF pilot plant equipped with an Aquasource membrane was directly operated on Gibraltar surface seawater in dead-end mode. The competitiveness of UF pre-treatment towards conventional pre-treatment was assessed by looking at the impact on RO hydraulic performances. The study showed that UF provided permeate water with higher quality than with a conventional pre-treatment. The main seawater compounds responsible for UF fouling were organic matter released by phytoplanktonic organisms. The combination of UF with a pre-coagulation at low dose helped in controlling this fouling and providing water in steady state conditions. The performance of RO membranes downstream of UF exceeded the usual operating conditions encountered in seawater desalination. The combined effect of higher recovery and higher flux rate promises to significantly reduce the RO plant costs.
Cyclic bioreactors - a discussion on technology application and possible future developments
Authors: Ng W.J.
Published: May 2018

Wastewater treatment systems based on cyclic reactors started to be applied more widely in Asia about two decades ago. A number of variants have been introduced but the focus of this paper is on the intermittent feed-intermittent decant variant, the SBR. Based on the basic SBR concept, specific reactor configurations which have been introduced include the pretreatment anaerobic reactor (anSBR), the aerobic reactor (aeSBR), and the sludge digester (SBD). This paper discusses some of the issues around the argument for selecting the SBR - particularly the aeSBR, equipment which are unique to this cyclic reactor, the concerns around such equipment selection, operating difficulties, and the possible future developments with this reactor concept.
Use of organic solution for the removal of hazardous chemicals: the more efficient and zero-emission decomposition processes by extraction, concentration and reaction in organic solutions
Authors: Okada M. , Nakano Y. , Ohkawa K. , Tsai T.Y. , Nishijima W.
Published: May 2018

We proposed a new process for ozone decomposition of hazardous chemicals in organic solution concentrated from water into the solution by using adsorbent or air-stripping. The target compounds studied were chlorophenols and TCE. Chlorophenols were adsorbed from water and desorbed into organic solutions like acetic acid by GAC and synthetics adsorbents, SP850 and SP207. The best adsorbent both for adsorption and desorption into acetic acid solution was synthetis one, SP850, and percent desorption was 100%. GAC was good for adsorption, but was not for desorption. Although more than 800 mg-TCE L−1 in acetic acid solution was decomposed by ozonation, little decrease in the decomposition rate was noted indicating that acetic acid can be reused for the next step of ozonation in the same acetic acid solution.
Microbiological contamination of dental unit water systems in general practices from Barcelona (Spain)
Authors: Araujo R. , Contreras N.
Published: May 2018

Dental Unit Water Systems (DUWS) can be a source of contamination to dentists and patients, especially those who are immunocompromised. Such organisms may originate from incoming water supplies and from oral cavities. The most common cause of dental unit water contamination is believed to be the formation and subsequent sloughing off of microbial biofilms from tubing within DUWS. There are no evidence-based guidelines currently available to dentists for the control of DUWS contamination in Europe. The aim of this study was to investigate the microbial load of water from DUWS, especially the presence of microbial pathogens which can be a source of cross-contamination between patients. Water and tube samples were obtained from 40 dental surgeries in Barcelona. The samples were taken from turbine and from air/water syringe. Twelve of these DUWS were fed with hard water from mains (with chlorine) and 28 dental units with bottle or tank deionized water. Microbial load was ranged from 0 to 3.6 × 103 colony-forming units/mL. Legionella sp., Mycobacterium sp., Pseudomonas aeruginosa and Candida sp. were found in 4, 8, 6, and 2 different surgeries, respectively. Inclusive oral streptococci were found in 2 dental units indicating that there is a back siphonage in the systems analysed.
Advances in standardizing and validating research techniques for pathogen monitoring in water
Authors: Connell K. , Pope M. , Miller K. , Scheller J. , Pulz J.
Published: May 2018

Designing and conducting standardized microbiological method interlaboratory validation studies is challenging because most methods are manual, rather than instrument-based, and results from the methods are typically subjective. Determinations of method recovery, in particular, are problematic, due to difficulties in assessing the true spike amount. The standardization and validation process used for the seven most recent USEPA 1600-series pathogen monitoring methods has begun to address these challenges. A staged development process was used to ensure that methods were adequately tested and standardized before resources were dedicated to interlaboratory validation. The interlaboratory validation studies for USEPA Method 1622, for Cryptosporidium, USEPA Method 1601 for coliphage, and USEPA Method 1605 for Aeromonas assessed method performance using different approaches, due the differences in the nature of the target analytes and the data quality needs of each study. However, the use of enumerated spikes in all of the studies allowed method recovery and precision to be assessed, and also provided the data needed to establish quantitative quality control criteria for the methods.