bluuebunny/crossref_metadata_2025 huggingface dataset:
Drinking water quality assessment practices: an international perspective
Authors: Steynberg M.C.
Published: May 2018

The complexity of compliance monitoring was acknowledged by The Standards and Monitoring Committee of IWA who initiated a task force to investigate international practices. Results from an initial survey indicated that although most countries do have drinking water quality guidelines, only a few are enforcing these guidelines. It was evident that most of these countries do not incorporate analytical variability in the application of analytical results for compliance studies. A clear link between the regulator, the producer and the analyst does not exist. An effective system that assesses compliance to drinking water specifications and at the same time ensures the consumer safe and healthy water, therefore, does not exist for most consumers. In an effort to provide guidance to members of IWA, the water supplier, the analyst and the regulator, workshops should be held during the next two conferences of IWA. The output of these workshops should be guiding documents and networking opportunities that will facilitate effective and efficient skills transfer for compliance monitoring of drinking water in all the countries of the world.
Flow structures in a dissolved air flotation pilot tank and the influence on the separation of MBBR floc
Authors: Lundh M. , Jönsson L. , Dahlquist J.
Published: May 2018

The objective of the study was to find ways of improvement of the dissolved air flotation process by studying the flow structure. The paper presents experimental data on flow structures and the relation between the flow structure and the removal efficiency. Measurements have been performed in a pilot plant with an Acoustical Doppler Velocimeter. The water velocity was measured in a grid net, giving insight into the flow structure. The removal efficiency was analysed at Malmö wastewater treatment plant in Sweden. The pilot plant separated biological floc from a Kaldnes Moving Bio-Bed Reactor (MBBR). The efficiency of the separation was analysed by measurements of suspended solids in the influent and the effluent. Air content was measured inside the tank and in the re-cycle. The result showed that basically two flow structures existed; the stratified and the short-circuit flow structure. The stratified flow structure seemed correlated to efficient separation of particles while the short-circuit flow structure seemed to have a negative effect, especially when the flow structure was affected by varying the re-cycle rate, i.e. the air content. Conclusively, the flow structure seemed to be correlated to type of flow structure. However, studies with higher concentration of suspended solids for verification were suggested.
Removal of nitrate from water in a novel ion exchange membrane bioreactor
Authors: Velizarov S. , Crespo J.G. , Reis M.A.
Published: May 2018

Biological denitrification in a novel ion exchange membrane reactor (IEMB) has been investigated. The polluted water was separated from the mixed denitrifying culture by a non-porous, mono-anion permselective membrane providing continuous exchange of nitrate for chloride added as a counter-ion to the biocompartment. A removal efficiency of 87% and a surface removal rate of about 1,400 mg NO3- m-2h-1 was achieved at a nitrate concentration of 150 mg NO3- L-1. The treated water stream was essentially free of ethanol, used as a carbon source, and NO2- ions whereas the original water conductivity was completely preserved due to very efficient Donnan exclusion of the cations present in the two solutions from the membrane used. The IEMB process showed higher removal efficiency and better nitrate selectivity compared to a Donnan dialysis process operated under similar conditions.
Biofilter pretreatment for the control of microfiltration membrane fouling
Authors: Park J. , Takizawa S. , Katayama H. , Ohgaki S.
Published: May 2018

A pilot scale biofilter pretreatment - microfiltration system (BF-MF) was operated to investigate the effect of biofilter treatment in fouling reduction of microfiltration. Biofiltration was expected to reduce the membrane fouling by removal of turbidity and metal oxides. The hollow-fiber MF module with a nominal pore size of 0.1 μm and a surface area of 8m2 was submerged in a filtration tank and microfiltration was operated at a constant flux of 0.5 m/d. Biofiltration using polypropylene pellets was performed at a high filtration velocity of 320 m/d. Two experimental setups composed of MF and BF/MF, i.e. without and with biofilter pretreatment, were compared. Throughout the experimental period of 9 months, biofilter pretreatment was effective to reduce the membrane fouling, which was proved by the result of time variations of trans-membrane pressure and backwash conditions. The turbidity removal rate by biofiltration varied between 40% to 80% due to the periodic washing for biofilter contactor and raw water turbidity. In addition to turbidity, metals, especially Mn, Fe and Al were removed effectively with average removal rates of 89.2%, 67.8% and 64.9%, respectively. Further analysis of foulants on the used membranes revealed that turbidity and metal removal by biofiltration was the major effect of biofiltration pretreatment against microfiltration fouling.
Perchlorate as a secondary substrate in a denitrifying, hollow-fiber membrane biofilm reactor
Authors: Nerenberg R. , Rittmann B.E.
Published: May 2018

In recent years, several oxyanions have emerged as drinking water micropollutants, including arsenate, selenate, bromate, and, most recently, perchlorate (ClO4-). Conventional water treatment processes typically are ineffective in removing these compounds, and advanced treatment processes are expensive. Biological reduction may provide a suitable treatment alternative, since these compounds can serve as electron acceptors. Other acceptors, such as nitrate (NO3-), must act as a primary electron acceptor. We tested our denitrifying, autotrophic, hydrogen-oxidizing hollow-fiber membrane for ClO4- reduction. The reactor is highly suited to drinking water treatment, as hydrogen (H2) is inexpensive, non-toxic, and does not leave residuals that can cause regrowth. When 1 to 2 mg/L ClO4- was supplied to reactor, which was at steady-state with 5 mgN/L NO3- but unacclimated to ClO4-, ClO4- removals increased from 40 to 99% over three weeks. Removals to 4 μg/L were also achieved in a natural groundwater having 6 to 100 μg/L ClO4-. Tests with variable NO3- and H2 showed that ClO4- reduction requires less than 30 μgN/L NO3- and at least 300-μg/L effluent H2. Therefore, partial denitrification is probably not consistent with excellent ClO4- removal. Mineral medium produced a gradual loss of ClO4--reducing bacteria, but they were re-enriched when tap water replaced minimal medium.
Large scale pilot plant for treating flocculated reservoir water and membrane integrity monitoring
Authors: Hagmeyer G. , Gimbel R. , Dautzenberg W.
Published: May 2018

The Wasserwerk des Kreises Aachen in Roetgen, Germany operates with financial help of the German Ministry for Education and Research and with scientific support of the IWW (Muelheim, Germany) a large scale membrane pilot plant. This pilot is equipped with twelve 6 m long pressure vessels resulting in a membrane area of about 1,620 m2 to produce about 150 m3/h of filtrate. The pilot plant was operated first with flocculated reservoir water as feed. The results show that this is a reasonable process especially if the backflush water of the plant is further treated with another membrane plant to achieve high overall recoveries up to 98-99%. Monitoring of membrane integrity is an important topic in this research. Every pressure vessel of the pilot can be connected to a particle counter by switching magnetic valves automatically. Corrupted fibres were detected by particle counting after about 8 month of operation. A correlation between the number of broken fibres and particle concentration in the filtrate could not be established and may not exist as it is discussed in this paper.
Assessment of the risk of infection associated with Coxsackie B viruses in drinking water
Authors: Vivier J.C. , Ehlers M.M. , Grabow W.O.K. , Havelaar A.H.
Published: May 2018

The risk of infection constituted by enteroviruses detected in drinking water supplies analysed in this study were assessed. Coxsackie B viruses (CBV) were used as a model in these assessments. A high proportion of Coxsackie B virus infections are asymptomatic. However, clinical manifestations may range from mild, undifferentiated febrile illness or upper respiratory tract infection to a severe, systemic and sometimes fatal disease of sensitive populations. Dose-response studies suggested that an exponential model best describes infectivity of CBV. The analysis of 172 samples of treated drinking water supplies described in this study revealed the presence of CBVs in 11% (water treatment unit A) and 16% (water treatment unit B) of the samples. This incidence of CBV was used as a basis for risk assessment. The results indicated that the drinking water supplies concerned constitute a risk of CBV infection of 3.91 × 10-3 (unit A) and 7.4 × 10-3 (unit B) per year. The estimated risk of infection are about an order of magnitude higher than the yearly acceptable risk of one infection per 10,000 consumers proposed for drinking water supplies.
Isolation and characterization of Escherichia coli O157:H7 and shiga toxin-converting bacteriophages from strains of human, bovine and porcine origin
Authors: Müller E.E. , Taylor M.B. , Grabow W.O.K. , Ehlers M.M.
Published: May 2018

Toxin-converting bacteriophages encoding the Stx2 gene were induced from strains of Escherichia coli O157:H7 isolated from sewage, bovine and porcine faeces. Toxin synthesis can be stimulated by the induction of integrated toxin-converting phages from the host E. coli O157:H7 organism by ultra-violet (UV) exposure. The UV-mediated DNA damage of E. coli O157:H7 triggers a bacterial SOS response resulting in phage release. Free ranging phages outside their E. coli O157:H7 hosts were detected but could not be isolated directly from environmental samples such as sewage and river water. E. coli O157:H7 colonies carrying the genes coding for Stx2 were isolated from 1 sewage sample (0.76% of positive samples), 8 cattle faecal samples (16.67% of positive samples) and 2 pig faecal samples (14.28% of positive samples). Characterization of E. coli O157:H7 was done by repetitive sequence analysis using ERIC-PCR to determine the relationships between the individual E. coli O157:H7 strains. The ERIC-PCR analysis revealed distinct patterns for all E. coli O157:H7 strains with some small differences between the strains. DNA sequencing of some of the E. coli O157:H7 positive isolates carrying the Stx2 genes were performed confirming the amplified DNA nucleotide sequences of Stx2. Electron microscopic analysis revealed, for the first time in South Africa, that Stx2-converting phages induced from E. coli O157:H7 have different morphologies to that of phage lambda which was previously described. The role of the induced integrated Stx2 phages in natural environments such as river and dam water remains unclear. With the induction of Stx2-converting phages from environmental E. coli O157:H7 isolates, it is now possible to determine the potential of these phages to convert non-pathogenic E. coli strains and other enterobacteriaciae into pathogenic strains.
International report: water and wastewater disinfection - trends, issues and practices
Authors: Jacangelo J.G. , Trussell R.R.
Published: May 2018

The prevention of waterborne diseases since the early part of this century can be attributed, in great part, to routine disinfection of water and wastewater. Issues surrounding disinfection differ from country to country. The objective of this paper is to provide an international report on water and wastewater disinfection practices. A background and history of disinfection is presented, followed by a discussion of microorganisms of concern in water and wastewater, disinfection practices, and issues and developments in specific countries. Additionally, selected similarities and differences between water and wastewater disinfection practices will be discussed. The information presented is based, in part, on the national reports on disinfection of water and wastewater that were submitted by 22 countries (Table 1); other information cited was obtained from the literature.
Numerical simulation of chlorine disinfection processes
Authors: Greene D.J. , Haas C.N. , Farouk B.
Published: May 2018

The efficacy of disinfection processes in water purification systems is governed by several key factors including reactor hydraulics, disinfectant chemistry and microbial inactivation kinetics. The objective of this work was to develop a computational fluid dynamics (CFD) model to predict flow structure, mass transport and chlorine decay in a continuous flow pilot scale reactor. These predictions were compared with experimental measurements for model validation. The current research demonstrates that inlet configurations can significantly impact reactor hydrodynamics.
Removal methods of nematoda contained in the effluent of activated carbon
Authors: Matsumoto N. , Aizawa T. , Ohgaki S. , Hirata T. , Toyooka K. , Kanbayashi T. , Tsutsumi Y. , Hasegawa T.
Published: May 2018

Effects of various alternative disinfectants, e.g. chlorine dioxide, ozone, ultraviolet radiation and chloramine, either alone or in combination with other physical treatments like sand filtration and membrane filtration, on the inactivation and removal of nematoda were studied. Ozone and chloramines were found to be effective for nematoda inactivation. Filtration alone was unable to remove nematoda completely. But the combination of UV radiation and sand filtration turned out to be very effective in the removal of nematoda from drinking water. 90% inactivation of nematoda needed a UV dose of (D10-value) 135 mJ/cm2, while 99% inactivation required 232.5 (135 + 97.5) mJ/cm2. This study was a part of a five-year national research project “Advanced Aqua Clean Technology for 21st Century” (ACT21).
Studies on mutagenicity and disinfection by-products in river drinking water disinfected with peracetic acid or sodium hypochlorite
Authors: Monarca S. , Feretti D. , Zerbini I. , Zani C. , Alberti A. , Richardson S.D. , Thruston A.D. , Ragazzo P. , Guzzella L.
Published: May 2018

The aim of this research was to study at a pilot plant the influence of peracetic acid (PAA) on the formation of mutagenic compounds in river waters used for human consumption. The results obtained using PAA were compared to those for the most commonly used disinfectant, sodium hypochlorite (NaClO). Ames test and three genotoxicity plant tests, Allium tests and Tradescantia/micronuclei (TRAD/MCN) test, were used to evaluate the mutagenic activity of disinfected water samples. Chemical analysis, using gas chromatography/mass spectrometry (GC/MS), was also performed to identify disinfection by-products (DBPs). A slight bacterial mutagenicity was found in raw river water and similar activity was detected in disinfected water samples. Plant tests gave genotoxicity only for raw river water. DBPs identified in PAA-treated water included carboxylic acids, a few non-halogenated alcohols and carbonyl-containing compounds, whereas some potentially mutagenic halogenated by-products were found in NaClO-treated samples. Although PAA appears to be promising for water potabilization, these results must be confirmed with different source waters and with higher concentrations of PAA.
Comparison of different advanced disinfection systems for wastewater reclamation
Authors: Salgot M. , Folch M. , Huertas E. , Tapias J. , Avellaneda D. , Girós G. , Brissaud F. , Vergés C. , Molina J. , Pigem J.
Published: May 2018

Several lines of reclamation have been tested in the Palamós/Vall-Llobrega (Girona, Spain) wastewater treatment plant. Each line consists of a filtration treatment (infiltration-percolation, sand filter, ring filter and physico-chemical treatment) plus a disinfection system (UV, peracetic acid, chlorine dioxide and ozonation). Every combination has been evaluated and compared with the other possibilities. This combination of filtration and disinfection allows the use of lower doses of disinfectants, thus minimising the negative impacts of the whole process and improving the reliability of the reclamation facilities.
Assessing the impact of dissolved organic carbon changes on disinfectant stability in a distribution system
Authors: Campos C. , Harmant Ph.
Published: May 2018

Maintaining disinfectant residuals throughout the entire water distribution system is considered an efficient strategy to guarantee the biological stability of drinking water as it flows from the plant to the customer tap. Dosed at the plant, the disinfectant disappears in the distribution system due to reactions with both water and pipe constituents. Among them, certain fractions of the organic matter content are directly responsible for the loss of disinfectant. This study presents an example of the impact of the organic matter UV absorbance on free chlorine decay for a surface water. In addition, this study illustrates the use of laboratory experiments together with a water quality model as a valuable tool to predict the impact of organic carbon concentration changes on chlorine residuals in interconnected distribution systems.
Measuring the effectiveness of multi-sector approaches to service provision
Authors: Caplan K. , Jones D.
Published: May 2018

Sustainable development is a global imperative, and strategic partnerships involving business, government and civil society may present a successful approach for the development of communities around the world. Business Partners for Development (BPD) is an informal network of partners that seeks to demonstrate that partnerships among these three sectors can achieve more at the local level than any of the groups acting individually. The Water and Sanitation Cluster of the BPD has been working with eight partnership projects around the world to determine the efficacy of the partnership approach in providing water and sanitation to the poor.

Measuring the effectiveness of these partnerships, however, proves challenging. Different interested and affected groups will measure the success of the initiative along different sets of criteria. Partnership elicits qualitative values such as trust, responsiveness and flexibility that are more likely to be “measured” by gut reactions rather than by more mechanical means. However, the creation and maintenance of a carefully selected set of indicators for a specific partnership project should enhance relations by increasing clarity and building stronger communication channels. The paper below provides considerations for the creation of partnership indicators.
Creating and optimizing new forms of public-private partnerships in Seattle
Authors: Haskins S. , Gale D. , Kelly L.
Published: May 2018

Seattle Public Utilities is pioneering a new form of public-private partnership in North America in the development of two new large water treatment plants. The Tolt and Cedar Treatment Plants, which provide drinking water for 1.3 million people, are being implemented using a design-build-operate (DBO) approach. This process has resulted in savings of 40% for the Tolt and 30% for the Cedar, relative to the estimated cost of implementing the projects using a conventional design-bid-build procurement with City operations for 25 years. In using the DBO approach, owners seek to optimize efficiency and the potential for innovation by conducting a competition to supply a bundled set of services including permitting, design, construction,and long-term operations. Benefits from this approach arise through design-build synergies, design-operate synergies, and through more focused competition than exists in the segmented design-bid-build model typically used. This paper will focus not only on the DBO approach and its resulting benefits, but perhaps more importantly on the critical issue of risk allocation. Finally, a discussion of our experience with these two premier projects will highlight the importance of a thoughtful procurement process and adherence to partnering approach to contract management in assuring the integrity of risk management principles.
Analysis of local velocity gradients in rapid mixer using particle image velocimetry technique
Authors: Park N.-S. , Park H.
Published: May 2018

Recognizing the significance of factual velocity fields in a rapid mixer, this study focuses on analyzing local velocity gradients in various mixer geometries with particle image velocimetry (PIV) and comparing the results of the analysis with the conventional G-value, for reviewing the roles of G-value in the current design and operation practices. The results of this study clearly show that many arguments and doubts are possible about the scientific correctness of G-value, and its current use. This is because the G-value attempts to represent the turbulent and complicated factual velocity field in a jar. Also, the results suggest that it is still a good index for representing some aspects of mixing condition, at least, mixing intensity. However, it cannot represent the distribution of velocity gradients in a jar, which is an important factor for mixing. This study as a result suggests developing another index for representing the distribution to be used with the G-value.
Key parameters controlling an adsorption process for the selective removal of arsenic from drinking water
Authors: Ouvrard S. , Simonnot M.-O. , Sardin M.
Published: May 2018

Arsenic can be selectively removed from water through adsorption on a natural manganese oxide. This paper presents some of the key parameters controlling such a process. Both production and regeneration steps were studied and the influence of three main controlling parameters was put to light. The water pH greatly influenced the adsorption capacity. Low water pH highly improved the treatment. The adsorption being under mass transfer limitation, flow rate influence was measured and optimization solutions were proposed. Finally, the impact of the regeneration procedure was evaluated on the adsorbent stability. It gave good arsenic elution results but the caustic elution step generated fine particles that could not be avoided. The following neutralization could however be adjusted in order to minimize further adsorbent dissolution.
A water authority's experience with HACCP
Authors: Mullenger J. , Ryan G. , Hearn J.
Published: May 2018

South East Water Limited (SEWL) is one of three retail water authorities operating in Melbourne, Australia. It was the first water authority in Australia to obtain HACCP accreditation for the supply of drinking water, in November 1999. This article presents an overview of the first two years' experience in developing and establishing a food safety management plan using Codex Alimentarius Hazard Analysis and Critical Control Points (HACCP) to ensure the water reaching customers is safe, aesthetically pleasant and meets operating licence requirements. HACCP has improved the way in which our distribution and reticulation systems are managed, primarily through the refinement and optimisation of standard operating procedures. In addition, more consideration has been given to the development of contingency plans and the appropriate use of system redundancy to ensure quality of supply. Accreditation was only the beginning of a process. Once attained, there was an ongoing need to maintain and refine hazard measurement and reduction procedures. The major challenge for SEWL has been the integration of HACCP company-wide. Spreading of HACCP was directly achieved through the involvement of operators, key personnel and subcontractors in the assessment of hazards and evaluating the appropriateness of critical control points. This not only assisted with improvements to the existing system, and the identification of system strengths and weaknesses, but was also an integral component in awareness training for HACCP. It was through assessment workshops and training that operators were able to see HACCP as primarily a summary of current practices, but with the focus of improving or maintaining water quality. The net benefits of HACCP are difficult to quantify. Overall there is a greater understanding of water quality issues, more streamlined work procedures, and an improved response to customer enquires relating to water quality. This has been most clearly demonstrated by a net decrease in customer complaints over the two years since HACCP was implemented.
Removal of microcystin variants with powdered activated carbon
Authors: Cook D. , Newcombe G.
Published: May 2018

Hepatotoxic microcystins resulting from cyanobacteria blooms occur in drinking water sources worldwide. Their removal in the water treatment process is essential if safe drinking water is to be produced. The presence of microcystins in raw water is problematic to the water treatment plant operator, as they are not removed by conventional water treatment practices (coagulation, flocculation, sedimentation and filtration). Powdered activated carbon (PAC) has been shown to have the potential to remove microcystin-LR; however, its success is dependent on the application of a sufficient dose for the production of water that is safe to consume. Currently there is no method available for determining PAC doses for the removal of microcystin-LR and little information exists on the removal of other microcystin analogues. In previous work the Homogeneous Surface Diffusion Model (HSDM) was successfully used to predict the adsorption of earthy-musty tastes and odours onto PAC. In this study, adsorption experiments were performed to determine whether the HSDM could be applied to two microcystin analogues: microcystin-LR (mLR) and microcystin-LA (mLA). The HSDM was used to predict the kinetics of mLR and mLA adsorption onto a wood-based PAC from a spiked sample of reservoir water. From this information PAC doses required to remove the toxic compounds were predicted for a range of conditions. These two variants were more difficult to remove than microcystin-RR (mRR) and microcystin-YR (mYR). The ease of removal was found to be in the following order: mRR > mYR > mLR > mLA.
Lead removal from drinking water - development and validation of point-of-use treatment devices
Authors: Sublet R. , Boireau A. , Yang V.X. , Simonnot M.-O. , Autugelle C.
Published: May 2018

Two lead removal water filters were developed to lower lead levels in drinking water below 10 μg.L-1 in order to meet the new regulation given by the European Directive 98-83, applicable in December 2013. An appropriate adsorbent was selected through a stringent research program among a wide range of media, and is composed of a synthetic zeolite and an activated carbon. Two prototypes were developed: the first is a faucet-mounted filter which contains a fixed bed of the adsorbent and a hollow fiber bundle, while the second is an under-sink cartridge made of a porous extruded block of carbon and adsorbent. Both are able to treat at least 1,000 litres of any water containing on average 100 to 150 μg Pb.L-1, by lowering the lead concentration below 10 μg.L-1. Once their safety considerations were addressed by an independent laboratory according to the French Ministry of Health recommendations, 20 prototypes were installed at consumers' taps in northeastern France. Their performance in terms of lead removal, HPC control and bad taste and odor reduction was followed for 6 months. This field testing program resulted in the validation of both prototypes which meet the new French Ministry of Health recommendations and assures that the filtered water is fully ED 98-83 compliant. Their commercialization will be launched first in France in middle 2002.
Binding of estrone to hollow fibre membranes in microfiltration of solutions containing trace estrone
Authors: Chang S. , Waite T.D. , Schäfer A.I. , Fane A.G.
Published: May 2018

Increased concern is being paid to the health and environmental risk caused by trace natural and synthetic hormones discharged from sewage treatment plants. This study, which is part of a larger project on the investigation of hybrid membrane processes for trace hormones removal in water recycling, focuses on binding of hormones to microfiltration membranes in filtration of solutions containing trace hormones. The adsorption capacity of the membrane, kinetics of adsorption and desorption of to/from microfiltration hollow fibre membranes, and the factors affecting adsorption to the membranes have been studied using estrone as model solute. The experiments showed that the adsorption of estrone to the microfiltration membranes could result in high retention of estrone molecules. However, since the mechanism of retention is adsorption rather than sieving, the retention decreases with increase in the amount of estrone accumulated on the membrane, and breakthrough occurs when the accumulated estrone on the membrane reaches an equilibrium concentration corresponding to the feed concentration. For long-term operation, although membranes could be saturated by hormone molecules, the membrane processes could still have a function of buffer for instantaneous high hormone concentration because the saturation surface concentration increases with the increase in the feed concentration. In addition, the experiments also indicated that the adsorption capacity of the membranes for hormones could be affected by membrane types, pH, affinity of hormones to water, as well as the presence of other organics. These results are of relevance to the potential release of trace hormones from water treatment systems where microfiltration membranes are used as a process barrier.
Demonstration of new sensory methods for drinking water taste-and-odor control
Authors: Bae B.-U. , Kim Y.-I. , Dugas D.W. , Burlingame G.A. , Dietrich A.M.
Published: May 2018

In order to demonstrate the practicality of two newly developed taste-and-odor methods, raw and filtered water samples from the Songchon water treatment plant, and tap water samples from houses were analyzed from July to October 2000 using three sensory methods (TON, 2-out-of-5 odor test and attribute difference test for the presence or absence of geosmin) and one instrumental method (closed-loop stripping analysis, CLSA, followed by gas chromatography, GC). Comparison of TON values with CLSA indicated a discernible relationship only when the odorant level was relatively high. The two newly developed methods, however, were more sensitive than TON when the odor intensity of samples was low. The attribute rating test for geosmin is more sensitive than the 2-out-of-5 odor test when the TON value is less than 10. These new methods seem better than current methods for identifying the occurrence of odor compounds in raw and filtered waters. They also have practical use in tracking the efficiency of treatment methods, such as adsorption and oxidation, used for controlling taste-and-odor episodes.
Photo-Fenton oxidation of pesticides
Authors: Wadley S. , Waite T.D.
Published: May 2018

The photo-Fenton process is becoming a practical treatment option for waters contaminated with pesticides and other organic compounds that are poorly biodegradable. This process can potentially be integrated into an existing water treatment process to enhance organic compound removal. It can operate at low concentrations of contaminant and can often completely mineralise the compound or convert it into a less toxic form. The process is most efficient at around pH 2.8; however, it has been found that with the addition of suitable complexing agents for Fe(III), the process can be operated at close to neutral pH. This study used citric acid as a complexing agent, 2,4-dichlorophenol (DCP) as a model contaminant and investigated the extension of the feasible pH range of the process from pH 5 to pH 8. The study involved synthetic solutions and light from a mercury arc lamp, with a bandpass filter used to isolate the emission band at around 360 nm. Low concentrations of DCP (12 μM) and Fe(II) (10 mM) were used to simulate conditions possible in the environment. In this work, no H2O2 was added, however, a relatively high concentration of citrate (100 μM) was used. Citrate is itself degraded in the process, and since it is highly biodegradable any excess could be consumed in a subsequent biological treatment process. The extent of degradation of DCP after 2 hours was found to be 91% at pH 5, 73% at pH 6, 74% at pH 7, and 59% at pH 8.
Adsorption of MIB by activated carbons produced using several activation techniques
Authors: McCallum R. , Roddick F. , Hobday M.
Published: May 2018

Water treatment authorities use activated carbon as the best available technology to remove low molecular weight organic compounds from potable water. In Australia, pollutants of concern include secondary metabolites from bacterial and cyanobacterial blooms which are highly odorous and, in some cases, toxic. Of these compounds, 2-methylisoborneol (MIB) is one of the most common and its unpleasant musty earthy odour can be detected at or above approximately 10 ng/L. Difficulties in using activated carbon to target such small organic compounds arise when the water has high concentrations of natural organic matter (NOM), as these compounds also adsorb on activated carbon. The adsorption of NOM on activated carbon increases the cost of using this material in water treatment due to competition with the target organic compounds, reducing the capacity of the activated carbon for the latter. The surface of activated carbon can be tailored during production to provide physical and chemical characteristics that can either aid or hinder the adsorption of particular compounds. One source of activated carbon currently under investigation at RMIT University is brown coal char waste from power stations. This waste, currently disposed of to landfill, is potentially an option for activated carbon production. This material has the advantage that it has already been carbonised at around 500°C in the power generation process. This means that less energy is required to produce activated carbon from power station char compared to coal, making the final product cheaper to produce. Previous work at RMIT has shown that steam activated power station char can remove organic compounds from water. Production of a range of activated carbons from power station char (PSC) was undertaken using different activation methods, including steam activation, steam activation with acid pre-treatment, alkali heat treatment, and Lewis acid heat treatment. The different activation methods produced activated carbons with different pore size distributions, in particular, the acid pre-treatment increased the surface area and porosity significantly compared with steam activation, and the alkali treatment increased the microporosity. Adsorption of MIB on these activated carbons was evaluated to determine the relationship between physical and chemical interactions of the activated carbon and adsorption. Adsorption of MIB on these activated carbons was found to be dependent on the secondary micropore volume. Lewis acid treatment and alkali treatment was not involved in the generation of many of these secondary pores, hence carbons from these treatments did not perform well in adsorption tests. The best adsorption results were achieved with steam activated or acid treated steam activated samples which performed comparably to commercial products. Initial results showed that competition from NOM adsorption was lowest with the PSC activated carbons, allowing greater adsorption of MIB, compared with the commercial activated carbons.
The role of membrane ξ-potential in solute rejection by low-pressure reverse osmosis membrane
Authors: Ozaki H. , Ikejima N. , Matsui S. , Terashima Y. , Takeda S. , Tari I. , Li H.
Published: May 2018

A new generation of reverse osmosis membranes, low-pressure reverse osmosis (LPRO) membranes, have been developed for operation under very low pressure (below 0.5 MPa). LPRO membranes have received attention especially for their application in the field of water and wastewater treatment, to provide a high water flux at low operating pressure while maintaining very good rejection levels of salts and organics. Our previous work on LPRO has shown that the rejection of some inorganic salts and organic compounds depends appreciably on the pH of the bulk solution, probably because LPRO membranes can have an electric charge. In this study we investigated experimentally the effectiveness of different LPRO membranes in separating inorganic salts and organic compounds from a bulk solution with different pH conditions. We also tried to measure membrane ξ-potential by using a streaming potential method. The results indicated that the membrane ξ-potential as well as the ion size or molecular weight of organics can be considered key factors in the rejection of ionic salts and dissociated organic compounds including pesticides and endocrine disruptors.
Reduction of cake layer by re-aggregation in coagulation-crossflow microfiltration process
Authors: Kim S. , Cho S.-H. , Park H.
Published: May 2018

Cake layer in crossflow microfiltration(CFMF) can be reduced by coagulation, enhancing membrane flux. This is because enlarging particle size by coagulation increases shear-induced diffusivity and the back-transport of rejected particles. However, it is known that the enlarged particles are disaggregated by the shear force of the pump while passing through it. This study looks at the disaggregation in relation to cake layer reduction. Kaolin and polysulfon hollow fiber microfilters are used for experiments. The reduction of cake resistance by coagulation is observed in a range of 17% to 53% at the various coagulation conditions. Particle size analysis results of the experiments show that aggregated particles in feed are completely disaggregated by the pump but re-aggregation of particles occurs in the membrane. This suggests that the re-aggregation of particles is critical to cake reduction and flux enhancement, since the aggregated particles are completely broken. The mechanisms for re-aggregation in the membrane are the same as those for coagulation in the feed tank. Charge neutralization is better for CCFMF than sweep flocculation although it has two drawbacks in operation.
Practical selection of microorganisms indicating the stability of pathogenic removal in water treatment plants
Authors: Chung H. , Rim Y. , Kwon O. , Yeom C. , Cho M. , Lee C. , Yoon J.
Published: May 2018

There have been several recent drinking water incidents in connection with detection of water borne pathogens in Korea. This has led to the need for research to find microorganisms that will indicate the stability of pathogenic removal in water treatment plants (WTPs). We investigated seven microorganisms as potential indicators: four for bacteria [E. coli, fecal coliform (FC), total coliform (TC) and heterotrophic plate counts (HPC)], two for protozoan [aerobic spore formers (ASF) and Clostridium perfringens (CP) spore], and one for viruses (F-specific RNA coliphage). Source water, treated water from each process, and finished water were analyzed periodically from three WTPs, chosen in view of the source water quality and plant size. This study concludes that HPC and ASF appeared to be good indicators of the stability of pathogenic removal. Although this study supports ASF as the best indicating microorganism, the potential use of HPC as an indicating microorganism was demonstrated in this study. From this study, the regrowth problem of HPC in water plants was shown to be negligible depending on the characteristics of the chlorination practice at the WTPs, and temperate climate conditions. The relative importances of each treatment process, for the removal of suggested indicating microorganisms, were found to be as follows: combined process of coagulation and sedimentation with prechlorination > filtration » disinfection, with emphasis on the necessity for the optimization of whole water treatment processes for effective microbial removal.
Comparison of UV and chlorine inactivation of particle and non-particle associated coliform
Authors: Örmeci B. , Linden K.G.
Published: May 2018

Bacteria associated with particles may be sheltered from chlorine and ultraviolet (UV) disinfection. The objective of this study was to compare the disinfection effectiveness of UV irradiation and free chlorine for naturally occurring particle-associated coliform (PAC) and non-particle associated coliform (NPAC) in wastewater using a single wastewater source, under identical laboratory protocols. Samples containing NPAC were obtained using three different methods: EGTA extraction, filtration, and blending followed by filtration. Unaltered wastewater was used for samples containing PAC. Wastewater samples were inactivated with UV irradiation at doses between 0-100 mJ/cm2, and with chlorine at CT values between 0-525 mg min/L. The dose-survival relationships and inactivation rates between PAC, NPAC, and chlorine and UV irradiation were then compared. As expected, both UV and chlorine were effective for inactivation of NPAC. However, under prolonged contact times, chlorine appears to be more effective for inactivation of PAC than UV irradiation. Contact time appears to be the most important factor in determining the effectiveness of chlorine disinfection of PAC, and chlorine CT alone was not a good indicator of disinfection effectiveness in wastewater. PAC was found to survive at UV and chlorine disinfection doses typically applied in a wastewater treatment plant.
Evaluation of assimilable organic carbon in the Yodo River and the effect of coagulation on its control
Authors: Kasahara S. , Ishikawa M.
Published: May 2018

Biodegradable organic compounds in Yodo River water, the coagulated water and those ozonated waters were characterized on the concentration of assimilable organic carbon (AOC), the apparent molecular size and the sensitivity to E260 (UV absorbance at the wavelength of 260 nm). High molecular (>5,000 Da) organic compounds which were insensitive to E260 were contained with relatively high concentration in Yodo River, whereas they were not detectable as AOC. The AOC concentration in Yodo River was reduced by coagulation because the phosphorus concentration sharply decreased. The AOC concentration rapidly increased with the reduction of E260 and slowly with the depolymerization of high molecular organic compounds during the ozonation. However, 40-50% of AOC increasing with the ozonation was reduced by the coagulation. Furthermore, batch incubations of native bacteria living in the Yodo River were conducted in order to examine the validity of the apparent AOC concentration as an indicator of the regrowth potential. The AOC concentration calculated as acetate carbon equivalent would not exactly represent the concentration of the available carbon for the assimilation. However, maximum cell numbers for the incubation period were generally proportional to apparent AOC concentrations even if phosphorus limitation. In conclusion, it is suggested that coagulation is an effective process in controlling the concentration of AOC and is a useful indicator to evaluate the regrowth potential of heterotrophic bacteria in Yodo River.
A decision support system for municipal wastewater reclamation and reuse
Authors: Dinesh N. , Dandy G.C.
Published: May 2018

Wastewater reclamation and reuse is being viewed increasingly as a sustainable approach to integrated water resources management in many countries including Australia. The technical feasibility of reclamation and reuse has been demonstrated by a number of successful projects. The current state-of-the art of reclamation technologies can produce water of any desired quality (including potable quality). However, the increasing number of efficient treatment processes has made the selection of an optimum treatment train a difficult task for planners and decision-makers. A decision support system (DSS) can be particularly useful in wastewater reclamation and reuse as it can provide assistance in the evaluation and selection of treatment alternatives for a given reuse application before exhaustive simulation or pilot studies are conducted. This paper highlights the ongoing research on the development of a computer based DSS named MOSTWATAR(©) (which stands for Model for Optimum Selection of Technologies for WAstewater Treatment And Reuse). MOSTWATAR(©) has a database of the performance characteristics and costs of commonly used reclamation technologies and an optimization module based on genetic algorithms to generate and optimize treatment trains. It also contains detailed reuse guidelines applicable in the various Australian States. This model is intended to assist planners and decision-makers in the techno-economic assessment of reclamation technologies and aid in the selection of the best 5 treatment trains for a given end use and location, wastewater characteristics, and flow rate. This paper describes salient features of the MOSTWATAR(©) package and demonstrates its application to a case study. The results from user-generated options are presented and it is shown that this model can be a very useful tool for selecting the best treatment trains for wastewater reclamation and reuse.
Reuse of an aerobically treated wastewater effluent for the removal of SO2 in the flue gas
Authors: Liu Y. , Ma L.M. , Fang H.H.P. , Gao T.Y. , Xu Z.X. , Wang Y.C. , Jing Z.G.
Published: May 2018

Aerobically treated wastewater effluent (ATWE), intrinsically having high alkalinity, was used to remove sulfur dioxide (SO2) in the flue gas of a coal power plant. Experimental results conducted in a four sieve-tray tower showed that ATWE absorbed SO2 in flue gas effectively. At a gas:liquid (G:L) ratio of 110:1, the respective SO2 removal efficiencies were 99% and 95% for flue gases containing 1,600 and 5,000 Mg/kL of SO2. When the G:L ratio increased to 220:1, the removal efficiency was slightly lowered to 93% for the flue gas containing 1,600 Mg/kL of SO2. ATWE had higher buffer capacity and SO2 removal efficiencies as compared to seawater, a common SO2 scrubbing medium serving as control. In addition, the equilibrium equation between SO2 partial pressure and concentration of bisulfite (HSO3-) in ATWE and the kinetic equation describing the rate of SO2 absorption in the sieve-tray tower by ATWE were established. The absorbing coefficients in the kinetic equation were determined to be 1.96 ± 0.37 mol/(m2ásábar) for gas phase and 0.00184 ± 0.00049 m/s for liquid film. The enhancement factor of the absorbing coefficient in liquid film was 14.28 ± 1.79, resulting in 93% of the decrease of liquid film resistance. The SO2 absorption rate in the sieve-tray tower was mainly affected by the gas film resistance, representing 96% of the total resistance. Experimental results of this study confirmed that the removal of SO2 from the flue gas of coal power plants by ATWE was cost-effective. This process does not require the addition of any chemicals and produces no secondary pollution.