bluuebunny/crossref_metadata_2025 huggingface dataset:
Defects Induced by Helium Implantation: Interaction with Boron and Phosphorus
Authors: Cayrel F. , Alquier D. , Roqueta F. , Ventura L. , Dubois C. , Mathiot D.
Published: February 2013

High dose He implantation, followed by a thermal annealing, is a suitable technique for metal gettering. Nevertheless, a strong interaction between the dopants and the defect layer has been evidenced. This can largely influence the dopant distribution. In order to study this interaction, p and n-type samples uniformly doped were implanted with helium (40 keV, 5×1016 He+.cm-2) and furnace annealed for various times and temperatures. In this paper, we shed light on the evolution of the dopant segregation. Using isochronal treatment, we found a large dependence of the dopant gettering phenomenon upon annealing temperature. Moreover, stability of the gettered fraction is observed for isothermal annealing. This study permits also to investigate the origin of the trapping mechanism involved for both boron and phosphorus.
Three Dimensional Modeling of Anisotropic Stress Effects in Thermal Oxidation of Silicon
Authors: Xu Xiaopeng , Strecker Norbert , Moroz Victor
Published: February 2013

Three-dimensional analyses of anisotropic stress effects during thermal oxidation of silicon are performed in this study using finite strain formulation. A reaction rate model that conjugates pressure to a crystalline direction dependent activation volume is employed for the modeling of facet formation in an STI MOSFET device. The numerical results agree well with TEM observations. The 3-D nature of stress evolution in fabrication process is demonstrated and the implication of stress relaxation on device performance in a strained SiGe based device is discussed.
The Influence of Interproximal Contact on Implant-Supported Fixed Partial Dentures in the Posterior Jaw: A Photoelastic Analysis
Authors: Naves Marina Melo , de Menezes Helder Henrique Machado , de Magalhães Denildo , de Araújo Cleudmar Amaral , Júnior Paulo Cézar Simamoto
Published: February 2013

The aim of this study was to analyze the effect of the separation of prosthetic crowns from fixed partial dentures by means of stress gradient evaluation. Three photoelastic models were created to examine contiguous implants with varying contact between the crowns (contact point [CP], contact surface [CS], splinted [SP]). The SP group presented the best results, followed by the CS group, indicating that the use of splinted prosthetic crowns and crowns with broad surface contacts is viable when considering the stress values.
Implants Placed in the Nasopalatine Canal to Rehabilitate Severely Atrophic Maxillae: A Retrospective Study With Long Follow-up
Authors: Peñarrocha David , Candel Eugenia , Guirado Jose Luis Calvo , Canullo Luigi , Peñarrocha Maria
Published: February 2013

To assess the survival rate of implants placed in the nasopalatine canal for the rehabilitation of patients with atrophic maxillae and the level of satisfaction of these patients. A retrospective study was performed between 2000 and 2009 of patients with severe atrophy of edentulous maxillae (Cawood and Howell's class V) rehabilitated with implant-supported prostheses with 1 implant placed in the nasopalatine canal. A preoperative computed tomography scan was obtained of all patients and all surgeries were performed by the same surgeon. The following parameters were assessed: neurosensory status of the anterior palate (using the pointed/blunt discrimination method); implant success rate according to criteria described by Albrektsson et al; patient satisfaction with the prosthetic treatment (using visual analogue scales). Thirteen patients with a mean age of 54.8 years were treated, 5 men and 8 women. Seventy-eight implants were placed: 13 in the nasopalatine canal, 6 in the zygomatic bone, 12 in the pterygomaxillary region, 2 in the frontomaxillary buttress and 45 in other locations. Six patients reported a slight decrease in sensitivity in the anterior palate after surgery, which disappeared in all cases within a few weeks. Two early failures (before prosthetic loading) and no late failures (after prosthetic loading) of nasopalatine implants were recorded, yielding a success rate for these implants of 84.6% after a mean follow-up of 70 months (range 24 to 132 months. High patient satisfaction with the prosthetic restoration was generally achieved in terms of comfort, stability, function, esthetics, and ease of cleaning. Residual bone is associated with the nasopalatine canal, even in patients with severe maxillary atrophy. This canal may be considered a possible location for an anterior implant when rehabilitating atrophic patients using implant-supported prostheses.
Comparative Microflora Assessment of Natural Sulci vs. Deep and Shallow Implant Sulci in Partial Edentulousness
Authors: Rismanchian Mansoor , Shahabouei Mohammad Hussein , Yaghinei Jaber , Babashahi Akram , Hassantash Zahra , Sadr-Eshkevari Pooyan , Fazel Akbar
Published: February 2013

The main cause of peri-implantitis and crestal bone resorption is bacterial infection. The present study aimed to comparatively assess the microbiological parameters in sulci around teeth and crowns supported by dental implants and also compare microbiological parameters around deep and shallow implant sulci. In this cross-sectional study, 34 partially edentulous patients with a total of 72 implants (22 deep vs. 50 shallow sulci) were included. Excluded were the patients with compromised systemic and periodontal health or smoking habits. All Implants (ITI) were at least 6 month in place covered by definite prostheses. Samples of gingival sulci were taken around teeth and implants with paper points and transported in Stuart Transport Medium. Samples were cultured and examined by dark field microscope to determine the microorganisms. Data were evaluated statistically in SPSS (v11.5) using chi-square test. Cocci G+, Cocci G-, Prevotella, Porphyromonas gingivalis, Bacteroid fragilis and Fusobacterium were found. The relative frequency of P. gingivalis was significantly higher in deep implant sulci compared to shallow implant sulci (p = 0.044) and natural sulci (p = 0.009). B. fragilis was also significantly more isolated from the deep implant sulci compared to shallow implant sulci (p = 0.001) and natural sulci (p = 0.064). Within the limitations of the present study, it may be concluded that peri-implantitis is more likely in deep sulci compared with shallow sulci in partial edentulousness.
Benthic algae stimulate leaf litter decomposition in detritus‐based headwater streams: a case of aquatic priming effect?
Authors: Danger Michael , Cornut Julien , Chauvet Eric , Chavez Paola , Elger Arnaud , Lecerf Antoine
Published: February 2013

In detritus‐based ecosystems, autochthonous primary production contributes very little to the detritus pool. Yet primary producers may still influence the functioning of these ecosystems through complex interactions with decomposers and detritivores. Recent studies have suggested that, in aquatic systems, small amounts of labile carbon (C) (e.g., producer exudates), could increase the mineralization of more recalcitrant organic‐matter pools (e.g., leaf litter). This process, called priming effect, should be exacerbated under low‐nutrient conditions and may alter the nature of interactions among microbial groups, from competition under low‐nutrient conditions to indirect mutualism under high‐nutrient conditions. Theoretical models further predict that primary producers may be competitively excluded when allochthonous C sources enter an ecosystem. In this study, the effects of a benthic diatom on aquatic hyphomycetes, bacteria, and leaf litter decomposition were investigated under two nutrient levels in a factorial microcosm experiment simulating detritus‐based, headwater stream ecosystems. Contrary to theoretical expectations, diatoms and decomposers were able to coexist under both nutrient conditions. Under low‐nutrient conditions, diatoms increased leaf litter decomposition rate by 20% compared to treatments where they were absent. No effect was observed under high‐nutrient conditions. The increase in leaf litter mineralization rate induced a positive feedback on diatom densities. We attribute these results to the priming effect of labile C exudates from primary producers. The presence of diatoms in combination with fungal decomposers also promoted decomposer diversity and, under low‐nutrient conditions, led to a significant decrease in leaf litter C:P ratio that could improve secondary production. Results from our microcosm experiment suggest new mechanisms by which primary producers may influence organic matter dynamics even in ecosystems where autochthonous primary production is low.
Network based controller systems for pre-conditioning of waste water in sewer systems
Authors: Franke Wolfram , Ettl Marina , Corben Tim , Kuhn Guido
Published: February 2013

Sewer network odour emissions have become a focus due to environmental regulations and, in the case Hydrogen Sulphide (H2S) induced corrosion, due to safety and sustainability. For these reasons the establishment of emission treatment is recommended. Sewer emission treatment focuses on local solutions rather than sewer-wide network treatment. The dosing of chemicals for this purpose is usually done section-wise. Obviously there is optimization potential when sewers are understood and treated as networks. Preventive treatment can be optimized by information from downstream and curative treatment by information from upstream. Such concepts demand communication technology and monitoring of several parameters at various locations in the sewer network.

In the presented case study a digital communications network is used to control H2S emissions and fat, oil and grease (FOG) disposal in a sewer network. Moreover it was shown that technical solutions are available to use sewers as controlled reactors rather than just let them be a source of problems.

An overview of today's standard dosing systems and strategies for odour and corrosion control is also given.
The microbial diversity, methane production, operational routine of an anaerobic reactor treating maize processing wastewater
Authors: Ince B. , Cetecioglu Z. , Celikkol S. , Ince O.
Published: February 2013

Industrial wastewaters have turned out to be a significant problem during the last decades. The best alternative for maize processing wastewaters due to high organic content and slow biodegradability characteristics is anaerobic treatment, which is successfully used in the treatment of medium-high strength industrial wastewaters. This study investigates a full-scale anaerobic expanded granular sludge bed reactor treating a maize industry wastewater in terms of reactor operation, methanogenic activity of reactor sludge, changes in composition and numbers of microbial populations during a 5-month period. Three samples were taken in 2-months intervals when the reactor was re-operated after a shut-down of 2 months. Combination of denaturing gradient gel electrophoresis (DGGE), quantitative real time polymerase chain reactions (Q-PCR) and specific methanogenic activity tests were used to investigate composition, diversity and quantity of microbial community with activity of acetoclastic methanogens. During monitoring period, COD removal efficiencies and organic loading rates varied in ranges of 79–95% and 0.65–3.85 kg COD/m3.d, respectively. Potential methane production rates of the reactor sludges decreased 27% with time that is from 394 to 287 mL CH4/gVSS.d. Archaea, bacteria, and methanogens in the sludge samples were quantified by Q-PCR and the results showed that while amount of archaea was decreasing, quantity of methanogens increased during the monitoring time. The DGGE results of the anaerobic sludge revealed that the microbial diversity dramatically changed, particularly in the last sample. Among these, the differences in archaeal community were more remarkable. Although an average COD removal efficiency of 86%±8.2 which was quite a reasonably stable performance was maintained during the monitoring period, remarkable differences were observed on both acetoclastic methanogenic activity and the methanogenic community. The increase in the numbers of total methanogens despite the decrease of acetoclastic methanogenic activity might be an indicator of dominating hydrogenotrophic methanogenic pathway. Further, construction of clone library was necessary to identify the species and their changes within the all three samples.
Demonstration and evaluation of an innovative water main rehabilitation technology: Cured-in-Place Pipe (CIPP) lining
Authors: Matthews John C. , Selvakumar Ariamalar , Condit Wendy
Published: February 2013

As many water utilities are seeking new and innovative rehabilitation technologies to extend the life of their water distribution systems, information on the capabilities and applicability of new technologies is not always readily available from an independent source. The U.S. Environmental Protection Agency (EPA) developed an innovative technology demonstration program to meet this need. The purpose of the demonstration program is to evaluate rehabilitation technologies that have the potential to reduce costs and increase the effectiveness of the operation, maintenance, and renewal of aging water distribution and wastewater conveyance systems. This paper provides an impartial assessment of the effectiveness and cost of a cured-in-place pipe (CIPP) lining technology for water main rehabilitation. This project demonstrated an innovative Class IV rehabilitation technology that met the project requirements and as part of the evaluation, multiple utilities expressed their willingness to use the technology in the future. The demonstration provided valuable information on the design, installation, and QA/QC of CIPP used to rehabilitate water mains, and makes recommendations for continued improvements in the process used for internal reinstatement of services. One issue that requires more study is the effect of pre-rehabilitation cleaning process on the service connection reinstatement process. Other issues contributing to the need for external reinstatement that should be studied and improved upon include: flush service connections that cannot be identified in smaller diameter pipes and difficulty drilling service connections located in folds.
Strategic planning approach for optimising investment at WWTPs
Authors: Krampe J. , Leak M.
Published: February 2013

From an asset management perspective there is an ongoing challenge to make strategic investment decisions which are based on maintaining asset serviceability, effluent quality requirements and providing for growth. Additionally, individual performance of treatment stages and changes in sewage flows and loads have to be considered to achieve an optimised outcome.

Typically, large scale capital projects are required to address the many challenges that face a WWTP. However, significant cost savings can be made if smaller optimisation projects are pursued to maximise the capacity of existing infrastructure and therefore defer high cost capital upgrades. To achieve this end, SA Water started a formal process to review the capacity of each process element of the Bolivar WWTP and found several opportunities to optimise current process performance. Based on these outcomes a future strategy document was developed that enables the next major plant upgrade to be deferred by 8–10 years. This paper summarises SA Water's approach to develop such a documentation to allow a strategic asset management, optimise its capital expenditure and achieve significant cost savings. It also highlights some of the projects that were identified during this process to improve the current treatment plant performance.
Impacts of water demand side policies on Mongolian residential users
Authors: Altai Zulgerel , Stoeckl Natalie , King David
Published: February 2013

The water industry in Ulaanbaatar, Mongolia, experiences water scarcity and managerial and economic problems due to global warming and financial crises. This paper explores several possible solutions by analysing householders' stated attitudes towards and stated (predicted) responses to different demand side policies. Using data from a survey of approximately 660 households (HHs) in Ulaanbaatar, this research is a seminal study of Mongolian residential water demand and is the first time the contingent behaviour method (CBM) has been employed to estimate price elasticity of water demand in this country. The CBM is particularly useful in data-poor environments, where one cannot use actual data to generate estimates. In this study, researchers use stated responses to a series of hypothetical changes in price to generate estimates of the price elasticity of demand for water of different types of HHs, including residents of formal apartments and those living in informal Ger areas, are characterized by a low level of public services, including water and sanitation services of the city. Householders' attitudes towards different price and non-price policies are also examined. The findings are of interest to those wishing to postpone water scarcity by better managing urban residential water demand – particularly in transit and developing economies.
KALLISTO: cost effective and integrated optimization of the urban wastewater system Eindhoven
Authors: Weijers S. R. , de Jonge J. , van Zanten O. , Benedetti L. , Langeveld J. , Menkveld H. W. , van Nieuwenhuijzen A. F.
Published: February 2013

The Kallisto project aims at finding cost effective sets of measures to meet the WFD derived goals for the river De Dommel. The project reasons from the both acute and long term impacts of the urban wastewater system on the quality and ecology of the river that are studied with an integral monitoring campaign in the wastewater system (WWTP and sewers) and river. By applying impact based RTC, the project aims at minimizing additional investments in infrastructure while meeting the requirements. Moreover, uncertainty is explicitly considered in the optimization and decision making process. The paper describes the overall project strategy, some preliminary results of modelling and monitoring of the components of the urban water system and the demonstration research for treatment techniques and the planned integration into optimization and decision making.
Assessment of sludge particle removal from wastewater by disc filtration
Authors: Wilén B.-M. , Johansen Ann , Mattsson Ann
Published: February 2013

To meet stricter effluent discharge limits of total phosphorus, microscreens can be applied for tertiary effluent treatment. The Rya WWTP has recently been upgraded with microscreens in the form of disc filters. Extensive characterisation of the wastewater from different locations in the plant (influent, after primary settling) and secondary settler effluent, was performed to increase the understanding of the potential of removing different components from the wastewater. The wastewater was fractionated by filtration through filter cloths with pore sizes 40, 20, 15, and 10 μm and through finer filters with pore size 1.2, 0.45, 0.2 and 0.1 μm. Particle size analysis (PSA) was used to assess the removal efficiency of the filter cloths. High removal degrees were achieved were particles larger or equal in size to the pore size were strained. Some floc break-up took place leading to an increased number of small particles (1–5 μm) after filtration. The suspended solids concentration could be reduced to 1 mg/l with total phosphorus concentrations of <0.2 mg/l. Some removal of metals could be observed when filtering wastewater with higher concentrations (influent and secondary settler effluent) whereas no effect could be seen for the effluent wastewater, probably due to the low concentrations present. The results from this study indicate a poor removal efficiency of pathogens measured as indicator microorganisms.
Estimation of hypolimnetic discharge on improvement of water quality and control of phytoplankton blooms in yamaguchi reservoir
Authors: Fukutani Akiko , Taguchi Yukio
Published: February 2013

Sakai water purification plant (Sakai WPP) and Higashi-murayama water purification plant (Higashi-murayama WPP) take water from Yamaguchi reservoir (20 m-effective depth) by Intake tower No.1 and No. 2. Yamaguchi reservoir, refilled with water after seismic reinforcement to the dam body, started its operation again in 2002. In the spring of 2004 and 2005, massive blooms of Asterionella spp. and Fragilaria crotonensis (diatoms) occurred, which resulted in sharp decreases in filtration capacity of Sakai WPP, taking slow sand filtration. Results of water analysis for the reservoir between 2003 and 2004 indicated that nutrients eluted from sediments during stratification periods were utilized for the blooms in the following springs. Since intake gates at five different depths enable us to conduct selective intake, we conducted hypolimnestic discharge; while Sakai WPP continued taking water with low turbidity and phytoplankton production, the lowest gates of Intake tower No.1 were also slightly opened in the middle of 2005. In April 2006, the lowest gate of Intake tower No. 2 was fully opened instead of the upper ones. Consequently, the scale of spring diatom blooms reduced after 2006. Nevertheless, rise in turbidity increased T-P, which resulted in massive blooms of Synedra spp. (diatoms) in 2009 when the water level was lowered to 8 m. This illustrated that this operation of the selective intake was not effective for conservation of the reservoir at low water levels.
Assessing and maintaining membrane performance in a post-sedimentation ultrafiltration process
Authors: Boyd Christopher C. , Duranceau Steven J.
Published: February 2013

A pilot test program was conducted to evaluate methods for maintaining the productivity of a hollow fiber ultrafiltration membrane operating at constant flux values of 49.2 and 62.3 gallons/ft2-day. The ultrafiltration pilot filtered settled water from a conventional surface water treatment plant in Florida. The testing assessed the impact of different chemical maintenance protocols on UF membrane performance. Seasonal variations in water quality necessitated changes in the type and combination of cleaning agents used to maintain membrane performance. Sodium hypochlorite, citric acid and sodium hydroxide were used during pilot testing as the fouling characteristics of the water changed with time. Pilot results were used to develop alternative chemically enhanced backwash strategies that varied with seasonally-impacted changes in feed water quality. Citric acid, with a target pH of <3, was found to be effective in August and September; whereas, a combination of citric acid and high pH sodium hydroxide chemically enhanced backwashes successfully maintained performance between November, 2010 and May, 2011.
Upgrade of a large scale oxidation ditch plant
Authors: Fouad Moharram , El-Morsy Ahmed
Published: February 2013

A large-scale oxidation ditch (OD) plant had been upgraded by modifying the aeration and stirring technique of the ditches. Through upgrade, surface turbine aerators have been installed together with the existing aeration rotors. A turbulent stirring was created by the addition of the new turbine aerators, while the recirculation motion achieved by the original rotors. The two aeration techniques (turbulent stirring and recirculation motion) were operated at different ratios ranging from 0.0–1.0. As a result, by operating the turbulent stirring and gradual dispensing with recirculation motion, the system version gradually converted from an OD to a conventional activated sludge. Firstly, the gradual conversion from recirculation motion to turbulent stirring was performed under constant oxygenation level (DO) approximately 1.0 mg/L. Secondly; the turbulent stirring was increased with constant running of recirculation motion associated with gradual increase of DO level up to 2.5 mg/L. The effect of aeration and stirring on removal efficiency, sludge production, and sludge settleability has been revealed. It was found that turbine aerators could be added successfully inside ODs to increase the whole system efficiency. Firstly, at constant DO level, under same aeration power, turbulent stirring increased the removal efficiency of COD from 65 to 74%. The observed sludge yield (Yobs) came down from 0.31 to 0.25 gm volatile suspended solids (VSS)/gm BOD. Furthermore, the sludge settleability was enhanced from SVI = 137 to 115. Secondly, increased DO level with the new turbulent stirring, increased removal efficiency of COD from 65 to 95%. Moreover, the system achieved a nitrification efficiency of 70%. Finally, the sludge settleability was improved from SVI = 164 to 92 with minimum sludge yield.
Constructed wetlands and sand filter applied as onsite post-treatment of anaerobic effluent
Authors: Sezerino P. H. , Bento A. P. , Decezaro S. T. , Carissimi E. , Philippi L. S.
Published: February 2013

This paper evaluates constructed wetlands and sand filter technologies applied as onsite post-treatment of anaerobic effluent, under environmental conditions of Southern Brazil. Three different onsite systems were evaluated, as follow: onsite system 1 (septic tank – ST followed by horizontal flow constructed wetlands – HFCW) with five years operation; onsite system 2 (ST followed by sand filter – SF) with three years operation and onsite system 3 (anaerobic pond – AP followed by vertical flow constructed wetland – VFCW) with one year operation. HFCW shows an average potential removal of 82, 84, 16, 50 and 90% of chemical oxygen demand (COD), biochemical oxygen demand (BOD), NH4+-N, PO43−-P and SS, respectively. Clogging phenomena occurred in the HFCW after three years operations with an average of 11 gSS m−2 d−1 loading rate applied. SF shows an average potential removal of 83, 88, 73, 76 and 88% of COD, BOD, NH4+-N, PO43−-P and SS, respectively. VFCH shows an average potential removal of 72, 80, and 71% of COD, NH4+-N, and SS, respectively, and also a very good nitrification (25 mgNO3−-N L−1 in the treated effluent) considering the high average COD loading rate (41 gCOD m−2 d−1) and average SS loading rate (15 gSS m−2 d−1) applied.
Free-living microscopic organisms as indicators of changes in drinking-water quality
Authors: Plutzer Judit , Törökné Andrea
Published: February 2013

Bacterial indicator organisms (e.g., coliforms, E. coli) and some chemical parameters (e.g., turbidity, ammonia) are basic monitoring tools used to measure both changes in drinking-water quality and the presence of hard-to-detect pathogenic bacteria, viruses and protozoa. Microscopically detectable free-living organisms, such as some groups of bacteria, fungi, nematodes, rotifers and protozoa, are usable as additional indicators of fecal or environmental contamination of drinking water as well as any changes in the drinking-water quality. Our aim in this paper is to summarize the results of microscopic examination of 913 drinking-water samples from different water sources in Hungary in 2004 and 2005 and to demonstrate how these results can be used to maintain safe and good-tasting drinking-water quality. A total of 277 drinking-water samples failed Hungarian microscopic water quality standards as a result of helminths (58%), protozoa (41%), iron bacteria (16%), sulfur bacteria (13%), fungi (11%), algae (5%) and multiple biological contaminants (34%). Based on these results, pipe washing or water storage tank cleaning was deemed necessary. In addition, a number of disinfection or filtration failures were found. Two detailed case studies show the usefulness of monitoring microscopic parameters to avoid disease outbreaks. To our knowledge this is the first paper discussing drinking-water microscopy based on Hungarian experience and practice, which could be useful and informative for other countries.
Field demonstration of bioaugmentation in trichloroethene-contaminated groundwater
Authors: Okutsu Noriya , Tamura Wataru , Mizumoto Masahiro , Ueno Toshihiro , Ishida Hiroaki , Iizumi Taro
Published: February 2013

A pilot test was conducted to evaluate the effectiveness of bioaugmentation. Dechlorinating consortium in which the dominant microorganisms were Dehalococcoides species (DHC) possessing the vinyl chloride reductase gene (vcrA). The pilot test consisted of a direct injection system, including 2 injection wells. One injection well was for bioaugmentation, and the other, located approximately 20 m away, was for biostimulation. TCE was rapidly dechlorinated to cis-DCE in both wells. The first indication of reduction beyond cis-DCE and VC was the occurrence of ethene 63 days after bioaugmentation in the augmented injection well (AIW). In conjunction with the ethene production, the concentrations of the DHC-16S rRNA gene and the vcrA increased to approximately 106 copies/mL. By day 119, the number of copies of those genes remained high in the AIW, and all chloroethenes declined to levels below the Environmental Quality Standards for Groundwater Pollution in Japan. Though the concentration of indigenous DHC also increased to approximately 106 copies/mL 182 days after injection of nutrients in stimulated injection well, the concentration of cis-DCE and VC remained high until 371 days. These results confirmed that bioaugmentation contributed to shortening the clean-up time better than biostimulation by increasing the initial DHC population in the groundwater.
Choosing the most appropriate technique for wastewater disinfection – parallel investigation of four disinfection systems with different preceding treatment processes
Authors: Bischoff A. , Cornel P. , Wagner M.
Published: February 2013

A variety of bacterial, viral and parasitic pathogens are transmitted via water. Adequate disinfection of wastewater is therefore vital to address the potential health risks of water reuse. A range of well-established methods is available for wastewater disinfection. The selection of the most appropriate technology plays a key role in enhancing the safety, acceptability and reliability of water reuse systems. The objective of this study was the parallel examination of well-established and emerging wastewater disinfection methods, with particular attention being paid to the preceding wastewater treatment processes. The disinfectants investigated were: ultraviolet (UV) radiation, ozone (O3), chlorine dioxide (ClO2) and electrolytically-produced chlorine gas (Cl2). In order to support the specific selection of the most appropriate disinfection method, multiple criteria were determined: concentrations of indicator organisms, effluent toxicity, microbiological stability of the effluent, costs, energy consumption, and supplementary effects. The results show that stringent hygienic treatment objectives can be met with each of the applied methods immediately after disinfection, while the results of the evaluation of the further criteria differ widely between the analysed disinfectants.
Comparison of denitrification-nitrification and step-feed activated sludge processes with dynamic simulation
Authors: Sahlstedt K. , Haimi H. , Yli-Kuivila J.
Published: February 2013

In conjunction with choosing the treatment process for the new wastewater treatment plant of Espoo, Finland (400,000 P.E.), Denitrification-Nitrification (DN) and Step-Feed activated sludge processes were compared in terms of required basin volume and consumption of aeration air and methanol. The comparison was made using dynamic process simulation. The advantages of the step-feed process reported in literature – smaller volume required to treat an equal load or ability to treat a higher load in an equal volume – were questioned. In terms of consumables, the two processes were found practically equal. This is, to the best of our knowledge, the first comparison of these process configurations with dynamic simulation.
Kristal® 2000 PVDF hollow fiber UF membrane in the pretreatment for seawater desalination
Authors: Peng Zanguo , Zhang Zhaoxuan , Mohan Pandurangan , Manimaran Kasinathan , Li Dongfei
Published: February 2013

Membrane technology has emerged as a dominant solution to seawater desalination due to its superior advantages such as stable output water quality, lower energy consumption, ease of operation and smaller footprint. However, the design of spiral wound reverse osmosis (RO) membranes used in desalination does not allow for backwash or air scouring, thus rendering the RO membrane highly susceptible to fouling. Pretreatment for the RO system is therefore essential to ensure a long service life of the RO membranes. For waters containing suspended solids of up to 75 mg/L (such as that in the SingSpring Desalination Plant at Tuas, Singapore), conventional pretreatment methods (such as dissolved air floatation and filtration (DAFF), chemical dosing and cartridge filtration) require regular operator intervention to produce a permeate of reasonably quality. Ultrafiltration (UF) as a pretreatment for seawater desalination can offer better treated water, lower operating costs, a smaller footprint, and flexibility in dealing with poor or varying feed water quality. By improving the pretreatment permeate water quality, reducing operating costs and the footprint, capital expenses can be lowered. Greater stability is also achieved during times of poor or variable feed water conditions (such as periods of algalbloom). A pilot study was conducted at SingSpring to track the performance of Hyflux's Kristal® 2000 hollow fiber UF membranes as pretreatment for the seawater reverse osmosis (SWRO) system. The results of the pilot study will enable the design of future large-scale UF-SWRO membrane projects for seawater desalination.
Demonstration of more than 30% of energy saving by the seawater desalination system combined with wastewater treatment system
Authors: Cheon Jihoon , Sekine Yasunori , Takabatake Hiroo , Noto Kazuhiko , Uemura Tadahiro , Ueda Shinjiro
Published: February 2013

In recent years, a system based on reverse osmosis (RO) has become the fastest growing segment of the seawater desalination market. For further expansion, Global Water Recycling and Reuse Solution Technology Research Association (GWSTA) proposed new desalination system simultaneously reducing both energy consumption and environmental impact of RO brine. Key point is seawater salinity reduction by dilution prior to RO treatment. The full scale plant to confirm the dilution effect was built and operated in Kitakyushu, Japan. As the results, stable operation data was obtained, which indicated 30% or less energy consumption compared with conventional seawater desalination system, and simultaneously new system can adjust brine salinity nearly equal to seawater.
Flood risk appraisal and management in mega-cities: a case study of practice in the Pearl River Delta, China
Authors: Chan F. K. S. , Mitchell G. , McDonald A. T.
Published: February 2013

In recent decades, the Pearl River Delta (PRD) region has experienced strong economic and population growth. By 2050 120 million people are expected to live in the region, which currently has eleven major cities, and the emerging mega-city formed by Hong Kong, Shenzhen and Guangzhou. The populous coastal cities and low lying flood plains in the PRD experience flood risk via: (i) intense precipitation from storms, (ii) inland pluvial flooding, (iii) storm surges. Climate change, including global sea level rise forecasts of more than 1 m by 2100, mean that flood risk is expected to increase in future. Sustainable flood risk management (SFRM) must be adopted to mitigate these risks. Strategies such as the UK's ‘making space for water’ programme seek to tackle flood risk through planning, but such a strategic approach is not evident in the PRD. Recent coastal land reclamation projects in the PRD illustrate the conflict between urban growth pressure and flood risk, and that more comprehensive, or sustainable, flood risk management is not currently practiced. This paper examines flood risk management practice in the PRD. It starts with a theoretical sustainable flood risk appraisal (SFRA) template developed from literature and global best practice, against which PRD practice is benchmarked. The paper discusses a case study in Hong Kong and Shenzhen where in-depth discussions with more than 30 stakeholders were held to understand barriers and constraints to realising SFRM. This research seeks to further the practice of SFRM in the PRD, and comparable urbanising mega-deltas in the region.
Emerging partnerships in water service provision in Owerri city, Nigeria
Authors: Onyenechere E. C.
Published: February 2013

The central question of this study is: what should be the approach to municipal water provision in Owerri city? Is it through reliance on the government, NGOs, International actors or the private water investors? For the study both primary and secondary data were obtained and analysed. The study found that though most residents of Owerri city rely heavily on commercial borehole owners and water tanker drivers/water peddlers for their daily supplies, the government through its SWA is in control, and there is an absence of a popularly acceptable regulatory framework/water policy. It also found out water projects by international agencies and donors such as World Bank in water service provision in Owerri city which improved supply in the past also led to the emergence of fragmentation in service provision. The study equally found that, water governance and its institutions in the study area which operated under national and local forces is now tending towards the international. The study recommends that government should have a robust collaboration with the private sector and other community based organizations for its initiated tripartite partnership to be successful.
Assessing the fate and biodegradation of cyanobacterial metabolites in Australian waters
Authors: Tang Tim , Hoefel Daniel , Mosisch Thorsten , Ho Lionel
Published: February 2013

With the exception of the saxitoxins, the cyanobacterial metabolites studied were shown to be biodegradable in two South Australian waters with the rate of biodegradation of the metabolites influenced by temperature and to a lesser extent, seasonal variations. The order of ease of biodegradability followed the trend: microcystin-LR > cylindrospermopsin > geosmin > 2-methylisoborneol > saxitoxins. Pseudo-first-order rate constants for the biodegradation of the metabolites ranged from 9.6 × 10−4 to 2.6 × 10−2 h−1.
The smart grid as a public health protection tool
Authors: Symmonds G. S. , Hill T. T. , Flynn J.
Published: February 2013

Since the introduction of the Safe Drinking Water Act, there has been marked reduction in the number of water-borne disease outbreaks attributed to water treatment systems. Over the same period, however, the percentage of disease outbreaks attributable to defects in the distribution system has increased exponentially. Interestingly, as a result of the continuous aging infrastructure employed by our water utilities, the number of waterborne disease cases has increased in the last decade. The smart grid for water can be used to significantly improve both the utility's understanding of water quality in the distribution system, but can dramatically increase the response time and provide the means to ensure public health protection. This paper will present the use of the Analytical Water Quality Assurance Program developed to provide instantaneous water quality notifications throughout the utility organization.
SWRO pre-treatment design and operation using Enflo-DAF™ technology
Authors: Amato Tony , Park Kuem-Seo , Yim Wonkyu , Kim Tschungil
Published: February 2013

The purpose of this paper is to present an overview of the design for both the full scale and pilot scale seawater reverse osmosis (SWRO) pre-treatment plant comprising Enflo-DAF™ dissolved air flotation (DAF) technology and dual media filtration (DMF) proposed and operating respectively at Ras Al Khair site in Saudi Arabia. The application of both DAF and DMF in the municipal water industry is regarded as well established; however the application of DAF to the treatment of seawater particularly at elevated temperatures and which is also prone to Red Tide or severe algae events is relatively new and there is a limited amount of experience in this area.
Potential impacts of slum urbanisation on channel bank storage in the Bang Pakong River, Thailand
Authors: Harriden K.
Published: February 2013

Generally regarded as social phenomena, this paper regards slum urbanisation as an environmental actor. Specifically, how slum developments modify hydrogeomorphological processes motivates this research. Using the Bang Pakong River, eastern Thailand, as a case study, a literature review was conducted. The literature reviewed indicated changes in physical processes such as channel bank stability, water quality, flow regimes and the hydrological balance equations can occur with slum development. Given the importance of channel banks as the physical basis of many slum sites, this paper focuses on the possible changes to channel bank storage in the Bang Pakong River following slum urbanisation. The research highlights possible changes to channel bank storage processes, notably decreased storage recharge rates; increased anthropogenic extraction; and probable water quality deterioration. Deeper scientific understanding of how river processes are affected by specific forms of urban development can contribute to better management of both informal urban settlements and rivers.
MBR vs. CAS: capital and operating cost evaluation
Authors: Young T. , Muftugil M. , Smoot S. , Peeters J.
Published: February 2013

Previous studies have investigated capital and operating cost comparisons between membrane bioreactors and conventional treatment technologies for particular treatment scenarios. This study expands on prior work with the development of an Excel and Biowin based tool to compare the capital and operating costs of equivalent size greenfield wastewater treatment facilities using membrane bioreactor (MBR) vs. conventional activated sludge (CAS) processes based on identical influent loading conditions, variable temperature and flow peaking factors, and varying levels of effluent treatment objectives. The resulting capital and operating cost tables developed using this tool indicate which system is most cost-effective for each scenario evaluated. The tool can also be used to easily compare the 20-year Present Worth cost impacts of changing input variables such as the cost of concrete, land, chemicals, or electricity.
Nitrate contamination of groundwater and it's implications in the Limpopo Water Management Area
Authors: Netshiendeulu N. , Motebe N.
Published: February 2013

The increasing nitrate level in groundwater within the Limpopo WMA is a problem that requires urgent attention and is not yet fully understood. Nitrate pollution of water has major health effects attached to it, like methaemoglobinaemia and cancer. It is important that the anthropogenic and natural sources of nitrate in this area be identified and it is also important to understand the relationship between these sources. A combination of statistics, GIS, water quality and isotopes was used to identify and to derive a relationship between the natural and anthropogenic sources of nitrate. The dominant source of nitrate in the study area is animal manure and sewage waste which originate from residential areas and cattle kraal. However a mixing relationship was observed between high nitrate originating from manure or sewage waste and low nitrate background water. Nitrate in the study area also originates from natural sources such as the soil and precipitation. The soil is influenced by the geology as shown by the presence of elevated Si concentration in the samples. This natural origin is shown by the presence of high Si (30 mg/L) which is associated with albite weathering. While land covered by natural vegetation such as tropical bushveld and savannah has low nitrate levels, and the lower limit for nitrogen-nitrate isotope is similar to that for residential and dryland agriculture (maize farming). Cluster analysis results showed a relationship between natural and anthropogenic sources (geology, soil, vegetation, mining, dryland agriculture and residential area) which have delta 18O and delta 15N isotopes signature similar to that for manure or sewage waste, soil and precipitation.
Recycling of refinery and petrochemical effluents employing advanced multi-barrier systems
Authors: Lahnsteiner J. , Andrade P. , Mittal R. D.
Published: February 2013

The Indian Oil Corporation Ltd. Panipat had to build two water reclamation plants as a response to the demands of the environmental authorities. The plants, which treat secondary refinery and various refinery/petrochemical process effluents, were commissioned in 2006 and 2010 respectively. Advanced multi-barrier systems (including ultrafiltration and reverse osmosis) have been employed in order to meet the stringent quality requirements for the recycling of boiler make-up water. Excellent results with regard to the removal of the major parameters such as total dissolved solids (TDS) and silica have been accomplished, e.g. silica is mainly removed by RO (from 11.6 mg/L in the UF outlet to 0.09 mg/L in the RO permeate (99.2% removal)) and is then reduced further to 0.007 mg/L (7 μg/L; total removal 99.94%) in the mixed bed ion exchanger (20 μg/L is the specified limit for boiler make-up water in various power plant guidelines). Both UF process units have shown relatively good performance. The older UF has been in operation for more than five years with still acceptable permeability values and a relatively low number of fibre breakages.
Estimating health risks to water users: Marrying hydrodynamic models and risk models
Authors: McBride G. B. , Stott R. , Papps D. , Palliser C. , Jenner G. , Macdonald G.
Published: February 2013

Epidemiological studies show that discharges of treated human and animal wastes to receiving waters are associated with elevated health risks both to recreational water users and to consumers of raw shellfish. Those studies have relied almost exclusively on faecal indicator bacteria, indicating the potential degree of pathogenicity of the affected waters. However, many receiving waters are substantially different in character from those covered by epidemiological studies. To account for that, QMRA (Quantitative Microbial Risk Assessment) techniques, based on particular pathogens and their dose-response characteristics, are increasingly being used in New Zealand to directly assess the health impacts of wastewater schemes. They have been used to study not only existing infrastructure but also a number of possible alternatives and so are now well-regarded by commissioners hearing permit applications. For coastal discharges QMRA models must generally be married with hydrodynamic models. We present case studies from several outfalls to demonstrate the uses of QMRA, how these can inform understanding of potential health risk to water users, and discuss information/research gaps. Given that coastal QMRA exercises focus on the sources of contamination (and use hydrodynamic models to convey the contaminants to points of exposure), the need for source load minimisation is a natural outcome of the assessment.