bluuebunny/crossref_metadata_2025 huggingface dataset:
Rainwater harvesting: quality assessment and utilization in The Netherlands
Authors: Schets F. M. , Italiaander R. , van den Berg H. H. J. L. , de Roda Husman A. M.
Published: January 2011

The use of roof-collected rainwater as a freely available and sustainable alternative to drinking water produced by drinking water companies increases worldwide. Initially, rainwater is free of microbial contamination, but it may become contaminated by animals and humans or, alternatively, human pathogens may grow in stored rainwater resulting in a significant human health risk from infectious diseases. This three-year study demonstrated that rainwater stored in different reservoirs in The Netherlands was frequently faecally contaminated and incidentally contained potential human pathogens such as Campylobacter, Cryptosporidium, Giardia, Aeromonas hydrophila and Legionella. Analysis of samples during a period with variable weather conditions showed a correlation between rainfall intensity and faecal indicator counts and increased detection of pathogens after heavy rainfall incidents. Outside temperature had a limited effect on both the temperature and the microbiological quality of the water in the reservoirs, which did not comply with Dutch drinking water legislation and should thus not be consumed without treatment. In general, a health risk may arise from exposure to pathogens when contaminated droplets are inhaled, ingested or come into contact with the skin. Health risks may be reduced by regular cleaning of the collection, storage and transport means, but to assess their efficacy field intervention studies are required.
Analysis of the evolution in the circulation of HAV and HEV in Eastern Spain by testing urban sewage samples
Authors: Rodriguez-Manzano Jesus , Miagostovich Marize , Hundesa Ayalkibet , Clemente-Casares Pilar , Carratala Anna , Buti Maria , Jardi Rosend , Girones Rosina , Hundesa Ayalkibet , Carratala Anna , Clemente-Casares Pilar
Published: January 2011

The aim of the study was to analyse the evolution of the prevalence of HAV and HEV in the population of eastern Spain by analysing the viruses excreted in urban sewage. Raw urban sewage samples were collected and analysed during several years using RT-PCR techniques and sequencing analysis. Two limiting regions were analysed, one of them having implemented HAV vaccination programs. Acute symptomatic HEV cases were also examined. Results were compared with those from previous studies in the area using identical methodology. The percentage of positive HAV samples in urban sewage fell from 57.4% to 3.1% in 5–10 years in the two studied areas in Spain. Around 30% of the urban sewage samples were positive for HEV in the absence of agricultural sources of contamination. HEV RNA was also detected in four clinical cases of acute hepatitis. The dramatic reduction in the presence of HAV in raw urban sewage observed in eastern Spain could be most likely related to the general improvement in sanitation. However, these improvements would not have an equivalent effect on the circulation of HEV and this observation could be explained by the presence of animal reservoirs for HEV, which act as external sources of infections.
Detection and phylogenetic analysis of hepatitis A virus and norovirus in marine recreational waters of Mexico
Authors: Félix Josefina León , Fernandez Yuridia Cháidez , Velarde-Félix Jesús Salvador , Torres Benigno Valdez , Cháidez Cristobal
Published: January 2011

An investigation was conducted to determine hepatitis A virus (HAV) and norovirus (NV) presence in marine recreational waters (MRWs) from two Mexican tourists beaches (Altata and Mazatlan), located at the northwestern state of Sinaloa, Mexico. Also, Binary Logistic Regression (BLR) analyses were conducted between physicochemical parameters (temperature, turbidity and salinity) and viral organisms (HAV and NV). A total of 32 MRWs samples were collected from April to July of 2006. Samples were processed according to the Environmental Protection Agency (EPA) adsorption-elution method. Overall, 18 MRWs samples (56.3%) were positive for HAV and NV; 4 (22.2%) were obtained from Altata and 14 (77.8%) from Mazatlan. HAV was detected in 3 MRWs samples (9.4%) and NV in 15 samples (46.8%). Phylogenetic analysis showed the presence of genotype I sub genotype B for HAV and NV genogroup II. BLR analysis showed significant correlations between NV and physicochemical parameters (temperature, turbidity and salinity) (p=0.017, p=0.08, p=0.048, respectively). No significant correlation between physicochemical parameters and HAV was observed. The results indicated that MRW quality of Sinaloa beaches is affected by human faecal pollution. Viral surveillance programs should be implemented to minimize health risks to bathers.
Influencing factors in the occurrence of injured coliforms in the drinking water distribution system in the city of La Plata, Argentina
Authors: Córdoba María Alejandra , Del Coco Valeria Fernanda , Minvielle Marta Cecilia , Basualdo Juan Ángel
Published: January 2011

The objective of this study was to evaluate the influencing factors in the occurrence of coliforms in the drinking water in La Plata (Argentina) from June 1999 to June 2001. A total of 180 samples were collected from Rio de La Plata (102 samples) and Puelche Aquifer (78 samples); 45 samples were collected for each of the four seasons. The membrane filter procedure was used for isolating bacteria, and each sample was tested for chlorine and pH. The highest percentage of samples positive for coliforms in the two tested media was obtained in summer while the highest percentage of negative samples was obtained in winter. No Escherichia coli was isolated. The percentage of injured coliforms fluctuated between 70 and 100%. The most frequently isolated bacteria was Enterobacter cloacae in summer, Enterobacter agglomerans in autumn and Klebsiella oxytoca in winter and spring. Significant correlations were observed between coliforms and the distance from the initial treatment point, and with the level of free chlorine. We conclude that drinking water contamination in La Plata occurs in the distribution system due to increased temperatures and reduced disinfectant levels, which result in bacterial regrowth.
A Cryptosporidium hominis outbreak in North-West Wales associated with low oocyst counts in treated drinking water
Authors: Mason B. W. , Chalmers R. M. , Carnicer-Pont D. , Casemore D. P.
Published: January 2011

An outbreak in the autumn of 2005 resulted in 218 confirmed cases of Cryptosporidium hominis. The attack rate (relative risk 4.1, 95%CI 2.8–9.1) was significantly higher in the population supplied by Cwellyn Water Treatment Works (WTW). A case–control study demonstrated a statistically significant association (odds ratio 6.1, 95% CI 1.8–23.8) between drinking unboiled tap water and C. hominis infection. The association remained significant in a logistic regression analysis, with an adjusted odds ratio of 1.30 (95 CI 1.05–1.61) per glass of unboiled tap water consumed per day. This evidence together with environmental and associated microbiological investigations, and the absence of effective treatment to remove Cryptosporidium oocysts at the WTW, led to the conclusion that the outbreak was waterborne. Oocyst counts in final treated water at the WTW and at different points in the distribution system were consistently very low, maximum count in continuous monitoring 0.08 oocysts per 10 litres. Data from continuous monitoring and the epidemic curve is consistent with the hypothesis that low numbers of oocysts of C hominis were present in treated water continuously during the outbreak and these were of sufficient infectivity to cause illness. All surface water derived water supplies present a potential risk to human health and appropriate control measures should be in place to minimise these risks.
Detection of Cryptosporidium species and sources of contamination with Cryptosporidium hominis during a waterborne outbreak in north west Wales
Authors: Chalmers Rachel M. , Robinson Guy , Elwin Kristin , Hadfield Stephen J. , Thomas Euron , Watkins John , Casemore David , Kay David
Published: January 2011

As part of investigations into the cause of a waterborne outbreak of Cryptosporidium hominis infection linked to a mains water supply, surface waters and wastewater treatment plants were tested for Cryptosporidium spp. Oocyst counts in base flow surface water samples ranged from nil to 29 per 10 l. Oocyst counts in effluent from a community wastewater treatment plant were up to 63 fold higher and breakout from one septic tank five logs higher. There were no peak (storm) flow events during the investigation. C. hominis, four named genotypes (cervine, muskrat II, rat, W19) and six new small subunit ribosomal RNA gene sequences were identified. Four of the new sequences were closely related to Cryptosporidium muskrat genotype I, one was closely related to the fox genotype and one to Cryptosporidium canis. C. hominis was found extensively in the catchment, but only at sites contaminated by wastewater, and in the treated water supply to the affected area. All were gp60 subtype IbA10G2, the outbreak subtype. Multiple routes of contamination of the reservoir were identified, resulting in persistent detection of low numbers of oocysts in the final water. This work demonstrates the utility of genotyping Cryptosporidium isolates in environmental samples during outbreak investigations.
Supply system factors associated with microbiological drinking water safety in regional New South Wales, Australia, 2001–2007
Authors: Cretikos Michelle , Byleveld Paul , Durrheim David N. , Porigneaux Philippe , Merritt Tony , Leask Sandy
Published: January 2011

Aim: To determine factors associated with microbiological safety of public drinking water systems in regional New South Wales (NSW), Australia.

Method: We analysed 107,000 end-user drinking water samples for an association between detection of Escherichia coli and drinking water system features, sample year and season using NSW Health Drinking Water Monitoring Program data, 2001–2007. We used negative binomial generalized estimating equations with adjustment for autocorrelation and clustering.

Results: We detected E. coli in over 2% of samples from 40% (129/323) of systems. E. coli detection was significantly more common in earlier years and during summer (p<0.001). On multivariate analysis E. coli detection was significantly associated with smaller systems; watercourse sources; no disinfection or disinfection with ultraviolet only; and higher post-treatment mean turbidity (all p≤0.01). Detection was most strongly associated with lack of disinfection (incidence rate ratio 12.6, p<0.001) and smaller supply systems (1% reduction in E. coli detection for each 1,000 person increase in supply population, p=0.004). Ultraviolet disinfection alone was the least effective disinfection method (p<0.001).

Conclusion: Even in developed countries, drinking water systems without disinfection or serving small populations appear vulnerable to the effects of faecal contamination, which presents a risk of waterborne disease outbreaks.
Assessment of E. coli and Salmonella spp. infection risks associated with different fecal sludge disposal practices in Thailand
Authors: Yajima A. , Koottatep T.
Published: January 2011

The proper management of fecal sludge (FS), to block the transmission pathways of pathogens, is rarely enforced in many parts of the world. Health risks associated with different disposal practices of FS in peri-urban settings of a large metropolis in Thailand were assessed; Tha Klong sub-district with indiscriminate FS dumping, and Klong Luang sub-district which has an FS treatment system. The study showed that indiscriminate FS dumping from along the canal banks and discharge of market waste were likely the major sources of E. coli and Salmonella spp. in contamination of the canal water. The increased microbial pathogen concentrations near the FS treatment facility also indicated contamination risks from poorly designed treatment facilities. Quantitative microbial risk assessment (QMRA) indicated very high water-related infection risk levels compared to the actual locally recorded disease occurrences. These results indicated that the QMRA model needs to be modified to take account of immunological differences between populations in developed countries, where the model was developed, and developing countries. In addition, further sensitivity factors are needed to reflect different societal behavior patterns, and therefore contact with potentially contaminated water, in different sub-populations of many less developed communities.
Estimators of annual probability of infection for quantitative microbial risk assessment
Authors: Karavarsamis N. , Hamilton A. J.
Published: January 2011

Four estimators of annual infection probability were compared pertinent to Quantitative Microbial Risk Analysis (QMRA). A stochastic model, the Gold Standard, was used as the benchmark. It is a product of independent daily infection probabilities which in turn are based on daily doses. An alternative and commonly-used estimator, here referred to as the Naïve, assumes a single daily infection probability from a single value of daily dose. The typical use of this estimator in stochastic QMRA involves the generation of a distribution of annual infection probabilities, but since each of these is based on a single realisation of the dose distribution, the resultant annual infection probability distribution simply represents a set of inaccurate estimates. While the medians of both distributions were within an order of magnitude for our test scenario, the 95th percentiles, which are sometimes used in QMRA as conservative estimates of risk, differed by around one order of magnitude. The other two estimators examined, the Geometric and Arithmetic, were closely related to the Naïve and use the same equation, and both proved to be poor estimators. Lastly, this paper proposes a simple adjustment to the Gold Standard equation accommodating periodic infection probabilities when the daily infection probabilities are unknown.
An international review of the challenges associated with securing buy-in for water safety plans within providers of drinking water supplies
Authors: Summerill Corinna , Smith Jen , Webster James , Pollard Simon
Published: January 2011

Since publication of the 3rd Edition of the World Health Organisation (WHO) Drinking Water Quality guidelines, global adoption of water safety plans (WSPs) has been gathering momentum. Most guidance lists managerial commitment and ‘buy-in’ as critical to the success of WSP implementation; yet the detail on how to generate it is lacking. This commentary discusses aspects of managerial commitment to WSPs. We argue that the public health motivator should be clearer and a paramount objective and not lost among other, albeit legitimate, drivers such as political or regulatory pressures and financial efficiency.
Understanding drivers and barriers: the key to water use behaviour change
Authors: Graymore Michelle , Wallis Anne , O'Toole Kevin
Published: January 2011

In southwest Victoria, like many other regions in Australia, drought, climate change and population growth have exposed gaps in water supply. To develop effective demand management strategies for rural and regional areas, this paper investigates the drivers and barriers to water saving in southwest Victoria. Although the majority of people felt water saving was important, the drivers for water saving differed between different groups. Residential users were saving water for altruistic reasons, while for farmers the drivers were farm viability and productivity. Although the barriers differed between property types, common barriers included lack of understanding of the impact their water use has on supplies, lack of knowledge, the pricing system and distrust of the water authority. The findings provide information for effective demand management strategies for the region.
Evaluation of an emerging water treatment technology: ceramic membranes
Authors: Kommineni S. N. , Bryck J. , Stringer C. , Stevens C. , Meyers N. , Karnik B. , Hoffman R. , Sullivan L.
Published: January 2011

Historically, low-pressure membranes (microfiltration (MF) and ultrafiltration (UF)) used in potable water treatment are made of polymers (polysulfone (PS), polypropylene (PP), polyethersulfone (PES), polyvinylidene fluoride (PVDF) etc). Recently, membranes made of ceramic materials (aluminium oxide) have been developed by MetaWater (Japan), Kubota (Japan) and others and is being marketed in the United States (US) by Krüger, Inc. (Cary, NC). Ceramic membranes offer several potential advantages over polymeric membranes, including higher mechanical robustness and ability to handle higher loading of particulates, higher resistance to oxidants and membrane cleaning chemicals, higher membrane integrity, longer service life and compact footprint. The authors conducted collaborative evaluations of this emerging technology at two different places; (i) Elm Fork Water Treatment Plant (WTP) of Dallas Water Utilities (DWU), Dallas, Texas, USA and (ii) Graham Mesa WTP, City of Rifle, Rifle, Colorado, USA. The evaluations included pilot testing of ceramic membranes in direct filtration mode (i.e. without clarification) and with coagulant addition. The water streams that were pilot tested at Elm Fork WTP included Trinity River water, spent filter backwash wastewater and lagoon recycle water (spent filter backwash water combined with clarifier blow down water). The City of Rifle pilot testing was conducted on Colorado River water. This paper presents the key results of these two pilot studies. Results of pilot testing were used to define the potential membrane flux, backwash protocols (interval and duration), chemical enhanced backwash (CEB) and clean-in-place (CIP) protocols. Pilot test results and engineering judgment were used for developing concept-level sizing and outlining parameters for future evaluation. This paper will discuss the key technical and economic considerations of the emerging treatment technology and its potential applications for potable water treatment. This paper will be of interest to water providers that are considering alternatives to treat challenging source waters (waters with high particulates and under heavy microbial influence), build new compact water treatment plants, increase plant capacity through membrane retrofits and treat recycle streams at existing WTPs.
Structural equation modeling for assessing of the sustainability of rural water supply systems
Authors: Masduqi A. , Endah N. , Soedjono E. S. , Hadi W.
Published: January 2011

As one of the basic human needs, water services should be sustainable. Researches related to the sustainability of water services have been conducted in several developing countries. However, there are no identical researches in Indonesia. This paper discusses the analysis of factors that contribute to sustainability of rural water supply systems in East Java, Indonesia. Data is collected by observing rural water supply facilities, interviewing water committees and water users, and taking documentation. The data is used to build a model, which was developed from theoretical or conceptual model. The model's development uses structural equation modeling (SEM). This model can show the factors that contribute to sustainability of rural water supply systems. The sustainability is influenced significantly by nine variables; they are selection of technology, water sources, investment cost, capability of operator, availability of spare parts, operation cost, technical operation, community participation, and institutional management.
Measuring sustainability of water supply: performance indicators and their application in a corporate responsibility report
Authors: Staben N. , Hein A. , Kluge T.
Published: January 2011

For many water supply companies, the sustainable exploitation of water resources has always been an integral part of their business, voluntarily accepting tasks and responsibility which benefit society and the environment in general, e.g. in resource protection, environmental monitoring, and encouragement of sustainable farming practices. However, these voluntary activities are often not sufficiently recognised internally and externally due to a missing sustainability framework and a less developed communication strategy. Therefore, a comprehensive framework for the measurement and reporting of corporate responsibility (CR) in water supply was developed, comprising the environmental and sustainability issues of resource protection and water supply, social responsibility and long-term economical development. This framework was successfully applied in a Balanced Scorecard (BSC) approach and served as basis for a CR report of a German regional water and wastewater company. The CR Performance Indicator system was imbedded in the IWA framework of Performance Indicators (PI), and as such is universally applicable in water and wastewater systems.
Sludge characterization at Kadahokwa water treatment plant, Rwanda
Authors: Uwimana A. , Nhapi I. , Wali U. G. , Hoko Z. , Kashaigili J.
Published: January 2011

A study was carried out to characterize the sludge produced at Kadahokwa Water Treatment Plant (KWTP) in Butare to assess the effectiveness of the sludge treatment and potential impacts of sludge disposal on the environment. Parameters analyzed were chromium, nickel, cadmium, lead, copper, zinc, iron, manganese, aluminium, total nitrogen, total phosphorus, potassium and cation exchange capacity (CEC). The results showed that 450±244.5 tons (dry weight) of sludge are produced annually. The concentrations of heavy metals in the sludge were below the standard limits for land application set by different countries. The high concentrations of nickel (42.3±2.5 ppm), chromium (29.9±6.2 ppm), cadmium (1.1±0.3 ppm) and lead (31.6±3.7 ppm) in the dried sludge posed a pollution risk for the wetland. The CEC was 28.4–33.3 cmol (+)/kg and pH was 6.50–7.45. It was concluded that the KWTP sludge is a poor source of total carbon, a moderate source of nutrients (NPK), and an important source of micronutrients, making it generally suitable for reuse for crop production. The CEC showed that the sludge could improve soil nutrient and water holding capacity. The higher concentration of aluminium (280 ppm) in the sludge creates an opportunity for recycling.
Evaluating the efficacy of pre-oxidation for enhancing removal of HAA5 precursors by conventional drinking water treatment
Authors: Zhang Junzhi , An Wei , Song Lanhe , Yu Jianwei , Wang Yongjing , Ma Gang , Yang Min
Published: January 2011

The formation potentials of five haloacetic acids (HAA5FP) in 13 surface water samples taken from eight cities from northeast to south China were evaluated using the simulated distribution system (SDS) chlorination method. These samples showed a wide range of HAA5FP levels (20 to 443 μg L−1). Four pre-oxidation methods were evaluated for their performance in enhancing HAA5FP removal from six water samples by coagulation. Pre-Cl2 and pre-KMnO4 were not effective. While pre-ClO2 showed some enhancing effects for all samples, pre-O3 exhibited markedly higher effects without producing perceptible oxidation by-products such as bromate and formaldehyde. An enhancement factor (EF) value of 13–17% was achieved at an ozone dose of 0.5 mg L−1 and the maximum EF values were 16–25% at an ozone dose of 1.5–2.0 mg O3 L−1 (0.3–0.7 mg O3/mg dissolved organic carbon (DOC)). A 3D contour plot was applied to interpret the effects of two independent variables (DOC and specific ultraviolet absorbance (SUVA254)) on the formation potential of HAA5 using a quadratic smoothing technique, and it was found that the enhancing effect on the removal of HAA5FP by pre-ozonation was attributed to the destruction of reactive sites of organic compound, which could be expressed by the changes of SUVA254.
Estimation of the virtual water trade between two Spanish regions: Castilla-la Mancha and Murcia
Authors: De Miguel Ángel , García Eloy , De Buestamante Irene
Published: January 2011

Virtual water is defined as the water needed to produce a product. We can use virtual water flow calculations to estimate the water efficiency of a country, as well as its economic dependence on water resources. Former studies on this area have focused on quantifying the virtual water flows between countries, in an international context. In this study we reduce the action framework to regions within a country, determining the virtual water balance between two Spanish regions: Castilla-La Mancha and Murcia. In 2004, Castilla-La Mancha exported to Murcia 2,453,442 tons of commercial products, from which 1,191,628 tons were agricultural goods. In terms of virtual water, it means 1,365 hm3, including food-processing, and industrial products. It is necessary to add 350 hm3 to the result, because of the water transfer (Tajo-Segura transfer) between the rivers basins of these regions, so the final virtual water number, in 2004, was 1,715 hm3. The other way round, Murcia exported in 2004 2,069,000 tons of products, from which 490,351 tons were agricultural goods. That supposes 712 hm3 of virtual water. Virtual water flow is unbalanced and displaced towards Murcia with a difference of 1,003 hm3.
Legionella pneumophila serogroup 3 prevalence in drinking water survey in Israel (2003–2007)
Authors: Yarom Rachel , Sheinman Rivka , Armon Robert
Published: January 2011

A 5-year survey (2003 to 2007) was carried out on various drinking water sources in Israel for detection of Legionella spp. The most frequently isolated species was L. pneumophila serogroup 3 (prevalence 60.44±5.6) followed by L. pneumophila serogroup 1 (26.98±5.2) and other serogroups and unidentified species (12.6±9.8). L. pneumophila serogroup 1 is the worldwide prevalent serogroup in water sources while serogroup 3 was only occasionally reported. Previous reports on L. pneumophila serogroup 1 as the main causative of respiratory disease in Israel revealed a drop from 52 to 15% in incidence during a 5-year survey, with a rise in the incidence of seropositivity to “other Legionellae”, mainly sg. 3. As antigenuria is the main clinical tool to detect Legionellosis among infected patients, the shift from serogroup 1 to serogroup 3 in water sources will go undetected for obvious reasons. The process of serogroups prevalence shift in water sources is an interesting issue that has to be investigated further in order to advance our understanding of Legionella epidemiology.
Ceramic membranes for water treatment
Authors: Mueller Uwe , Biwer Gerhard , Baldauf Guenther
Published: January 2011

Ceramic membranes, different in pore size and membrane material, were applied to remove particulate and dissolved matter from different spent filter backwash water types as well as from dam water. The study was conducted in pilot scale under conditions typical for waterworks at a dam water treatment plant. A comparison of different ceramic membranes implied that total membrane resistance was more influenced by feed water type and by operation than by membrane type for the waters tested. Nevertheless, ceramic membranes seem to accumulate during operation less organic foulants especially polysaccharides compared to organic membranes leading to lower total membrane resistances for ceramic membranes during filtration process. Ceramic membranes may be considered to be applicable to treat spent filter backwash water as well as source water in public water supply.
Design of drip irrigation lateral for optimum capital and operating cost
Authors: Wu P. T. , Zhu D. L. , Jin J. , Niu W. P.
Published: January 2011

The drip irrigation system cost can be reduced effectively by using optimal design methods and decreasing the system pressure. In this paper, a two-stage optimum drip irrigation lateral design model is developed based on a new uniformity formula that includes hydraulic variation, emitter manufacture’s variation, and field roughness variation. The non-linear objective function minimizes the capital cost and the present values of the lateral operating cost. In the first stage, the pipe diameter and the emitter average pressure are taken as decision variables for the specified uniformity and lateral length. In the second stage, a commercially available pipe size that is very close to the diameter obtained in the first stage is selected. It has an allowable pressure that is a little more than or equal to 1.5 times of the maximum lateral pressure obtained in the first stage. The emitter average pressure is calculated for a known diameter. The model is applied to a case study in which the result indicates that a lateral with a larger diameter and the lower emitter average pressure can be economically justifiable. A drip irrigation system with a lower pressure should be developed on the basis of this study.
Life cycle assessment of three water systems in Copenhagen - a management tool of the future
Authors: Godskesen B. , Zambrano K. C. , Trautner A. , Johansen N.-B. , Thiesson L. , Andersen L. , Clauson-Kaas J. , Neidel T. L. , Rygaard M. , Kløverpris N. H. , Albrechtsen H.-J.
Published: January 2011

Environmental life-cycle assessment (LCA) was applied to evaluate three different water systems of the water sector in Copenhagen, Denmark, including technologies within water supply, facilities recycling water and treatment of sewer overflow. In these three water systems LCA was used to evaluate the environmental impacts of each of the processes involved. The overall conclusion was that LCA is suitable as a decision support tool in the water sector as it provides a holistic evaluation platform of the considered alternatives categorized in environmental impact categories. The use of LCA in the water sector of this region has limitation since it not yet considers impact categories assessing freshwater scarcity and ecological sustainability.
Chemical monitoring strategy for the assessment of advanced water treatment plant performance
Authors: Drewes J. E. , McDonald J. A. , Trinh T. , Storey M. V. , Khan S. J.
Published: January 2011

A pilot-scale plant was employed to validate the performance of a proposed full-scale advanced water treatment plant (AWTP) in Sydney, Australia. The primary aim of this study was to develop a chemical monitoring program that can demonstrate proper plant operation resulting in the removal of priority chemical constituents in the product water. The feed water quality to the pilot plant was tertiary-treated effluent from a wastewater treatment plant. The unit processes of the AWTP were comprised of an integrated membrane system (ultrafiltration, reverse osmosis) followed by final chlorination generating a water quality that does not present a source of human or environmental health concern. The chemical monitoring program was undertaken over 6 weeks during pilot plant operation and involved the quantitative analysis of pharmaceuticals and personal care products, steroidal hormones, industrial chemicals, pesticides, N-nitrosamines and halomethanes. The first phase consisted of baseline monitoring of target compounds to quantify influent concentrations in feed waters to the plant. This was followed by a period of validation monitoring utilising indicator chemicals and surrogate measures suitable to assess proper process performance at various stages of the AWTP. This effort was supported by challenge testing experiments to further validate removal of a series of indicator chemicals by reverse osmosis. This pilot-scale study demonstrated a simplified analytical approach that can be employed to assure proper operation of advanced water treatment processes and the absence of trace organic chemicals.
A Markov-Chain Model for the Analysis of High-Resolution Enzymatically 18O-Labeled Mass Spectra
Authors: Valkenborg Dirk , Burzykowski Tomasz
Published: January 2011

The enzymatic 18O-labeling is a useful quantification technique to account for between-spectrum variability of the results of mass spectrometry experiments. One of the important issues related to the use of the technique is the problem of incomplete labeling of peptide molecules, which may result in biased estimates of the relative peptide abundance. In this manuscript, we propose a Markov-chain model, which takes into account the possibility of incomplete labeling in the estimation of the relative abundance from the observed data. This allows for the use of less precise but faster labeling strategies, which should better fit in the high-throughput proteomic framework. Our method does not require extra experimental steps, as proposed in the approaches developed by Mirgorodskaya et al. (2000), López-Ferrer et al. (2006) and Rao et al. (2005), while it includes the model proposed by Eckel-Passow et al. (2006) as a special case. The method estimates information about the isotopic distribution directly from the observed data and is able to account for biases induced by the different sulphur content in peptides as reported by Johnson and Muddiman (2004). The method is integrated in a statistically sound framework and allows for the calculation of the errors on the parameter estimates based on model theory. In this manuscript, we describe the methodology in a technical matter and assess the properties of the algorithm via a thorough simulation study. The method is also tested on a limited dataset; more intense validation and investigation of the operational characteristics is being scheduled.
Learning Monotonic Genotype-Phenotype Maps
Authors: Beerenwinkel Niko , Knupfer Patrick , Tresch Achim
Published: January 2011

Evolutionary escape of pathogens from the selective pressure of immune responses and from medical interventions is driven by the accumulation of mutations. We introduce a statistical model for jointly estimating the dynamics and dependencies among genetic alterations and the associated phenotypic changes. The model integrates conjunctive Bayesian networks, which define a partial order on the occurrences of genetic events, with isotonic regression. The resulting genotype-phenotype map is non-decreasing in the lattice of genotypes. It describes evolutionary escape as a directed process following a phenotypic gradient, such as a monotonic fitness landscape. We present efficient algorithms for parameter estimation and model selection. The model is validated using simulated data and applied to HIV drug resistance data. We find that the effect of many resistance mutations is non-linear and depends on the genetic background in which they occur.
A Comparison of Multifactor Dimensionality Reduction and L1-Penalized Regression to Identify Gene-Gene Interactions in Genetic Association Studies
Authors: Winham Stacey , Wang Chong , Motsinger-Reif Alison A
Published: January 2011

Recently, the amount of high-dimensional data has exploded, creating new analytical challenges for human genetics. Furthermore, much evidence suggests that common complex diseases may be due to complex etiologies such as gene-gene interactions, which are difficult to identify in high-dimensional data using traditional statistical approaches. Data-mining approaches are gaining popularity for variable selection in association studies, and one of the most commonly used methods to evaluate potential gene-gene interactions is Multifactor Dimensionality Reduction (MDR). Additionally, a number of penalized regression techniques, such as Lasso, are gaining popularity within the statistical community and are now being applied to association studies, including extensions for interactions. In this study, we compare the performance of MDR, the traditional lasso with L1 penalty (TL1), and the group lasso for categorical data with group-wise L1 penalty (GL1) to detect gene-gene interactions through a broad range of simulations.

We find that each method has both advantages and disadvantages, and relative performance is context dependent. TL1 frequently over-fits, identifying false positive as well as true positive loci. MDR has higher power for epistatic models that exhibit independent main effects; for both Lasso methods, main effects tend to dominate. For purely epistatic models, GL1 has the best performance for lower minor allele frequencies, but MDR performs best for higher frequencies. These results provide guidance of when each approach might be best suited for detecting and characterizing interactions with different mechanisms.
Accuracy and Computational Efficiency of a Graphical Modeling Approach to Linkage Disequilibrium Estimation
Authors: Abel Haley J , Thomas Alun
Published: January 2011

We develop recent work on using graphical models for linkage disequilibrium to provide efficient programs for model fitting, phasing, and imputation of missing data in large data sets. Two important features contribute to the computational efficiency: the separation of the model fitting and phasing-imputation processes into different programs, and holding in memory only the data within a moving window of loci during model fitting. Optimal parameter values were chosen by cross-validation to maximize the probability of correctly imputing masked genotypes. The best accuracy obtained is slightly below than that from the Beagle program of Browning and Browning, and our fitting program is slower. However, for large data sets, it uses less storage. For a reference set of n individuals genotyped at m markers, the time and storage required for fitting a graphical model are approximately O(nm) and O(n+m), respectively. To impute the phases and missing data on n individuals using an already fitted graphical model requires O(nm) time and O(m) storage. While the times for fitting and imputation are both O(nm), the imputation process is considerably faster; thus, once a model is estimated from a reference data set, the marginal cost of phasing and imputing further samples is very low.
Can Rising Inequality Explain Aggregate Trends in Marriage? Evidence from U.S. States, 1977-2005
Authors: Coughlin Tristan P. , Drewianka Scott D
Published: January 2011

We investigate the hypothesis that rising wage inequality caused declines in the U.S. aggregate marriage hazard since 1970. Despite confirming previous findings that inequality accounts for much of the decline among young adults before 1990, we find that the aggregate marriage hazard became much less sensitive to inequality thereafter. Our explanation for the weakened relationship relies on the theoretical prediction, which we verify empirically, that inequality influences marital decisions of young singles much more than those of older singles. The aggregate marriage hazard thus became less responsive to inequality over this period because the unmarried population became older.
Oligopoly on a Salop Circle with Centre
Authors: Madden Paul , Pezzino Mario
Published: January 2011

We study an oligopolistic market in which consumers located around the perimeter of a Salop circle buy either from firms around this perimeter (providing horizontally differentiated goods) or from a firm located at the centre of the circle (providing a homogeneous good). An entry-pricing game is studied. The market equilibria and social optima indicate various possible market failures, including cases in which the market is served only by perimeter firms whilst central provision would be socially optimal (in this sense, more extreme than the standard Salop excessive product differentiation). Moreover, for some parameters, the standard Salop result might be reversed.
The Urine Albumin-to-Creatinine Ratio
Authors: Erman Arie , Rahamimov Ruth , Mashraki Tiki , Levy-Drummer Rachel S. , Winkler Janos , David Iskra , Hirsh Yehudit , Gafter Uzi , Chagnac Avry
Published: January 2011

Background and objectives

Microalbuminuria predicts graft loss and death in the renal transplant population. Measurement of the urinary albumin-to-creatinine ratio (UACR) is recommended for its detection. There is uncertainty regarding the optimal UACR cutoff values. Few studies have examined the accuracy of UACR in the general population and none have been conducted in renal transplant recipients. The aim of this study is to determine the performance of UACR in the renal transplant population.

Design, setting, participants & measurements

Renal transplant recipients with a daily urinary albumin excretion rate of up to 300 mg accurately carried out a 24-hour urine collection and provided a morning urine sample for the measurement of albuminuria and UACR. The performance measures of UACR for the detection of microalbuminuria (30 to 300 mg/d) were calculated using different cutoffs.

Results

Median albuminuria was 23 mg/d, and median UACR was 17 mg/g. The area under the receiver-operating characteristic curve was 0.94 in men and 0.98 in women. The optimal cutoff was 21 mg/g in men and 24 mg/g in women. In men, the 30-, 17-, and 21-mg/g cutoffs provided a sensitivity of 0.79, 0.89, and 0.87. In women, the 30-, 25-, and 24-mg/g cutoffs provided a sensitivity of 0.90, 0.97, and 1.0.

Conclusions

These data show that in the renal transplant population, lower gender-specific cutoffs should be used for the detection of microalbuminuria than the recommended 30-mg/g cutoff. These data support the need for a reappraisal of the 30-mg/g cutoff for the detection of microalbuminuria.
Heart Failure in Long-Term Peritoneal Dialysis Patients
Authors: Wang Angela Yee-Moon , Wang Mei , Lam Christopher Wai-Kei , Chan Iris Hiu-Shuen , Lui Siu-Fai , Sanderson John E.
Published: January 2011

Background and objectives

Heart failure occurs frequently in end-stage renal disease patients. However, there are no prospective, longitudinal follow-up data on its prevalence, severity, and risk factors in long-term peritoneal dialysis (PD) patients.

Design, setting, participants, & measurements

A prospective observational study was conducted in 220 long-term PD patients followed up for 4 years or until death. Echocardiography was obtained at baseline. Primary study end points were heart failure and mortality.

Results

Eighty-six patients had a previous history of heart failure at study entry. The cumulative 4-year survival probability was 37.4% and 64.7% for patients with and without previous heart failure, respectively (P < 0.0001). During follow-up, 87 patients (40.9%) developed heart failure, of which 53 were recurrence and 34 were new-onset heart failure. Diabetes, background atherosclerotic vascular disease, systolic hypertension, left ventricular (LV) mass index, systolic dysfunction, and hypoalbuminemia were significant risk factors predicting heart failure in the entire cohort. Diabetes and LV mass and volume index were significant predictors of new-onset heart failure. Systolic hypertension, LV volume index, and hypoalbuminemia were significant predictors of recurrent heart failure.

Conclusions

Heart failure is a highly prevalent complication in long-term PD patients and predicts adverse clinical outcomes. More attention should be focused on improving BP and volume control and identifying treatment strategies that effectively lower atherosclerotic burden and reverse LV hypertrophy, remodeling, and systolic dysfunction in PD patients.
Statistical Requirements for Properly Investigating a Null Hypothesis
Authors: Schumm Walter R.
Published: January 2011

Issues involved in the evaluation of null hypotheses are discussed. The use of equivalence testing is recommended as a possible alternative to the use of simple t or F tests for evaluating a null hypothesis. When statistical power is low and larger sample sizes are not available or practical, consideration should be given to using one-tailed tests or less conservative levels for determining criterion levels of statistical significance. Effect sizes should always be reported along with significance levels, as both are needed to understand results of research. Probabilities alone are not enough and are especially problematic for very large or very small samples. Pre-existing group differences should be tested and properly accounted for when comparing independent groups on dependent variables. If confirmation of a null hypothesis is expected, potential suppressor variables should be considered. If different methods are used to select the samples to be compared, controls for social desirability bias should be implemented. When researchers deviate from these standards or appear to assume that such standards are unimportant or irrelevant, their results should be deemed less credible than when such standards are maintained and followed. Several examples of recent violations of such standards in family social science, comparing gay, lesbian, bisexual, and transgender families with heterosexual families, are provided. Regardless of their political values or expectations, researchers should strive to test null hypotheses rigorously, in accordance with the best professional standards.
Meditation and Attention: A Comment on a Recent Article
Authors: Telles Shirley , Naveen K. V. , Balkrishna Acharya
Published: January 2011

Meditation and attention are considered associated in different ways. For example, contemporary concepts state that to meditate, a practitioner has either to (i) focus attention on the object of meditation (FA) or (ii) maintain vigilance and disengage their attention consciously from all distracters (OM). The Indian sage Patanjali ( circa 900 B.C.), mentioned that there are two stages of meditation, which differ subtly from the descriptions of FA and OM. One stage is called dharana, or focusing attention on the object of meditation. Another stage is called dhyana, during which all thoughts remain effortlessly directed to the object of meditation, excluding all other thoughts. Vigilance and attention are not required during dhyana, which is the actual phase of meditation. In a previous study, participants who practiced dharana performed better in a task for selective attention than those who practiced dhyana. Brainstem auditory evoked potential changes during the two states differed. Descriptions of yoga practices from ancient texts can give added insights about meditation and attention, supported by objective assessments.
Scoring the VIA Survey of Character
Authors: Diamond Mark R. , O'brien-Malone Angela , Woodworth Rosalind J.
Published: January 2011

The VIA Survey of Character (VIA) is a self-report inventory designed to measure and assess 24 character strengths that are linked conceptually to six fundamental “virtues“—Wisdom and Knowledge, Courage, Humanity, Justice, Temperance, and Transcendence, as developed by Peterson and Seligman in 2004. Despite its popularity, the current presentation of the VIA is not easy to score; researchers must either use a limited online scoring facility or must use outdated scoring keys. This paper presents a full description of the scoring key.
The Swedish Version of the Parent-Rated Junior Temperament and Character Inventory (J–TCI)
Authors: Kerekes Nóra , Brändström Sven , Ståhlberg Ola , Larson Tomas , Carlström Eva , Lichtenstein Paul , Anckarsäter Henrik , Nilsson Thomas
Published: January 2011

To evaluate the psychometric characteristics of the Swedish version of the Junior Temperament and Character Inventory (J–TCI), it was sent to parents of 9- and 12-yr.-old twins in Sweden. The final number of responders was 196 parents who rated 92 female and 104 male twin pairs. The inventory of one twin, randomly chosen from each pair, was included in the analyses. Reward Dependence, Persistence, and Cooperativeness were scored higher in girls; Novelty Seeking was higher in the 9-yr.-olds and Persistence in the 12-yr.-olds. Pearson's correlations showed that some dimensions were not statistically independent from each other, even if the covariance was moderate. Internal consistency (Cronbach's alpha) was satisfactory for Harm Avoidance, Novelty Seeking, Self-Directedness, and Cooperativeness (.68–.81), while it was lower in those dimensions that had fewer items. The Swedish parent version of the J–TCI shared about the same psychometric characteristics as found in international samples.