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The impact of incorporating recovery data on protozoan concentration estimates was investigated for Cryptosporidium and Giardia using a large dataset (n = 99) of [oo]cyst assay results with paired recovery estimates. Stochastic [o...
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The impact of incorporating recovery data on protozoan concentration estimates was investigated for Cryptosporidium and Giardia using a large dataset (n = 99) of [oo]cyst assay results with paired recovery estimates. Stochastic [oo]cyst concentration was estimated using three approaches: Ⅰ - no availability/consideration of recovery, Ⅱ - limited recovery data, where sample recovery was considered as an independent random variable, and Ⅲ - every [oo]cyst assay result was adjusted for a concurrently derived recovery estimate. Critically, Approach Ⅰ underestimated [oo]cyst concentrations by about 100% compared to Approaches Ⅱ and Ⅲ, which were similar. The impact of dataset size on statistical uncertainty about the concentration estimate for Approach Ⅱ was investigated; little improvement in parameter uncertainty was achieved beyond n = 20. It is suggested that recovery data be incorporated into source water concentration estimates, especially when used to infer health risks to consumers, so as not to underestimate the risk. Where none is available, conservatively low recoveries should be assumed. When designing monitoring programmes, recovery data should be collected as a pair with [oo]cyst count data for an initial period at least, so that site-specific relationships between those parameters may be ascertained and incorporated into source water concentration estimates.
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The United States Environmental Protection Agency is committed to developing new recreational water quality criteria for coastal waters by 2012 to provide increased protection to swimmers. We review the uncertainties and shortcomi...
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The United States Environmental Protection Agency is committed to developing new recreational water quality criteria for coastal waters by 2012 to provide increased protection to swimmers. We review the uncertainties and shortcomings of the current recreational water quality criteria, describe critical research needs for the development of new criteria, as well as recommend a path forward for new criteria development. We believe that among the most needed research needs are the completion of epidemiology studies in tropical waters and in waters adversely impacted by urban runoff and animal feces, as well as studies aimed to validate the use of models for indicator and pathogen concentration and health risk predictions.
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An assessment of the effects of the transition from conventional chlorination to UV disinfection on potable water biofilm growth and pathogen incidence was made. Two hydraulic systems were tested, one a 1.0 km polyethylene pilot-s...
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An assessment of the effects of the transition from conventional chlorination to UV disinfection on potable water biofilm growth and pathogen incidence was made. Two hydraulic systems were tested, one a 1.0 km polyethylene pilot-scale system within the Lovo waterworks, Stockholm, Sweden, as well as Hasselby and Nockeby municipal distribution systems within the greater Stockholm area. Biofilms were propagated on coupons and the amount of biomass analysed by standard culture and molecular methods. There was no measurable difference in biofilm biomass or pathogen incidence in the transition from conventional chlorination to UV-treatment in any system examined. With the exception of aeromonads, frank (salmonellae, enterobacteria) and opportunistic (legionellae) pathogens as well as indicator bacteria (E. coli, coliforms, enterococci) could not be detected within biofilms in either the pilot-scale or large-scale municipal system. Free-living protozoa were detected almost ubiquitously in biofilm samples in either experimental system though their exact significance and impact remains unknown and warrants further investigation.
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The obJectives of this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. Furthermore, the system may provide an increased supply...
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The obJectives of this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. Furthermore, the system may provide an increased supply of safe water for irrigation with low operational costs and produce commercially valuable plants for small communities in arid and semi-arid areas. A commercial hydroponic system was adapted for this study and consisted of five gullies, 3 m long by 100 mm wide. Primary treated effluent was used to irrigate lettuce in one series and a commercial nutrient solution was used to irrigate the same type of lettuce in another series as a control, both by nutrient film technique (NFT). Nutrient and suspended solids were efficiently removed by the NFT plant system. While no uptake of F-RNA bacteriophages were detected within lettuce leaves, uptake was apparent from spiked virus-sized particles (fluorescent 0.1 mu m microspheres) and equivocal from spores of the faecal bacterium, Clostridiuni perfringens. Microbial data was used in a beta-Poisson dose response model and indicated that the probability of infection for a single ingestion event of NFT grown lettuce grown on primary treated municipal effluent was about 1.7 for viruses. Moreover, plants accumulated heavy metals in leaf tissues at concentrations higher than the maximum recommended levels for Australian and New Zealand food (As= 6.5, Cd = 3.8, Pb= 20 mg kg-1). Hence, it is recommended to evaluate ornamental or non-edible crops, such as essential oils, pyrethrum or flowers for sewage treatment. A c
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