Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborne microorganisms (e.g., microbial pathogens).Undisinfected effluent samples from several municipal wastewater treatment facilities were collected for analysis. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale chlorination and dechlorination and UV irradiation under conditions that allowed compliance with relevant discharge regulations and such that disinfectant exposures could be accurately quantified. Disinfected samples were subjected to a battery of assays to assess the immediate and long-term effects of wastewater disinfection on waterborne bacteria and viruses.In general, (viable) bacterial populations showed an immediate decline as a result of disinfectant exposure; however, incubation of disinfected samples under conditions that were designed to mimic the conditions in a receiving stream resulted in substantial recovery of the total bacterial community. The bacterial groups that are commonly used as indicators do not provide an accurate representation of the response of the bacterial community to disinfectant exposure and subsequent recovery in the environment. UV irradiation and chlorination/dechlorination both accomplished measurable inactivation of indigenous phage; however, the extent of inactivation was fairly modest under the conditions of disinfection used in this study. UV irradiation was consistently more effective as a virucide than chlorination/dechlorination under the conditions of application, based on measurements of virus (phage) diversity and concentration.Taken together, and when considered in conjunction with previously published research, the results of these experiments illustrate several important limitations of common disinfection processes as applied in the treatment of municipal wastewaters. In general, it is not clear that conventional disinfection processes, as commonly implemented, are effective for control of the risks of disease transmission, particularly those associated with viral pathogens. Microbial quality in receiving streams may not be substantially improved by the application of these disinfection processes; under some circumstances, an argument can be made that disinfection may actually yield a decrease in effluent and receiving water quality. Decisions regarding the need for effluent disinfection must account for site-specific characteristics, but it is not clear that disinfection of municipal wastewater effluents is necessary or beneficial for all facilities. When direct human contact or ingestion of municipal wastewater effluents is likely, disinfection may be ne...
Knowledge of the various microcomponents of residential water consumption can play an essential role in setting effective water supply plans and policies. However, there is insufficient data regarding the microcomponents of domestic water use (toilet, laundry, bath, and kitchen) in developing countries. This study measured the microcomponents of residential water use in Chiang Mai and Khon Kaen, Thailand, using a small accumulative water meter attached directly to each household tap. In addition, residents were surveyed to obtain information about income, home bathing facilities, and laundering methods. Results showed water consumption per capita for every use to be distributed lognormally in Chiang Mai and Khon Kaen. Water consumption for toilet use was higher in Chiang Mai than in Khon Kaen, but the study found little difference between the two cities in other microcomponents of residential water consumption. In this research, historical differences in the cities' water resources appeared to have no effect on residential water consumption.
A global water resources model was developed to assess the impact of climate change on water resources. The model consists of six modules, namely, land surface, river, agriculture, reservoir operation, environmental flow, and irrigation.One of the primary purposes of this model is to analyze availability of water resources at daily temporal resolution. We estimated the global distribution of water stressed area due to not only the limitation of annual total water resources but also the strong seasonality of them. The results show that the number of population living under water stressed condition reaches its peak around 2050 and remains high until the end of 21 st century under SRES A1B scenario.
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