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SODIS, solar disinfection of water in plastic bottles, is a well-known water treatment method utilized in communities lacking water treatment infrastructure. While SODIS is commonly employed by individuals and family units needing clean drinking water, a larger, community-scale solar disinfection system is presented in this paper as an alternative, appropriate, humanitarian engineering technology. A community-scale system may be acceptable for communities that reject the individual-bottle SODIS method. To test the treatment effectiveness of such a system, experiments were conducted to quantify the solar inactivation rate of total coliform bacteria from contaminated source water. Solar disinfection configurations in tanks and bottles were analyzed for the effect of ultraviolet (UV) light index, water temperature, tank color, plastic covering, and duration of sun exposure. A black tank, covered with a clear, plastic drop cloth with a thickness of 2 MIL (0.0508 mm) provided an effective inactivation rate of total coliforms. A contour plot of UV index versus water temperature provides guidelines for minimum required sun exposure times for disinfection. [ABSTRACT FROM AUTHOR]

This paper presents the results of a community-scale drinking water treatment system assessment by University of Mississippi School of Engineering students and the organization Living Waters for the World (LWW). Communities facing a severe lack of sustainable and clean drinking water use LWW microfiltration, ozone water treatment, ultraviolet, and chlorination systems worldwide. Students worked on two projects: (1) evaluation of the ozonation system by measuring several water quality parameters, and (2) creation of a chlorine concentration table based on strength and volume of bleach added to a batch of water. The students' assessment determined that the LWW ozone disinfection and microfiltration system effectively treats water by removing and inactivating bacteria that could cause adverse health effects in humans. When developing the chlorination table, students considered typical units of measurement and tools available in disadvantaged communities. Students learned and performed water quality testing while considering technical and social implications of the treatment systems. [ABSTRACT FROM AUTHOR]

Fecal indicator bacteria (FIB) have long been used as a marker of fecal pollution in surface waters subject to point source and non-point source discharges of treated or untreated human waste. In this paper, we set out to determine the source(s) of elevated FIB concentrations in Cucamonga Creek, a concrete-lined urban stream in southern California. Flow in the creek consists primarily of treated and disinfected wastewater effluent, mixed with relatively smaller but variable flow of runoff from the surrounding urban landscape. Dry and wet weather runoff contributes nearly 100% of FIB loading to Cucamonga Creek, while treated wastewater contributes significant loading of nutrients, including dissolved organic carbon (DOC), phosphorus, nitrate, and ammonium. FIB concentrations are strongly positively correlated with DOC concentration in runoff (Spearman's ρ ≥ 0.66, P ≤ 0.037), and microcosm studies reveal that the survival of Escherichia coli and enterococci bacteria in runoff is strongly dependent on the concentration of both DOC and phosphorus. Below threshold concentrations of 7 and 0.07 mg/L, respectively, FIB die off exponentially (die-off rate 0.09 h-1). Above these thresholds, FIB either grow exponentially (growth rate 0.3 h-1) or exhibit a periodic steady-state in which bacterial concentrations fluctuate around some mean value. The periodic steady-state pattern is consistent with a Lotka—Volterra predator—prey oscillation model, and the clearance rate (20 μL predator-1 h-1) obtained by fitting the model to our data is consistent with the hypothesis that predacious protozoa regulate FIB concentrations in runoff at high DOC concentrations. Collectively, these results indicate that FIB impairment of Cucamonga Creek is best viewed as an ecological phenomenon characterized by both bottom-up and top-down control. [ABSTRACT FROM AUTHOR]