A primary concern of developing countries throughout the world is that of obtaining safe drinking water. Waterborne diseases are still common in developing countries since drinking water sources are contaminated and the conventional rural water treatment plants are often inefficient to produce safe drinking water. This situation in developing countries is a major problem in terms of preventing public health. It is estimated that diarrhea accounted for 99% of the 69 million deaths among children before the age of five. Inadequate operation and maintenance after installations caused by a lack of trained operators, by a treacherous supply of chemicals and spare parts, and by financial problems lead to produce unhealthy drinking water. Since major urban water supplies are also not always capable of maintaining a regular supply of qualitatively good water, the distributed water is often considered unsafe for direct consumption. Treatment of water at the household level (etc. boiling) or purchasing of mineral water for consumption is more real than an exception in urban areas of developing countries. Recently, another small-scale approach using the lethal effect of sunlight has gained importance to sanitary contaminated water. Solar disinfection (SODIS) is one of the simplest methods for providing acceptable quality drinking water and consists of filling transparent containers (plastic bags, plastic bottles or glass bottles) with water and exposing the containers to sunlight for approximately 6 hours. Because of the low cost and easy usage, solar disinfection is commonly used in developing countries in Asia, Africa and South America. The aim of this literature review is to give information about solar disinfection mechanism, to compare the efficiency of solar disinfection on different microorganisms based on the past studies, and to discuss the several applications of solar disinfection in the world.

The effect of configuration of activated sludge systems on heavy metal toxicity was investigated. Two bench-scale completely mixed activated sludge systems were operated identically in order to determine the toxic effects of Cr(VI), Zn(II) and industrial wastewater on the activated sludge biomass. One system was operated with an aerobic selector and the other without. Batch experiments based on OECD 209 (Organisation for Economic Cooperation and Development) were performed using a respirometer to find out potential toxicity reduction effect of an aerobic selector. The IC 50 (concentration of a chemical that exhibits 50% respiration inhibition) values of Cr(VI), Zn(II) and industrial wastewater in the activated sludge were determined. Results indicated that the heavy metals and industrial wastewater caused less inhibitory effect on the selector activated sludge system in comparison to the conventional activated sludge system. Cr(VI) was found to exert higher inhibition on both systems.

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The aim of the present study was to evaluate responses of potential indicator bacteria (i.e. Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis) to the ultraviolet (UV) radiation and the UV/hydrogen peroxide (H 2 O 2 ) disinfection processes of surface waters with different qualities in terms of humic content. The UV and the UV/H 2 O 2 processes were applied to waters containing various concentrations

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