Solar photochemical technology for potable water treatment in the tropics: Disinfection and detoxification

Clean water is scarce in many countries, and the goal of universal access to water and sanitation has not yet been achieved. Standard water treatment techniques are often expensive both in capital investment and operation and maintenance, particularly in lesser developed communities where resources are scarce.; Solar photochemistry has shown promise as an appropriate alternative technology for treatment of water, and provides potential for simultaneous disinfection and destruction of organic chemicals. The need for simultaneous treatment arises when conditions of contamination of source water, such as ground water, occurs. Potential sources of contamination are industrial and agricultural runoff or leakage of underground storage tanks (gasoline) and sewerage lines.; In a series of bench scale experiments, three photochemical technologies, TiO{dollar}sb2{dollar} photocatalysis, dye photosensitization and a combination of dye photosensitization and TiO{dollar}sb2{dollar} photocatalysis, were evaluated for their efficacy for simultaneous removal of coliform bacteria and aromatic hydrocarbons in drinking water under a variety of pH and photochemical concentration conditions.; Series of 100 ml and 500 ml reactors, containing various concentrations of TiO{dollar}sb2{dollar}, and two pH levels (4 and 7), were inoculated with mixed bacteria species, benzene, toluene, and xylene, and illuminated under ultraviolet light for several hours. Under most conditions both the chemical and bacteriological contaminants were destroyed within an hour.; In photosensitization experiments, the 500 ml reactors were charged with several concentrations of rose bengal or methylene blue and neutral, pH 7, or basic, pH 10, water. After inoculation with Escherichia coli, benzene and toluene, the reactors were illuminated for four hours in sunlight. In all cases, the water was disinfected within one hour; however, destruction of the chemical contaminants did not occur.; The 500 ml hybrid reactors, loaded with 0.01% TiO{dollar}sb2{dollar} and/or 5 mg/L methylene blue, were also illuminated in sunlight. The inoculations of Escherichia coli, benzene, and toluene were completely destroyed after two hours in all of the reactors which contained TiO{dollar}sb2{dollar}; however, the presence of methylene blue inhibited the reaction.