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Reduction of surfactants and coliforms in domestic wastewater by fenton processes

Abstract:

In many developing countries, domestic wastewater is one of the major pollution sources to water bodies, and advanced oxidation processes appear nowadays as a promising solution to this problem. In this work, the conventional Fenton process, and the chelate-modified Fenton process with citric acid, were tested for surfactants and fecal coliforms removal from an effluent of a domestic wastewater treatment plant located in Quito city, Ecuador. The best conditions (agitation requirements, H2O2 concentration and Fe2+:H2O2 molar ratio) for the conventional Fenton process were found. These conditions were applied to the chelate-modified Fenton process with citric acid. For this process, two Fe2+:citrate molar ratios (1:1 and 1:1.25) were tested at four pH values (2.80, 4.50, 6.00, and 7.84). The best results were achieved with a H2O2 concentration of 56.33 mM, a Fe2+:citrate:H2O2 molar ratio of 1:1:9, continuous stirring and a pH value of 6. The application of these conditions allowed a complete removal of fecal coliforms, a 97 % reduction of surfactants and an 89 % decrease in chemical oxygen demand in 15 min of treatment. The resulting treated waters complied with water quality standards for discharge to water bodies according to the Ecuadorian legislation. This work provides valuable data on the effectiveness of these treatments, thus presenting them as potential solutions for the problematic of domestic wastewater treatment.