Genotoxicity of Organic Substances in Municipal Sewage and Its Ozonated Products

Abstract

Some organic substances contaminated in industrial wastewaters are not easily decomposed through biological treatment plant. In order to investigate the genotoxicity of the substances which remain in effluent from a municipal sewage treatment plant receiving industrial wastewaters, bacterial and mammalian assays were applied to the concentrated samples of secondary effluent. Ozonation was applied to decompose hard-biodegradable organic matters and to decrease its genotoxic intensity. Genotoxicity was surveyed for the concentrated samples using umu test system which can detect the umuDC genes that are known to cause error-prone repair. Positive results were observed in the case of Sep-pak-methanol extracts of secondary effluents with microsomal activation. Results of umu test showed negative in the ozonated samples of the effluent. Genotoxic substances in secondary effluents were decomposed by ozone into non-genotoxic substances. The concentrated sample was fractionated by gel chromatography using Sephadex LH-20 which can separate the molecule in the range from 100 to 5,000. A fraction of the effluent was determined as positive in umu test. The substances were detected in the range of over 5,000 molecular size.