Reduction of mutagenicity of municipal wastewaters by land treatment

The disposal of complex mixtures such as wastewater on agricultural lands poses known and unknown environmental risks. Mutagens may be introduced into the ecosystem and perhaps concentrated by crop plants or leached into ground water supplies. The purpose of this study was to determine the biological effect of a mutagenic wastewater before and after application to soil. An XAD-8 methanol extract of wastewater from the municipal sewage treatment facility at Sauget, IL, was a potent, direct acting mutagen when assayed with Salmonella typhimurium. One and 3 ml of extract were brought up to 10 ml volumes with water and added to 10g of sterile or nonsterile native clay loam. These mixtures were incubated at room temperature for 0, 24 and 48h. After separation of solid and liquid portions by filtration, dichloromethane was added to extract the organic fractions from each component. Solvent extractions were evaporated to dryness under vacuum and brought up in DMSO. Tests for mutagenic activity were conducted using Ames strain TA98. Addition to the soil for greater periods of time decreased the mutagenic activity. The solid component exhibited greater mutagenic activity than the liquid.