Wastewaters of private household septic tanks and cesspools have been treated with peracetic acid (1-2 g L(-1)). Adding 1 g L(-1) peracetic acid to wastewaters was easy and has been found to be effective in destroying enteric indicator microorganisms. The careful mixing of peracetic acid and wastewater was found to be important. Winter periods with frozen soil, ice and snow did not constitute extra problems. The bad smell of these wastewaters almost totally disappeared during the treatment. When wastewaters treated with peracetic acid were emptied into animal slurry tanks, hygienization still continued in the mixture of animal slurry and the wastewaters. These wastewaters could thus be released into agricultural soil without risk of microbiological pollution to groundwaters.