Impact of selected insecticides on the anaerobic stabilization of municipal sewage sludge

The aim of the studies was to indicate whether the insecticides have toxic impact on the course of the process of sewage sludge methane fermentation and their biochemical durability is. The research proved that representatives of insecticides from the group of chlorinated hydrocarbons and phosphoorganic compounds can be toxic to anaerobic biocenosis. The series of insecticide toxicity with respect to anaerobic biocenosis is the following: Chloroorganic compounds>phosphoorganic compounds. The compounds studied can be put into a series with respect to their toxicity as follows: metoxychlor>chlorfenvinphos>fenitrothion>malathion, and for commercial products as follows: Metox>Enolofos>Owadofos>Sadofos. Pesticides from the group of chlorinated hydrocarbons and phosphoorganic compounds can be biodegraded in anaerobic conditions. The degree of decomposition was as follows, for: metoxychlor 99.3-99.9%, chlorfenvinphos 38.1-97.6%, fenitrothion 75.3-99.9%, and malathion, 84.2-99.9%. The study confirms that pesticides (in particular doses), while having a toxic effect on anaerobic biocenosis, are at the same time biologically decomposed in the analyzed conditions of methane digestion. The research has also developed and supplemented the current knowledge on the changes of pesticides in the environment and provides a complete list of compounds toxic to methane fermentation biocenosis.