Microbial Degradation of Pesticides.

The toxicity and degradation of pesticides introduced into sanitary sewer facilities has yet to be extensively studied. For this reason, the effect and fate of eight pesticides were investigated using the BOD method with a sewage inoculum. Six of the eight chemicals Carbaryl, Malathion, Diazinon, Dursban, Dichlorvos, and 2,4,-dichlorophenoxyacetic acid did not retard oxygen consumption by a 0.33 sewage inoculum in a one-week test period at concentrations ranging from 0.1 to 100 micro gml of active ingredient. Baygon at 10 and 100 micro gml was toxic in the test period. Ficam at 1 and 10 micro gml also slowed oxygen consumption during the decomposition of sewage as compared to a control with no pesticide. The BOD method was used to test the biodegradation of the pesticides with each chemical being used as a sole carbon source for an adapted or unadapted inoculum. Carbaryl was readily degraded, and Malathion and Diazinon also appeared to undergo oxidation, although the reaction was incomplete. Dichlorvos, Baygon, and 2,4-D were resistant to breakdown when tested by the BOD method.