Bioremediation of chlorinated pesticide–contaminated soil using anaerobic sludges and surfactant addition

Methanogenic granular sludge and wastewater fermented sludge were used as inocula for batch tests of anaerobic bioremediation of chlorinated pesticide contaminated soil. Results obtained for both types of biomass were similar: 80 to over 90% of γ -hexachlorocyclohexane (γ-HCH), 1,1,1-trichloro-2,2-bis-(4-methoxyphenyl)ethane (methoxychlor) and 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)ethane (DDT) removed in 4–6 weeks. Residual fractions of these pesticides persisted till the end of the 16-week experiment. DDT was degraded through 1,1-dichloro-2,2-bis-(4-chlorophenyl)ethane (DDD). Accumulation of this product corresponded stoichiometrically only to 34–53% of removed DDT, supposedly due to its further transformations, finally resulting in formation of detected 4,4′-dichlorobenzophenone (DBP). Addition of 0.5 mM Tween 80 nonionic surfactant resulted in about a twofold decrease of γ -HCH and methoxychlor residual concentrations, as well as considerably lower DDD accumulation (7–29%) and higher DBP production. However, 1.25 mM dose of this surfactant applied together with granular sludge brought DDD levels back to that observed for treatments with the sludge alone, also impairing DBP formation.