Slurry bioreactors with simultaneous electron acceptors for bioremediation of an agricultural soil polluted with lindane

Abstract

The purpose of our study was 2-fold: (i) to evaluate the effect of dominant electron acceptor [either aerobic, methanogenic, or sulfate-reducing slurry bioreactor (SB)] and biostimulation with sucrose on lindane removal from heavy soil and (ii) to assess the effect of the type of combined environments [partially aerated methanogenic (PAM) and simultaneous methanogenic-sulfate reducing (M-SR)] and addition of silicone oil as solvent on lindane removal from a clayish agricultural soil with high levels of organic matter.In the first experiment, the main effect of electron acceptor was significant (p<0.0001); lindane removals followed the order SR>A≫M SBs. On the other hand, co-substrate sucrose was not significant (p=0.67). Yet, the interaction was moderately significant (p<0.007); co-substrate influence was distinct depending on the type of electron acceptor. In our case, co-substrate slightly improved lindane removal in both anoxic SBs (SR and M units), whereas lindane removal in A-SB with sucrose was lower than A-SB without sucrose. Metabolites from lindane transformation in our single electron acceptor SBs were consistent with lindane metabolites reported in the literature for anaerobic and aerobic degradation of the insecticide.In the second experiment, both factors [simultaneous electron acceptor (SEA) combination and solvent addition] were significant (p<0.0001). Removal of lindane in SEA-SBs, PAM and M-SR without silicone oil was low (∼16%). On the other hand, the order of lindane removals in SBs with oil silicone M-SR SB was significantly superior (65%) to that of PAM SB (39%).Finally, in our work, SBs with SEA where one of the anaerobic metabolites is methanogenic were not as successful as SBs with single electron acceptors for removal of lindane from heavy soil.