Microbial dechlorination activity during and after chemical oxidant treatment

Potassium permanganate (PM) and sodium persulfate (PS) are used in soil remediation, however, their compatibility with a coinciding or subsequent biotreatment is poorly understood. In this study, different concentrations of PM (0.005-2g/L) and PS (0.01-4.52 g/L) were applied and their effects on the abundance, activity, and reactivation potential of a dechlorinating enrichment culture were investigated. Expression of the tceA, vcrA and 16S rRNA genes of Dehalococcoides spp. were detected at 0.005-0.01 g/L PM and 0.01-0.02 g/L PS. However, with 0.5-2g/L PM and 1.13-4.52 g/L PS no gene expression was recorded, neither were indicator molecules for total cell activity (Adenosine triphosphate, ATP) detected. Dilution did not promote the reactivation of the microbial cells when the redox potential was above -100 mV. Similarly, inoculated cells did not dechlorinate trichloroethene (TCE) above -100 mV. When the redox potential was decreased to -300 mV and the reactors were bioaugmented for a second time, dechlorination activity recovered, but only in the reactors with 1.13 and 2.26 g/L PS. In conclusion, our results show that chemical oxidants can be combined with a biotreatment at concentrations below 0.5 g/L PM and 1g/L PS.