TREATMENT OF PENTACHLOROPHENOL WITH MANGANESE OXIDE ADDITION TO BIOTIC AND ABIOTIC SEDIMENTS

Laboratory microcosms containing subsamples of a complex environmental sediment were used to evaluate the addition of oxidized manganese as the primary electron acceptor in the presence of pentachlorophenol (PC P) as the primary electron donor. Manganese oxide (MnO2) particles wer e added to poisoned abiotic and non-poisoned biotic microcosms and inc ubated at 11 degrees C in the presence of sediment samples that were s hown capable of mineralizing PCP with indigenous microorganisms. Reduc tion in PCP concentration and production of reduced manganese was meas ured for both abiotic and biotic systems. PCP was observed to be trans formed most rapidly and to the greatest extent in non-poisoned microco sms. Rate and extent of PCP transformation were increased when MnO2 wa s added. Rate and extent of PCP transformation were least, but still s ignificant, in abiotic (poisoned) microcosms when MnO2 was added. Redu ction in PCP sediment concentration was consistently correlated with a n increase in production of reduced manganese (Mn+2). The addition of MnO2 was therefore shown to cause a decrease in PCP concentration in a naturally occurring complex environmental sediment. Reduced iron was observed suggesting that both manganese and iron were used as primary electron accepters. Moreover, higher concentrations of Mn+2 were found in solution than Fe-+2. This may support thermodynamic evidence that manganese is preferentially used over iron in some redox reactions. Ad dition of synthetic MnO2 particles via a permeable reaction wall or di rect slurry injection, may represent a potential treatment approach fo r the abiotic as well as biotic reduction of PCP in sediment and groun d water environments.