Effects of surfactants on pentachlorophenol biodegradation by Sphingomonas chlorophenolicum sp. strain RA2

Pentachlorophenol (PCP) is a widespread environmental contaminant often found at wood-preservation sites in the United States. The toxicity of PCP has led the Environmental Protection Agency to place it on the National Pollutant Priorities List. Methods to clean sites contaminated with PCP must be capable of PCP removal from the soil and destruction of the compound. One of the preferred technologies for remediation of PCP-contaminated sites is bioremediation. However, the bioavailability of soil-sorbed PCP is a major factor limiting the speed and effectiveness of bioremediation. The potential exists to combine bioremediation of PCP with surfactant washing of contaminated soils.;Surfactant-aided bioremediation of PCP using Sphingomonas chlorophenolicum sp. Strain RA2 was investigated in both batch studies and in soil columns coupled to immobilized bacterial columns. Anionic and cationic surfactants tended to be more inhibitory than nonionic surfactants. At low PCP concentrations, higher surfactant concentrations inhibited PCP degradation rates. Lower temperatures also inhibited PCP degradation rates.;The kinetics and mechanism of the nonionic surfactant Tergitol NP10 (TNP10) inhibition and enhancement of PCP biodegradation were investigated in batch studies. PCP degradation followed Monod with growth kinetics. Inhibition by TNP10 over a threshold of inhibition of approximately 100 mg/L was described by a competitive inhibition model with a single inhibition constant. The mechanism of TNP10 inhibition was due to sequestration of PCP into surfactant micelles. At substrate-toxic levels of PCP (>100 mg/L), TNP10 enhanced PCP degradation.;Columns containing contaminated soil from a wood-preserving site in Denver were coupled to biocolumns containing immobilized RA2. The effects of TNP10 on soil desorption and biodegradation of PCP were studied in a one-dimensional flow regime. Results indicated that TNP10 increased desorption rates of PCP-related compounds. The immobilized bacteria were capable of degrading effluent PCP and related compounds. Immobilized bacteria were also more tolerant than suspended bacteria to the addition of TNP10.