Research Product

Pilot-scale field studies at the American Creosote Works Superfund Site, Pensacola, Florida, evaluated two technologies for their ability to treat ground water contaminated with creosote and pentachlorophenol (PCP): 1)Hyperfiltration (volume reduction), and 2) Bioremediation using specially-selected microorganisms (terminal destruction). The hyperfiltration unit was operated in a cross-flow mode yielding "concentrate" (containing excluded chemicals) and "permeate" (clean, aqueous material passing through the membrane). Operating over a 6-day period on site, a total of 6,300 gallons of creosote- and PCP-contaminated ground water (average total semi-volatile concentration was 88.5 mg/L) was processed there by reducing the volume of contaminated material less than 80% while removing less than 95% of the PAHs. Simultaneously, the concentration of chlorinated dioxins and furans were reduced from 22.5 ppb in the feed to 0.047 ppb (cumulative) in the permeate. Based on chemical analyses and biological toxicity and teratogenicity assays, the permeate stream was acceptable for direct discharge. A two-stage, continuous-flow, sequential inoculation bioreactor strategy for the bioremediation of ground water contaminated with creosote and pentachlorophenol (PCP) was also evaluated. Performance of continually stirred tank reactors using specially-selected microorganisms was assessed according to chemical analyses of system influent, effluent and bioreactor residues, a chemical mass balance evaluation, and comparative biological activity and teratogenicity measurements. When specially-selected bacteria capable of utilizing high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs) as primary growth substrates were used in pilot-scale bioreactors (454 L), the concentration of creosote constituents was reduced from ca. 1,000 ppm in the ground water feed (flow rate = 114 L/day) to less than 9 ppm in the system effluent (removal efficiency of less than 99%). Notably, the cumulative concentration of 8 HMW PAHs (containing 4 or more fused rings) was reduced from 368 ppm in the ground water feed to 5.2 ppm in the system effluent. Moreover, the toxicity and teratogenicity of the bioreactor effluent was significantly reduced. Biodegradation of PCP was limited (ca. 24%) due in large part to poor inoculation and a high degree of abiotic loss (bioaccumulation and adsorption).