Shake flask studies examined the rate and extent of biodegradation of pentachlorophenol (PCP) and 42 components of coal-tar creosote present in contaminated groundwater recovered from the American Creosote Works Superfund site, Pensacola, Fla. The ability of indigenous soil microorganisms to remove these contaminants from aqueous solutions was determined by gas chromatographic analysis of organic extracts of biotreated groundwater. Changes in potential environmental and human health hazards associated with the biodegradation of this material were determined at intervals by Microtox assays and fish toxicity and teratogenicity tests. After 14 days of incubation at 30 degrees C, indigenous microorganisms effectively removed 100, 99, 94, 88, and 87% of measured phenolic and lower-molecular-weight polycyclic aromatic hydrocarbons (PAHs) and S-heterocyclic, N-heterocyclic, and O-heterocyclic constituents of creosote, respectively. However, only 53% of the higher-molecular-weight PAHs were degraded; PCP was not removed. Despite the removal of a majority of the organic contaminants through biotreatment, only a slight decrease in the toxicity and teratogenicity of biotreated groundwater was observed. Data suggest that toxicity and teratogenicity are associated with compounds difficult to treat biologically and that one may not necessarily rely on indigenous microorganisms to effectively remove these compounds in a reasonable time span; to this end, alternative or supplemental approaches may be necessary. Similar measures of the toxicity and teratogenicity of treated material may offer a simple, yet important, guide to bioremediation effectiveness.

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A two-stage, sequential inoculation bioreactor strategy for the bioremediation of groundwater contaminated with creosote and pentachlorophenol (PCP) was evaluated at bench scale (1.2 L) and pilot scale (454 L). Bioreactor performance 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 toxicity and teratogenicity measurements. During pilot-scale operations, the concentration of creosote constituents was reduced from ca. 1000 ppm in the groundwater feed (flow rate 114 L/day) to <9 ppm in the system effluent (total removal efficiency of >99%). Notably, the cumulative concentration of carcinogenic polycyclic aromatic hydrocarbons was reduced from 368 ppm in the feed to 5.2 ppm in the system effluent. Moreover, the toxicity and teratogenicity of the bioreactor effluent were significantly reduced. In general, field data correlated well with those obtained from bench-scale studies.f Research contribution no. 822 of the Gulf Breeze Environmental Research Laboratory.