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.

S1unypha.w biological treatment k a relarivcly new dcvelopmnt for t k remediation of hazardous wastes, oflering signijicant advantages over otkr bwremdiation technology currently in use. It k highly &wive for a variety qfwastes, and its rate of degradation is up to ten times faster than land treatment.Bioremediation generally refers to the breakdown of organic compounds (contaminants) by microorganisms. Biological processes have beenxsed for well over one hundred years for the treatment of organic-bearing municipal and industrial wastewaters. Aerobic processes, such as activated sludge and trickling filters, are used in virtually every city in the United States for treatment of dilute municipal wastewaters. Anaembicprocessesarenearly aswidelyusedtoanverttkumcentrated sludges resulting from municipal wastewater treatment into methane gas (McCarty 1988,Blackbum 1988. Duringthepast twenty years, anaerobicpmesseshave been widely applied throughout the world for the treatment of high-organic-content wastewaters, particularly in Europe. Furthermore, land treatment has been used as awastetreatmentand disposaltechmlogybythepetmleumindustryforovertwentyfive years (Ryan 1986, Ryan et al. 1986). Using biological treatment processes to clean up hazardous wastes, however, is still considered an innovative technology.Only in the last ten years have scientists and engineers s t a m to develop biological processes for the cleanup of contaminated soils, sludges, and water (Brubacker and Exner 1988). OVERVIEW OF AVAILABLE BIOREMEDIATION TECHNOLOGlESZn-sia, pumpand-treat, solid-phase, slurry-phase, soil heaping, and cornposting are techniques currently used to clean up contaminated soils, sludges, and water

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