Date of Award

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Stephen D. Field

Second Advisor

D. Dean Adrian

Abstract

The scope of this research project was to develop a bioremediation process for accelerated oxidation of bioresistant hazardous waste sludges in continuous flow sludge reactors. Benzo(a)pyrene (BaP) was selected as the target compound due its strong bioresistance, highly carcinogenic nature, extremely low aqueous solubility, and extremely low allowable release limits for land disposal. BaP is often a major hazardous organic component in many hazardous waste impoundments when source wastes have originated from either petroleum refining or associated petrochemical facilities. There is evidence that the biodegradation rate of high molecular weight polynuclear aromatic hydrocarbons (PNA's) is the rate limiting step in liquid-solids contact systems in spite of the low solubilities of these compounds (Sherman et al., 1989). The biological half-lives reported in the technical journals for low concentrations of high molecular weight PNA's typically varies from 1-3 years for land disposal, 1-3 days in static batch reactors, and 2-3 days in mixed batch reactors. There is virtually no published data for successful treatment of high concentrations of PNA's in high-solids suspended growth reactors. The recalcitrance of the PNA's is believed due to the lack of suitable co-substrates containing primary source carbon which would permit rapid acceleration of the biodegradation process and foster fortuitous transformation of BaP and other PNA's. Bench-scale pulsed-flow continuous sludge reactors feeding petrochemical sludge containing 8,700-35,000 mg BaP/kg of dry feed solids averaged 90% w/w destruction at equilibrium conditions. The biological half-life of BaP varied from 0.8-1.4 days and demonstrated that an enhanced environment increased the destruction of BaP at rates up to 2.5 times faster than mixed batch reactors, and 300-1000 times faster than land treatment. Steady state models were developed which predicted total suspended solids, BaP substrate, and oil co-substrate concentrations. The rapid contact bioremediation process (RCBP) developed in this dissertation research, has demonstrated that destruction of the anthropogenic-source annual production and existing accumulations of bioresistant toxic hydrocarbons is a practical goal. This research describes how indigenous microbial consortia can adapt to new strategies for destruction of bioresistant compounds if the microbial environment is appropriately enhanced.

Pages

246

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