This paper reports on attempts to develop an economically feasible bioremediation technique for contaminants with low bioavailability. To this end, different options for a combined physicochemical and biological treatment process were evaluated for soils contaminated with polycyclic aromatic hydrocarbons (PAH). Options evaluated for enhanced bioremediation included pre-extraction with surfactant solutions, a washing pretreatment, which consisted of attrition in the presence of different additives and fractionation by size as well as biodegradation in presence of different additives. Pre-extraction with surfactant solutions will not be feasible because of associated surfactant costs. Washing pretreatment resulted in a seriously enhanced bioavailability, even when performed without additives. Special designed surfactant combinations, which stimulate biodegradation without preferential degradation of surfactants, exhibited substantial enhancement of biodegradation rates if their composition and concentration is adapted to the actual contaminated soil. However, even under improved conditions biodegradation rates were too slow to obtain low enough residual values in reasonable times. Therefore, a new two-stage bioreactor system was developed, which enhances removal rates drastically (> 90% in 3 days). Progress achieved was illustrated in relation to published results of other bioreactor approaches.
(originally presented at ACHEMA 2000 - International Meeting on Chemical Engineering, Environmental Protection and Biotechnology, 22. – 27. 5. 2000 Frankfurt am Main)
Keywords:
bioavailability, bioreactors, soil remediation, surfactant combinations, PAH, pyrene,
biodegradation, soil washing, soil fines
The Author welcomes related discussions, comments and is very interested in passing so far confidential information for research or commercialisation purposes.
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