Comparison of bio-augmentation and composting for remediation of oily sludge: A field-scale study in China

Two bioremediation technologies were performed in order to explore a better treatment process for an oily sludge restoration in China during 2004. The bioremediation by augmentation of biopreparation was compared with a conventional composting. The oily sludge and oil-polluted soil were received from an oil production plant. The total hydrocarbon content (THC) varied from 327.7 to 371.2 g kg^-1 of dry sludge and the THC in contaminated soil was 151.0 g kg^-1. Before application of preparation, straw, sawdust, top sand and pure soil were added in different proportions to the sludge and soil and mixed thoroughly. Such sludge and soil composites were used for negative controls and for activation of indigenous oil degrading microorganisms with addition of fertilizer (positive controls). For composting, crude manure and straw were added to the oily sludge and the THC was 101.4 g kg^-1. The biopreparation was applied every 2 weeks and experiment lasted 56 days under the ambient temperature. The sludge was mixed and watered every 3 days. After three times of biopreparation application, the THC decreased by 46-53% in the oily sludge and soil, while in the positive controls (activation of indigenous microorganisms) the THC decreased by 13-23%, and there was no oil degradation in negative controls After composting, the THC decreased by 31% in the oily sludge. The planting of Tall Fescue (Festuca arundinace) revealed a decrease of sludge toxicity after application of both bioremediation technologies and additionally decreased the THC by 5-7%.