Abstract
Huge amount of aged oily sludge was generated during the drilling and transportation of crude oil. Sometimes, the sludge exhibited characters of combined pollution, such as saline-alkali oily sludge. Orthogonal experiments of L16(45) were conducted to evaluate the long-term effects of total petroleum hydrocarbons (TPH) concentration, microbial agents (Oil Gator and ZL) and bulking agents (peat and wheat bran) on the biodegradation of aged saline-alkali oily sludge. Compared with the control group, the significant improvement in the removal rate of TPH was exhibited with the addition of microbial agents and bulking agents after 231 days of the experimental period. Based on the values of mean range (R), it was revealed that the predominant influencing factor of the bioremediation was TPH concentration. After biostimulation and bioaugmentation, the quantity of petroleum hydrocarbon-degrading bacteria in the oily sludge increased by 2–4 orders of magnitude. Furthermore, the bioremediation improved the microbial diversity based on the analysis of PCR-DGGE. It was inferred that the addition of microbial agents and bulking agents reconstructed the microbial ecological niche. The principal component analysis indicated that the differentiation of the microbial community was generated by the biostimulation and bioaugmentation in comparison with the control samples.
Highlights
Sludge is classified as a hazardous waste in China
The 16 trials were at different total petroleum hydrocarbons (TPH) concentration levels, they all showed a similar two-phase degradation trend: the TPH degradation was at a typical first-order kinetic in the first 105 days, and levelled off during the 105 to 231 days
In comparison with the control, a significantly higher removal rate of TPH was observed in other trials, which indicated that the microbial agents and bulking agents showed a positive effect on the elimination of TPH
Summary
Sludge is classified as a hazardous waste in China. Its accidental or deliberate releases pose a serious environmental& 2018 The Authors. Sludge is classified as a hazardous waste in China. As 2 petroleum contains hazardous chemicals, such as benzene, toluene, ethylbenzene, xylenes and naphthalene [1], it is toxic, mutagenic, carcinogenic and hazardous to the environment and human health [2,3]. The treatment methods, such as natural attenuation, incineration, solvent extraction and landfill, are usually high-cost or time-consuming [4,5]. Bioremediation has recently attracted significant interest as a reliable and relatively cost-effective technology to deal with this type of pollution [6,7]
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