Insight into Oily Sludge Treatment by High-Temperature Bioaugmentation: Petroleum Components Degradation and Microbial Community Regulation

Thermochemical washing of oily sludge is a highly effective strategy for resource recovery. However, the lingering petroleum components within washed sludge still pose considerable environmental pollution risks. In this study, high-temperature bioaugmentation technology was used to promote the removal of petroleum components, and the potential of this technology in the deep treatment of washed oily sludge was investigated, specifically petroleum component degradation and microbial community regulation. The results showed that the petroleum degradation performance was greatly enhanced by the introduction of thermophilic bacteria combined with 200 mg/kg of biosurfactant (T2 group). Under these conditions, the petroleum and moisture contents were successfully reduced to 19.6 g/kg and 4%, respectively. In particular, the contents of n-alkanes and polycyclic aromatic hydrocarbons in the T2 group decreased significantly to 1098.5 and 494.3 mg/kg, respectively, relative to the blank group (4428.5 and 850.7 mg/kg). High-throughput sequencing results indicated that exogenous thermophilic bacteria (Ureibacillus and Bacillus) could rapidly emerge as the dominant genera in the system. In addition, microbial association network and functional analyses revealed that high-temperature bioaugmentation shifted microbial interactions from competition to cooperation, as evidenced by increased positive correlation ratios and modularity values, as well as functional diversification from two modules in the blank group to four modules in the biofortified treatments, thereby enhancing synergistic degradation capabilities for hydrocarbons. This study provides a newly developed approach to oily sludge treatment that simultaneously achieves reduction and harmlessness.