Influences of extracellular polymeric substances (EPS) recovered from waste sludge on the ability of Jiaozhou Bay to self-remediate of diesel-polluted seawater

The introduction of EPS recovered from waste sludge may have an impact on the process of microbial remediation of oil-contaminated seawater. This study investigated the effect of EPS on the self-remediation capacity of diesel-polluted seawater in Jiaozhou Bay. Hydrocarbon attenuation and microbial activity were monitored in seawater collected from five islands after diesel and N, P addition, with and without EPS, incubated under aerobic conditions. Compared to seawater without EPS, degradation of TPH (total petroleum hydrocarbon) doubled and improved degradation of non-volatile (C16–C24) hydrocarbons to some extent in EPS-added seawater. The introduction of EPS led to changes in microbiota richness and diversity, significantly stimulating the growth of Proteobacteria and Firmicutes phyla or Bacillus and Pseudomonas genera. RT-qPCR analysis indicated EPS caused higher increases in cytochrome P450 gene copies than alkB. Prediction of alkane decay genes from 16S rRNA sequencing data revealed that EPS addition obviously promoted genes related to ethanol dehydrogenation function in the microbial community. Additionally, EPS enhanced the enzymatic activities of alkane hydroxylase, ethanol dehydrogenase, phosphatase and lipase, but increased protease and catalase inconspicuously. The above outlook that environmental sustainability of EPS from waste sludge for diesel-contaminated seawater remediation may provide new perspectives for oil spill bioremediation.