Efficient pollutants removal and microbial flexibility under high-salt gradient of an oilfield wastewater treatment system

Abstract

The treatment of hypersaline oilfield wastewater (HSOW) is a challenge due to its complex composition and low biodegradability, especially in coastal areas. In this study, an HSOW treatment system of gas flotation and biochemistry technology combined with constructed wetland (CW) was investigated. The combined treatment system could efficiently remove COD, NH4+-N and oil under high salinity (1.36–2.21 × 104 mg/L), with average removal rates of 98.5%, 99.9% and 96%, respectively. Meanwhile, different salinity shaped particular community structures and functions. The abundance of Marivita, Parvibaculum, etc. was highly correlated with salinity. Co-occurrence network resulted that the microorganisms were highly interconnected, and formed a functional group of petroleum degrading. Pseudomonas, Rosevarius, Alternaria, etc. were the key genera. Moreover, functional prospected revealed that high salinity reduced the energy metabolism activity. This study will optimize the combined process and provide the basis for further extraction of high-efficiency degradation strains for HSOW enhanced treatment.