Investigation into ozonation flotation for enhancing treatment of drilling wastewater in gas field operations

A significant volume of drilling wastewater is produced in the petroleum and natural gas industry, characterized by elevated levels of particulate matter and organic substances. Reusing wastewater from drilling operations is a crucial method for addressing water scarcity issues during oil and gas field development. Thus, a hybrid process combining ozonation and coagulation (HOC) was employed as an integrated method for treating secondary effluent from drilling wastewater, combining ozonation and coagulation within a single reactor. During the HOC procedure, a substantial quantity of microbubble flocs containing ozone was produced. Under ideal conditions—neutral pH, polyaluminum chloride (PAC) application of 40 mg Al/L, ozone application of 0.8 mg/L, and a reaction period of 15 minutes—the elimination rates for UV₂₅₄, UV₂₈₀, and Dissolved Organic Carbon (DOC) achieved 20.07%, 37.97%, and 14.51%, respectively. According to fluorescence analysis, benzene rings, proteins, and humic acids underwent significant reduction. Fourier transform infrared spectroscopy (FT-IR) analysis revealed that absorption onto and transfer across the interface of ozone microbubble aggregates were the main mechanisms for eliminating C-O functional groups. X-ray Photoelectron Spectroscopy (XPS) analysis indicated a notable reduction in oxygenated functional groups in the treated discharge of drilling wastewater using ozone microbubble aggregates in contrast to traditional microbubble aggregates. Surprisingly, the ratio of oxygenated groups actually rose following ozone microbubble aggregate treatment. This suggests a synergistic effect during the treatment process, involving oxidation, adsorption, and flotation processes.