Characteristics of Dissolved Ozone Flotation for the Enhanced Treatment of Bio-Treated Drilling Wastewater from a Gas Field

Working fluid preparation using treated drilling wastewater is of great potential for drilling wastewater reuse, especially in water-deficient and ecologically fragile areas, which require low levels of organic matter and suspended solids. This study established the dissolved ozone flotation (DOF) process as the advanced treatment process to replace the original electrocatalytic system (ECS) which exhibited low organic and suspended solids removal efficiency. Higher and more stable organic matter, suspended solids and turbidity removal efficiency were obtained for the DOF process. Consequently, the lower fouling potential and higher water production rate of treated water from DOF process was observed for the following reverse osmosis (RO) system. In addition, brine drilling fluids can be successfully prepared using DOF effluent directly, which exhibited promising practical implications in the advanced drilling wastewater treatment. Based on organic matter fractionation and RDA analysis, the HOA, HON and HI contents significantly impacted brine drilling fluid preparation. Based on XPS analysis, the aromatic carbon species in the HOA, HON and HI fractions were found to be the critical factors deteriorating the brine drilling fluid preparation. However, oxygen-containing groups played a positive role. For the DOF process, the removal of HOA, HON and HI fractions and enhanced generation of oxygen-containing groups in ozone flotation ozone led to the favorable brine drilling fluid preparation performance using DOF effluent directly