Supercritical water oxidation of a pesticide wastewater

Abstract

In this research, we studied supercritical water oxidation (SCWO) of a pesticide wastewater under a wide range of operation conditions in two reaction plants. The results show that reaction temperature, oxidant coefficient (OC), and residence time (t) can improve the wastewater XCOD (removal efficiency of chemical oxygen demand). The residence time and OC have important influences on XCOD at higher reaction temperatures (>500°C). It is significant to increase the preheating rate for the XCOD improvement of the pesticide wastewater in SCWO. XCOD and XTN (removal efficiency of total nitrogen) are 99.42% and 86.70% at 600°C, 25MPa, OC=3.0 and t=2.0min, respectively. More than 92wt% total organic carbon (TOC) and 86.70wt% total nitrogen in the wastewater are converted into CO2 and N2 under the above conditions, respectively. Inconel 625 can be used as the reactor material in the wastewater SCWO plant, and its corrosion rate is approximately 0.6mm/year at 600°C, 25MPa and OC=3.0 conditions. We also primarily design a 100t/d SCWO plant for the tested pesticide wastewater treatment on the basis of accomplished investigations. SCWO together with traditional wastewater treatment methods is proposed to harmlessly dispose the complicated wastewater. This information is valuable for guiding the large-scale SCWO plant design for pesticide wastewater treatment.