Supercritical water oxidation of a pesticide wastewater

• Residence time and OC have important influences on the XCOD at higher reaction temperatures (>500 °C).
• The corrosion rate of Inconel 625 is approximately 0.6 mm/year at 600 °C, 25 MPa and OC = 3.0 conditions.
• SCWO together with traditional wastewater treatment methods are proposed to harmlessly dispose the complicated wastewater.
• The primary design of a 100 t/d SCWO plant for the tested pesticide wastewater treatment is provided.

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, 25 MPa, OC = 3.0 and t = 2.0 min, respectively. More than 92 wt% total organic carbon (TOC) and 86.70 wt% 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 0.6 mm/year at 600 °C, 25 MPa and OC = 3.0 conditions. We also primarily design a 100 t/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.

Supercritical water oxidation (SCWO) is a promising technology to deal with organic wastewater. Based on currently accomplished investigations, a primary plant design scheme for the tested pesticide wastewater SCWO is provided, in which excess oxygen is recovered to reuse and traditional wastewater treatment methods are applied to improve the whole system's economic feasibility.Figure optionsDownload high-quality image (89 K)Download as PowerPoint slide