Comparative life cycle assessment of traditional and emerging methods for high concentration organic wastewater treatment

Two traditional methods, including incineration and the sequencing batch reactor activated sludge process (SBR), and two emerging methods, including supercritical water oxidation (SCWO), catalytic wet oxidation (CWO) combined with SBR (CWO-SBR), for high concentration organic wastewater treatment were compared from the view of environmental impact. The printing ink wastewater generated from the surface treatment of electronic products was selected as the typical wastewater and diluted to various concentrations for sensitivity analysis. Simapro 9.3 software was selected to explore the environmental impacts of the four processes with Traci impact assessment method and Ecoinvent 3.8 database. Moreover, two tools including the total environmental impact and comprehensive competitiveness were used for quantitative comparison. The total environmental impacts for the incineration and SCWO processes gradually decrease with increasing chemical oxygen demand (COD) concentration for more steam output and less fuel and electricity consumptions, but opposite trends appear for the CWO-SBR and SBR processes, indicating higher COD concentrations exhibit smaller environmental impacts for the incineration and SCWO processes. The incineration and SBR processes have the slightest and highest total environmental impacts of 0.030 and 1.117 at the base case of COD = 234,000 mg/L, respectively. The trends of the comprehensive indexes for the four processes with increasing COD concentration are similar to those of the total environmental impacts. The SCWO process has the highest comprehensive index of 0.956 at the base case, followed by the incineration, CWO-SBR, and SBR processes, with values of 0.783, 0.460, and 0.158, respectively.