Efficient treatment of high-concentration pharmaceutical wastewater with high-salinity by chemical synthesis coupling with evaporation: From lab-scale to pilot-scale

Abstract

This study focused on the treatment of high-concentration pharmaceutical wastewater with high-salinity by pretreatment of chemical synthesis coupling with evaporation. Via chemical synthesis, this pretreatment process was developed to remove the organic matter that inhibited evaporation of wastewater, resulting in improved evaporation efficiency. Lab-scale results demonstrated that under the optimum conditions (∼pH 9, 2 mL/L demulsifier, 98 mM/L H2O2, 3 h of aeration time, 80 °C, 500 mg/L PAC, and 20 mg/L PAM), 54.9 % of COD was successfully removed by single pretreatment and 98.6 % after coupling with evaporation. Compared to the 80.1 % COD removal efficiency of direct evaporation of 100 mL with 30 min, the pretreatment process coupling with evaporation demonstrated superior performance and halved the evaporation time. A pilot-scale chemical synthesis pretreatment (120 t/d) was further developed to treat pharmaceutical wastewater of both high COD concentrations and high salinity. Under the optimal conditions determined in the lab-scale experiments, the pilot-scale achieved a COD removal efficiency of 49 % with a single pretreatment and 95.8 % after coupling with mechanical vapor recompression (MVR). Additionally, the obtained salt appeared visually clean and white compared to that obtained from the treated wastewater without pretreatment. Furthermore, to elucidate the possible mechanisms driving the efficient removal of COD, GC–MS was performed on the wastewater before and after pretreatment, and the resulting products from pretreatment in pilot-scale applications were further determined by both FTIR and GC–MS. It was proposed that the aldol condensation reaction increased the formation of carbon chains to macromolecular compounds might be the possible mechanism. This study gives insights into the future application of low-investment and low-cost technology in the treatment of high-concentration pharmaceutical wastewater with high salinity in industry.