Combination of sonophotolysis and aerobic activated sludge processes for treatment of synthetic pharmaceutical wastewater

• Aerobic activated sludge process was only able for partial TOC removal from a SPWW.
• UV/US/H2O2 process at optimum condition was able to remove more than 90% TOC in SPWW.
• Effects of various operational parameters on the UV/US/H2O2 process were studied.
• Combined UV/US/H2O2 and aerobic AS resulted in higher mineralization while lower oxidant consumption.
• Combined processes reduced retention time in both sonophotoreactor and bioreactor.

The performance and effectiveness of sonophotolytic process, aerobic activated sludge (AS) process, and their combination in reduction of total organic carbon (TOC), chemical oxygen demand (COD), and biological oxygen demand (BOD) from a synthetic pharmaceutical wastewater (SPWW) are evaluated. Batch mode experiments are performed to obtain optimal experimental operating conditions of the sonophotolytic process. An ultrasonic power of 140 W, initial pH solution of 2, and air flow rate of 3 L min−1 are found to be optimal operating conditions. The initial optimum molar ratio of H2O2/TOC was found to be 13.77 for the sonophotolytic process operated in batch mode. In continuous mode, a 90% TOC reduction was obtained in the sonophotolytic process after 180 min retention time, whereas only 67% in an aerobic AS process for retention time of 48 h. However, combined sonophotolytic and aerobic AS processes improved the biodegradability of the SPWW with 98% TOC and 99% COD removal while reducing the retention time in sonophotoreactor and aerobic AS bioreactor to 120 min and 24 h, respectively. Besides, the consumption of H2O2 was reduced significantly in the combined processes.