Fate and removal of pentachlorophenol and diethylhexyl phthalate from textile industry wastewater by sequencing batch biofilm reactor: Effects of hydraulic and solid retention times

Abstract

This study aimed to examine the effects of hydraulic retention time (HRT) and solid retention time (SRT) on the removal of diethylhexyl phthalate (DEHP) and pentachlorophenol (PCP) from real textile wastewater. Experiments were conducted daily and at different SRTs (10 d, 15 d, and 20 d) and HRTs (36 h, 48 h, and 60 h). The results showed that the optimal HRT and SRT for DEHP removal were 48 h and 20 d, respectively, and the removal efficiency reached 83.27%. Meanwhile, the highest removal efficiency was 75.5% for PCP at an HRT of 60 h and an SRT of 15 d. The addition of biocarriers to the reactor system was intended to facilitate microorganism growth and increase the average removal efficiencies of PCP and DEHP. Short HRTs and SRTs resulted in low micropollutant removal efficiencies. Based on the mass balance calculations, it was determined that biodegradation and sorption onto sludge were the main removal mechanisms for PCP and DEHP. The findings also revealed that using the optimal HRT and SRT is critical to achieve the highest growth of the bacteria responsible for the biodegradation of selected micropollutants. In the biocarrier amended system, biodegradation served and sorption onto sludge contributed to PCP removal. Conversely, the major removal mechanism for DEHP varied depending on the operating conditions. In particular, with increasing SRT, biodegradation became the dominant removal mechanism.