Anaerobic/aerobic cycle effect on di(2-ethylhexyl) phthalate and pentachlorophenol removal from real textile wastewater in sequencing batch biofilm reactor

This study aims to investigate the treatability of pentachlorophenol encountered in cotton textile plants and di(2-ethylhexyl) phthalate used in synthetic textile production. They were selected as model micropollutants. Experiments were carried out at different anaerobic/aerobic (A/O) sequences (4 h/16 h, 8 h/12 h, 12 h/8 h, 16 h/4 h) at constant hydraulic retention time (36 h) and solid retention time (15 d) to determine the effect of biocarriers addition and anaerobic/aerobic cycle time on micropollutant removal from real textile wastewater. During the study period, sequencing batch reactor and sequencing batch biofilm reactor, which contains K3 Kaldnes bio-carrier with 50% filling ratio, were fed with a real textile wastewater. Reactors were operated with a total cycle period of 24 h (fill: 0.5 h; react: 20 h; settle: 2 h; decant: 1 h; idle: 0.5 h). Their performances were compared in terms of PCP, DEHP and macro pollutants (BOD5, COD, TOC, TN, TP, and color) removals. The average DEHP and PCP concentrations in feed wastewater were 124.5 ± 5.24 and 12.8 ± 0.27 μg/L, respectively. The maximum DEHP removal efficiencies were 72.2% for SBBR at 4 h/16 h (A/O) and 42.1% for SBR at 8 h/12 h (A/O) sequence. The PCP removal efficiency was not affected significantly by the change of aeration times and remained 51.1%–56.5% for SBBR and 35.0%–43.2% for SBR. The addition of biocarrier caused 30.0% and 13.0% increase in removal efficiency for DEHP and PCP, respectively.