Influence of cosubstrate and hydraulic retention time on the removal of drugs and hygiene products in sanitary sewage in an anaerobic Expanded Granular Sludge Bed reactor

Abstract

Diclofenac (DCF), ibuprofen (IBU), propranolol (PRO), triclosan (TCS) and linear alkylbenzene sulfonate (LAS) can be recalcitrant in Wastewater Treatment Plants (WWTP). The removal of these compounds was investigated in scale-up (69 L) Expanded Granular Sludge Bed (EGSB) reactor, fed with sanitary sewage from the São Carlos-SP (Brazil) WWTP and 200 mg L−1 of ethanol. The EGSB was operated in three phases: (I) hydraulic retention time (HRT) of 36±4 h; (II) HRT of 20±2 h and (III) HRT of 20±2 h with ethanol. Phases I and II showed no significant difference in the removal of LAS (63 ± 11–65 ± 12 %), DCF (37 ± 18–35 ± 11 %), IBU (43 ± 18–44 ± 16 %) and PRO (46 ± 25–51 ± 23 %) for 13±2–15 ± 2 mg L−1, 106 ± 32–462 ± 294 μg L−1, 166 ± 55–462 ± 213 μg L−1 and 201 ± 113–250 ± 141 μg L−1 influent, respectively. Higher TCS removal was obtained in phase I (72 ± 17 % for 127 ± 120 μg L−1 influent) when compared to phase II (51 ± 13 % for 135 ± 119 μg L−1 influent). This was due to its greater adsorption (40 %) in the initial phase. Phase III had higher removal of DCF (42 ± 10 % for 107 ± 26 μg L−1 influent), IBU (50 ± 15 % for 164 ± 47 μg L−1 influent) and TCS (85 ± 15 % for 185 ± 148 μg L−1 influent) and lower removal of LAS (35 ± 14 % for 12 ± 3 mg L−1 influent) and PRO (−142 ± 177 % for 188 ± 88 μg L−1 influent). Bacteria similar to Syntrophobacter, Smithella, Macellibacteroides, Syntrophus, Blvii28_wastewater-sludge_group and Bacteroides were identified in phase I with relative abundance of 3.1 %–4.7 %. Syntrophobacter was more abundant (15.4 %) in phase II, while in phase III, it was Smithella (12.7 %) and Caldisericum (15.1 %). Regarding the Archaea Domain, Methanosaeta was more abundant in phases I (84 %) and II (67 %), while in phase III it was Methanobacterium (86 %).