Methanogenic potential of diclofenac and ibuprofen in sanitary sewage using metabolic cosubstrates

Diclofenac (DCF) and ibuprofen (IBU) are widely used anti-inflammatory drugs and are frequently detected in wastewater from Wastewater Treatment Plants and in aquatic environments. In this study, the methanogenic potential (P) of anaerobic sludge subjected to DCF (7.11 +/- 0.02 to 44.41 +/- 0.05 mg L-1) and IBU (6.11 +/- 0.01 to 42.61 +/- 0.05 mg L-1), in sanitary sewage, was investigated in batch reactors. Cosubstrates (200 mg L-1 of organic matter) in the form of ethanol, methanol:ethanol and fumarate were tested separately for the removal of drugs. In the DCF assays, P was 6943 +/- 121 mu molCH(4), 9379 +/- 259 mu molCH(4), 9897 +/- 212 mu molCH(4) and 11,530 +/- 368 mu molCH(4) for control, fumarate, methanol:ethanol and ethanol conditions, respectively. In the IBU assays, under the same conditions, P was 6145 +/- 101 mu molCH(4), 6947 +/- 66 mu molCH(4), 8141 +/- 191 mu molCH(4)and 10,583 +/- 512 mu molCH(4), respectively. Without cosubstrates, drug removal was below 18% for 43.10 +/- 0.01 mgDCF L-1 and 43.12 +/- 0.03 mgIBU L-1, respectively. Higher P and removal of DCF (28.24 +/- 1.10%) and IBU (18.72 +/- 1.60%) with ethanol was observed for 43.20 +/- 0.01 mgDCF L-1 and 43.42 +/- 0.03 mgIBU L-1, respectively. This aspect was better evidenced with DCF due to its molecular structure, a condition that resulted in a higher diversity of bacterial populations. Through the 16S rRNA sequencing, bacteria genera capable of performing aromatic ring cleavage, beta-oxidation and oxidation of ethanol and fatty acids were identified. Higher relative abundance (>0.6%) was observed for Smithella, Sulfuricurvum and Synthophus for the Bacteria Domain and Methanosaeta (>79%) for the Archaea Domain. The use of ethanol favored greater mineralization of organic matter and greater methane production, which can directly assist in the metabolic pathways of microorganisms. (C) 2020 Elsevier B.V. All rights reserved.