Sludge-based activated carbon from two municipal sewage sludge precursors for improved secondary wastewater-treatment discharge-effluent

Abstract

This study investigated the use of sludge-based activated carbon (SBAC) sorbent as an integrated waste-to-resources approach for the removal of contaminants from wastewater. We measured the ability of SBAC sorbents from two types of municipal sewage sludge (SS) precursors (thickened waste SS “TWSS-SBAC” and biosolids “Bio-SBAC”) from a Canadian wastewater treatment plant (WWTP) to stabilise emerging contaminants (ECs) from precursor SS and to remove ECs from the discharged effluent. The ECs were from pharmaceutical and personal care products (PPCPs), including antibiotics, disinfectants, and antibacterial hand-sanitisers and soaps, which were commonly used during the COVID-19 (coronavirus disease of 2019) pandemic. We measured the removal efficacy of Bio-SBAC at two dosages (1 g/L and 10 g/L) and TWSS-SBAC at one dosage (1 g/L) via 30-min batch adsorption tests for eleven PPCPs at mean concentrations of 2–2337 ng/L in the discharged effluent, and compared the results with those of other techniques and sorbents reported in literature. At both dosages, Bio-SBAC removed PPCPs, including four blood regulator compounds that have been extensively used since the pandemic outbreak (furosemide, gemfibrozil, glyburide, and warfarin), with their levels decreasing below the detection limit. The percentage removal for ibuprofen, 2-hydroxy-ibuprofen, and naproxen were 91.6–99.8% using 1 g/L. The antimicrobial compounds triclosan and triclocarban were completely removed at both dosages. Ninety-nine percentage of bisphenol A was removed at 1 g/L dosage and was completely removed at 10 g/L. TWSS-SBAC showed similar performance as Bio-SBAC in removing PPCPs from the final effluent to improve the quality of wastewater discharged from a WWTP.