Post‐treatment of up‐flow anaerobic sludge blanket reactor effluents in activated sludge process‐based system for anionic surfactants

Abstract

AbstractThis paper presents the performance of two full‐scale up‐flow anaerobic sludge blanket–activated sludge process (UASB‐ASP)‐based sewage treatment plants (STPs) (surface and diffused aeration‐based activated sludge processes as post‐treatment units). Performance of this combination is compared with UASB–polishing ponds and UASB–ozonation‐based STPs. Post‐treatment units removed 89 and 92% of anionic surfactants (AS) by surface and diffused aeration, respectively. Finally, 0.61 and 0.23 mg/L of AS were discharged from post‐treatment steps after overall reduction of 90–92%. Final concentrations from UASB‐ASP‐based STPs were low compared with UASB–polishing ponds (3.60–4.91 mg/L) and UASB–ozonation (1.52 and 0.53 mg/L). Overall, UASB‐ASP‐based STPs were working efficiently for the removal of organics in terms of chemical oxygen demand (COD) (84%) and biochemical oxygen demand (BOD) (93%), but they need further modifications for the removal of AS up to the level of risk quotient [risk quotient (RQ)] ≤ 1 for no risk to aquatic environment.