Efficient and sustainable removal of linear alkylbenzene sulfonate in a membrane biofilm: Oxygen supply dosage impacts mineralization pathway

Linear alkylbenzene sulfonate (LAS) can be thoroughly mineralized within sufficient oxygen (O₂), but which is energy intensive and may causes serious foaming problem. Although cometabolism can achieve efficient LAS removal within a wide range of O₂ dosages, how O₂ dosage systematically affects LAS metabolic pathway is still unclear. Here, membrane aerated biofilm reactor (MABR) enabled accurate O₂ delivery and bulk dissolved oxygen (DO) control. MABR achieved efficient removal of LAS (>96.4 %), nitrate (>97.8 %) and total nitrogen (>96.2 %) at the three target DO conditions. At high DO condition (0.6 mg/L), LAS was efficiently removed by aerobic mineralization (predominant) coupled with aerobic denitrification biodegradation with the related functional enzymes. Pseudomonas, Flavobacterium, Hydrogenophaga, and Pseudoxanthomonas were dominant genus contributing to four possible LAS aerobic metabolic pathways. As O₂ dosage reduced to only 29.7 % of the demand for LAS mineralization, O₂ facilitated LAS activation, benzene-ring cleavage and a portion of respiration. NO₃^--N respiration-induced anaerobic denitrification also contributed to ring-opening and organics mineralization. Desulfomicrobium and Desulfonema related two possible anaerobic metabolic pathways also contributed to LAS removal. The findings provide a promising strategy for achieving low-cost high LAS-containing greywater treatment.