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. <i>Pseudomonas, Flavobacterium, Hydrogenophaga</i>, and <i>Pseudoxanthomonas</i> 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. <i>Desulfomicrobium</i> and <i>Desulfonema</i> 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.