The influent COD/N ratio controlled the linear alkylbenzene sulfonate biodegradation and extracellular polymeric substances accumulation in an oxygen-based membrane biofilm reactor

This work evaluated the fates of linear alkylbenzene sulfonate (LAS), chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺−N), and total nitrogen (TN) when treating greywater (GW) in an oxygen-based membrane biofilm reactor (O₂-MBfR). An influent ratio of chemical oxygen demand to total nitrogen (COD/TN) of 20 g COD/g N gave the best removals of LAS, COD, NH₄⁺−N and TN, and it also had the greatest EPS accumulation in the biofilm. Higher EPS and improved performance were linked to increases in the relative abundances of bacteria able to biodegrade LAS (Zoogloea, Pseudomonas, Parvibaculum, Magnetospirillum and Mycobacterium) and to nitrify (Nitrosomonas and Nitrospira), as well as to ammonia oxidation related enzyme (ammonia monooxygenase). The EPS was dominated by protein, which played a key role in adsorbing LAS, achieving short-time protection from LAS toxicity and allowed LAS biodegradation. Continuous high-efficiency removal of LAS alleviated LAS toxicity to microbial physiological functions, including nitrification, nitrate respiration, the tricarboxylic acid (TCA) cycle, and adenosine triphosphate (ATP) production, achieving the stable high-efficient simultaneous removal of organics and nitrogen in the O₂-MBfR.