Environmental sustainability: a pressing challenge to biological sewage treatment processes

The operation of current biological sewage treatment processes is mainly based on the bio-oxidation principle with the input of substantial amount of energy for oxidation of sewage COD and ammonia. Meanwhile, an extremely large quantity of waste sludge is inevitably produced through biological conversion of soluble chemical oxygen demand (COD) to biomass. With tightened effluent discharge standards worldwide, upgrading of the current mainstream biological process with advanced treatment units appears necessary, while making the whole system highly complicated and costly with enlarged footprint. In such a situation, the sewage treatment philosophy has been seriously challenged by its environmental sustainability. Therefore, this article proposes that A-B process enabling direct capture of wastewater chemical energy should be considered as a feasible option toward energy self-sufficient sewage reclamation with minimized sludge production. Furthermore, a conceptual integrated anaerobic membrane bioreactor with reverse osmosis system is elucidated for reclaiming sewage to NEWater-like product water, and it may offer a new avenue to overcome the challenges faced in the current sewage treatment plants.