Technology feasibility and economic viability of an innovative integrated ceramic membrane bioreactor and reverse osmosis process for producing ultrapure water from municipal wastewater

Abstract

Nowadays, it has been widely accepted that the production of ultrapure water (e.g. NEWater in Singapore) from municipal wastewater reclamation is a promising alternative to alleviate the severe water scarcity. However, the current NEWater production process is extremely complicated, with intensive excess sludge production and large footprint. To address these emerging issues, an innovative process integrating moving bed ceramic membrane bioreactor (MBCMBR) and reverse osmosis (RO) was developed for reclamation of municipal wastewater to ultrapure product water. In this process, the MBCMBR was developed for simultaneous COD and nitrogen removal, while RO was designed for ultrapure water production. The results obtained under different DO conditions showed that more than 99.7% of COD and 96.7% of total nitrogen were removed in the MBCMBR-RO process. It was demonstrated that the product water could meet the NEWater and Chinese Class IV standards in terms of total organic carbon, ammonium, nitrate and phosphate, with an insignificant RO membrane fouling propensity evidenced by a dTMP/dt smaller than 0.06 bar/day. In addition, more than 36% and 60% of reduction in footprint and excess sludge production could be achieved in the proposed integrated process against the current NEWater production process. Moreover, the NEWater-like product water produced from the MBCMBR-RO process can be safely discharged to any surface water, while it can also be supplied to various industrial sectors at an attractive commercial price. Consequently, this study offers an innovative approach for producing ultrapure water from municipal wastewater with small footprint, less sludge production and remarkable economic viability.