Anoxic/aerobic granular active carbon assisted MBR integrated with nanofiltration and reverse osmosis for advanced treatment of municipal landfill leachate

Abstract

Anoxic/aerobic granular active carbon assisted membrane bioreactors (A/O-GAC-MBR) integrated with nanofiltration (NF)–reverse osmosis (RO) were used for leachate treatment of the Taizhou Municipal Landfill plant. In order to investigate the effect of GAC on the performance of MBR, a hybrid MBR with GAC dosed and a conventional MBR were operated in parallel. Two pilot scale MBRs showed excellent and stable removal efficiency with average above 80% for chemical oxygen demand (COD) and ammonia-nitrogen (NH3-N). It was noticed that the amount of high-valence metal ions were removed more than low-valence ones. By comparison, the addition of GAC not only improved the removal of hazardous organic pollutants and heavy metals, but also enhanced bioflocculation and particle size of flocs, which greatly alleviated membrane fouling. NF and RO membranes were then used for advanced treatment of MBR effluents. NF membrane exhibited excellent color removal rate of 93.75% compared to 41.82% of A/O-MBR. With the advantage of NF pretreatment, RO membrane held a steadier and higher flux as well as salt rejection than other cases reported. The final permeate from RO was proved to exceed related qualification for reutilization and can easily be recycled in industry.