Efficient Hybrid Process of Fenton–Electrocatalytic Membrane Reactor–Biological Aerated Filter for the Treatment of Nanofiltration Retentate from Landfill Leachate without Concentrated Liquor Discharge

Treatment of nanofiltration (NF) retentate from landfill leachate is a significant challenge due to its poor biodegradability and high toxicity. In this study, a novel hybrid and integrated process based on the fixed-bed electrocatalytic membrane reactor (FBER) was developed to treat the NF retentate via combining the Fenton and biological aerated filter (BAF) process. The Fenton and FBER processes were employed in order to degrade the refractory pollutants and improve the biodegradability of the NF-concentrated leachate for the subsequent BAF process. The removal of chemical oxygen demand (COD) reached 64.6% through the Fenton process under an initial pH of 3, molar [H2O2]/[Fe2+] ratio of 2/1, and H2O2 dosage of 90 mmol L–1. After treatment with the FBER process, the ratio of BOD5 to COD (B/C) increased from 0.05 to 0.38 under a voltage of 2 V and residence time of 10 min, indicating good biodegradability. Lastly, the removal rate of chroma and COD reached 99.5 and 93% of NF retentate after 48 h of BAF treatment, which can meet the standards of wastewater discharge in China. Our present work demonstrates a highly efficient hybrid process for the treatment of the NF retentate.