Two-stage biodegradation coupled with ultrafiltration for treatment of municipal landfill leachate

The municipal landfill leachate was treated in a hydrolysis–acidification reactor (HAR)/aerobic bio-contact oxidation reactor (ABOR) following a pretreatment with ultrafiltration (UF) membrane. Experiments were conducted continuously for 44 days at a constant flow rate of 20 l d−1 and organic loading rates (OLRs) from 0.75 to 1.5 kgCOD m−3 per day. The results showed that COD of the leachate steadily decreased from 20,015 mg l−1 to less than 3000 mg l−1, and NH4-N decreased from 368.6 mg l−1 to 259.3 mg l−1 in the UF process. The COD and NH4-N removal efficiency of HAR was 56.7% and 27.7%, and that of ABOR was 94.6% and 86.7%, respectively. The total COD and NH4-N removal efficiency reached 99.6% and 93.2%, respectively. UF and HAR played a critical role in raising the biodegradability of the landfill leachate, while ABOR had an important function on removing the dissolved NH4-N in leachate.