Pretreatment of municipal landfill leachate by a combined process

Abstract

Biodegradability enhancement of landfill leachate using air stripping followed by coagulation/ultrafiltration (UF) processes was introduced. The air stripping process obtained a removal efficiency of 88.6% for ammonia nitrogen (NH 4–N) at air-to-liquid ratio of 3500 (pH 11) for stripping 18 h. The single coagulation process increased BOD/COD ratio by 0.089 with the FeCl 3 dosage of 570 mg l −1 at pH 7.0, and the single UF process increased the BOD/COD ratio to 0.311 from 0.049. However, the combined process of coagulation/UF increased the BOD/COD ratio from 0.049 to 0.43, and the final biological oxygen demand (BOD), chemical oxygen demand (COD), NH 4–N and colour of leachate were 1223.6 mg l −1, 2845.5 mg l −1, 145.1 mg l −1 and 2056.8, respectively, when 3 kDa molecular weight cut-off (MWCO) membrane was used at the operating pressure 0.7 MPa. In ultrafiltration process, the average solution flux ( J V ), concentration multiple ( M C ) and retention rate ( R) for COD was 107.3 l m −2 h −1, 6.3% and 84.2%, respectively.