Biodegradability enhancement of municipal landfill leachate

The method of enhancing the biodegradability of landfill leachate via air stripping followed by coagulation/ultrafiltration (UF) processes is introduced. In this study, the air stripping process obtained a removal efficiency of 88.6% for ammonia nitrogen (NH₃-N), at an air-to-liquid ratio (A/L) of 3 300 (pH = 11) and after 18 h of stripping. The single coagulation process increased the BOD (biological oxygen demand)/COD (chemical oxygen demand) ratio by 0.089 with a FeCl₃ dosage of 570 mg/L, at pH 7.0, and the single UF process increased the BOD/COD ratio from 0.049 to 0.311. However, the combination of coagulation and UF increased the BOD/COD ratio from 0.049 to 0.423, and the final BOD, COD, NH₃-N, and colour of the leachate were 1 023 mg/L, 2 845 mg/L, 145 mg/L, and 2 056, respectively, when a 3 kDa molecular weight cut-off (MWCO) membrane was used at an operating pressure of 0.7 MPa. In the ultrafiltration process, the average solution flux (J_V), concentration multiple (M_C), and retention rate (R) for the COD were 107.3 L/(m²·h), 6.3, and 84.2%, respectively