Long-term monitoring and prediction for leachate concentrations in Shanghai Refuse Landfill

Parameters such as pH, concentrations of Cl-, turbidity, NH3-N, CODCr and BOD5 (simplified as COD and BOD respectively in the following text) in leachate generated in the large-scale testing landfill unit and closed landfill units at Shanghai Refuse Landfill were monitored from April 1995 to October 1998. The mathematical simulation formula between these parameters and refuse age were established based on the data obtained from the testing landfill unit and justified by the data obtained at the closed landfill units from 1989 to 1993. The long-term predictions for the leachate concentrations for the Landfill were made using the mathematical simulation formula established. It was predicted that the COD and BOD may be reached to the strictest standard for pollution control on municipal solid wastes landfill in China, i.e., COD < 100 mg L-1 and BOD < 30 mg L-1, after 15 yr natural attenuation. The time predicted for NH3-N concentrations to reach the discharging standard, 15 mg L-1, was found to be at least 23-26 yr or even longer. The predictions for concentrations of Cl-, turbidity, and pH values in leachate are also given. The natural attenuation of Cl- is the slowest and might be decreased to 200 mg Cl- L-1, the agricultural irritation standard, after at least 58 yr.