ABSTRACT
Leachate poses a number of environmental problems. This is due primarily to the extreme variability of sources of this material and, therefore, the heterogeneity of its composition. Operating and closed landfills generate leachate whose quality and quantity depend on how the landfill was constructed, operated, and ultimately closed. Currently, a number of options exist for the containment and treatment of this type of wastewater. The option presented here uses a surface-flow constructed wetland treatment system installed at the Chunchula, AL closed landfill to provide the required leachate treatment for discharge into state and federal waters in conformity with the National Pollution Discharge Elimination System (NPDES) guidelines.
The construction of this full-scale operating wetland treatment system was started during the summer of 1992 and became fully functional in October 1993. The treatment system operates under permits issued by the Alabama Department of Environmental Management (ADEM) and remains in compliance with permit conditions as established by state and federal environmental agencies.
The treatment system encompasses approximately 1.29 ha of surface-flow wetlands located within the property boundaries of the old landfill. The wetlands receive contaminated groundwater, which is pumped from a confining layer located beneath the unlined but capped landfill. The treated effluent discharging from the wetlands is subsequently mixed with 58untreated storm water and eventually discharged into a receiving waterway Effluent compliance with established state and federal water quality standards is assured through monthly analyses for BOD5, COD, pH, TOC, NH3, and heavy metals including Ar, Cd, Cr, Cu, Pb, Hg, Ni, Ag, and Zn. This system was originally designed to treat both the generated leachate and the leachate-contaminated groundwater at a hydraulic loading rate of 5 × 10 g/day. However, in spite of the fact that the original design loading volumes have been frequently exceeded by over 20 times, there has been no noticeable change in the quality of the treated leachate. Constructed wetland deoigo, permkdnâ, treatment efficiencies, and removal processes are discussed.
