The purpose of this study was to investigate treatment alternatives for a leachate from a municipal landfill in Roanoke County, Virginia. A continuous flow, laboratory scale, single sludge waste treatment system utilizing the Modified Ludzack Ettinger (MLE) nitrification/denitrification process with the addition of phosphorus and methanol was operated to determine its effectiveness in removing total nitrogen, organic compounds and metals from the leachate. The system was compared with the effectiveness of a totally aerobic activated sludge system operated in various configurations and at different mean cell residence times (MCRT’s) with and without the addition of methanol. The ability of activated carbon to remove organics from the leachate was briefly examined.

The early results from this study indicated that the MLE process could successfully treat the leachate by removing up to 84% of the total nitrogen present while operating at high MCRT’s (eight days or greater). The MLE process removed as much as 56% of the total nitrogen at the lowest MCRT operated (1.5 days), By comparison, a maximum removal of only 30% was achieved for the completely aerobic activated sludge system operating under the same conditions.

The MLE process and the completely aerobic process were not effective in removing the organics from the leachate as evidenced by a leachate COD removal of only 2% to 5%. Limited studies with activated carbon proved successful in substantially reducing the COD from the effluent of the biological treatment systems.

The MLE process consistently reduced the iron concentration in the leachate from the average level of 18.6 mg/l to levels below 1.0 mg/l.

Towards the end of this 584-day study, there were indications that toxic agents were intermittently entering the leachate from the landfill as evidenced by two episodes of severe nitrification inhibition during operating periods when nitrification should have been essentially complete. This raises doubts concerning the ability of biological nitrification/denitrification to successfully treat the Dixie Caverns landfill leachate on a long-term basis without special treatment for the removal of the unknown toxic components.