LEACHATE FLOW-RATE BEHAVIOR THROUGH GEOTEXTILE AND SOIL FILTERS AND POSSIBLE REMEDIATION METHODS

This paper presents flow rate data in the form of system permeability values using various filtration schemes involving both geotextiles and natural soil filters. The tests were conducted over a 20-month period using six different types of leachate. In total, 96 different combinations were evaluated. In all cases, permeabilities decreased over time due to a combination of sediment clogging and/or biological clogging. When a steady state permeability value appeared to be reached, after approximately 6 months, the first of four remediation schemes were attempted. It was seen that water backflush is the most effective in reinstituting high flow rates, followed by backflushing with leachate and nitrogen gas. The least effective remediation scheme was vacuum extraction. Biocide treated geosynthetics were also evaluated, but results were inconclusive. This was due to the long times required and/or the remnants of the micro-organisms which could not pass through the various filtering systems. The long-term minimum permeability values were not identified, nor were the design required permeabilities for the various landfills, in question. These important items are currently being investigated.