A laboratory and outdoor pilot-scale investigation was conducted on the use of selected sorbents for removing leachate contaminants from three industrial sludges. The laboratory results indicated that, rather than a single sorbent, a combination of acidic and basic sorbents is required in a layered system for removal of all the measurable contaminants from the leachates. These combinations are illite, vermiculite, and a natural zeolite for the acidic leachate; illite, acidic fly ash for the neutral leachate; and illite, kaolinite, and a natural zeolite for the alkaline leachate. The sorbent capacities exhibited by the natural sorbents are comparable to those exhibited by refined sorbents. The outdoor pilot study, which was limited to the treatment of the calcium fluoride sludge leachate, using lysimeters, some 80 times larger than the laboratory lysimeters, revealed that the sorbent effectiveness depends on the velocity of the leachate through the sorbents and the sorbent removal capacity for specific contaminants. Except for magnesium, effective reductions of the measurable leachate constituents were achieved with the use of illite, acidic fly ash, and a zeolite in the weight ratio of 2:2:1. Sorbent costs have been estimated for various combinations required for treating leachate from calcium fluoride sludge over a ten-year period of landfill operation. For the illite/acidic fly ash/zeolite combination and the illite/acidic fly ash/basic fly ash combination, costs are $1.37 and $0.45 per ton of sludge, respectively.

Includes bibliographical references (pages 39-40). Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Industrial Environmental Research Laboratory, Cincinnati, Ohio, submitted by New Jersey Institute of Technology, under grant no. Contract Number: R803717 02.