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REUSE OF DRINKING WATER TREATMENT WASTE FOR REMEDIATION OF HEAVY METAL CONTAMINATED GROUNDWATER
Holmes, R.R., M.L. Hart, and J.T. Kevern.
Groundwater Monitoring & Remediation 39(4):69-79(2019)

Drinking water treatment waste (DWTW) from lime softening was incorporated as a recycled, low-cost additive to cement-based filter media (CBFM) for the removal of lead, cadmium, and zinc in groundwater. Jar testing at three different metal concentrations and breakthrough column testing using synthetic groundwater were performed to measure removal capacity and reaction kinetics. Results from jar tests showed that as DWTW content increased at low concentrations, removal approached 100%. At high metal concentrations, removal decreased due to saturation or exhaustion of the removal mechanisms. The removal occurred through the formation of metal carbonate precipitates, surface sorption, and ion exchange with calcium according to the preferential series Pb+2>Zn+2>Cd2+. Removal kinetics measured through column tests exceeded estimated calculations derived from batch jar testing isotherms due to the large formation of oolitic metal carbonates. Pb, Cd, and Zn were concentrated in the column precipitates from 0.29, 0.23, and 20.0 µg/gi n the influent solution to ~200, 130, and 14,000 µg/g in the reacted DWTW-CBFM. The concentrative abilities of CBFM through precipitate and oolitic mineral formation suggest the potential for a minable waste product that might close the waste-product cycle for DWTW.



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