PERMEABLE REACTIVE CONCRETE: NOVEL REMOVAL OF HEAVY METALS USING DRINKING WATER TREATMENT WASTE

This research investigated a novel, waste-valorizing method of passive groundwater remediation which incorporates drinking water treatment waste (DWTW) into a pervious concrete matrix to mechanically and chemically remove up to 100% of heavy metals (lead, cadmium, zinc) from synthetic groundwater. Groundwater transport of heavy metals is a significant problem for historic mines and waste tailings which can contaminate local wells and surface waters, especially locally in the Ozark Plateau and now in Colorado. Current remedial techniques can be expensive, both to install and maintain, and include active pump and treat technologies or passive reactive barriers using zero-valent iron, persulfate, or activated carbon. Our research shows pervious concrete actively remediates heavy metals by itself, but the addition of DWTW acts as both an internal curing agent for the concrete and enhances removal rates. Jar tests were performed on 2”x4” cylinders submerged in synthetic groundwater with concentrations of 1.0, 0.1, and 0.01 mmol (in equal parts) of Cadmium, Lead, and Zinc for 72 hours in continuously stirred sealed containers. Concrete mix designs replaced Portland cement with DWTW at 25% and 0%. Samples had a void contents of 25% with a 0.4 water to cement ratio. ICP-MS method EPA 200.8 was performed to measure the metals concentrations before and after submersion. The addition of DWTW resulted in removal levels of 90-100 percent, which were equivalent or greater than those of the Portland cement control and comparable to current techniques. Ongoing studies include removal reaction kinetics and toxicity characterization leachability procedures.