THE USE OF MINE DRAINAGE TREATMENT SOLIDS TO DECREASE WATER EXTRACTABLE PHOSPHOROUS IN DAIRY MANURE

The treatment of polluted mine drainage creates large amounts of residual solids that must be managed. These mine drainage residuals (MDR) are traditionally treated as wastes that are landfilled, buried, or pumped into abandoned underground mines. Pennsylvania has a huge mine drainage problem and produces thousands of tons of MDR annually. Finding value in MDR so that the disposal costs might be lessened has been an industry objective for decades. MDR commonly have a high ion exchange capacity and one potential use is as a sorbent of dissolved oxy-anions. Pennsylvania has a phosphorous pollution problem due in part to the land application of nutrient-rich manures from dairy operations. This project is assessing the feasibility of using mine drainage solids for P control in dairy manure operations. The project has three objectives: 1) chemical characterization of MDR produced in Pennsylvania; 2) determination of the capacity of various MDR samples for decreasing water extractable phosphorous (WEP) in dairy manure; and 3) testing the concept’s practicality at active dairy farms. This presentation will provide results from the characterization and treatment assessment tasks. Twenty MDR samples were collected from sites with varying AMD chemistry and treatment technology. AMD chemistry variation ranged from alkaline waters contaminated only with Fe to low pH acidic waters containing Fe, Al, and Mn. Treatment technologies included passive, hydrogen peroxide, calcium oxide, calcium hydroxide, and lime slurry. The samples were characterized according to pH, neutralization capacity, chemical composition, and hazardous metal concentrations. Solid produced passively or with hydrogen peroxide were all relatively pure Fe minerals, while solids produced with lime products were typically dominated by Ca minerals. Metals concentrations were evaluated relative to the ceiling concentrations in EPA’s 503 Biosolids Rule. Two MDRs exceeded As and three samples exceeded Ni. In the dose/effect testing different quantities of each MDR were added to manure samples and then analyzed for WEP. The testing showed consistently that WEP was decreased by MDR additions. The P-removal capacity of the MDR samples varied in a manner that was attributable to particle size and chemical composition.