English

Abstract

A laboratory-scale, four-stage continuous flow reactor system was constructed to test the viability of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) passive co-treatment. Synthetic AMD of pH 2.6 and acidity of 1870 mg/L as CaCO3 equivalent containing a mean 46, 0.25, 2.0, 290, 55, 1.2 and 390 mg/L of Al, As, Cd, Fe, Mn, Pb and Zn, respectively, was mixed at a 1:2 ratio with raw MWW from the City of Norman, Oklahoma and introduced to the system which had a total residence time of 6.6 days. During the 135-d experiment, dissolved Al, As, Cd, Fe, Mn, Pb and Zn concentrations were consistently decreased by 99.8, 87.8, 97.7, 99.8, 13.9, 87.9 and 73.4 %, respectively, pH increased to 6.8 ±0.1, and net-alkaline effluent produced. At a wasting rate of 0.69 % of total influent flow, the system produced sludge with Al, As, Cd, Cr, Cu, Fe, Pb and Zn at least an order of magnitude greater than the theoretical influent mix, which presents a possible environmental liability if not sustainably recovered or disposed. These results indicate that passive co- treatment is a promising approach that can be optimized and applied to improve water quality with minimal use of fossil fuels and refined materials.