Physical and engineering properties of treatment plant residuals and disposal

Abstract

In recent years, management of water treatment plant (WTP) residuals has become more expensive and complicated because of numerous federal, state, and local guidelines and regulations. In this study, alum‐coagulated residuals from two WTPs were tested for their engineering properties for ultimate land disposal as sanitary landfill cover material. After partial drying, the residuals were characterized by fine particle size distribution, high specific resistance, high plasticity index, low dry unit weight, and low shear strength. In this condition, the residuals were unsuitable for landfill cover application. However, residual properties were improved by blending the residuals with natural topsoil. The blending, performed at different ratios of the WTP residuals and the natural topsoil, resulted in a reduction of the plasticity index and an increase of the dry unit weight and shear strength. By varying the blending ratio, it was possible to achieve a soil mix that could be used as landfill cover material. In this research, a blend of 20% residuals and 80% natural soil provided a mix suitable for landfill cover application. Other residual management issues are also addressed.