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Management and disposal of water treatment plant residuals have become more expensive and complicated because of numerous federal, state, and local guidelines and regulations. This research sought to develop physical and engineering quality data on plant residuals and to investigate the feasibility of using dewatered residuals as sanitary landfill cover. Testing was conducted to determine the physical and engineering properties of alum-coagulated residuals from two water suppliers in Arlington, Texas. The residuals had fine particle size distribution, high specific resistance, high plasticity index, low dry unit weight, and low shear strength-properties that rendered them unsuitable for landfill cover application. However, blending the residuals with natural topsoil improved the physical properties of the residuals to such a level that the mixture could be used for landfill cover. Of the proportions tested, a blend of 20% residuals and 80% natural soil resulted in the optimum moisture content, maximum dry unit weight, and a plastic limit within the workable range. The numerous regulations governing residual disposal can drive up costs and limit options. This study offers utility managers a beneficial application for residual disposal rather than disposing of residuals in landfills as a waste product or discharging them into wastewater sewer lines. |
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