Evaluating the Impacts of Sludge Incineration Using a Risk Based Approach

Abstract

The viability of continued sludge incineration at Central Contra Costa Sanitary District wastewater treatment plant is presented as a case study. A risk based approach was utilized to assess the long-term feasibility and cost of continued incineration compared to other available sludge handling methods. Three major tasks were conducted as part of the study: an incinerator capacity evaluation; a risk assessment; and, an evaluation of solids handling technologies. The study focused on toxics most often encountered in sewage incinerator emissions, including arsenic, beryllium, cadmium, chromium, lead, mercury, nickel, poly-chlorinated dibenzo-p-dioxins, and polychlorinated dibenzo-p-furans. The results of the study indicate that continued incineration of sludge is viable for Central Contra Costa Sanitary District, and that the most cost effective solids handling method is incineration using two duty units with backup provided by chemical stabilization. To confirm costs and design criteria, pilot testing of two potential back-up methods is currently being conducted.These methods are chemical stabilization and indirect drying.