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Thermo-Oxidization of Municipal Wastewater Treatment Plant Sludge for Production of Class A Biosolids
Holder, E., R. Grosser, AND A. Dougherty. Thermo-Oxidization of Municipal Wastewater Treatment Plant Sludge for Production of Class A Biosolids. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/080, 2015.
The objective of this research project was to evaluate and optimize a novel Waste Activated Sludge (WAS) thermal-oxidation sludge treatment process employing a combination of heat and hydrogen peroxide for production of Class A biosolids and to generate a reliable dataset that could substantiate these claims.
Bench-scale reactors were used to test a novel thermo-oxidation process on municipal wastewater treatment plant (WWTP) waste activated sludge (WAS) using hydrogen peroxide (H2O2) to achieve a Class A sludge product appropriate for land application. Reactor temperatures ranging from room temperature to 90oC were tested with doses of 0.05, 0.1, and 0.2 g H2O2/g volatile suspended solids (VSS) applied. Measurements included total suspended solids (TSS), VSS, fecal coliform counts, settling characteristics, and nutrient concentrations for chemical oxygen demand, total phosphorus, ammonia nitrogen, and total Kjeldahl nitrogen. The best results, in terms of volatile solids destruction, were obtained with an H2O2 dose of 0.2g/g VSS at 90oC, but a temperature ≥ 65oC achieved fecal coliform removal without re-growth potential, and 0.1 g H2O2/g VSS yielded an acceptable product, albeit with less solids mass reduction. A market analysis was performed including development of conceptual treatment trains and cost estimates. The preliminary conclusion of this analysis was that thermo-oxidation capital costs are much less than those for implementing existing technologies, although the operating cost of the thermo-oxidation process, per ton TSS, may be higher. Lower capital costs may place the process within the budgetary limitations of small municipalities. Accordingly, the most attractive target market for this process is believed to be smaller WWTPs with influent wastewater flows in the range of 1-6 million gallons per day (mgd) that utilize extended aeration activated sludge systems, e.g., oxidation ditches, producing 4,000-20,000 gallons per day (gpd) of WAS.