Energy Potential of Wastewater Sludge: Economic and Ecological Efficiency

Abstract

Recently, many major cities in the world have faced a serious environmental problem caused by the presence of a large amount of waste and the established practice of their treatment. The paper presents an assessment of the energy potential of wastewater sludge (WWS) in the context of Novosibirsk city. According to our estimates, the total amount of generated semi-liquid WWS is about 132,000 tons per year, the theoretical energy output amounts to 67 GW per year, which is more than three times the total heat produced by small boiler plants in the region. Chemical compositions of WWS and stone/brown coals differ slightly. WWS contains 24.5% less carbon than coal and 5% less carbon than brown coal. The proportion of sulfur in WWS exceeds its specific content in coal by only 0.2% and in brown coal - by 4%. Seven alternative wastewater sludge utilization options have been developed, based both on new non-traditional waste incineration technologies and on finished turnkey technologies. WWS utilization options are evaluated in terms of economic efficiency, energy value, and environmental impact. The efficient option is the one associated with the utilization of WWS based on combustion with coal in a thermal power plant.