Energy Balance and Economic Analysis of Multi-Source Sewage Sludge Drying and Incineration
Since the first domestic sludge incineration project was commissioned at Shanghai's Shidongkou Wastewater Treatment Plant in 2004, sludge mono-incineration has been progressively adopted in economically developed Chinese cities. However, decentralized planning of wastewater treatment facilities and variable sludge characteristics complicate the centralized design and operation of incineration plants. This study, based on the planning and engineering design of a sludge incineration plant in Qingdao, analyzes sludge from major municipal wastewater treatment plants, which differ significantly in moisture and organic content due to varying influent characteristics and treatment processes. An energy balance model was constructed using data on sludge moisture and organic content, leading to a sludge allocation scheme and a simplified cost calculation method for heterogeneous sludge. This supports differentiated pricing and rational distribution in drying and incineration projects. Additionally, comparing conventional dewatering (to 76% moisture) and deep dewatering (to 65% moisture) from a "wastewater treatment plant + incineration" perspective, the study evaluates full-process costs and carbon emissions. Results show that deep dewatering increases dewatering costs and emissions but reduces transport and incineration costs and emissions, yielding lower total costs and emissions. The findings provide a basis for optimizing municipal sludge treatment planning and process selection.