Toward energy self-sufficiency in small municipal wastewater treatment plants: assessment of energy recovery potential, process economic balance, and greenhouse gas avoidance

Abstract

The objective of this study was to quantitatively assess the energy recovery potential from both biogas and the incineration of dewatered sludge, aiming to meet the energy demand of a small municipal wastewater treatment plant (MWTP) with a treatment capacity below 50 L s −1 . The energy potential of sludge incineration was characterized based on its gross calorific value, while energy production from biogas generated during the anaerobic digestion of municipal sludge was also evaluated. In addition, the feasibility of using the produced biogas for the thermal drying of dewatered sludge was analyzed. The results indicate that biogas utilization could generate 1462 kWh d −1 , corresponding to 83.17% of the total electricity consumption of the MWTP. Furthermore, the mass reduction achieved through sludge drying resulted in an annual cost savings of US$ 27,763 related to sludge disposal. The incineration of dried sludge could generate an additional 432.52 kWh d −1 . Overall, the combined energy recovery strategy could lead to a reduction of approximately 150 t CO 2 eq year −1 in greenhouse gas emissions due to methane avoidance at the studied MWTP. These findings suggest that such integrated approaches can encourage investments in MWTPs aimed at achieving energy self-sufficiency while enhancing environmental performance. Graphical abstract

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