Biogas Production Modelling Based on a Semi-Continuous Feeding Operation in a Municipal Wastewater Treatment Plant

Anaerobic digestion is a common method for treating sewage sludge in municipal wastewater treatment plants (WWTPs). However, modelling this process can be very challenging due to the complexity of biochemical reactions. This paper presents a novel methodology that estimates biogas production from sewage sludge by considering the semi-continuous sludge-feeding process of the digester. In most WWTPs, the sewage sludge treatment operates in a dynamic process; therefore, using a time-dependent tool that represents this dynamic process is essential for accurately representing biogas production. The biogas production results from the proposed model are compared against the historical data for a large-scale WWTP located in Sydney, Australia. The proposed model shows great accuracy and follows the historical data trend very precisely. The average biogas production based on historical data for 2020, 2021, and 2022 was 37,337 m3/d, 31,695 m3/d, and 23,350 m3/d, whereas for the proposed model, it was 37,960 m3/d, 30,465 m3/d, and 23,080 m3/d. Over the three-year period, the average biogas production was 30,794 m3/d for historical data and 30,503 m3/d for the proposed model, which shows a great level of accuracy (R2 of 0.85 and average error of 4.64%) on the results of the proposed model and WWTP historical data.