Optimizing primary sludge fermentation for the Canadian climate conditions

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Primary sludge fermentation has recently been implemented in many centralized wastewater treatment plants worldwide, which provides a breakdown of unsaturated fats into volatile fatty acids (VFAs). The VFAs-rich sludge fermentation liquor can be utilized on-site as an exogenous carbon source for the biological nutrient removal (BNR) processes. The proposed collaborative research focuses on developing efficient operational strategies for sludge fermentation that suit Canadian climate conditions. Due to the more stringent regulations for nutrients (nitrogen and phosphorus) removal, many wastewater treatment plants across Canada have already adopted or are considering implementing primary sludge fermentation to produce readily biodegradable carbon sources for the effective operation of the BNR process. The residual solids from the fermentation process are usually mixed with waste activated sludge and processed in an anaerobic digestion (AD) facility. Thus, in addition to BNR, the performance of sludge fermentation operation would also influence the AD process. In general, various process parameters of the fermentation process can influence VFAs yields and spectrums, including temperature, sludge characteristics, residence times, pH, etc., ultimately influencing the operation of BNR and AD. Thus, holistic process optimization is critically needed to effectively deploy sludge fermentation in wastewater treatment plants. Consequently, this proposed project aims to develop fundamental knowledge and engineering approaches toward optimizing the primary sludge fermentation process in wastewater treatment plants considering the diverse climate conditions in Canada between the summer and winter months. In this proposed project, the research team will undertake detailed and systematic bench-scale studies, machine learning and process simulation activities, and pilot validation of the lab and modeling results. In addition to improving the existing operation of the partner organization's full-scale facility, the experience and knowledge generated in this project will enhance operational approaches to sludge fermentation in other wastewater treatment plants across Canada.