Sustainable transformation: Unlocking energy positivity in municipal wastewater treatment through innovative advanced primary treatment configurations for maximum solids separation

Abstract

Motivated by the growing need for sustainable wastewater management and environmentally friendly solutions for wastewater treatment in the future, the current study explored all possible configurations for advanced primary treatment (APT) on a long-term assessment, encompassing extensive lab and pilot-scale studies for removing particulate organic carbon (POC) in municipal wastewater treatment plants (WWTPs). This study primarily aimed to have a comprehensive insight into various APT configurations for municipal wastewater treatment. The physical-APT method employed a microsieve (MS) with an adjustable drum to 20 and 100 µm mesh. The flocculation process was integrated with one or two consecutive sedimentation tanks to simulate the chemical-APT method. Lastly, the chemical-physical-APT (ChPh-APT) approach was emulated by combining the flocculation process with the MS technique. Considering the best-case scenario to remove utmost POC, the results illuminated a substantial potential for biogas production enhancement by around 85 % (from 1.3 to 2.4 g (cap. d)-1 converted chemical oxygen demand (COD) to biogas) through ChPh-APT configuration. Furthermore, estimations showed that maximum POC removal can significantly reduce energy demand from 42 to 28 kWh (cap. a)-1 while simultaneously increasing green electricity generation from 11 to 33 kWh (cap. a)-1. This transformation will eliminate dependency on external energy sources and significantly increase by-product generation like volatile fatty acids (VFA), Polyhydroxyalkanoate (PHA), and hydrogen (H2) in the concept of a biorefinery. The possible increase in the production of H2 can be from roughly 32 to 58 L (cap. d)-1, PHA recovery from 1.3 to 2.4 g (cap. d)-1, and VFAs from about 12 to 22 g (cap. d)-1. Consequently, this transformation will enhance the efficiency of municipal WWTPs and turn them into energy-positive, sustainable, and resource-recovery entities.