Renewable Energy Generation and GHG Emission Reduction Potential of a Satellite Water Reuse Plant by Using Solar Photovoltaics and Anaerobic Digestion

Wastewater treatment is a very energy-intensive process. The growing population, increased demands for energy and water, and rising pollution levels caused by fossil-fuel-based energy generation, warrants the transition from fossil fuels to renewable energy. This research explored the energy consumption offset of a satellite water reuse plant (WRP) by using solar photovoltaics (PVs) and anaerobic digestion. The analysis was performed for two types of WRPs: conventional (conventional activated sludge system (CAS) bioreactor with secondary clarifiers and dual media filtration) and advanced (bioreactor with membrane filtration (MBR)) treatment satellite WRPs. The associated greenhouse gas (GHG) emissions were also evaluated. For conventional treatment, it was found that 28% and 31.1% of the WRP’s total energy consumption and for advanced treatment, 14.7% and 5.9% of the WRP’s total energy consumption could be generated by anaerobic digestion and solar PVs, respectively. When both energy-generating units are incorporated in the satellite WRPs, MBR WRPs were on average 1.86 times more energy intensive than CAS WRPs, translating to a cost savings in electricity of $7.4/1000 m3 and $13.3/1000 m3 treated, at MBR and CAS facilities, respectively. Further, it was found that solar PVs require on average 30% longer to pay back compared to anaerobic digestion. For GHG emissions, MBR WRPs without incorporating energy generating units were found to be 1.9 times more intensive than CAS WRPs and 2.9 times more intensive with energy generating units. This study successfully showed that the addition of renewable energy generating units reduced the energy consumption and carbon emissions of the WRP.