Energy Efficiency, Climate Change Mitigation and Adaptation

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In South Africa, high electricity costs and shortages pose a critical threat to wastewater treatment operations, particularly those reliant on energy-intensive activated sludge processes (ASPs). With the majority of municipal WWTPs being ASPs, which use significant energy to meet stringent effluent standards, the reliance on coal-derived electricity compounds both operational costs and carbon footprints. To address these challenges the Water Research Commission funded this project aimed at evaluating energy efficiency (EE) and greenhouse gas (GHG) emissions across three representative WWTPs in South Africa, situated in Gauteng. The project's primary objectives included conducting energy audits, assessing GHG emissions, identifying feasible energy efficiency measures, calculating potential cost savings and developing frameworks for climate mitigation and adaptation strategies linked to EE and for incorporation of EE in the Green Drop Certification programme. The findings underscored the substantial energy savings potential that can be achieved in the aeration systems (up to 40% of total consumption costs) and energy generation that can offset 100% of the aeration energy requirements thereby reducing the amount of electricity purchased from the grid through the adoption of EE measures.   

Moreover, integrating EE initiatives with climate change mitigation and adaptation strategies is a key pathway to reducing GHG emissions and improving resilience to climate impacts, particularly temperature rises and flow fluctuations. The project recommended a framework that can be used by municipalities to develop comprehensive climate mitigation and adaptation strategies linked to EE. A framework for inclusion of EE and GHG reduction criteria in the Green Drop certification program to incentivize municipalities to adopt sustainable wastewater management practices was also developed. By aligning energy efficiency goals with broader sustainability and climate resilience objectives, municipalities can enhance operational efficiency while reducing environmental impact. Furthermore, the project emphasized the importance of tailored approaches across different WWTP sizes, recognizing the diverse challenges and opportunities faced by large, medium, and small-scale facilities. Energy conservation strategies, particularly targeting aeration (the primary energy consumer in ASP) were highlighted alongside the evaluation of alternative energy generation technologies like anaerobic digestion and catalysed hydrothermal carbonization.