Environmental performance of extended activated sludge and sequential batch reactor using life cycle assessment

Although several studies have been published on the application of life cycle assessment (LCA) on wastewater treatment plants (WWTP), few have been reported from developing countries. In this study, the environmental impacts of a sequential batch reactor (SBR) and extended activated sludge process (EASP) treatment technologies were evaluated and analysed using LCA. SimaPro (R) 9.1.1.1 software was used, together with the ecoinvent 3.6 database, and the ReCiPe midpoint (H) methodology. A functional unit of 1m(3) of treated wastewater was used. Normalised results showed that freshwater eutrophication, freshwater ecotoxicity, and human toxicity were the key impact categories. EASP indicated the highest impact result on all evaluated impact categories. Electricity consumption was the main contributor to freshwater ecotoxicity and human toxicity impact categories. Residual phosphorus in the effluent stream was the dominant contributor to freshwater eutrophication. Primary treatment had the highest environmental burden of EASP, due to raw wastewater pumping. Secondary treatment had the highest environmental burden on SBR due to aeration. SBR was the preferable option as it scored less on all the key impact categories evaluated. The coal-based South African electricity mix was found to be highly influential on both the EASP and SBR.