Sustainability assessment of a municipal sewage treatment plant using a single green performance indicator

A Municipal Sewage Treatment Plant (MSTP) involves multiple processes for treating wastewater. In a MSTP, there are resources consumed, emissions as well as effluent discharged that could potentially cause environmental problems. There has bezen much research about environmental impact of a MSTP such as the MSTP carbon footprint, MSTP energy consumption and MSTP emission discharge. Although these studies have contributed towards reduction of environmental impact of a MSTP, so far, there has not been any study done to quantify the overall green performance of an MSTP. This paper extends the Green Index (GI) tool for the assessment of an MSTP environment. This study is focused on investigating the green performance of two types of MSTP, namely the Ludzack-Ettinger process and Bardenpho process. The conventional process is used as the benchmark for the purpose of comparison. The GI development for a MSTP involves two stages. The first stage involves formulation of a weighting scheme by applying factor analysis on the green elements data of the MSTP. This is followed by formulation of the GI using stock market composite index. The GI allows the use of a single index to be used to quantitatively assess the overall green performance, and the actual measure of the overall greenness of the MSTP facility. A single quantitative index to substitute multiple green elements would help organisations to objectively compare and select the type of MSTP process that is greener, promotes cleaner production, and has less adverse impact towards the environment. GI could help organisations to quantitatively and effectively monitor and analyse the actual green performance of a process in a retrofit or a conservation program. Result shows that GI would help organisation to choose which process would have less environmental impact. The GI graph accommodates facility manager with a figurative tool to visualise on the performance of MSTP either for retrofit or conservation programmed