Eco efficiency assessment of domestic wastewater treatment system in Malaysian urban areas

Abstract

The main purpose of wastewater treatment is to protect humans against waterborne diseases and safeguard aquatic bio-resources like fish. However, there are environmental costs associated with attaining the required level of water quality such as greenhouse gas emissions due to energy production and eco-toxicity from sludge applications on land. The goal of this study is to assess the eco-efficiency of large-scale sewage treatment plants (STPs) in urban areas, focusing specifically on variations in treatment technologies. Life cycle assessment (LCA) and cost benefit-analysis (CBA) were the analytical tools used to evaluate environmental and economic impacts, respectively. For the purpose of this assessment, three STPs in the major Malaysian cities of Kuala Lumpur, Penang, and Johor Bahru were chosen. These STPs employed different treatment technologies. The Jelutong STP in Penang used a sequence batch reactor to treat domestic wastewater. The Bunus STP in Kuala Lumpur as well as the Medini STP in Johor Bahru employed Aerobic activated sludge. Based on the STP data, Bunus STP had the highest performance in terms of wastewater pollutant removal through 96% biological oxygen demand, 90% chemical oxygen demand, and 68% phosphorus. Based on the LCA for 1m3 treated wastewater, STP Bunus Kuala Lumpur had the highest global warming potential(GWP) and acidification potential (AP) at 2.69E-01 kg CO2-eq and 2.11E-03 kg SO2, respectively. Jelutong STP had the highest eutrophication potential (EP) and human toxicity potential (HTP) at 1.47E-02 kg PO4-3 and 5.63E-02 kg DCB-eq, respectively. Medini STP had the highest terrestrial toxicity (TETP) at 2.0E-02 kg DCB-qq. From CBA analysis, Medini STP had the highest operating cost for 1m3 domestic wastewater treatment with RM 0.635 per day and RM232 per year, followed by Bunus STP with RM 0.311 per day and RM 111.6 per year as well as SBR Jelutong Penang with RM 0.157 per day and RM 57.4 per year. In terms of electricity consumption for 1m3 domestic wastewater treatment, aerobic activated sludge Medini STP consumed the highest amount of energy at RM1.02 per day. This is followed by Bunus STP at RM 0.27 per day and Jelutong with RM 0.19 per day. The LCA and CBA framework developed for Bunus plant 1 m3 domestic wastewater flow rate (as a hypothetical example) minimized the environmental impact of GWP by 25%, EP by 3%, AP by 26%, TETP by 3%, and HTP by 3%. In addition, the suggested scenario maximized the benefit of 1m3 domestic wastewater by RM 2.17 per day. The study revealed very different impacts for the three plants, drawing attention to the importance of treatment process choice. The integration of LCA and CBA using the developed framework improve the sustainability of domestic wastewater treatment system in Malaysian urban areas.