Life cycle impact assessment and life cycle cost assessment for centralized and decentralized wastewater treatment plants in Thailand

This research investigates the cost-effectiveness of four sludge treatment scenarios for centralized (C) and decentralized (D) wastewater treatment plants (WWTP) using life cycle cost assessment (LCCA). The environmental impacts and costs are quantified by Stepwise2006. The most environmentally and financially viable WWTP construction option for Bangkok, Thailand (2022–2031) is determined in terms of LCCA and net present value (NPV). The environmental costs of D-treatment scenarios are lower than those of C-treatment scenarios. The total environmental costs of C- and D-fertilizer scenarios are lower than those of C- and D-dewatering scenarios. The net cash flow per functional unit of C-WWTPs is higher than that of D-WWTPs. The C-fertilizer scenario is the most environmentally and economically viable treatment scenario due to the lowest LCCA deficit (−5.58 THB(2020) per m(3) treated effluent). Composting should thus be adopted for treating sludge. The most environmentally and financially viable WWTP construction option is option I (building four C-WWTPs within 10 years) due to the lowest LCCA deficit (−19925 million THB(2020)) and smallest financial loss (NPV = −6309.96 million THB(2020)). Essentially, the local administration of the capital should adopt option I as a guideline in formulating the wastewater treatment management policy of 2022–2031.