Environmental impacts and cost-effectiveness of Thailand’s centralized municipal wastewater treatment plants with different nutrient removal processes

This research investigates the organic and nutrient removal efficiency of eight centralized municipal wastewater treatment plants (WWTP) in Thailand’s capital Bangkok, under five treatment schemes. The environmental impacts were assessed using life cycle assessment, and the cost-effectiveness was determined by life cycle cost assessment. The five treatment schemes were contact stabilization (scheme A/base case), activated-sludge with nutrient removal (scheme B), cyclic activated-sludge (scheme C), two-stage activated-sludge (scheme D), and vertical loop reactor activated-sludge (scheme E). The results showed that scheme A achieved the highest organic removal efficiency (93.01% on average), with all other treatment schemes achieving more than 83% removal efficiency. Scheme E achieved the highest total phosphorus and total nitrogen removal efficiencies (69.12% and 59.74% on average), and scheme C was effective in removing total Kjeldahl nitrogen and ammonia (82.84% and 89.12% on average). The environmental impact assessment indicated that electricity use was the major contributor of almost all environmental impact categories except aquatic eutrophication. Scheme E had the lowest environmental impacts in almost all categories except aquatic eutrophication. Total costs (including operation, maintenance, and environmental costs) of WWTPs with nutrient removal were lower than without nutrient removal. Scheme E had the lowest total cost (2.754 THB2017 per m3) and lowest compounds removal costs, in addition to highest nutrient removal efficiency. Scheme E is the most cost-effective scheme with lowest environmental impacts (i.e., the most eco-efficiency scheme). •Environmental impacts and cost-effective of different WWTP schemes are assessed.•Vertical loop AS scheme efficiently removes total phosphorus and total nitrogen.•Total costs of WWTPs with nutrient removal are lower than without nutrient removal.•Vertical loop AS is the most cost-effective scheme with lowest environmental impacts.