Life Cycle Assessment as an environmental evaluation tool for control strategies in wastewater treatment plants

•Multicriteria evaluation of control strategies for wastewater treatment plants.•Feasibility of investment for cost/performance and life cycle analysis.•Better environmental impacts by nitrogen-rich return flows based control strategies.•Efficient ammonia peaks reduction by use of return flows from storage tank.

The objective of this paper is to show the potential additional insight that results from adding indicators based on Life Cycle Assessment (LCA) to the evaluation criteria of plant performance in the control strategies of wastewater treatment plants. Our assessment combines plant-performance evaluation criteria as effluent quality and operational cost defined by the Benchmark Simulation Model, jointly with a detailed environmental evaluation for impact category provided by LCA. Comparison of control strategies shows that the use of ammonia and carbon controllers provides best effluent quality index, whilst the control strategy that uses ammonia, carbon and storage tank controllers has the lowest values as regards operational cost (the storage tank decrease the operational cost index into a 15%). However, environmental analysis indicates that the control strategy using ammonia, carbon and storage tank controllers generates the lowest environmental impacts in all impact categories except eutrophication; whereas the control strategy using only the carbon controller has the lowest impact on eutrophication (6% lower than the higher control strategies), but the largest impact on the remaining categories (from a 9% higher for terrestrial Ecotoxicity to a 97% higher for the Photochemical oxidation). According to the multiple evaluation criteria results, the control strategy using ammonia, carbon and storage tank controllers is considered as most suitable to implement, highlighting the importance of environmental analysis as an additional source of information for decision makers. The results reported here underline the importance of taking into account integration of the plant performance criteria with environmental evaluation based on LCA for control strategies in wastewater treatment plants.