Integrating external costs with life cycle costs of emissions from tertiary treatment of municipal wastewater for reuse in cooling systems

Abstract

Tertiary treatment is needed to render secondary-treated municipal wastewater usable in power plant cooling systems. Various tertiary treatment options exist to provide different levels of water quality. This paper integrates life cycle inventory emissions from a life cycle assessment approach with direct costs to determine the optimal treatment alternative based on cost-effectiveness and environmental sustainability. The costs of damage due to air emissions released during construction and operation of tertiary treatment alternatives were estimated using a hybrid based approach and were converted to external damage costs. Greenhouse gas emission (CO2 eq.), acidifying gas emission (SO2 and NOx), and particulate matter (PM2.5) emission unit costs were obtained from a Social Carbon Costs study, and cost factors from the Air Pollution Emission Experiments and Policy model were used to determine the total costs of emissions. The sum of average air emissions impact costs for the selected treatment processes were found to be between 5 and 8% of the total costs for tertiary treatment. Accounting for the external air emission costs provides a measure to assess the relative environmental costs of tertiary treatment options for reuse of treated municipal wastewater in cooling systems. Environmental costs of other emissions to air, water and land, as well as benefits stemming from offsetting freshwater withdrawal by reusing treated effluent in power plant cooling systems were not included in the analysis.