A Financial and Environmental Analysis of Constructed Wetlands for Industrial Wastewater Treatment

Abstract

SummaryThe Dow Chemical Co. (Dow) is actively working to develop an approach to value ecosystem services and incorporate them in business decisions. This study investigates the use of replacement cost methodology (RCM) for financial analysis and life cycle assessment (LCA) for environmental assessment. The case study analyzes a business decision made in 1995, where a constructed wetland was built instead of a sequencing batch reactor to solve a regulatory compliance issue in meeting suspended solids requirements for a wastewater treatment system at the Union Carbide Corp. (a subsidiary of The Dow Chemical Co.) plant in Seadrift, Texas. The financial results indicate that the total net present value savings calculated for implementing the constructed wetland instead of the sequencing batch reactor is $282 million over the project's lifetime. The LCA demonstrates that the lower energy and material inputs to the constructed wetland resulted in lower potential impacts for fossil fuel use, acidification, smog formation, and ozone depletion and likely lead to lower potential impacts for global warming and marine eutrophication. The result from the inventory of land use shows that both the upstream land burdens (for the sequencing batch reactor) and the on‐site acreage of the constructed wetland are similar in magnitude and importance, contrary to the assumption that green infrastructure always requires greater land area. This case study illustrates how Dow can consider financial and environmental analyses in comparing gray and green infrastructure solutions and further understand the benefits of implementing green infrastructure in an appropriate industrial application.