title: Cost-effectiveness of nitrogen mitigation by alternative household wastewater management technologies.
abstract: Household wastewater, especially from conventional septic systems, is a major contributor to nitrogen pollution. Alternative household wastewater management technologies provide similar sewerage management services but their life cycle costs and nitrogen flow implications remain uncertain. This paper addresses two key questions: (1) what are the total costs, nitrogen mitigation potential, and cost-effectiveness of a range of conventional and alternative municipal wastewater treatment technologies, and (2) what uncertainties influence these outcomes and how can we improve our understanding of these technologies? We estimate a household nitrogen mass balance for various household wastewater treatment systems and combine this mass balance with life cycle cost assessment to calculate the cost-effectiveness of nitrogen mitigation, which we define as nitrogen removed from the local watershed. We apply our methods to Falmouth, MA, where failing septic systems have caused heightened eutrophication in local receiving water bodies. We find that flushing and dry (composting) urine-diversion toilets paired with conventional septic systems for greywater management demonstrate the lowest life cycle cost and highest cost-effectiveness (dollars per kilogram of nitrogen removed from the watershed). Composting toilets are also attractive options in some cases, particularly best-case nitrogen mitigation. Innovative/advanced septic systems designed for high-level nitrogen removal are cost-competitive options for newly constructed homes, except at their most expensive. A centralized wastewater treatment plant is the most expensive and least cost-effective option in all cases. Using a greywater recycling system with any treatment technology increases the cost without adding any nitrogen removal benefits. Sensitivity analysis shows that these results are robust considering a range of cases and uncertainties.
authors.affiliation: The University of Texas at Austin, Dept. of Civil, Architectural, and Environmental Engineering, 301 E. Dean Keeton St. C8600, Austin, TX 78712-8600, United States. Electronic address: alisonwood@gmail.com.
authors.forename: Alison
authors.initials: A
authors.lastname: Wood
authors.affiliation: The University of Texas at Austin, 301 E. Dean Keeton St. C2100, Austin, TX 78712-2100, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Blackhurst
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH, 45268, United States.
authors.forename: Troy
authors.initials: T
authors.lastname: Hawkins
authors.affiliation: ORISE Research Fellow, U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, United States.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Xue
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH, 45268, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Ashbolt
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, Microbiological and Chemical Exposure Assessment Research Division, 26 W. Martin Luther King Drive, Cincinnati, OH, 45268, United States.
authors.forename: Jay
authors.initials: J
authors.lastname: Garland
mesh_terms: D003362:Cost-Benefit Analysis; D005191:Family Characteristics; D006801:Humans; D009584:Nitrogen / Q000737:chemistry*; D014481:United States; D014865:Waste Disposal, Fluid / Q000191:economics* / Q000379:methods; D062065:Wastewater / Q000737:chemistry*
chemical_list: D009584:Nitrogen; D062065:Wastewater
keywords: Advanced septic; Blackwater digestion; Compost toilet; Cost-effectiveness; Diversion toilet; Household wastewater; Nitrogen