Wood Alison, Blackhurst Michael, Hawkins Troy, Xue Xiaobo, Ashbolt Nicholas, Garland Jay
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.
The University of Texas at Austin, 301 E. Dean Keeton St. C2100, Austin, TX 78712-2100, United States.
J Environ Manage. 2015 Mar 1;150:344-354. doi: 10.1016/j.jenvman.2014.10.002. Epub 2015 Jan 6.
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.
生活污水，尤其是来自传统化粪池系统的污水，是氮污染的主要来源。替代性生活污水处理技术提供类似的污水处理服务，但其生命周期成本和氮流影响仍不确定。本文探讨了两个关键问题：（1）一系列传统和替代性城市污水处理技术的总成本、氮减排潜力和成本效益分别是多少，（2）哪些不确定性因素影响这些结果，以及我们如何提高对这些技术的理解？我们估算了各种生活污水处理系统的家庭氮质量平衡，并将这种质量平衡与生命周期成本评估相结合，以计算氮减排的成本效益，我们将其定义为从当地流域去除的氮。我们将我们的方法应用于马萨诸塞州的法尔茅斯，在那里，化粪池系统故障导致当地受纳水体的富营养化加剧。我们发现，与用于灰水管理的传统化粪池系统配套的冲洗式和干式（堆肥）尿液分流马桶，生命周期成本最低，成本效益最高（每从流域去除一公斤氮的美元数）。在某些情况下，堆肥马桶也是有吸引力的选择，特别是在最佳情况下的氮减排方面。为高水平氮去除而设计的创新/先进化粪池系统，对于新建房屋来说是具有成本竞争力的选择，但在成本最高的情况下除外。在所有情况下，集中式污水处理厂都是最昂贵且成本效益最低的选择。使用任何处理技术的灰水回收系统都会增加成本，且不会带来任何氮去除效益。敏感性分析表明，考虑到一系列情况和不确定性，这些结果是稳健的。
