Cooper Jennifer A, Loomis George W, Amador Jose A
Laboratory of Soil Ecology and Microbiology, University of Rhode Island, Kingston, Rhode Island, United States of America.
New England Onsite Wastewater Training Center, University of Rhode Island, Kingston, Rhode Island, United States of America.
PLoS One. 2016 Sep 1;11(9):e0162104. doi: 10.1371/journal.pone.0162104. eCollection 2016.
Climate change may affect the ability of soil-based onsite wastewater treatment systems (OWTS) to treat wastewater in coastal regions of the Northeastern United States. Higher temperatures and water tables can affect treatment by reducing the volume of unsaturated soil and oxygen available for treatment, which may result in greater transport of pathogens, nutrients, and biochemical oxygen demand (BOD5) to groundwater, jeopardizing public and aquatic ecosystem health. The soil treatment area (STA) of an OWTS removes contaminants as wastewater percolates through the soil. Conventional STAs receive wastewater from the septic tank, with infiltration occurring deeper in the soil profile. In contrast, shallow narrow STAs receive pre-treated wastewater that infiltrates higher in the soil profile, which may make them more resilient to climate change. We used intact soil mesocosms to quantify the water quality functions of a conventional and two types of shallow narrow STAs under present climate (PC; 20°C) and climate change (CC; 25°C, 30 cm elevation in water table). Significantly greater removal of BOD5 was observed under CC for all STA types. Phosphorus removal decreased significantly from 75% (PC) to 66% (CC) in the conventional STA, and from 100% to 71-72% in shallow narrow STAs. No fecal coliform bacteria (FCB) were released under PC, whereas up to 17 and 20 CFU 100 mL-1 were released in conventional and shallow narrow STAs, respectively, under CC. Total N removal increased from 14% (PC) to 19% (CC) in the conventional STA, but decreased in shallow narrow STAs, from 6-7% to less than 3.0%. Differences in removal of FCB and total N were not significant. Leaching of N in excess of inputs was also observed in shallow narrow STAs under CC. Our results indicate that climate change can affect contaminant removal from wastewater, with effects dependent on the contaminant and STA type.
气候变化可能会影响美国东北部沿海地区基于土壤的现场污水处理系统（OWTS）处理废水的能力。较高的温度和地下水位会通过减少用于处理的非饱和土壤体积和氧气量来影响处理效果，这可能导致病原体、营养物质和生化需氧量（BOD5）更多地输送到地下水中，危及公众和水生生态系统健康。OWTS的土壤处理区（STA）在废水渗入土壤时去除污染物。传统的STA接收来自化粪池的废水，渗滤发生在土壤剖面的较深处。相比之下，浅窄型STA接收经过预处理的废水，其在土壤剖面中较高位置渗入，这可能使它们对气候变化更具弹性。我们使用完整土壤中宇宙来量化传统型和两种浅窄型STA在当前气候（PC；20°C）和气候变化（CC；25°C，地下水位升高30厘米）条件下的水质功能。在CC条件下，所有STA类型对BOD5的去除率均显著提高。传统STA中磷的去除率从75%（PC）显著降至66%（CC），浅窄型STA中从100%降至71 - 72%。在PC条件下未释放粪便大肠菌群（FCB），而在CC条件下，传统型和浅窄型STA分别释放高达17和20 CFU 100 mL-1。传统STA中总氮去除率从14%（PC）增至19%（CC），但浅窄型STA中则从6 - 7%降至低于3.0%。FCB和总氮去除率的差异不显著。在CC条件下，浅窄型STA中还观察到氮淋失超过输入量的情况。我们的结果表明，气候变化会影响废水中污染物的去除，其影响取决于污染物和STA类型。
