Water Resources Center, University of Minnesota, 1985 Buford Avenue, St. Paul, MN 55108, USA.
Department of Civil, Environmental, and Geo- Engineering, 500 Pillsbury Drive S.E., Minneapolis, MN 55455, USA.
Sci Total Environ. 2021 Apr 10;764:144179. doi: 10.1016/j.scitotenv.2020.144179. Epub 2020 Dec 17.
Chloride pollution of groundwater and surface water resources is an environmental concern in many regions. While use of road salt for winter road maintenance is known to be a major source of chloride in the environment, limited research has investigated the environmental impacts of chloride discharged from water softeners, particularly in areas with hard water. A chloride budget was developed for the state of Minnesota to estimate the amount of chloride discharged from household water softeners as well as other domestic, agricultural, commercial, and industrial sources. The analysis used multiple data sources, including salt sales records and wastewater monitoring data, and used statistical, spatial, and survey methods to estimate chloride loading from major sources statewide. Annual chloride mass contributions were estimated for the following sources: household water softener use; human excretions; household product use; chloride concentrations in drinking water; atmospheric deposition; road salt use; dust suppressant use; fertilizer application; industrial discharge; and livestock excretions. A mass balance for 96 wastewater treatment plants with effluent monitoring data showed that across these facilities, discharge from water softeners was the largest chloride source. A statewide chloride budget found that road salt was the largest source of chloride to the environment, but that WWTPs and fertilizer were also substantial sources, discharging 221,300 t and 209,900 t annually. Water softeners were estimated to contribute 65% of the chloride discharged to all 613 municipal WWTPs statewide. Methods used in this analysis could be applied to other communities, watersheds, or states with similar conditions. The results of the analyses indicate that water softening is an important chloride source in areas with hard water and underscore the importance of identifying and characterizing chloride sources in less urban areas, where deicing salt may be a less important contributor and receiving water bodies are often lakes, reservoirs, and streams.
地下水和地表水资源的氯化物污染是许多地区的一个环境关注点。虽然冬季道路维护中使用的道路盐被认为是环境中氯化物的主要来源，但有限的研究调查了水软化器排放的氯化物对环境的影响，特别是在硬水地区。明尼苏达州制定了氯化物预算，以估计家庭水软化器以及其他家庭、农业、商业和工业来源排放的氯化物量。该分析使用了多种数据源，包括盐销售记录和废水监测数据，并使用统计、空间和调查方法来估计全州主要来源的氯化物负荷。以下来源的年度氯化物质量贡献被估计：家庭水软化器的使用；人类排泄物；家用产品的使用；饮用水中的氯化物浓度；大气沉积；道路盐的使用；防尘剂的使用；肥料的应用；工业排放；和牲畜排泄物。对 96 个具有废水监测数据的污水处理厂的质量平衡表明，在这些设施中，水软化器的排放是最大的氯化物来源。全州范围的氯化物预算发现，道路盐是环境中氯化物的最大来源，但污水处理厂和肥料也是大量来源，每年排放 221300 吨和 209900 吨。据估计，水软化器对全州所有 613 个市政污水处理厂排放的氯化物的贡献率为 65%。本分析中使用的方法可应用于具有类似条件的其他社区、流域或州。分析结果表明，在硬水区，水软化是氯化物的重要来源，并强调了在较少城市地区确定和描述氯化物来源的重要性，在这些地区，除冰盐的贡献可能不那么重要，而受纳水体通常是湖泊、水库和溪流。
