Mulchandani Anjali, Edberg Justin, Herckes Pierre, Westerhoff Paul
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, USA; NSF Nanosystems Engineering Research Center on Nanotechnology Enabled Water Treatment, USA.
NSF Nanosystems Engineering Research Center on Nanotechnology Enabled Water Treatment, USA; School of Energy, Matter and Transport Engineering, Arizona State University, Tempe, AZ 85287, USA.
Sci Total Environ. 2022 Jun 15;825:153966. doi: 10.1016/j.scitotenv.2022.153966. Epub 2022 Feb 17.
Atmospheric water harvesting (AWH) is an emerging technology for decentralized water supply and is proving to be viable for use in emergencies, military deployment, and sustainable industries. The atmosphere is a freshwater reservoir that contains 12,900 km of water, 6-fold more than the volume of global rivers. Dehumidification water harvesting technologies can be powered by solar, wind, or electric sources. Compressor/refrigerant-based dehumidifiers operate via dew point condensation and provide a cold surface upon which water vapor can condense. Conversely, desiccant-based technologies saturate water vapor using a sorbent that is then heated, and the supersaturated water vapor condenses on a surface when interacting with cooler ambient process air. This work compares productivity, energy consumption, efficiency, cost and quality of water produced of two water-harvesting mechanisms. Electric-powered compressor and desiccant dehumidifiers were operated outdoors for more than one year in the arid southwestern USA, where temperatures ranged from 3.1 to 43.7 °C and relative humidity (RH) ranged from 6 to 85%. The compressor system harvested >2-fold more water than the desiccant system when average RH during the run cycle was >30%, average temperature was >20 °C, and average dew point temperature was >5 °C. Desiccant systems performed more favorably when average RH during the run cycle was <30%, average temperature was <20 °C, and average dew point temperature was <5 °C. Water collected by compressor-based technologies had conductivity up to 180 μS/cm, turbidity up to 190 NTU, and aluminum, iron and manganese near or above the US EPA secondary drinking water standard. Dissolved organic carbon (DOC) averaged <2 mg C/L but ranged up to 12 mg C/L. Water collected by desiccant-based technologies had significantly lower conductivity, metals, and turbidity, and DOC was always <6 mg/L. Aldehydes such as formaldehyde and acetaldehyde and carboxylic acids such as formic acid and acetic acid were primary contributors to DOC. The differences in harvested water quality were attributed to differences in the condensation method between compressor and desiccant AWH technologies. Multiple strategies could be employed to prevent these volatile organic compounds (VOCs) from contributing to DOC in harvested water, such as pretreating air to remove VOCs or post-treating DOC in harvested liquid water.
大气取水（AWH）是一种新兴的分散式供水技术，已被证明可用于应急、军事部署和可持续产业。大气是一个淡水储存库，含有12900立方千米的水，是全球河流体积的6倍。除湿取水技术可以由太阳能、风能或电力驱动。基于压缩机/制冷剂的除湿器通过露点冷凝运行，并提供一个冷表面，水蒸气可以在其上冷凝。相反，基于干燥剂的技术使用一种吸附剂使水蒸气饱和，然后加热，当与较冷的环境工艺空气相互作用时，过饱和水蒸气在一个表面上冷凝。这项工作比较了两种取水机制的生产率、能源消耗、效率、成本和产水质量。电动压缩机和干燥剂除湿器在美国西南部干旱地区户外运行了一年多，那里的温度范围为3.1至43.7°C，相对湿度（RH）范围为6至85%。当运行周期内的平均相对湿度>30%、平均温度>20°C且平均露点温度>5°C时，压缩机系统的取水量比干燥剂系统多两倍以上。当运行周期内的平均相对湿度<30%、平均温度<20°C且平均露点温度<5°C时，干燥剂系统表现更优。基于压缩机技术收集的水的电导率高达180μS/cm，浊度高达190 NTU，铝、铁和锰接近或高于美国环境保护局二级饮用水标准。溶解有机碳（DOC）平均<2 mg C/L，但范围高达12 mg C/L。基于干燥剂技术收集的水的电导率、金属含量和浊度明显较低，DOC始终<6 mg/L。甲醛和乙醛等醛类以及甲酸和乙酸等羧酸是DOC的主要贡献者。产水质量的差异归因于压缩机和干燥剂AWH技术之间冷凝方法的差异。可以采用多种策略来防止这些挥发性有机化合物（VOCs）对收集水中的DOC产生影响，例如对空气进行预处理以去除VOCs或对收集的液态水中的DOC进行后处理。
