Ocasio Daniel, Sedlak David L
Department of Civil & Environmental Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
ACS ES T Eng. 2022 Oct 14;2(10):1933-1941. doi: 10.1021/acsestengg.2c00116. Epub 2022 Jun 3.
Due to the challenges of providing centralized drinking water infrastructure in low-income and rural settings, point-of-use (POU) disinfection systems are an attractive option for enhancing access to safe drinking water. Electrochlorinators offer an easily scalable and adaptable alternative to POU disinfection systems that require frequent replenishment and accurate dosing of chlorine, but they also require addition of salts on a regular basis. To address this need, we developed an electrochemical disinfection system that efficiently produces chlorine without any chemical inputs. To convert the low concentration of chloride in source waters (i.e., 10-200 mg L) to free chlorine (i.e., HOCl/OCl), an anion exchange membrane was positioned between two electrodes, creating two separate chambers. By providing continuous water flow through the catholyte while operating the anolyte in the batch mode, chloride was concentrated into the anolyte, where it was more efficiently converted into chlorine. This approach allowed us to produce chlorine at rates that were about 50% faster than that of an undivided cell operating under similar conditions. Chlorate production was approximately 20% slower in the separated cell compared to an undivided cell; concentrations in finished water never exceeded the World Health Organization's provisional guideline value of 0.7 mg L. The performance of the system was further improved by retaining some of the anolyte between operating cycles. This helped avoid periods of high cell potential before salts were concentrated in the anolyte chamber. Use of an anion exchange membrane and a recycled anolyte mode of operation reduced energy consumption by 30%-70% relative to an undivided cell. The energy required to disinfect water ranged from approximately 0.05 to 1 kWh m, depending on the chloride content and conductivity of the source water.
由于在低收入和农村地区提供集中式饮用水基础设施存在挑战，使用点（POU）消毒系统是增加安全饮用水获取的一个有吸引力的选择。电解氯化器为需要频繁补充和精确投加氯的POU消毒系统提供了一种易于扩展和适应的替代方案，但它们也需要定期添加盐。为满足这一需求，我们开发了一种无需任何化学投入就能高效产生氯的电化学消毒系统。为了将源水中低浓度的氯化物（即10 - 200毫克/升）转化为游离氯（即HOCl/OCl），在两个电极之间放置了一个阴离子交换膜，形成两个独立的腔室。通过在阴极电解液中提供连续水流，同时以分批模式操作阳极电解液，氯化物被浓缩到阳极电解液中，在那里它能更有效地转化为氯。这种方法使我们产生氯的速度比在类似条件下运行的无分隔电池快约50%。与无分隔电池相比，分隔电池中氯酸盐的产生速度大约慢20%；成品水中的浓度从未超过世界卫生组织0.7毫克/升的临时指导值。通过在操作周期之间保留一些阳极电解液，系统性能得到了进一步改善。这有助于避免在盐在阳极电解液腔室中浓缩之前出现高电池电位的时期。使用阴离子交换膜和循环阳极电解液操作模式相对于无分隔电池可将能耗降低30% - 70%。消毒水所需的能量范围约为0.05至1千瓦时/立方米，具体取决于源水的氯化物含量和电导率。
