Locally Enhanced Electric Field Achieved by Surface Etching Enhances Copper Ionizing Disinfection of Water
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Sui, Wenxiaoshan
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Abstract
Water is key to life. However, what if the seemingly pure water that we drink every day could contain invisible contamination? This is the struggle that many people worldwide, even people in the United States, are still facing. Billions of people have access to little or no sanitation due to the high capital and maintenance costs of centralized drinking water treatment plants (DWTPs). With the ongoing pandemic and increased occurrences of natural disasters, the disadvantages of traditional water treatment plants are getting more recognized by the public and governments. A solution is needed now more than ever.
To solve these problems, a disinfection alternative that is both flexible and cost-effective is necessary. This leads to the development of point-of-use (POU) or household water treatment (HWT) devices. However, current disinfection technologies adopted by POU devices (i.e., filtration, ozonation, etc.) have their drawbacks and limitations. Among all the available technologies, chlorine disinfection is one of the most popular methods used in both the DWTP and POU devices. However, although it effectively inactivates pathogens, chlorine runs the risk of introducing disinfection byproducts (DBPs), which are potentially fatal to humans. Thus, it is crucial to develop other POU disinfection methods which do not introduce DBPs without sacrificing the promising performance of chlorine disinfection.
In terms of antibiotic behavior, copper is one of the possible substitutions for chlorine. In addition to being cheap and abundant, copper is very effective in killing pathogens. However, copper does impose threats on human health when present in high concentrations. Thus, to alleviate copper’s drawback in toxicity, copper ionization technique is developed and utilized in locations such as hospitals and nursing homes where high level of hygiene is required. Through adjusting the voltage and the current, copper ionization technique, or copper ionization cell (CIC), shows promising pathogen inactivation with a controllable low copper release. Recently, a POU device called Coaxial Electrode Copper Ionization Cell (CECIC) is reported with promising disinfection performance, removing ~6-log of bacteria with only 200 ppb total copper release under energy-efficient operation conditions.
With the previous success brought by CECIC, this thesis investigates whether modified the copper electrode with rougher surface morphology could increase electric field strength and lead to higher disinfection efficiency with a lower copper release. The investigation found that the desirable copper surface morphology could be easily fabricated through a one-step chemical etching process, with 5 minutes being the optimal etching time. It is also found that the etched electrode performed better under 1 V, achieving 1.15-log more inactivation using approximately 30% less copper at an operating flow rate of 10mL/min. And regarding long-term performance, through employing the novel electrode, the copper ionization cell consumes a much lower level of copper (~53 μg) for every 1-log inactivation of E. coli, compared with the copper concentration (~120 μg) of the conventional cell with a pristine electrode.
In conclusion, this thesis’s novel findings and phenomena have deepened the current knowledge in water disinfection using CECIC and brought a lot of new potentials in future research and real-world implementation.
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2022-01-07
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