Need Arsenic Removal? Call PAUL!
Featured Image Caption: The Carnon River is known to be impacted from metal mining in the area. Arsenic is one of the pollutants contaminating this body of water. “Carnon River pollution” by John Gibson CC BY-SA 2.0 via Wikimedia commons
Primary Source Article: Channa, N., Gadhi, T. A., Mahar, R. B., Ali, I., Sajjad, S., Freyria, F. S., Bonelli, B., Widderich, S., & Frechen, F.-B. (2024). Efficient and Rapid Combined Electrocoagulation–Filtration of Arsenic in Drinking Water. Water (Basel), 16(12), 1684-. https://doi.org/10.3390/w16121684
Secondary Source Article: Song, P., Yang, Z., Zeng, G., Yang, X., Xu, H., Wang, L., Xu, R., Xiong, W., & Ahmad, K. (2017). Electrocoagulation treatment of arsenic in wastewaters: A comprehensive review. Chemical Engineering Journal (Lausanne, Switzerland : 1996), 317, 707–725. https://doi.org/10.1016/j.cej.2017.02.086
Clean water is a basic need that is fundamental to survival for all life on Earth. However, basic does not necessarily mean accessible. In both developed and developing countries, arsenic contamination is a real threat. Arsenic (As) contamination can come from human activities such as mining, fracking, or can be naturally occurring in soils and foods. Arsenic can accumulate in tissues over time and negatively impact the growth and development of humans, plants, and wildlife. Chronic arsenic exposure can cause skin, lung, bladder, and liver cancer in mammals and decrease crop yields. In order to find better ways to filter arsenic from water, Channa and colleagues came up with a two stage treatment for As contaminated water. The first stage involves a traditional filtration system and the step introduces PAUL, a filtration unit that can purify water. Using the two step filtration method, scientists were able to demonstrate that As contaminated water could be rapidly filtered.
The Traditional Method of Filtering Water
Arsenic is typically filtered through a process called electrocoagulation. The process involves hooking up two metal electrodes to an electric source and placing the electrodes in the desired contaminated water of interest. When current runs through these electrodes, electrons are released and react with ions in the water. In this case, arsenic and ions found in tap water react with the ions and a sludge is produced, leaving behind the purified water. The benefit of this process is that you don’t have to add chemicals since the electrons released from the electrodes cause the solids to form. However, removing the solids can be expensive. Devising a way to filter out solids is an important step in treating arsenic contaminated water. Channa and colleagues proposed a two step method for treating contaminated water. The first involves treating the water through the EC method and then using PAUL to clean up the solid mess.
Meet PAUL
Portable Aqua Unit for Lifesaving (PAUL) is a water backpack that can filter up to 1200 liters of water per day. Inside the filter are a series of filter sheets and a collection channel that picks up solids. The water backpack is typically used to remove bacteria, viruses, and pathogens. PAUL is currently being used in developing countries that need clean water. In this study, researchers decided to use PAUL to solve the problem of filtering out the resulting sludge from the EC process. Researchers mixed tap water with varying concentrations of Arsenic and other ions under different scenarios to determine if PAUL was effective in a broad range of conditions.
Results and Challenges
Overall, using the 2 step process for removing arsenic was highly effective within a short period of time. However, there are still challenges to solve before using this method as a bulk water cleaning process. Some of the challenges were that the experiments were performed at a neutral pH; this has not been tried in water conditions where the pH can range from 5 to 8.5. Another issue is that during the treatment, the electric current decreased over time because the electrodes containing the metals reacted in solution. This challenge is expected when using an electrochemical cell. It is a catch-22 situation: an electrical current is driving the electrodes to release electrons so that they can react with the chemical species you want to filter out. But, reacting with the arsenic means less of the metal driving the electrical current that is driving the process in the first place. Finally, how does one dispose of the sludge properly?
Still, the two step process of EC and PAUL is a promising start to researching how to clean arsenic contaminated water at a large scale. If scientists can address these challenges, the environment can be a safer place for humans and wildlife.
Want to know PAUL better? Check out this website! http://waterbackpack.org
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