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Formation of Chemical Byproducts During Water Treatment Studied
July 11, 2018

Synthetical chemicals are ever-present in modern life—in our medications, cosmetics and clothing—but what happens to them when they enter our municipal water supplies?

Because these chemicals are out-of-sight, out-of-mind, we assume they cannot harm us after we flush them down the sink. However, most water treatment infrastructures were not designed to remove synthetic organic chemicals like those found in opioids, personal care products and pharmaceuticals.

During flash flooding, water treatment systems can become overwhelmed, allowing untreated effluent and household chemicals to flow into local waterways. Credit: Sarah Bird/Michigan Tech.

Consequently, trace concentrations of those chemicals are present in effluent: the water discharged from treatment plants into lakes, rivers and streams. Although found in extremely small concentrations, just nanograms or micrograms, the toxicity is not well understood in human bodies and ecosystems.

Worse, we know even less about the effects on human and ecosystem health of byproducts created during advanced oxidation water treatment processes; thousands of chemical byproducts can be created in just minutes.

Therefore, it’s crucial that scientists and treatment plant managers understand the mechanisms by which chemical byproducts are created during the treatment process. Daisuke Minakata, assistant professor of civil and environmental engineering at Michigan Technological University, with coauthors Divya Kamath and Stephen Mezyk, sought to understand those mechanisms using acetone as a test case.

Their results are published in the article, “Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Process” in the journal Environmental Science and Technology, published by the American Chemical Society.

“When we do water treatment using advanced chemical oxidation, those oxidants destroy target organic compounds but create byproducts,” Prof. Minakata says. “Some byproducts may be more toxic than their parent compound. We need to understand the fundamental mechanisms of how the byproducts are produced and then we can predict what to be produced from many other chemicals. We found more than 200 reactions involved in acetone degradations based on computational work.”

According to information, a limitation of the work is that the model applies solely to structurally simple organic contaminant like acetone, rather than broadly multiple chemical degradation processes. Organic chemicals have extraordinarily complex structures, and we lack the computational capacity to calculate the reaction pathways. Prof. Minakata’s team used the Superior supercomputer at Michigan Tech. Superior puzzled away on the acetone pathways with hundreds of calculations—some of which can take more than weeks.

Understanding the mechanisms of chemical byproduct formation isn’t just important for water treatment; it’s also advancing what we know about chemical reactions in the atmosphere and inside our bodies.

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