4-Step Test Tells Waste Plants Whether To Use Ozone.
Is ozone useful for zapping micropollutants, or does it leave too many byproducts? A new test aims to find out.
In a study published in the journal Water Research, a team of experts from three European research institutions “present a test to evaluate the suitability of ozone treatment for urban wastewater,” according to a statement from Ecole Polytechnique Federale de Lausanne, which supported that research along with ETH Zurich and Eawag.
Micropollutants are a hot regulatory issue in Switzerland, where environmental overseers called for around 100 wastewater treatment plants to upgrade their treatment technology. Over the next two decades, nearly one in seven Swiss wastewater treatment plants will be overhauled to improve their micropollutant treatment processes.
Plant operators “have to decide whether to use powdered activated carbon to adsorb micropollutants, or ozone to destroy them,” the statement said.
So, how do they pick?
“According to Urs von Gunten who led the study, both approaches have similar efficiencies, but differ in other important ways. Once used, powdered activated carbon is incinerated with the sewage sludge, effectively destroying any adsorbed micropollutants. However, it requires significant maintenance operations. Ozone treatment, by contrast, is easy to automate and clean to handle. Micropollutants are broken apart chemically, and the fragments are then released into the environment,” the statement said.
As the U.S. EPA points out, ozone has drawbacks. “Low dosage may not effectively inactivate some viruses, spores, and cysts. Ozonation is a more complex technology than is chlorine or UV disinfection, requiring complicated equipment and efficient contacting systems.”
So when should it be used? The new test introduced by the European research team gives operators a four-step process for testing whether ozone is a good choice, per the statement:
von Gunten and his team developed a four-step test procedure to assess whether the wastewater from a specific plant can be safely treated with ozone. Not only does it involve assessing the efficiency of micropollutant abatement and the formation of oxidation byproducts, the test also includes a series of biological assays to test the toxicity of the treated wastewater before and after treatment. “The idea is that the test, which will be carried out by a private laboratory, will assist cantonal agencies and federal authorities in deciding how best to upgrade wastewater treatment plants,” he says.
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