The combination of ozone and chlorine kills most bacteria and viruses in wastewater
The combination of ozone and chlorine kills most bacteria and viruses in wastewater

Common water treatment method can lead to formation of toxic compounds: Study

ANI | Updated: Feb 05, 2020 20:58 IST

Washington D.C. [USA], Feb 5 (ANI): In the midst of the increasing practice of wastewater purification and reuse, a group of researchers has found that ozone treatment and subsequent chlorination can convert trace amounts of some pharmaceuticals in wastewater into toxic disinfection byproducts (DBPs).
They report their results in Environmental Science & Technology.
The combination of ozone and chlorine kills most bacteria and viruses in wastewater. Compared with chlorine treatment alone, ozone also reduces the formation of many DBPs.
Recently, however, scientists have discovered that ozone can increase the formation of potentially toxic halonitromethanes, such as chloropicrin, in chlorine-treated wastewater.
Jiaming Lily Shi and Daniel McCurry wanted to determine which molecules in the wastewater were being converted to chloropicrin and how.
To find out, the researchers collected wastewater samples from three treatment plants in Southern California. The team discovered that ozone treatment produced nitromethane, which could have been formed from some nitrogen-containing drugs in the wastewater, including stimulants such as ephedrine and methamphetamine and certain antidepressants.
Then, chlorination transformed the nitromethane into chloropicrin. The pharmaceuticals, which enter wastewater through sewage, are not removed completely by conventional wastewater treatment.
Future work should address how effectively processes that occur after ozone treatment can remove the nitromethane intermediate, the researchers say. (ANI)

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