Researchers found that while conventional biological treatment plants significantly reduced viral load in effluent, the plants did not reduce the wastewater’s viral load to undetectable levels.
Experts recommend treatment with solutions like chlorine or UV disinfection to eliminate risk of infection
It has been understood for some time that conventional wastewater treatment plants (WWTPs) often do not eradicate all viruses from wastewater. During pandemics, overwhelming viral loads in wastewater mean more virus remains in WWTP outfall. Now, a research team from Ben-Gurion University of the Negev has confirmed that the general rule applies specifically to COVID-19 (SARS-CoV-2).
Dr. Oded Nir of the Zuckerberg Institute for Water Research and Professor Ariel Kushmaro of the Avram and Stella Goldstein-Goren Department of Biotechnology Engineering have led the first survivability study on COVID-19 using RNA detection.
Researchers collected samples of raw sewage and wastewater during the main stages of wastewater treatment at two Israeli WWTPs during the pandemic’s first-wave lockdown in April, as well as during the second wave in July. When the samples were analyzed, researchers found that while the plants significantly reduced viral load in effluent, the conventional biological treatment at the plants did not reduce the wastewater’s viral load to undetectable levels.
Potential Risks
As fresh water becomes more scarce globally, wastewater reuse has grown by leaps and bounds. When wastewater is biologically treated to a high level, it generally is considered safe for reuse applications such as toilet flushing, dust reduction, or agricultural irrigation under normal conditions.
However, this study shows that traces of the COVID-19 virus often remain after conventional treatment. This raises concerns that, when the wastewater is reused, animals or WWTP workers may be exposed to the virus.
The findings are especially salient for the researchers at Israel’s Ben Gurion University because Israel reuses almost 90% of its wastewater, more than any other country. Approximately 75% of it is used for agricultural irrigation.
Solutions for Safe Water Reuse
While the exact risk is not yet known, the researchers urge elevated treatment measures to ensure the safety of recycled wastewater.
On a hopeful note, the researchers did come across a few study samples in which the virus was not detected at all, and they were all samples that had been disinfected with chlorine. Only one chlorine-disinfected sample still had detectable levels of the virus, probably from an inadequate chlorine dose. The researchers have recommended tertiary treatment with chlorine to minimize risk.
On the other side of the world, guidance offered this year by the United States Occupational Safety and Health Administration (OSHA) suggests that WWTPs with ultraviolet (UV) radiation disinfection stages also will be able to clear the virus from wastewater.
Fluence builds UV or chlorine disinfection stages, tailored to your target effluent, into our Aspiral™ line of Smart Packaged WWTPs, as well as other sustainable water and wastewater treatment solutions. Contact our experts to learn more.
