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Can disinfection in sewage treatment help protect against COVID-19 risks?

In this series of posts, Riverkeeper compiles the available information – and unanswered questions – on the possible risks the COVID-19 virus may pose via sewage-contaminated water.

New York is at the center of the COVID-19 pandemic, and it’s urgent that we stay focused on preventing transmission through the known routes – interpersonal contact and contact with surfaces contaminated with the COVID-19 virus.

At the same time, Riverkeeper is actively studying the available information on the risks the COVID-19 virus may pose to individuals or communities via sewage-contaminated water. Riverkeeper recognizes that our organization is not expert in epidemiology or infectious diseases.Click the links below to explore this topic further.

Q. What is the role of disinfection in the sewage treatment process, relative to COVID-19 virus?

A. Disinfection is believed to be effective at killing the COVID-19 virus, but not all sewage is disinfected before being discharged to the Hudson River or its tributaries.

There is an emerging consensus among regulatory and health agencies, and the wastewater industry that, based largely on studies of other viruses in the coronavirus family, disinfection of sewage with chlorine or other methods should effectively denature the COVID-19 virus before it is discharged to water. Because these viruses are generally considered to be easier to kill than E. coli, a bacteria commonly used nationwide to assess compliance with treatment standards, a well-functioning treatment plant that includes disinfection in its treatment process, and is in compliance with the Clean Water Act should eliminate the COVID-19 virus.

We note that Riverkeeper remains concerned that New York State relies on a fecal indicator bacteria, fecal and total coliforms, that has not been recommended by the U.S. Environmental Protection Agency since 1986. (E. coli is a subset of fecal coliforms, which are themselves a subset of total coliforms. E. coli is currently recommended by EPA, as is Entero.) While many other states have updated their water quality standards based on the EPA’s 2012 Recreational Water Quality Criteria, New York State has not updated its standards for freshwaters like most of the Hudson River and its tributaries, or for pollution discharges to them.

Importantly, permit conditions require residual chlorine concentrations that must be calibrated to effectively kill coronaviruses, and dechlorination processes must effectively reduce chlorine levels before discharge to the river. Chlorine is toxic to aquatic life even at very low concentrations. The alewife floater, a mussel that was decimated by the invasion of the zebra mussel in the Hudson River, is an example of a Hudson River species that is particularly sensitive to trace amounts of chlorine. Spring is a particularly important time in the Hudson River Estuary, as it serves as an extraordinary nursery for millions of migratory fish from the Atlantic Ocean. The springtime migration of river herring, striped bass and Atlantic sturgeon are a reminder that the extraordinary cycles of the living world will continue through and beyond the challenges of this awful pandemic – if we do our part to protect them.

Enforcement is an important concern, given the U.S. Environmental Protection Agency on March 26 announced it would relax enforcement of all environmental laws. Fortunately, to date, the New York State Department of Environmental Conservation (DEC), which has the authority to enforce pollution discharge pollution compliance under the Clean Water Act, has announced just the opposite: Despite requests to relax permit requirements, the DEC has indicated it expects full compliance with water pollution discharge permits. Plants must be able to remain in compliance to ensure that there is both sufficient chlorine to kill pathogens and sufficient dechlorination to remove chlorine before it is discharged.

The public is often surprised to learn that New York State does not require disinfection of all sewage effluent. Many small treatment plants — such as those that serve remote schools, healthcare facilities, apartment buildings or other buildings outside sewered areas — are not designed to disinfect effluent. It has been New York State priority in recent years to upgrade larger treatment plants that lack disinfection. But even many of these larger community treatment plants are required to disinfect sewage effluent only in the warmer months. The latter is the case because of a DEC policy that recognizes that most public use of water occurs in warmer months, and that there are both costs to communities and risks to aquatic life from use of chlorine.

Statewide, 100 treatment plants aren’t currently disinfecting, and won’t be required to start until sometime in May (start date varies by facility and permit). They have the capacity to discharge 358 million gallons per day of sewage that is treated without disinfection. Of these, 44% of plants (44) are in the Hudson River watershed, and they have the capacity to discharge 243 million gallons per day of sewage that is treated without disinfection.

Another 216 smaller treatment plants statewide are not required to disinfect effluent at any time of year, and they collectively have the capacity to discharge 217 million gallons per day of sewage that is treated without disinfection. One-third of these plants (70) are in the Hudson River Watershed, and they have the capacity to discharge 71 million gallons per day of sewage that is treated without disinfection.

Statewide, 16% of sewage effluent, by volume, that is currently discharged not disinfected. (in April, prior to the start of seasonal disinfection requirements at many treatment plants) In the Hudson River Watershed at this time (in April), 42% of sewage effluent is not disinfected. Click here for lists of Hudson River Watershed sewage treatment plants that do not disinfect year-round, or at all. (Information in the three paragraphs above based on Riverkeeper’s analysis of DEC’s “Current Descriptive Data of Municipal Wastewater Treatment Plants,” which relies on 2004 data.)

The bottom line: Disinfection is a key step in protection of public health from viruses, and hundreds of millions of gallons of sewage are discharged every day without disinfection.


Is COVID-19 virus present in water?

Is recreation along the Hudson still safe? Assessing the risk from the COVID-19 virus

Will Riverkeeper gather water quality data during the COVID-19 pandemic?

Can better water infrastructure help protect public health amid virus outbreaks?

Is public drinking water at risk from the COVID-19 virus?

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