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Coronavirus And The Water Cycle — Here Is What Treatment Professionals Need To Know

Guest Column | March 5, 2020

By Nicole McLellan, David Pernitsky, and Arthur Umble

As the global health community tracks the spread of this virus, it’s important for water and wastewater professionals to keep updated on potential impacts.

It's hard to miss the headlines. The recent outbreak of novel coronavirus (2019-nCoV or COVID-19) has dominated news cycles in recent weeks. The World Health Organization (WHO) is calling it “public enemy number one.” But what information do we have that is related to coronaviruses in water and wastewater systems? And what can water- and wastewater-system operators do to protect public health?

Modern water and wastewater treatment systems play an important role in public health protection. With the potential for environmental transmission, water and wastewater operators need to know the potential for survival of this type of virus in water and wastewater treatment systems.

Coronaviruses, named for the crown-like spikes on their surface, were first identified in the mid-1960s. Currently, seven coronaviruses are known to infect people and make them ill. Three of these — MERS-CoV, SARS-CoV, and COVID-19 — emerged in the last 20 years and are examples of how some coronaviruses that infect animals can evolve to infect humans. COVID-19 is a new variety of coronavirus and is an enveloped, single-stranded (positive-sense) RNA virus.

So, what is the fate of coronavirus in sewage and wastewater treatment plants? Or in the aquatic environment? And should we be worried about the efficacy of water treatment filtration and disinfection processes for coronavirus removal and inactivation?

The short answer: No — if we take proper precautions and risk considerations.

The long answer: This is a new virus without an extensive body of literature on the effectiveness of water and wastewater treatment processes. And real-life experiences will vary due to water quality and treatment plant details.

According to a 2008 University of Arizona study, coronaviruses have not been found to be more resistant to water treatment than other microorganisms such as E. coli, phage, or poliovirus — which are commonly used as surrogates for treatment performance evaluations. Results from bench-scale studies suggest that the survival of coronaviruses is temperature-dependent, with greater survival at lower temperatures. Therefore, coronavirus is expected to be reduced in raw wastewater and surface waters in warmer seasons. 

How is it transmitted?

Human viruses do not replicate in the environment. For a coronavirus to be transferred via the water cycle, it must have the ability to survive in human waste, retain its infectivity, and come in contact with another person — most likely via aerosols. Findings suggest that COVID-19 can be transmitted through human waste.

Should a major virus pandemic occur, wastewater and drinking water treatment industries would face increased scrutiny. Utilities would need to respond rapidly to minimize occupational and public health risks based on the available evidence. Wastewater effluents would possibly impact recreation, irrigation, and drinking waters. While wastewater treatment does reduce virus levels, infective human viruses are often detected in wastewater treatment plant effluent.

Information for wastewater treatment plant operators

Typically, human waste entering a sewage system is carried through an underground pipe system to a municipal treatment plant. Wastewater treatment plants receiving sewage from hospitals and isolation centers treating coronavirus patients — and domestic sewage from areas of known large contamination — may have elevated concentrations of viruses. Wastewater is treated by a variety of processes to reduce the pollution impacts on nearby receiving waters (lakes, rivers) and disinfected.

Currently, major data gaps exist on the potential role of the water cycle in the spread of enveloped viruses. The lack of detection methods for these strains of viruses is a main reason this type of information is still relatively unknown. Most detection methods are designed and optimized for non-enveloped enteric viruses, and there just isn’t enough information available.

In general, secondary wastewater treatment is credited with removing 1-log (90 percent) of viruses, though broad studies suggest the level of virus removal is highly variable, ranging from insignificant to greater than 2-log removal (99 percent). Because of this variability, the primary process for the inactivation of viruses in wastewater treatment is chemical disinfection (e.g., chlorination) and/or by ultraviolet light.

Drinking water treatment is an effective barrier

Surface-water treatment plants with upstream wastewater impacts are the most susceptible to having coronavirus contamination in the raw water supply during, and after, an outbreak. Viruses are exposed to several potentially inactivating stresses in surface waters, including sunlight, oxidative chemicals, and predation by microorganisms. Generally, enveloped viruses are more susceptible to common drinking water disinfectants than non-enveloped viruses.

Based on published research, water treatment processes that meet virus removal/inactivation regulations are effective for coronavirus control.

For example, drinking water quality guidelines from Health Canada note conventional treatment with free available chlorine can achieve at least 8-log inactivation of viruses in general. Of course, disinfection performance must be continuously monitored (e.g., turbidity, disinfectant dose, residual, pH, temperature, and flow). Optimized conventional filtration can achieve 2-log (99 percent) virus removal and is just one of many processes water treatment facilities incorporate to make our water safe to drink.

Modern drinking water treatment plants are well equipped to remove and disinfect viruses through filtration and disinfection processes.

So now what?

By and large, these viruses are not considered a major threat to the wastewater and water industries due to their low concentrations in municipal wastewater and high susceptibilities to degradation in aqueous environments. According to new OHSA guidance, there is no evidence to suggest that additional, COVID-19-specific protections are needed for employees involved in wastewater treatment operations.

The WHO found that risk communication and community engagement (RCCE) has been integral to the success of response to health emergencies. Action items related to coronavirus include communicating about preparedness measures and establishing a system for listening to public perceptions to prevent misinformation.


Basic recommendations for treatment-plant operators when dealing with a potential virus outbreak

So far, this virus does not appear to survive well in the environment and can be eliminated effectively by water treatment, especially chlorination, and would pose a minimal risk through drinking water. As the outbreak continues, more water-quality experiments are needed before major conclusions can be drawn on their fate within treatment processes. While this will be tricky, especially as viruses continue to replicate and evolve, quantitative risk assessments should be a top priority for enveloped viruses in wastewater, recreational waters, and drinking water.

Treatment-plant operators can download this white paper for more details on the current state of knowledge on coronaviruses as it relates to our practice. For additional reputable and reliable sources of information that are updated frequently with technical guidance, public health information, and the latest research visit the Water Environment Federation’s coronavirus site

Lead Photo: The spikes on the surface of coronaviruses give this virus family its name — corona, which is Latin for “crown.”

About the authors

Nicole McLellan is an environmental scientist. She has an academic background in environmental microbiology and civil engineering for drinking water treatment performance evaluations.

David Pernitsky is the global practice leader for water treatment. He has more than 25 years of environmental engineering experience, managing many challenging studies.

Arthur Umble is Stantec’s global lead for wastewater practice. He develops strategies and provides solutions for complex wastewater treatment challenges.

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Comments (9)

Geoff Jensen· 3 weeks ago

We must thank the authors for this sensible evaluation of the public health risks from Coronovirus Corvid 19. It would appear they are indicating that there are potential risks from Coronovirus in wastewater for example aerosols from uncovered activated sludge aeration tanks and in discharging untreated sewage into cold (bathing) water through Combined Sewer storm Overflows of which there are 31,000 in the UK alone.

Matthew· 2 weeks ago

Hmm, I have one of these uncovered sludge aeration tanks on the other side of my fence downwind of my garden and house. Seems I'm right to be concerned?

Ben Tangena· 3 weeks ago

Of course, chlorination, UV or Reverse Osmosis in drinking water treatment are effective barriers against all viruses, also coronavirus. But what will happen if such a barrier fails? Then the coronavirus can spread through the distribution system. What is the risk if you drink such contaminated water? In other words: Is the oral intake of coronavirus a significant route for infection?

1 reply · active 3 weeks ago

Vadim Malkov· 3 weeks ago

This is why we need to stick to WQ monitoring - you cannot control what you do not measure!

kondala rao g· 3 weeks ago

Very informative article and quite useful in understanding the impact of controlling corona viruses in water and wastewaters.

Joaquin Alayola· 2 weeks ago

Very good article, very focused, especially in this time of exaggeration and disinformation. Based on what the author has stated, I would like to highly recommend the reliable and sustainable online disinfection system (directly on the water stream): BlueSense OXAQUA manufactured in the Netherlands, is a natural generator of Electrochemically Activated Water (ECA Water). This system produces hypochlorous acid (HOCI) naturally in drinking water to disinfect flows of up to 10 m3 / hour, without adding chemicals or precursors such as sodium chloride (the concentration must be greater than 20 ppm of chlorides). OXAQUA also creates a residual oxidant up to the point of use by the end-user. OXAQUA uses chlorides naturally present in water to generate up to 2 ppm of free chlorine in the form of hypochlorous acid. This strong oxidant is known to prevent the spread of bacteria, viruses, algae, and molds in drinking water and hot water systems.

Ray Walton· 2 weeks ago

This info seems to be deliberately 'suppressed' here in the UK.

Is CORONAVIRUS - COVID-19 present in Raw Sewage? …

YES…AND STILL, THE RAW SEWAGE IS BEING DISCHARGED INTO UK RIVERS, STREAMS, CANALS, SEA, ETC. BY UK PRIVATISED WATER AND SEWAGE COMPANIES NATIONWIDE AND AUTHORISED BY GOVT AND THE ENVIRONMENT AGENCY… TO PROFITEER AND SAVE MONEY ON PROPER SEWAGE TREATMENT THAT WOULD SOMEWHAT LESSEN THE RISK OF SPREADING THE CONTAMINATION... THE PUBLIC PAY FOR RAW SEWAGE TREATMENT IN THEIR WATER AND SEWAGE BILLS.

Chris· 1 week ago

This comment is disturbing knowing I work with alot of people who work in the sewer still everyday even today.... I am self isolating after coming home out of country

Philip Monro· 3 days ago

Am I over concerned regarding the amount/concentration of "human sewage" if there are conference halls being filled with 2000 beds where the plumbing for that conference hall was never designed for the safe disposal/disinfection of "human sewage". Am I also being alarmist as to the low probability of the conference center's "wastewater supply AND THE MAIN DRAINS THEY ARE CONNECTED TO to being "with minimum / fast/temporary wastewater plumbing coping? FINALLY, if this error leads to massive, wider contamination (or even rupture of the system) just how will this significantly larger network of pipe-work be safely disinfected at ACCEPTABLE intervals and with potential repairs if ruptured? Dr. Philip Monro PhD