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Coronavirus And
The Water Cycle
Here Is What
Treatment Professionals Need To Know
.
This is a new virus without an extensive body of literature on
the effectiveness of water and wastewater treatment processes - 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
By Nicole McLellan, David Pernitsky, and Arthur Umble
The spikes on the
surface of coronaviruses give this virus family its name — corona, which is Latin
for “crown.”
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 for 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.
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.
 |
| Basic recommendations for treatment-plant operators when dealing with a potential virus outbreak |
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 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.
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 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.
https://www.wateronline.com/doc/coronavirus-and-the-water-cycle-here-is-what-treatment-professionals-need-to-know-0001
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