Our June COVID-19 webinar covered wastewater surveillance and how wastewater agencies can help monitor the spread of the virus in communities.
The webinar was sponsored by WEST YOST.
COMING-UP: The next CASA-CWEA COVID-19 webinar is on July 22nd. The title is Overcoming O&M Challenges to Maintain Essential Services. The webinar is free for water and wastewater professionals.
Member Questions and Answers
Questions from members and answers by our COVID-19 webinar speakers. Q&A compiled from our last three webinars.
Has infective coronavirus been found in wastewater?
WEF answer: To date, the scientific community has found no evidence of viable COVID-19 virus in wastewater systems. While there is still a lot we don’t know, it appears that contracting COVID-19 through exposure to wastewater is unlikely. Read more details at wef.org/coronavirus
CDC answer: Currently, there is no evidence that coronavirus survives the disinfection process for drinking water and wastewater.
- The COVID-19 virus has not been detected in drinking water.
- The risk of transmission through feces is expected to be low based on data from previous outbreaks of related coronaviruses, such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).
- At this time, the risk of transmission of COVID-19 through sewerage systems is thought to be low.
No coronavirus-specific protections are recommended for employees involved in wastewater management operations, including those at wastewater treatment facilities.
I keep hearing about the virus RNA, what is the difference between RNA and DNA when it comes to transmission?
CDC Answered: Some viruses have RNA, others have DNA. This doesn’t tell us much about transmission or infectivity. COVID-19 virus is an RNA virus. Molecular methods that are being used for detection of the virus in wastewater rely on the detection of fragments of nucelic acids (so RNA in this case), which is why you keep hearing about it. But as the speakers will mention today, detecting RNA does not mean the virus is infective.
Do we find COVID-19 virus in human feces?
CDC Answered: Virus RNA has been detected consistently in patient feces but that doesn’t tell us much about infectivity or the virus in feces. Infective virus data is more contradictory.
To this date, only two studies (Zhang et al., 2020a; Wang et al., 2020) were able to detect infective virus in feces. These studies confirmed viral persistence with electron microscopy but did not quantify the viral particles detected.
A study by Wolfel et al. (2020) in Nature suggested they were unable to isolate infective COVID-19 virus. It is difficult to estimate the number of studies unable to isolate infectious virus in feces since scientific studies do not usually publish negative results (i.e., when the virus is not detected) as it may only be a reflection of deficiencies in sample collection, preparation, or analysis.
Can the virus get into the eyes of individuals?
CDC answered: Yes, contact with mucous membranes can result in infection. That’s why using eye protection, not touching your eyes/face after handling wastewater is very important and frequently washing your hands is important.
Please explain why it is known as COVID-19?
CDC answered: COVID-19 stands for Coronavirus disesase 2019 (because it was identified in the 2019 outbreak in Wuhan). COVID-19 is the disease. The COVID-19 virus is known as the coronavirus and scientifcially as SARS-CoV-2.
Any concerns about virus entry from cuts or scratches on arms, legs or hands?
CDC answered: There are many pathogens that can enter the body through cuts and result in infections. In general, the CDC and OSHA recommend that workers:
- Keep open sores, cuts, and wounds covered with clean, dry bandages.
- Avoid touching face, mouth, eyes, nose, or open sores and cuts while handling human waste or sewage.
- Use waterproof gloves to prevent cuts and contact with human waste or sewage.
The hyper-sterilization we’re told to follow has a risk of creating “superbugs” for which there will not be any effective vaccine or bugs that are no longer destroyed by sterilization methods. How is CDC addressing this?
CDC answered: CDC is continuing to monitor antibiotic resistance in hospitals and in the community. Additionally, we are conducting studies to specifically examine the impact of COVID-19 on antibiotic resistance.
Does operating a hydro flushing truck where mist or vapor would come up out of a manhole is there a risk of potentially getting infected?
WEF answered: We will be studying that soon and hope to have some data. Recommend N95 or some other type of respirator and not just concern with SARS-CoV-2 but other viruses in wastewater as well. Recommend PPE if jetting in the sewer lines. Read our interview with three collection system leaders.
I am hearing words like “thought to” or “we think” is the virus infective in wastewater or not?
WEF answered: Unfortunately, there is a lot we don’t know about COVID-19 virus. What we do know is wastewater is full of other pathogens that are more resistant than coronaviruses and wastewater workers need to be protected from. As a result, our regular protective practices should work for this virus as well.
Can the virus live in soil and in land applied biosolids?
WEF answered: Not expected to survive very well. It’s much more susceptible to inactivation than other traditional water born viruses. The virus is very sensitive to heat so even mesophilic digestion should inactivate it very readily.
Is it thought that there is any more risk of infection for wastewater collection system workers and is there any studies being conducted regarding collection system exposure level?
WEF answered: The closer you are to the source (i.e., the positive case), the higher the likelihood that infective virus may be present. This is partially because we expect some environmental die off of viruses in the collection system and because our staff at WWTP interact with all matrices not just raw sewage at the headworks. WEF is conducting research on collection system and wastewater exposure caused by aerosals.
How bad is coronavirus mutation?
CDC answered: Viruses can always mutate, however we don’t think the mutation rate in this virus is very high, not like HIV where mutation occurs very rapidly. There was a story on the news recently about a mutation but the short answer is that we don’t think that is being interpreted correctly. We have seen no evidence that it is becoming more or less infectious over time, mutations or not.
We have heard the coronavirus can infect cats and dogs, could the coronavirus infect fish?
CDC answered: There is no evidence, from the US or other countries, that the SARS-CoV-2 can survive wastewater treatment and be present in plant effluent. Raising the disinfectant in effluent has other environmental and health impacts, so it should not be done without cause.
There is no evidence that the virus can infect fish. More information on COVID-19 and animals can be found here.
What are some other examples of viruses that are more resistant to disinfection than the coronavirus?
CDC answered: Any enteric, non-enveloped viruses like Norovirus, Adenovirus, Rotavirus, Poliovirus, etc. Coliphages are also expected to be conservative predictors of COVID-19 removal.
Is there risk of contracting the virus from a swimming pool or a hot tub?
CDC answered: The risk from disinfected water systems such as pools and hot tubs is thought to be very low. It is important to maintain social distancing while using these facilities.
Is there a minimum time someone is considered “exposed” with a mask or without a mask when less than 6 feet apart?
CDC answered: There is no minimum time. Close contact is defined as
a) being within approximately 6′ (2 meters) of a COVID-19 case; close contact can occur while caring for, living with, visiting, or sharing a healthcare waiting area or room with a COVID-19 case
– or –
b) having direct contact with infectious secretions of a COVID-19 case (e.g., being coughed on)
Why does the coronavirus lose its spikes (receptors)?
CDC answered: The virus is susceptible to chemicals found in wastewater, and there are enzymes in the wastewater (RNAases) which can rapidly break down the exposed RNA molecule.
In wastewater, how long does it take for the virus to die when exposed to a diluted disinfectant in wastewater?
CDC answered: We do not have data on this virus in sewage. We are basing our assessment on the closely related SARS virus. SARS virus can be inactivated by chlorine in sewage in 10 minutes or less depending on the disinfectant dose and residual. Chloramines are less effective. This data is from a paper by Wang et al.
What lessons did we learn from the 2003 SARS outbreak at the Amoy Garden apartment complex in Hong Kong? A broken sewer line may have contributed to the spread with no direct physical contact.
CDC Answered: Great question. There is a good paper on this in The Lancet by Gormley et al. (2020): click here to open the report. The review highlights important lessons that can be adapted based on the lessons we learned from the SARS outbreak in Amoy Gardens.
Wastewater Based Surveillance
Do researchers find the COVID-19 in the plant effluent? Should we raise the chlorine residual to kill the virus if possible?
CDC answered: The virus has not been detected in effluent when it was detected in influent. This supports our understanding that the treatment methods and disinfection are sufficient for inactivating the virus and no changes are needed.
What does PCR stands for?
CDC answered: Polymerase Chain Reaction. It is a method widely used in molecular biology to rapidly make millions of copies of a specific part of RNA or DNA that is unique to the target organism you’re trying to detect in your sample.
Is there a better virus detection method than PCR?
CDC answered: There are cell culture assays. These would help us understand virus infectivity and survival better; however, these are difficult to conduct and often require additional safety precautions in the lab (Biosafety Level 3).
Has there been any tests actually looking for intact virus?
CDC answered: Studies have looked for infectious, intact virus in stool. As Dr. Charles Gerba presented, some studies have reported infectious virus and some have not. There are limitations to each of those studies, so it is still unclear whether infectious virus is present in stool.
What is concentration efficiency?
WEF answered: The detection of viruses usually requires their concentration from large volumes of water/wastewater. In the case of untreated wastewater, only a liter is often needed, but when assessing water/ wastewater treatment processes volumes of 10 to 1000 L are often processed to reach appropriate equivalent sample volumes.
The type of virus and its physicochemical properties play a role in the efficiency of the concentration process. Manipulation of sample can result in changes in pH, addition of adsorbents and eluents have differing effects on different viruses.
Should we consider using robots to collect sample to protect the wastewater worker?
WEF answered: Not to my knowledge. Composite samples are collected over 24 hours and brought to the lab when ready for analysis by Ops. When grab samples are required, things get trickier and are often collected by lab staff.
Safety practices have been put in place for labs running PCR on wastewater samples where the samples are pasteurized (heat treated) first to reduce risk of infection with COVID-19 virus.
What is the CDC’s current recommendations for localities on whether or not to conduct wastewater surveillance monitoring?
CDC answered: CDC is not recommending widespread wastewater monitoring for COVID-19. Monitoring for other contaminants should continue.
Knowing that COVID is widespread, but that concentrations vary by location: Can sewage testing determine the magnitude of community infection?
CDC answered: We are currently evaluating models to determine whether sewage virus concentrations can be used to estimate community infection.
How will WBE surveillance likely be financed? From county and municipal operating budgets?
CDC answered: Discussions are ongoing to determine how this work can be funded.
What is the expectation for sentinel sites for sample taking purpose? Would they be in randomized parts of the collection system or solely at end of system?
CDC answered: We are currently working to understand that. It could be that different sampling schemes are needed for different communities or different goals.
Do we have any information on what effect pre-chlorination at a wastewater treatment has on the detected concentration of SARS-CoV-2?
CDC answered: There is limited anecdotal information suggesting that pre-chlorination reduces the detection of SARS-CoV-2. Understanding this issue and how widely this is implemented will be critical for actionable sewage surveillance.
What level of granularity is needed to contain localized pandemic outbreaks? For example, sampling at the utility level may not be sufficient to manage outbreaks and minimize impact to local populations.
CDC answered: You are correct. We are currently evaluating what sampling schemes are needed to accomplish specific goals. Community prevalence can likely be assessed at the plant. Understanding neighborhood differences or impacts of specific facilities (universities, prisons, hospitals) may require more sampling within the collection system.
Does the composite sample need to be refrigerated during collection period?
CDC answered: Refrigeration during collection and transport to the lab is ideal to prevent decay of the virus signal.
Can you account for sewer dilution by expressing virus level per gram of TSS (assumes TSS is proportional to amount of feces present)?
CDC answered: TSS is one of the variables we are considering for normalization. Although it is an imperfect measure of fecal input, it does have the advantage of being easily measured.
Are there any initial findings in which wastewater collection system pretreament chemicals for odor control skew research outcomes for the virus?
CDC answered: I am not aware of any assessments of odor control treatments on SARS-CoV-2 detection, but we will keep that in mind as we review data.
What are the lower limits of detection to be able to quantify the concentration of RNA, not just detect the presence of the RNA?
CDC answered: In practice we have seen detection limits hovering around about 1,000 copies per liter if you take into account recovery as well as processing because when you do the testing you do all the concentrations as Jay mentioned you are only actually testing a subset of that one liter sample after the concentration. SO that is where our effective detection limit seems to be right now. But there are definitely a lot of detections in wastewater systems right now because there are a lot of cases.
We’ve been speaking with other countries that are now in a case free period, which makes it a very interesting discussion about how they might be approaching sampling and volumes and needing to process tens of liters in order to have a meaningful interpretation of that, which makes the method different and standardization change.
What should be the goal for time between sampling and results availability?
CDC answered: To be useful for public health action, the turnaround time from sample to result will need to be quite short, measured in days.
Are any resources yet available to guide how wastewater should be sampled, i.e. headworks, lift stations, or in septic tanks for large decentalized systems?
CDC answered: We are still evaluating sampling designs and developing guidance and best practices for this work.
Are there other population surveillance methods in addition to WBE?
CDC answered: Antibody testing can provide information on population-level infection numbers that include asymptomatic infection, however, these tests have not been incorporated on a broad scale. The existing surveillance methods all rely on some medical care, at least to get tested.
Use of a vaccine with the antigen (in 6-8 months when developed) will make data harder to interpret the sewer data?
CDC answered: It depends on the type of vaccine. Live virus vaccines could be detectable in sewage, as they are for polio. Inactivated or component vaccines are unlikely to be detected in sewage.
Utility Responses to the Pandemic
For alcohol-based hand sanitizers, is there a recommended minimum contact time for maximum effectiveness, or is the disinfection effectiveness immediate upon contact?
CDC answered: Kampf et al. (2020) conducted a meta-analysis reviewing 22 published papers evaluating the survival of human and veterinary coronaviruses on inanimate surfaces.
They report that coronaviruses can survive on surfaces up to nine days and that good disinfection practices can be protective.
They recommend a dilution of 1:50 of 5% sodium hypochlorite (resulting in a final dilution of 0.1%) or 0.5% hydrogen peroxide, and a contact time of 1 minute for larger areas. For smaller areas, they recommend 70% ethanol (62% to 71%; carrier tests) for one minute as per WHO recommendations.
If N-95 masks are only for healthcare workers, what do you recommend for wastewater and construction workers to use for face mask when they have to be at closer than 6′ from each other for work?
CDC answered: Cloth face coverings are not the same as PPE face masks like N95s. For working near others, a cloth face covering that covers your mouth and nose, fits closely to the sides of your face, and has two layers of tightly woven fabric is recommended.
What is considered high temperature when doing temperature checks on employees?
EBMUD answered: 100.4 degrees F or higher
What is the cost of the wastewater testing for COVID-19? Also, is the test just showing the presence or does it show the an infection rate?
EBMUD answered: For us, the main cost was sample shipping and staff time. We did not have to pay for the analysis. The test currently only shows presence and concentrations of virus RNA. This doesn’t imply infectivity or risk. The main purpose of this work is aiding public health decision making.
What do you think about using UVC equipment to disinfect employee offices (in adiditon to typical cleaning)?
CWEA response: read “The Power of UV Light in Fighting the COVID-19 Pandemic” a new UV research article by Paula Hansen and Artem Dyachenko from EBMUD
The CDC has provided UV disinfection guidance on their website.
Why is the focus only on feces? What of sputum? We know it has infective virus. Is there concern that the portion of SARS-CoV-2 from spututm is infective, even if that from feces is not?
CDC answered: We would expect some infective virus to reach our plants from saliva, respiratory secretions, possibly urine, etc. We often discuss feces because the virus concentrations in volume/weight of feces/urine tend to be highest, shedding is constant throughout the day and organic matter/nutrients in the matrix is protective resulting in longer survival.
How are your employees being tested? Are they going to testing sites?
EBMUD answered: We don’t test on site. There is a location nearby that is set up because we are essential workers, wastewater operators and lab staff. Completely voluntary and team members can go every two weeks.