Healthcare Facility Wastewater
Can sanitary sewers be used for the disposal of Ebola-contaminated patient waste?
A sanitary sewer is a system of underground pipes that carries sewage and wastes from homes and other buildings to a wastewater treatment plant for disposal. The World Health Organization (WHO) states sanitary sewers may be used for the safe disposal of waste, such as feces, urine, or vomit, from patients with Ebola.1
At this time, there have been no reports of Ebola spreading through sewage.2,3 In the United States, wastewater treatment processes are designed to inactivate or remove infectious agents, making it unlikely that Ebola virus could spread through sewers.
Why can sanitary sewers be used for waste disposal from Ebola patients?
In the United States, human waste, blood, and other potentially infectious materials are routinely released into sanitary sewers. Wastewater treatment plant processes are designed to inactivate or remove human disease-causing organisms (pathogens), including bacteria, viruses, protozoa (such as Giardia and Cryptosporidium), and helminthes (parasitic worms).
Workers directly handling sewage pipes and in the prescreening stage of wastewater treatment are at the highest risks for exposure to disease-causing organisms. These workers should follow the guidelines provided in the CDC Interim Guidance for Managers and Workers Handling Untreated Wastewater from Suspected or Confirmed Individuals with Ebola in the U.S.(http://www.cdc.gov/vhf/ebola/prevention/handling-sewage.html) to prevent exposure to Ebola when working with untreated wastewater.
Have enveloped viruses like Ebola(http://www.cdc.gov/vhf/ebola/hcp/survivability-ebola-medical-waste.html) been transmitted to wastewater treatment plant workers?
In an enveloped virus, such as Ebola, hepatitis B, hepatitis C, and HIV, the core of the virus is surrounded by a lipoprotein outer layer. This lipoprotein envelope makes enveloped viruses more susceptible to destruction by numerous physical and chemical agents than viruses without a lipoprotein envelope (called non-enveloped viruses, e.g., norovirus, rotavirus, adenovirus, poliovirus).
Several studies have investigated wastewater treatment plant workers for evidence of infection or prevalence of antibodies (antibodies are proteins that are produced by the body's immune system when it detects harmful substances). The studies looked at both enveloped viruses and enteric non-enveloped viruses that can affect the gastrointestinal tract (stomach).
A few studies evaluated the prevalence of antibodies to hepatitis B, parainfluenza virus, and hepatitis C. Studies found a significantly higher prevalence of anti-hepatitis B virus antibodies in wastewater treatment plant workers, but other risk factors were not taken into account, such as sexual behavior, injection drug use, or possible exposure in the healthcare environment.4,5 These factors could have influenced the study results. Other studies reported a significantly higher prevalence of antibodies towards parainfluenza virus type 1.6 Another study reported two cases of hepatitis C in wastewater treatment plant workers.7 There have been no other published reports of infections of wastewater treatment plant workers with bloodborne pathogens such as hepatitis B, hepatitis C, or HIV, or other enveloped viruses such as Ebola or influenza.
Why does CDC not recommend disinfecting patient waste in the toilet?
For several reasons, the CDC does not currently recommend disinfection of patient’s waste in the toilet before disposal in sanitary sewer systems.
There are no published data on the effectiveness of disinfectants against viruses in human waste, such as feces and urine. Thus, there are currently no U.S. Environmental Protection Agency (EPA)-registered disinfectants approved for use against enveloped or non-enveloped viruses in feces, urine, or vomit in the toilet before their disposal in the sanitary sewer system. The EPA requires all disinfectants be used according to instructions on the product label. If the product is not used according to these instructions, there is no guarantee of its effectiveness.
In addition, viruses (including Ebola) will associate with particles and organic material in patient waste and be protected from disinfectant, thereby decreasing the effectiveness of the disinfectant.8 Organic and nitrogenous components of patient wastes will also react with disinfectants that are halogen-based (such as sodium hypochlorite, or bleach), further reducing the efficacy of disinfection.9
Lastly, there are safety concerns to healthcare workers and the patient when commercial bleach is used for this application. Bleach is a strongly corrosive agent and it may react chemically with organic compounds to produce harmful vapors.10 Use in this application would require additional ventilation of the patient’s room. Our current recommendations are consistent with the expert opinion contained in the WHO guidance.
Although CDC does not recommend disinfecting patient waste in the toilet, our facility may be asked to disinfect before discharge. What procedures have been used by other facilities to treat Ebola virus-contaminated waste prior to discharge into the sanitary sewer?
CDC recognizes that the wastewater treatment community and other stakeholders have concerns allowing waste to enter the sanitary sewer system. Wastewater treatment plant processes are designed to inactivate or remove pathogens; however, some wastewater treatment systems may require hospitals caring for patients with Ebola to treat the waste before discharge into sanitary sewers.
Various sources have used different approaches to treat waste before discharge in the U.S. based on their experience treating Ebola patients, including:
- Use portable toilets and add solidifying agents to the patient’s waste before disposal as Ebola-associated solid waste.
- Add a hospital grade disinfectant at the manufacturer’s recommended concentration to the toilet containing the patient’s waste, then hold the waste in the toilet for 2.5 times the recommended contact time before flushing.11
- Add bleach or quaternary ammonium compounds to the toilet containing the patient’s waste for 5 minutes before flushing (type and concentration of disinfectants used in this protocol were not provided to CDC).12
If you are a plumber or other facility worker responsible for addressing plumbing issues, you should be instructed by your employer if such pretreatment practices are used in your workplace. Please contact your employer if not provided.
What can healthcare facilities do to minimize the risk of Ebola exposure to facility workers responsible for addressing plumbing issues?
Healthcare facilities should minimize flushing of excess toilet paper or flushable wipes to prevent clogging, which can result in sewer backups. Routine maintenance on relevant sanitary sewer lines should be postponed until after the discharge of patients with Ebola from the hospital.
Survival in Wastewater
How effective are wastewater treatment processes at removing or inactivating Ebola?
Information is limited about the survival of Ebola in water and wastewater systems. However, there are abundant data about the survival of similar enveloped viruses in the environment. Ebola would be expected to respond similarly to other enveloped viruses, and would be inactivated more rapidly than the non-enveloped viruses. Dilution of the viruses in the wastewater system will reduce their concentration. In addition, the combination of virucidal agents and the biological, chemical, and physical properties of wastewater, such as pH, temperature, and the presence of predatory microorganisms that could breakdown the virus, are expected to effectively inactivate and remove enveloped viruses from wastewater.8
Source water from wastewater treatment plant discharges or runoff from waste-related biosolids pose minimal risk of Ebola exposure when applied to land in compliance with EPA requirements.13
How effective are septic systems at removing or inactivating Ebola?
Septic systems are onsite, clustered and decentralized wastewater treatment systems. Viruses are not significantly inactivated in septic tanks14 and septic tank effluents (liquid waste) may contaminate groundwater with enteric viruses that can affect the gastrointestinal tract (stomach).15,16 As the effluent from septic tanks percolates through the soil to groundwater, viruses and other pathogenic microorganisms are removed. To prevent contamination of the drinking water supply, septic systems should be situated to provide appropriate setback distances from groundwater supply wells.17,18
Survival in Drinking Water
How effective are drinking water treatment processes at removing or inactivating Ebola?
Notably, there are no case reports or epidemiologic data that Ebola can be transmitted through exposure to or consuming treated drinking water from surface water sources. If Ebola were present in surface water supplies used for public consumption, it would likely be destroyed by chemical disinfection methods used at water treatment plants. Although there are no published scientific studies on the detection of Ebola virus in water sources used for public drinking water, enveloped viruses like Ebola are more susceptible to chlorine disinfection than non-enveloped viruses.19,20 The required concentration of disinfectant with the proper contact time needed to achieve an EPA compliant 4-log10 virus inactivation (99.99%) using free chlorine are sufficient to inactivate non-enveloped viruses in drinking water, including rotaviruses, adenoviruses, and polioviruses. Chlorine dioxide and ozone disinfection are also effective for inactivating viruses.21 In addition, Ebola is more susceptible to UV radiation than other non-enveloped viruses.22
Can Ebola be spread through untreated public and private drinking water from ground water sources?
Under normal circumstances, the Ebola virus would be destroyed naturally before reaching any aquifer. The biological, chemical, and physical properties of the soil (such as pH, temperature, adsorption to surfaces, and predation by other microorganisms) would inactivate and remove the virus during transit through the soil and groundwater. Ebola is not expected to be found in untreated groundwater supplies in the absence of high levels of Ebola-contaminated sewage leaking directly into underground aquifers.
With regard to septic systems, the required setback distances between groundwater supply wells and potential sources of contamination (e.g., leaking septic systems) are expected to provide inactivation during virus transit through the soil.17,18 If there are cases of concern that untreated groundwater may have become contaminated with Ebola, public water suppliers and private well users should contact their local and state drinking water and health experts to determine if precautions are needed before the well water is used for drinking.