A recent study in the onsite wastewater industry has implications for treatment plant employees. Find out where your greatest risks might be and how you can increase protection.


A study of pathogen risks for those who work in the onsite wastewater industry has some interesting implications for those who work in treatment plants. Although the work might be different, professionals in both fields work with the same material — human waste.

The study by the Washington On-Site Sewage Association was funded by a $138,000 Safety and Health Investment Project Grant from the Washington State Department of Labor & Industries. It looked at risks for those who service household septic tanks.

“Whatever illnesses or infections they [residents] have are in the sewage,” says WOSSA Executive Director John Thomas. “The infective dose threshold for many pathogens is quite low.”

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The study, which included field sampling, task observation and laboratory analysis, found risks can be minimized with the proper use of personal protective equipment (PPE). However, the study also concluded much of the PPE in use does not adequately provide protection from  pathogens.

Common risks
Sewage contains hundreds of known viruses, bacteria, protozoa and parasites. But some of WOSSA’s finding were a bit surprising. “We found viable MRSA bacteria — a staph infection resistant to antibiotics — in liquid sampling,” says Thomas.

One worker was hospitalized for a week with a MRSA infection of his face and sinuses.

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“We also had positive tests for a family of bacteria that includes chlamydia, a sexually transmitted disease, from aerosolized wastewater being dumped at a septage handling facility.”

Other documented illnesses involved such things as pinkeye, intestinal infection from the Giardia parasite, hepatitis and illness from E. coli.

“Public beaches are closed in Washington when E. coli reaches 126 colony forming units per 100 mL,” says Thomas. “In our field samples, raw sewage commonly contained 160,000/100 mL.”

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Direct contact with wastewater is an obvious source of exposure. Thomas says the most surprising finding was the scope of inhalation exposure, which occurred in tasks common to working with onsite systems and treatment plants such as jetting, back-flushing and pumping residual water after washing down tanks. Positive samples were found as far as 60 feet away.

“Our testing showed the aerosol cloud was much bigger than we thought,” says Thomas.

PPE findings
Thomas says many workers in the onsite field wear nitrile (rubber) gloves, but they are probably wearing the wrong kind. Those rated for “industrial use” or “food handling” are not appropriate for working with wastewater. Thomas says exam grade gloves, also called “medical grade,” are the only type of nitrile gloves that will protect from pathogens. Typical work gloves, of course, provide no pathogen protection.

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“A lot of employers provide dust masks or other kinds of face masks,” says Thomas. “Upgrade them to an N95 surgical mask, sometimes called a procedure mask, and that will give appropriate protection for airborne pathogens. One field test of an N95 mask showed it had more than 10,000 colonies of bacteria on it. A simple dust mask is not designed to protect a worker from that kind of exposure.”

As for eye protection, he says, workers should protect against splashes, sprays and airborne aerosols from multiple angles: “Goggles are sometimes needed rather than just a pair of safety glasses.”

Spreading the word
Thomas is now presenting the findings to onsite professionals in Washington using a lesson plan developed with assistance from the state’s Safety and Health Investment Project. The material is available to others to educate those who work with sewage.

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Among the recommendations being taught are basic hygiene rules for workers, such as:

  • Wash hands after working with waste, especially before eating or drinking.
  • Avoid touching the face, mouth, eyes, nose or open sores and cuts.
  • Wash hands with soap and water before and after using the toilet.
  • Before eating, remove soiled work clothes and eat away from sewage-handling activities.
  • Do not smoke or chew tobacco or gum while handling sewage.
  • Keep open sores, cuts and wounds covered with clean, dry bandages.
  • Gently flush eyes with safe water if sewage contacts the eyes.
  • Wear rubber boots at the work site and during transport of sewage.
  • Remove rubber boots and work clothes before leaving the work site.
  • Wash contaminated work clothing daily with 0.05 percent chlorine solution (one part household bleach to 100 parts water).

Thomas’s message to employers is simple.

“Reducing exposure to pathogens is a responsibility under OSHA’s General Duty Clause to provide a safe workplace. There are simple steps they can do that — without costing a lot more money than they’re spending now — will make sure their employees are adequately protected.”


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