Microbiologist Investigates Link Between Failing Septic Systems & Illness

Because viruses can travel fast from a failing septic system to a drinking water supply, pumpers are an important part of a public health plan.

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Mark Borchardt has studied the relationship between septic systems, groundwater and disease for many years. What he found has meaning for pumpers, the people who write septic codes, and the millions of people who depend on septic systems to treat their wastewater and wells to provide their drinking water.

Borchardt has a doctorate in microbiology and works at a central Wisconsin laboratory funded by the U.S. Department of Agriculture and the U.S. Geological Survey. In September 2012, he and several colleagues published a study of disease-causing virus DNA in the well water of 14 communities. All 14 showed traces of at least one virus, and like most groundwater-based systems these did not disinfect the incoming water.

Another study found a greater risk of viral diarrhea in areas with a high concentration of septic systems and holding tanks. A third study described what happened in northeastern Wisconsin when a fitting on a restaurant’s new septic system broke. Although the broken fitting contaminated water with norovirus — causing disease in 229 people and putting six of those in the hospital — the real surprise was how rapidly viruses move through soil under the right conditions.

Pumper: In the restaurant case, you introduced two dyes of two different colors into the system — into a toilet in the building and at the pump sending effluent to the drainfield — and both showed up in the restaurant’s well water very quickly?

Borchardt: There was a broken fitting on one of the septic tanks, so contaminated water from that reached the restaurant well in only six days. The drainfield was quite a distance away, but contaminated water from it reached the well in 15 days. That is not nearly enough time to make water safe. Norovirus can live in groundwater for up to two years, and we know viruses move through soil faster than dye because being particles they are forced to find openings in the aquifer, unlike dissolved dye, which is slowed by diffusion into the aquifer material. You need time and distance so viruses can be filtered out by soil particles and die along the way.

In this part of Wisconsin the aquifer is in dolomite. Once a virus gets into the bedrock there’s very little filtration, and a virus can move quickly through fractures in the rock. Think of a well three-dimensionally. It intersects all the fractures in the rock. Just by bad luck, when that well was drilled it connected through a network of fractures to the drainfield.

No one ever figured out why that fitting broke. The message is to take care during construction. When we investigated this we ignored the new system because it was new. It was up to code. But as the evidence accumulated, it pointed to the septic system. The investigation concluded it was probably one ill worker, who was sick at work, who shed the virus into the wastewater system. You don’t need much. Just 10 viruses are enough to start an infection.

It’s understood among longtime residents there, in spring you just don’t drink from your well. They call it the brown-water season. Everything from the surface is being flushed through the bedrock by the spring rains.

Pumper: What does this say about septic codes?

Borchardt: It suggests states may have to rethink how they set standards. Right now in Wisconsin we have a single code. It’s a one-size-fits-all proposition for a state that is one of the most hydrogeologically diverse states in the nation.

There is good evidence that most disease outbreaks happen in areas where the bedrock is karst. That’s limestone eroded by the movement of groundwater, and you see ridges and sinkholes. We know there have been disease outbreaks around the nation because of geology. I thought I had discovered something new at the restaurant, but then I found newspaper headlines from the 1950s talking about the same sort of well contamination.

Counties are slowly coming to grips with weaknesses in their codes. It becomes a property rights issue. Every couple of years some legislator in Wisconsin introduces a bill to allow people to dispose of wastewater as they choose, even by spreading it on their own land.

In my part of Wisconsin the soil is not conducive to septic systems, and a lot of people have holding tanks. Pumping them is expensive so some people don’t, and then the tanks overflow. Some people run a pipe to the nearest ditch to channel the effluent off their property, and children play in the contaminated soil and pick up diseases. In one case a tank overflowed, and rather than fix the tank the owners built a footbridge over the effluent stream.

Pumper: Does this upend our assumptions about how well traditional septic tanks work to stop the spread of disease?

Borchardt: No. They do work. It’s a good technology, and it has allowed a lot of people to live out in the country. Problems are related to the factors I alluded to: the amount of filtration in the soil and the time it takes for groundwater to move. You could add loading, the amount of wastewater we’re putting into the soil.

This is what our study of septic and holding tank concentration showed. What you have to do is somehow break the cycle in which pathogens move from wastewater to groundwater and then into drinking wells. If wastewater systems are so advanced that no contaminants reach groundwater, you could drink that water and you would be fine.

At the restaurant they put UV disinfection on the well water. I would prefer the wastewater system be improved because that would prevent groundwater contamination in the first place.

Pumper: Do we know how large a problem faulty septic systems are?

Borchardt: There’s been no real research on that at the national level. Our 2003 study of septic system density and illness was surprising, but it was tough for me to put together even the $60,000 to fund that. The U.S. Centers for Disease Control was interested in this subject around the year 2000, but then 9/11 happened and priorities shifted. Recent research by the U.S. Environmental Protection Agency has focused on urban systems.

Pumper: What could pumpers do to help? For example, would it help to pay attention when people complain about stomach flu or other intestinal illnesses?

Borchardt: No. That sort of information — called anecdotal evidence by people who track diseases — is not worth much because there are too many possible explanations. There is much, much more that needs to be done before specialists can declare an outbreak.

The best thing pumpers can do is do their jobs well. What they do is a public health service. They’re in the job of preventing disease outbreaks. It may not be advertised that way, but it is, and it is a very important link in the system to keep people alive and healthy.



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