Joan B. Rose, PhD, is an international leader in water microbiology, water quality and public health safety at Michigan State University. She co-directs both MSU’s Center for Advancing Microbial Risk Assessment (CAMRA) and its Center for Water Sciences (CWS).
Climate change is causing extreme weather like rain and flooding. Excessive amounts of rain overtasks septic systems, and the runoff is negatively affecting Michigan’s rivers and lakes. What needs to be done?
Most rural communities rely on wells for drinking water and on-site wastewater systems, namely septic tanks for handling the sewage generated by individual households, restaurants, hotels and other small businesses. In the U.S., about 60 million people rely on septic systems which is equivalent to about 25% of the population.
In Michigan, about 35% of the population uses septic tanks, which translates to about 1.3 to 1.4 million people. This means 560 million gallons of raw sewage per day are generated by these on-site systems.
Figure 1 shows the density of septic tanks in lower Michigan. The highest density is around some of our urban centers where development did not include sewers and treatment. Sewage contains hundreds of pathogens including bacteria like (Campylobacter, E.coli, and Salmonella) viruses (like adenoviruses and noroviruses) and protozoa (like Cryptosporidium and Giardia). The conventional septic tank is not designed to treat these pathogens and the systems rely on the soil to “remove” them. However, it is now known that bacteria, viruses and nutrients (phosphorous and nitrogen) move with the water from these drainfields as it travels toward ground and surface waters. Viruses, in particular, are so small that they can travel quickly as bio-nano particles with the water.
The studies in Michigan have used new human microbial fecal source-tracking tools to show large scale pollution in surface waters arises from septic system discharges — and transport was linked to rainfall.
Heavier rainfall events and flash flooding are on the rise, and this means higher frequency and intensity of heavy rainfall will likely be in our future.
Besides property damage, there are serious concerns associated with the rapid movement of viral and bacterial pathogens to both ground water and surface water, thus impacting both drinking water and recreational beaches in Michigan. Michigan is one of the few states without a state sanitary code and thus has fragmented regulation of septic tanks. This not only impedes assessment of the problem, but the solutions. Michigan has little information that could be used to guide the prioritization and funding of rural wastewater infrastructure using the dollars that will come into the state with the new Infrastructure Investment and Jobs Act. Our rural communities may be left out when it comes to modernizing wastewater collection and treatment or building key resource recovery facilities as part of a circular economy.
To achieve a resilient Michigan, while advancing our economy and protecting water quality and health, more effort is needed toward assessment and solutions. While development of a state sanitary code moves forward, the state can take advantage of the Michigan Network for Environmental Health and Technology which provides water quality testing and source tracking around the state. This knowledge can be used to address critical infrastructure needs for wastewater benefiting not only Michiganders, but the 40 million citizens that rely on the Great Lakes for safe drinking water, recreation and their livelihoods.
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