Many historians view the development of sewage systems as a crucial part of modern civilization. Humans instinctively find ways to reduce exposure to their own waste. Today, we have advanced systems to clean water of biosolid pollution and monitor disease spread within communities. This week, Water Treatment 411 will explore water’s historic role in public health, and how recent scientific innovations are changing that relationship.
Early Practices
In 3500 BC, wastewater sanitation was in its infancy. Mesopotamian residents had a system to carry waste to cesspits. A thousand years later, terracotta pipes in the Indus Valley civilization used gravity and simple physics to separate liquid waste from solids. Water sanitation slowly advanced until the 20th century, save for a scientific recession during the Dark Ages.
After the World Wars, the conversation shifted from management to treatment. Processes such as aeration helped, but they still struggled to control industrial growth. In the early 1970s, the U.S. passed the Clean Water Act to address water pollution from waste and chemicals. The act injected the industry with finances and education and is responsible for the system we know today.
Disease Monitoring
Wastewater monitoring can track the prevalence of several respiratory and infectious diseases, even in asymptomatic carriers. Dr. John Snow, the father of epidemiology, worked with officials in 1854 to detect the source of a cholera outbreak and the method of transmission before germ theory was even proven. A century later, we began regularly testing water as an early detection method. This water surveillance helped eradicate polio.
During the COVID-19 pandemic, PCR wastewater testing was used to limit outbreaks before they started. Epidemiologists didn’t have to wait for someone to test themselves after experiencing symptoms; they could monitor the water and alert communities when pathogens rose. This helped limit hospitalizations and the stress on healthcare workers and systems.
How do we do it?
About 1,500 wastewater surveillance sites submit data to the CDC each week. When a new site begins tracking, the CDC requires 8 weeks of data using the same lab method to avoid data fluctuations. After receiving this information, the CDC validates and logs it. After 2 years, experts can categorize wastewater viral activity levels (WVAL).
This thorough process ensures that data is evaluated considering its circumstances. If a rural community in Wyoming were evaluated the same way as densely populated New York City, the data may show low virality, despite a large quantity of confirmed cases.
You can find interactive WVAL maps for illnesses such as RSV, measles, monkeypox, and more on the CDC website. Despite its importance, this surveillance is in jeopardy as federal budget cuts could reduce the program from $125 million to $25 million, despite studies and public officials certifying its importance.
What’s next?
Now, new methods of observation and analysis widen possibilities of testing and treating diseases.
Some infectious diseases, such as norovirus, are typically concealed within vesicles. Historically, researchers struggled to pull this information from wastewater. But recent advancements allowed scientists to isolate and extract novel information. These new samples will offer a deeper understanding of how pathogens survive and spread and could inform a new age of wastewater treatment.
“Our findings … raise questions for wastewater treatment, water reuse, and public health protection, as current approaches may allow viruses hidden in vesicles to escape wastewater treatment,” said Yun Shen, an assistant professor in the study, in a conversation with Claire Sabin of George Washington University.
Some health departments are taking surveillance one step further to stop outbreaks. In Minnesota, a severe form of pneumonia, Legionnaires’ disease, was detected in the public water supply in 2023. Unlike most forms of pneumonia, Legionnaires’ is caused by waterborne pathogens. Some outbreaks are tied to specific treatment plants, such as in Flint, Michigan, where poor water quality and subpar infrastructure caused an outbreak that killed at least 12 people in 2014.
Researchers in Minnesota used chloramine disinfection to limit their outbreak. After 24 weeks of treatment, all samples from distribution sites and premise plumbing tested negative for Legionnaires’ pathogens.
Water systems and public health are closely tied in their history and goals. The relationship has evolved from instinctual habits to intentional prevention and now, diligent monitoring. But new research suggests the dynamic may be shifting again towards disinfection and treatment.
