As we continue to note the changes brought by our collective COVID experience, there are a few that have potentially far-reaching effects that go beyond concerns about viral load. One of the more interesting has to do with the development of the National Wastewater Surveillance System by the Centers for Disease Control. The NWSS was launched in September of 2020 as part of the agency’s efforts to track the presence of SARS-CoV-2 virus in wastewater samples collected nationwide.
The benefit of such a broad effort is the ability to benchmark the scope of a virus’ penetration in an entire population. As we learned over the past couple of years, many people who are infected will be asymptomatic, excluding them from more conventional tracking data. Whether exhibiting symptoms or not, all of those infected will shed virus when using the toilet, however, allowing researchers to gauge the rate of serious illness across a population and levels of contagion for any particular “bug.” This information is useful in projecting the impact a virus may have on healthcare providers as well as aid in the pursuit of an effective vaccine.
The technique has flaws, to be sure. Communities served by septic systems will not provide any data from waste generated there. Any facility that pretreats waste as a matter of course will likely skew the numbers, and large institutions that have full or partial treatment facilities (prisons and universities, for example) are also not included in resulting data. Standard statistical practices do allow researchers to compensate for the quantifiable effects of these populations, however.
It's worth mentioning that the practice of Wastewater Surveillance predates out pandemic by quite a bit. One of the earliest documented uses of the underlying principles of WWS dates to the Broad Street cholera outbreak of 1854 in London. While germ theory had yet to be proven, Dr. John Snow applied early epidemiological theory by comparing water from disease-stricken households to those without disease. His research allowed local officials to trace the outbreak to a single pump on Broad Street.
Epidemiologists also used wastewater analysis to track and contain outbreaks of polio in the 1940s.
While development of our NWSS continues apace, the use of wastewater monitoring, like all technical advances, comes with growing concerns about its administration and the “laws of unintended consequences.” Beyond immediate pandemic concerns, those setting up facilities and processes need to address operational issues when the system is directed toward non-specific pathogens. What kinds of tests should be used? What is the optimal schedule for these tests to be run? What local environmental factors need to be considered? How will the ongoing effort be funded?
Last, but certainly not least, NWSS creates an interesting intersection between the ethical obligations associated with handling health data and the administration of public utilities. In the case of Covid, the extent of disease spread combined with the need for immediate solutions made the need for policies about individual privacy and data security secondary considerations. As the methodology becomes standardized and more wide-spread, attention is turning to the kinds of concerns covered by HIPAA regulations. As things progress, we’re seeing an increased focus on training personnel engaged in wastewater analysis in applicable ethical practices.
These efforts are being guided by guidelines established by the World Health Organization that can be summarized by the following steps:
When it comes to the role of engineers in making NWSS part of the WWTP development plan, we can add the efficient (and ethical) generation and management of data to the list of things we try to make easier and better.