Water Reuse and Quantitative Microbial Risk Assessment
This study allows us to better understand the quality of harvested storm water and rainwater used for purposes other than drinking water. If there are pathogens present in the system, we will be able to estimate the risk of infection from exposure to these pathogens. The results of this study could be applied to other water reuse systems and might also be used to create treatment recommendations to ensure human health is protected.
On average, each person in the United States uses 100-150 gallons of water every day. Usually, this water comes from the same sources that provide drinking water, even though most is not used for drinking, but for flushing toilets, washing clothes, watering lawns, and other activities. The high demand for water in Minnesota means that, in some places, we are draining our drinking water resources faster than they are refilling. Reusing water is an alternative solution for non-drinking water demands, and some cities and organizations in Minnesota have already started reusing water. However, water reuse is relatively new in the state of Minnesota, and the possible health risks of reusing water are not well understood. In addition, the water treatment guidelines for water reuse are currently limited.
Currently, two systems are being studied for this project. One is a city park irrigation (watering) system that uses storm water from a collection pond to water ball fields. The second is a residential building using rainwater collected from the roof to flush the toilets. Sampling is ongoing at these two locations. From analysis of the samples, we hope to learn more about the quality of the water in the systems and if it changes under various conditions, such as after an intense rainfall or during extremely hot weather. Once we know what pathogens, if any, are present in these water reuse systems, the Health Risk Assessment (HRA) unit of MDH will conduct the QMRA portion of the study.
QMRA is a method that uses mathematical equations to estimate the probability that someone would be infected from exposure to water containing pathogens. By using QMRA, we not only know if there are pathogens present in the water reuse systems, but if their presence will have an impact on health. The results from our QMRA study will tell us if there is reason to be concerned over the amount of pathogen present in the system and if it is necessary to take further steps to protect public health.
$1,150,000 the first year and $1,150,000 the second are for addressing public health concerns related to contaminants found in Minnesota drinking water for which no health-based drinking water standards exist, including accelerating the development of health risk limits, including triclosan, and improving the capacity of the department's laboratory to analyze unregulated contaminants.
- From analysis of the samples, we hope to learn more about the quality of the water in the systems and if it changes under various conditions, such as after an intense rainfall or during extremely hot weather.
- The results from the QMRA study will tell us if there is reason to be concerned over the amount of pathogen present in the system and if it is necessary to take further steps to protect public health.