This week the City of Yuma self-reported several compliance issues to the Arizona Department of Environmental Quality (ADEQ). As required by law, the City is required to notify its customers of these issues. The City does want to assure the public that this is not an emergency, the City’s drinking water is safe and no action is necessary from residents. The City has taken several steps to resolve these issues and ensure this does not happen again.
A problem occurred with the City’s chlorine dioxide generator, and too much chlorine dioxide was released.
The City monitors its water system to ensure that its drinking water meets health standards set by the Environmental Protection Agency (EPA). The EPA regulates the maximum concentration of chlorine dioxide in drinking water to be no greater than 0.8 parts per million (ppm).
Chlorine dioxide is a water additive (disinfectant) used to disinfect drinking water - it helps make water safe to drink and destroys bacteria, viruses, and some types of parasites. In addition it removes unpleasant odor and taste.
The City recently learned water samples taken July 24, 2020 through March 6, 2022 at its Aqua Viva Water Treatment System revealed levels of chlorine dioxide exceeding the maximum levels for drinking water established by the EPA. During this time period there were 70 instances when the City’s chloride dioxide levels were higher than the standard set by the EPA, and ranged between 0.85 to 2.04 milligrams of chlorine dioxide per liter. Because additional testing of the drinking water was not conducted, the City cannot be sure of the quality of the City’s drinking water during that time.
Chlorine dioxide breaks down very quickly in the water system, dissipates within 48 hours, and can be removed through home reverse osmosis systems. However, according to the EPA, the potential health effects from long-term exposure of high levels of chlorine dioxide include anemia and nervous system effects in infants and young children.
As soon as the City became aware of these concerns, staff conducted an extensive review of its internal procedures, equipment, and data collection. The City took immediate action to correct the situation and reduce the chlorine dioxide levels in the drinking water to an acceptable level, including making the appropriate adjustments to its chlorine dioxide generator. Other operational changes have been made to ensure the efficacy and accuracy of the data being collected.
“Providing high-quality drinking water to our residents is the City’s utmost priority and as soon as the City realized there were concerns we contacted the ADEQ and notified you, our customers,” explained Acting City Administrator Jay Simonton. “We want to assure our residents that the City has taken swift action to resolve these issues to ensure that it does not happen again.”
This is not an emergency, and residents do not need to take any action. However, if you have specific health concerns, consult a medical professional.
Treatment Techniques
Separate from the issues discussed above, the City monitors for Total Organic Carbon (TOC) and alkalinity in its water supply. This information tells the City whether disinfection byproduct (DBP) precursors are being effectively removed from the water supply.
TOC is a measure of the amount of organic compounds contained in a water sample and is a good measure of water quality due to the fact that raw water with high TOC requires additional treatment before it is acceptable for consumption.
For almost 20 years, the City operated its water utility under an ADEQ waiver that did not require compliance with the TOC standard due to Yuma’s source water, the Colorado River, which has very low TOC levels.
In August of 2021, ADEQ determined the City did not qualify for the waiver and required the City to demonstrate compliance with the TOC removal standards. The City is required to remove an average of 15% TOC over a 12-month period, but the City’s average removal rate was 13% in 2021. Due to the City not achieving the necessary percentage removal of TOC, the City is not able to demonstrate the 15% level of DBP precursor removal and is required to notify its customers.
The City has been and continues to be in compliance with health standards for DBPs trihalomethanes (TTHMs) and haloacetic acids (HAA5s).
The City is working with the ADEQ to ensure the appropriate data is reported to accurately reflect the water quality being provided and will be able to demonstrate compliance with the requirements of the disinfection byproducts rule treatment technique.
Residents do not need to take any action.
Original source can be found here.
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