Water Quality Terms to Know

All Consumer Confidence Reports carry listings of regulated substances found in water and charts showing measurement data about those substances. Yet, many people do not know the definitions behind those terms.

This page provides that information. In addition, the Environmental Protection Agency (EPA) and the Tennessee Department of Environment and Conservation (TDEC) prescribe regulations to limit certain contaminants in water provided by public water systems.

Fluoride
Fluoride is naturally found in nature among rocks, dirt, and water. As a chemical, fluoride is added to drinking water in very small, controlled concentrations to help keep your teeth strong and protect them from cavities.

Haloacetic Acids (HAA5)
These chemicals can form as by-products when water is disinfected with chlorine. They occur when the disinfectant mixes with natural substances in the water. There are five regulated compounds in the HAA5 group.

Nitrate
As a regulated substance in drinking water, nitrate typically comes from run-off from fertilizer use, leaching from septic tanks, sewage, and erosion of natural deposits.

PFAs (Per- and Polyfluoroalkyl Substances)
PFAs are a class of man-made chemicals used for decades in numerous industrial and consumer products ranging from nonstick pans to waterproof clothes to food packaging (and many others). Their strong carbon-fluorine bonds make them persistent in the environment, and they don’t break down easily. Because of this, scientists are continuing to measure their interactions with drinking water and effects on the human body.

Total Organic Carbon (TOC)
TOC is naturally present in our environment and may come from natural sources (decaying plant or animal matter) or synthetic sources (pesticides, fertilizers, detergents, and other chemicals). The concentration of carbon found in organic compounds present in water influences treatment efficiency and the formation of disinfection by-products.

Total Trihalomethanes (TTHMs)
This represents four specific disinfection by-products. TTHMs form when chlorine – or other disinfecting agents – react with natural materials in the water. Just like HAA5, they are carefully monitored to make sure drinking water is safe. The water treatment processes applied by Consolidated Utility District are designed to reduce TTHMs to levels well below the limits required by the EPA and TDEC.

Turbidity
Sometimes called “cloudiness,” turbidity measures the clarity of the water as an indicator that our treatment process is functioning properly. In our area, various kinds of river sediment and tiny inorganic and organic matter can contribute to turbidity. However, turbidity at the low levels in CUD’s water does not present any risk to your health.

Abbreviations found on water quality charts …

AL (Action Level)
The concentration of a contaminant that, if exceeded, requires treatment or other requirements that a water system must follow.

MCL (Maximum Contaminant Level)
As the highest level of a contaminant allowed in drinking water, MCLs are set as close to the MCLGs as feasible using the best available treatment technology.

MCLG (Maximum Contaminant Level Goal)
Below this goal, there is no known or expected risk to health. MCLGs allow for a margin of safety.

MRDL (Maximum Residual Disinfectant Level)
This refers to the highest level of a disinfectant allowed in drinking water. Addition of a disinfectant is necessary for the control of microbial contaminants.

ppb (parts per billion)
For reference, 1 ppb represents one part of a substance in one billion total parts — equal to one drop of water in a 10,000-gallon pool.

ppm (parts per million)
This unit of measurement defines very low concentrations of a substance within a mixture. For reference, 1 ppm is roughly equivalent to 1 drop of ink in a 55-gallon barrel of water, or 1 second in 11.5 days.

ppt (parts per trillion)
This measures extremely low concentrations, defined as one part of a substance in one trillion. This would equal one drop of contaminant in 18 million gallons of water or one second out of 32,000 years.