Glossary
MRDL: Maximum Residental Disinfectant Level: The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
MRDLG: Maximum Residential Disinfectant Level Goal: This is the lowest amount of disinfectant chemical drinking water should have, because it is the lowest amount needed to make sure bacteria and viruses can't live.
MCL: Maximum Contaminant Level: This is the highest level allowed of a pollutant in drinking water. MCLs are set as close as possible to the goal using the best available technology.
MCLG: Maximum Contaminant Level Goal: The goal level of a pollutant in drinking water. Below this amount, there is no known or expected health effect.
NTU: Nephelometric Turbidity Units, measure of very small particulate matter in water.
ppm: parts per million, or milligrams per liter (mg/l), the equivalent of 1 cent in 10 thousand dollars or 1 drop of water in a hot tub.
ppb: parts per billion, or micrograms per liter (ug/l), the equivalent of 1 cent in 10 million dollars or 1 drop of water in an Olympic-sized swimming pool.
ppt: parts per trillion, o nanograms per liter (nanogram/l), the equivalent of 1 cent in 100 million dollars or 1 drop of water in a 6-acre lake.
TT: Treatment Technique: A process that is required to reduce the amount of pollutant in drinking water.
