Action Level (AL) – the concentration of a contaminant, which if exceeded, triggers treatment or other requirements that a water system must follow.
Chlorine Residual – the amount of chlorine in water available for disinfection.
Disinfection By-product (DBP) – Chemical compounds that result from the addition of chlorine to water containing organic substances.
HAA (Haloacetic acids) – the combined concentration of the following five contaminants; Dibromo-, Dichloro-, Monobromo-, Monochloro-, and Trichloro –, acetic acids.
Inorganic Contaminant – chemical substances of mineral origin, such as iron or manganese.
Maximum Contaminant Level (MCL) – the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as possible.
Maximum Contaminant Level Goal (MCLG) – the level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.
Maximum Residual Disinfectant Level (MRDL) – 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.
Maximum Residual Disinfectant Level Goal (MRDLG) – the level of a disinfectant in drinking water below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
mg/l – (milligrams per liter) corresponds to one part of liquid in one million parts of liquid (parts per million or ppm).
Microbiological Contaminant – Very small organisms, such as bacteria.
N/A – not applicable.
nd – not detected at testing limits.
ng/l – (nanograms per liter) corresponds to one part of liquid in one trillion parts of liquid (parts per trillion or ppt).
NTU – Nephelometric Turbidity Unit - a measurement of particles in water.
Organics – substances containing the element carbon. These can be naturally occurring or man-made, and can include pesticides, solvents, and by-products of disinfection.
pCi/L – Pico curies per liter; units of concentration of radioactive substances.
Radionuclides– Contaminants giving off ionizing radiation.
TTHM – (Total Trihalomethanes) – the combined concentration of the following four contaminants;
Bromodichloromethane, Bromoform, Chloroform, and Dibromochloromethane.
TON (Threshold Odor Number) – The greatest number dilutions of a sample with “odor-free” water yielding a definitely perceptible odor.
Treatment Technique (TT) – A required process intended to reduce the level of a contaminant in drinking water.
µg/l – (micrograms per liter) corresponds to one part of liquid in one billion parts of liquid (parts per billion or ppb).
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