Learn about the different types of contaminants that might put your family at risk.

One of the elements (Mg) making up the earth’s crust, the compounds of which when dissolved in water make the water hard.  The presence of magnesium in water is a factor contributing to the formation of scale and insoluble soap curds.
An element (Mn) sometimes found dissolved in groundwater, usually with dissolved iron but in lower concentrations.  Causes black stains and other problems similar to iron.
manganese greensand
Greensand which has been processed to incorporate in it pores and on its surface the higher oxides of manganese.  The product has mild oxidizing power and is often used in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide, and their removal from water. 
manganese zeolite
Synthetic gel zeolite which has been processed in the same manner as manganese greensand and used for similar purposes.
mechanical filter
A filter primarily designed for the removal of suspended solid particles as opposed to filters with additional capabilities.
The selected materials in a filter that form the barrier to the passage of certain suspended solids or dissolved molecules.
Singular form of media.
The abbreviation of milligrams per liter.
microfiltration (MF)
The separation or removal of particulates of more than 0.02 μm or less than 10.0 μm size from liquids.
A linear measure equal to one millionth of a meter, or .00003937 inch.  The symbol for the micron is the Greek letter “μ.”
micron rating
The term applied to a filter or filter medium to indicate the particle size above which all suspended solids will be removed throughout the rated capacity.  As used in industry standards, this is an “absolute,” not “nominal” rating.
One thousandth of an inch.
The prefix used with units of measure to indicate one thousandth of the unit.  Example: a milliliter is one thousandth of a liter.
milligram per liter (mg/L)
A unit concentration of matter used in reporting the results of water and wastewater analyses.  In dilute water solutions, it is practically equal to the part per million, but varies from the ppm is concentrated solutions such as brine.  As most analyses are performed on measured volumes of water, the mg/L is a more accurate expression of the concentration and is the preferred unit of measure. 
A unit of length equal to one thousandth of a micron often used to express the wavelength of colors of visible light in colorimetric analytical procedures.  The symbol for the millimicron is “mμ.”
A term applied to inorganic substances, such as rocks and similar matter found in the earth strata, as opposed to organic substances such as plant and animal matter.  Minerals normally have definite chemical composition and crystal structure.  The term is also applied to matter derived from minerals, such as the inorganic ions found in water.  The term has been incorrectly applied to ion exchangers, even though most of the modern materials are organic ion exchange resins.
mineral acidity
Acidity due to the presence of inorganic acid such as hydrochloric, sulfuric, and nitric acid, as opposed to acidity due to carbonic acid or organic acids. 
The molecular weight of a chemical compound expressed in grams.
The simplest combination of atoms that will form a specific chemical compound; the smallest particle of a substance which will still retain the essential composition and properties of that substance and which can be broken down only into atoms and simpler substances.
most probable number (MPN)
The term used to indicate the number of organisms which, according to statistical theory, would be most likely to produce the results observed in certain bacteriological tests; usually expressed as a number per 100 ml of water.