Particulate matter is material which is non-soluble inorganic or organic impurities that may be exist in a water supply. It can be considered as the residue present on a filter media after water is passed through the filter. These can be related to total suspended solids determined by a Standard Methods No. 2540-D. It is important to mind the fact that total suspended solids should not be correlate with the definition of Total Solids.
Definition of particulate matter in water must reference a size. In general, particles become non-visible when the size is less than 40 µm. For water purification applications, it appears appropriate to define as the no dissolved inorganic and/or organic material that will be removed by a particulate removal filter.
Particulate removal filters, a properly operating, back-flushable particulate removal filter will remove particles greater than or equal to 10 µm in size. Subsequently, it is appropriate to establish a definition for particulate matter as non-dissolved inorganic or organic material with a size greater than 10 µm.
These material is either dirt; iron oxides or hydroxides; other metallic oxides or hydroxides; tiny organisms such as slime, algae, or iron rich species of bacteria such as Leptothrix and Clonothrix; and dissolved inorganic ions that react with precipitate generation cations and anions (like calcium, magnesium, barium, sulphate and carbonate).
In some cases, it may exist as a very fine material. This is generally true for non-dissolved inorganic compounds. If a sample of water containing fine particle is dispersed into a test tube with a round bottom, a darkened room and flashlight can be used to visualize this particle.
While reference to the total suspended solids measurement is related to the concentration of particulate matter, a review of a raw water analysis, particularly from a municipal supply, may provide an important additional analytical method as the turbidity of particulate matter. Higher total suspended solid concentrations and/or turbidity levels are an indication of high levels of particulate matter in water.