What are polyphosphates?
Polyphosphates are water treatment chemicals used to solve specific water quality problems resulting from inorganic contaminants (iron, manganese, calcium, etc.) in ground water supplies and also to maintain water quality (inhibit corrosion, scale, biofilm, reduce lead and copper levels) in the distribution system. Polyphosphates are used in water treatment along with many different phosphate compounds that exist for use in the water treatment process. Polyphosphates work together, stabilizing water quality and minimizing color, scale, deposits, corrosion, and chlorine demand in drinking water systems.
What are the problems that polyphosphates help to solve?
Polyphosphates are used in residential water systems to perform three broad functions: inhibit corrosion of plumbing and plumbing fixtures and sequester nuisance metals in the water supply (iron, manganese, calcium, magnesium). They can also improve the quality of water in the home by removing scale deposits & tuberculation, discourage microbial film formation/regrowth, and stabilizing free chlorine municipal water treatment disinfectant residuals.
How do polyphosphates work in a water system?
Polyphosphate type chemicals react with soluble metals (iron, manganese, calcium, magnesium, etc.) by sequestering (bind-up) the metals to maintain their solubility in water. The polyphosphate sequestering process minimizes the risk of discoloration, staining, scaling, taste/odor and other water quality complaints.
Are polyphosphates safe and approved for water systems
Various forms and purity grades of polyphosphates exist. All Carus polyphosphate additives are either food quality grade or certified to ANSI/NSF Standard #60 Drinking Water Treatment Chemicals as approved for use in potable drinking water.
What other benefits of polyphosphate treatment exist?
Polyphosphates easily adapt to any pre-existing water quality without changing the water chemistry. Referred to sequestrates, polyphosphates have a selective function, yet wide range of performance. Primary treatment benefits include: corrosion control, lead/copper control, sequestration of iron/manganese, control of calcium carbonate scale, and water softening, etc.
Scale Inhibition and Removal The formation of scale on surfaces in potable (drinking) water systems is due to the crystallization of carbonates or sulfates of magnesium or calcium from solution. Very low levels of polyphosphates (1-10 ppm) interfere with crystal growth. This type of scale inhibition is referred to as a threshold property because it occurs at a level much lower than would be required for a stoichiometric reaction. Threshold inhibition by polyphosphates of calcium and magnesium carbonate formation is particularly effective at a pH range of 8 to 10 where carbonate scale in potable water is a major problem. Calcium sulfate scale is often a problem at lower pH ranges. The same mechanism of scale inhibition that can occur with calcium carbonate at a high pH range can also occur with calcium sulfate at a lower pH range at similar low (1-10 ppm) levels of polyphosphate addition. Experience has shown that polyphosphates not only inhibit scale formation, but they can also help remove existing hard deposited carbonate or sulfate scale. Pipelines carrying potable water treated with polyphosphate for extended periods of time (several months) first show a gradual softening of the scale followed by disintegration and removal. The soft scale particles are deflocculated by the polyphosphate and carried away resulting in a clean piping system.