Description : Polyphosphate Scale Inhibitor
Polyphosphates are water purification chemicals that are employed to correct problems caused by inorganic groundwater contaminants (iron, manganese, calcium, etc.) and also to preserve water quality in distribution systems.
In the treatment of potable (drinking) water polyphosphates are used to:
- Prevent “red” (from iron) and “black” (from manganese) water
- Reduce soluble lead and copper in potable water
- Clean or dissolve precipitated mineral scale already existent in water distribution lines
- Prevent and/or retard scale formation (from minerals depositing) and corrosion (from low pH and/or dissimilar metals) in the water distribution system
Scaling is caused by the hardness salts present in water, particularly the compounds of calcium and magnesium. The level of water hardness is categorised as follows:
|Classification||mg/L or PPM (parts-per-million)||Grains per Gallon or GPG|
|Soft||0 – 17||0 – 1|
|Slightly Hard||17 – 60||1 – 3.5|
|Moderately Hard||61 – 120||3.5 – 7.0|
|Hard||121 – 180||7.0 – 10.5|
|Very Hard||180 +||10.5 +|
Below is a general guide to the water hardness in Australian capital cities –
Total Hardness as Calcium Carbonate mg/L
|Melbourne||10 – 26|
|Hobart||5.8 – 34.4|
|Sydney||39.4 – 60.1|
|Perth||29 – 226|
|Adeliade||134 – 148|
Hard Water contains dissolved minerals in the form of Calcium (Ca), Magnesium (Mg), and Iron (Fe). Hard water has a tendency to form scale deposits in pipes, hot water systems and on plumbing fixtures. It also reduces the ability of soap to dissolve in water and will form soap scum.Hard water is ideally treated by ion exchange water softeners. There are other controversial methods used to treat water including magnetic and electromagnetic methods. The efficacy of these treatments is based predominantly on testimonial evidence, and not widely accepted by the scientific community. More about magnetic and electromagnetic water treatment.
Polyphosphate scale and corrosion inhibitor media sold per Kg.
100% polyphosphate granules are ideal for reducing and inhibit scale build up caused by the permanent hardness salts of Calcium and Magnesium present in hard water.
Polyphosphates do not remove iron or hardness salts from water. Generally, polyphosphate feeders are effective in low volume, cold water applications. The polyphosphate dissolves into the water and coats the iron, calcium and magnesium in it, making it impossible for these agents to precipitate out of the water and create the problems associated with hard water.
However, polyphosphate treatment may not prevent iron or hardness salts from precipitating when water is boiled for a time, as in cooking or in the brewing of tea or coffee, as boiling can cause reversion to the orthophosphate which has no equivalent sequestering action.
Polyphosphates may inhibit corrosion mechanisms of aggressive or corrosive water supply.
Dosage Recommendations for polyphosphate:
Typically, in order to sequester iron, manganese and calcium it requires a 1:1 mole ratio with polyphosphate. This is generally achievable when dealing with iron and manganese that are usually in levels that are less than 5 mg/L. However, polyphosphates act as crystal modifiers that need only a fraction of that ratio to effectively modify the crystalline structure of calcium/magnesium. In theory, a hexametaphosphate dosage of 500 mg/L is required to actually sequester 200 mg/L of calcium (as calcium carbonate). However, a dosage of only 2 -4 mg/L of hexametaphosphate is all that is required to modify the crystal growth of calcium carbonate. By modifying the crystalline structure, these compounds will not precipitate into scale and actually stay in solution through repelling and suspension. This crystal growth modification function prevents the formation of mineral scale within water distribution systems. Polyphosphates will also dissolve already deposited mineral scale deposits within the system thereby increasing the carrying capacity of the water system. Polyphosphates are cathodic inhibitors that interfere with the cathodic site of the electrochemical corrosion cell formation.
The polyphosphate is food grade and safe for drinking water applications.
- CAS NO.: 94551-68-5
- EINECS NO.: 233-343-1
- Type: Chemical Auxiliary Agent
- MF: (NaPO3)6
- Polyphosphate can be combined with carbon if required.