Phosphate products for water treatment come from a broad group and encompass a wide variety of chemical compounds for water treatment applications. The applications of each phosphate product depend upon the specific properties or treatment desires for the water source.
Since water quality varies throughout Florida, polyphosphate alone, or in combination with orthophosphate, can effectively control many water quality issues. Blended Phosphates are used to prevent dirty, discolored (red from iron and black from manganese) water; to prevent and/or control scale formation (from minerals) and corrosion control in the water distribution system; and to decrease soluble lead and copper in potable water delivered to the consumer’s tap.
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Our AQUAGOLD blended phosphate products are comprised of several polyphosphates along with dry monosodium phosphate. These formulations are aimed at dealing with numerous conditions that a municipal distribution will typically encounter from time to time.
The proper selection of ortho-phosphates will provide excellent corrosion protection. We use monosodium phosphate in a dry form to formulate our products. Some companies use phosphoric acid (neutralized with NaOH) as their ortho-phosphate. This can definitely compromise the integrity of the product causing product stability problems resulting in a gelling of the product. The solubility of the product is also decreased since the balance between potassium and sodium salts is greatly affected.
Red and black water problems can be easily resolved through the use of properly selected polyphosphates. The sodium acid pyrophosphate (SAPP) or tetra-potassium pyrophosphate (TKPP) are the preferred polyphosphates needed for the sequestration of iron, manganese and hardness. The “release” factor of these metals is critical and some chain lengths of polyphosphates cannot properly hold onto these metals. Some companies will not use pyrophosphates in their blended phosphate product formulations due to the higher costs. This certainly will adversely impact the sequestration ability of the blended phosphate product.
Polyphosphates have the ability to control the film formation of the corrosion inhibitor and maintain the desired film thickness for your system. Improper polyphosphate selection will not accomplish this and design “C” factors will not be attained resulting in too much deposition throughout the distribution system.
It is always a good practice to conduct flushing of your system once or twice per year. This eliminates much of the sedimentation that builds up throughout the distribution system. With polyphosphates, your system has the ability to scrub away most of the build-up that is typically seen within a system. If your blended phosphate is comprised primarily of short chain polyphosphates, you may realize that several of these chains may cleave off before they can properly perform on the sedimentation.
Proper combinations of polyphosphates will provide for excellent control of chlorine residuals which ultimately will allow you to use the correct amount of chlorine. If your chlorine usage increases then a slight adjustment to blended phosphate feedrate can bring the chlorine usage back within the calculated feedrate range.
Polyphosphates have been proven to prevent the development of biofilms within a community’s distribution system. When the chlorination usage increases significantly within a system, this is usually the first sign of a biofilm aggressively developing in the piping. Polyphosphates have the ability to scrub away the deposits and maintain at the desired level/thickness. Some polyphosphates can revert (Hydrolyze) quicker than other polyphosphates compromising the effectiveness of their cleaning ability and actually increase the ortho-phosphate level. This can actually provide the adverse effect resulting in a compromised condition of the treatment program.
It becomes rather apparent that the selection of blended phosphates is a rather detailed science. Improper phosphate selection can cause a municipality to lose faith in the excellent chemistry that blended phosphates provides. Some companies will choose lower cost phosphates to include in their product formulations. This will not offer your community the stable and reliable product that you are expecting to receive.