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Reverse osmosis is a water purification technique developed in 1950’s by US government to remove dissolved solids in saline and brackish water. The principle involves application of waterline pressure over untreated water against a semipermeable membrane. The separated H2O molecules pass through the membrane into a reservoir while contaminants remain on the other side. Over the years, RO has been extensively used for treating industrial feed water. While the primary method for demineralization is Ion exchange method, RO systems are adopted when large volumes of water need to be treated economically.
The life, efficiency & productivity of an RO Membrane water treatment system is greatly reduced due to a phenomenon called RO Membrane Scaling. During RO system operation, as the water moves through the membrane, the concentration of dissolved and suspended solids keep on increasing at the boundary layer. When the concentration exceeds saturation value, there occurs a tendency of deposition and crystallization on the membrane surface. Smaller depositions act as nuclei for more salt accumulation thus decreasing effectiveness of membranes and invoking frequent cleaning of the system. Scalants mostly include low soluble salts of calcium, barium, strontium as carbonates and sulfates and fine reactive silica crystals. Their low solubility makes them difficult to remove during cleanup processes.
Scaling can be minimized by pretreatment processes like ion exchange, chemical treatment like lime softening etc. but these incur higher costs. In some cases, acidification is practiced to remove insoluble carbonates and sulfates and most commonly Hydrochloric Acid is used. Recently, the popular choice of RO scale treatment is the use of Antiscalants. Reverse Osmosis Antiscalants are specialized chemical formulations added to the untreated feed water to increase the solubility of sparingly soluble salts that cause scaling. They mostly comprise of acrylates and phosphonates that greatly inhibit carbonate and sulfate precipitation. Since they offer an online scale protection advantage, RO Antiscalants have become an essential part of operations involving reverse osmosis systems. Such systems avoid mineral scaling and need less frequent cleaning, show greater efficacy with high permeate quality, decreased water and energy consumptions and longer operation life.
Nalco PermaTreat PC-191 is an RO Membrane Antiscalant manufactured by Nalco Company. It is a highly effective scale inhibitor engineered specifically for RO systems. It is suitable for treating brackish, highly saline and effluent feed water in RO filtration, Nanofiltration and Ultrafiltration systems. It is compatible with all types of RO membranes and can extend membrane life thus cutting down operating and maintenance costs.
Nalco PermaTreat PC-191’s characteristics can be ideally summarized as:
• Effective against scales of calcium, strontium, barium salts of carbonate, sulfate and oxide origin
• Zero scaling in system upto 2.6 LSI
• Cleans by dispersing particulate fouling
• Effective even at low feed water pH upto 5.9
• Can be fed directly or as diluted solution in system
• Prevents formation of Iron scales
Nalco PermaTreat PC-191 helps resolve all scaling issues in RO Filtration systems and at all instances, the costs incurred are lower than would be for Ion exchange hardness removal methods.
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