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.
