How does antiscalant work for a
reverse osmosis water treatment application?
An antiscalant is a pretreatment injected into the feedwater before the
feedwater enters the RO membranes. Its presence delays the reaction
between calcium magnesium and bicarbonate. This results is scale not
forming as the water is being purified by the RO. As the duration of the
water in the membrane system is relatively short during the treatment,
scale formation is prevented.
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What is the difference between Flocon 260 Antiscalant/Dispersant and
Coagulant?
Flocon 260 Antiscalant is used to keep water hardness from precipitating
during reverse osmosis treatment of water. The antiscalant also
contains a dispersant which prevents iron or aluminum in water from
reacting with the antiscalant and making it ineffective.
Coagulant, on the other hand, works just the opposite.
It is used to cause the suspended solids that may be present in water to
coagulate and settle out. By coagulation we mean that the very
fine particles of suspended matter come together to become a larger
cluster which will settle more easily than the smaller suspended
particles. The fine suspended particles in the water normally have
an electrical charge. The coagulate facilitates the removal of the
charge, allowing the particles to coagulate and settle. In
short, coagulant is used to remove suspended solids.
In membrane process, coagulants are used only in rare
situations. Many coagulants can be harmful for the membranes.
Coagulants are commonly used in municipal water treatment systems.
In short: Antiscalant is used for hardness, which is dissolved
in the water, and coagulant is used for suspended solids.
* Click here for more details and ordering information on Flocon 260
Antiscalant/Dispersant
Can excessive Antiscalant foul the membranes?
Excessive antiscalant can cause fouling of the membrane.
This fouling can be cleaned by flushing the membranes with water at a pH
of 2-3.
Antiscalant (organo-posphonate) and AM-88 (sodium meta-bisulphite for
dechlorination) are sometimes both used for pretreatment. In this
case, is there any chemical reactions which would cause fouling of the
membrane?
There is no chemical reaction between the two chemicals.
We are dosing a cationic coagulant before sand filter in our seawater
desalination RO pretreatment system. Meanwhile, Flocon 260 (anionic) is
dosed after sand filter. I wonder whether these two chemicals may react
and result in fouling on RO membrane.
Flocon 260 is typically not compatible
with cationic polymers. If we knew the exact polymer you
are using, we would be able to give a definite answer. There are
alternative Antiscalants that may be used (FLOCON 40), but in order to
determine whether this will work, we will need a complete water
analysis. The FLOCON 40 does not offer much scale control for most
of the 'sulfite' scales.
What is the dose rate and method of
injection for Flocon antiscalant?
Dose Rate
The amount of
Flocon required to inhibit scale formation depends on the degree of
supersaturation of the insoluble salts at the point of highest
concentration in the system. The degree of supersaturation in turn
depends on the concentration of the ionic species in the feedwater, the
overall salinity of the feed, the temperature of the feedwater, the
percentage of the feedwater recovered as permeate and the type of
membrane used for the application.
|
FLOCON
Solution Concentration* % |
Amount of
Solution to be Injected per 1,000 Gallons of Feed Water, In
Gallons |
|
3 ppm |
5 ppm |
|
100 |
0.003 |
0.005 |
|
50 |
0.006 |
0.010 |
|
20 |
0.015 |
0.025 |
|
10 |
0.030 |
0.050 |
* Use soft water
or RO permeate to mix with Flocon.
Dose Method
Flocon should be
added to a membrane system prior to the final cartridge filter. If
media filtration or activated carbon is used, Flocon should be applied
after these treatment stages.
Flocon should be
delivered by dosing pump from a dilution tank, direct from the drum or
from a bulk storage facility, into the feedwater at a rate that is
determined by the size of the membrane system, the recommended dose rate
and the delivery range of the dosing pump. It is recommended that the
dosing pump be adjusted by the stroke length, while maintaining stroke
frequency at a high level as possible to achieve even distribution of
the Flocon in the membrane system feedwater.
CAUTION - Biological Activity:
Flocon contains a
preservative that is effective up to a dilution of 1 part Flocon to 15
parts of system permeate water. General periodic cleaning of the dosing
system is recommended as part of the planned maintenance program.
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