Watch on YouTube: RO Antiscalant: Same Water, Same Hours — Why One Membrane Scales | RXSOL
Two RO membranes can run on the same feed water for the same hours, and one still comes out scaled while the other stays clean. The difference is usually the antiscalant polymer dose. As water passes through the membrane, hardness salts concentrate, and without treatment they crystallise into a crust. Our RXSOL Antiscalant Polymer (part no. RXSOL-33-3302-020) keeps those salts in solution, so they leave with the reject water. A typical dose is 1 to 3 mg/L, set by your feed water. You inject it into the feed line after the multimedia filter and before the cartridge filter.
The video above shows this as a split-screen experiment: two identical RO watermakers, one dosed and one not. This page covers the same ground in writing, from why scale forms to how to set up the dosing point on your skid and what to do if a membrane has already scaled.
Why one RO membrane scales and the other stays clean
Inside each pressure vessel, water is pushed through the membrane. Clean water passes through as permeate, and the dissolved salts stay behind. The further the water travels along the membrane, the saltier it gets, so it is most concentrated at the reject end.
Eventually the hardness salts are packed past their limit. Without treatment they come out of solution: crystals form at the reject end and spread back along the membrane as a crust. The usual scale formers are calcium carbonate, the sulphates and silica.
The same process runs on a ship's watermaker, a hotel RO skid, a desalination train and a wastewater reclamation unit. Running at a higher recovery rate makes the reject end more concentrated, so the scaling risk is greatest where you push the system hardest.
Signs your RO membrane is scaling
Your gauges will show scale before you can see it on the membrane. On a scaling unit, watch for three trends:
- Normalised permeate flow drops.
- Pressure drop across the vessels climbs.
- Salt passage rises, so more salt gets into your product water.
If your logs show all three moving the wrong way, clean the membrane first. Antiscalant can only protect a clean membrane.
What antiscalant polymer does on an RO membrane
RXSOL Antiscalant Polymer is a liquid, highly concentrated, polymer-based product. It is a super-threshold antiscalant and antifoulant. It stabilises supersaturated salt solutions, so the hardness salts stay dissolved instead of forming scale on the membrane. Seed crystals stay tiny and flush out with the reject stream.
It controls calcium carbonate, calcium sulphate, barium sulphate, strontium sulphate, calcium fluoride, silica and iron, even at high recovery rates. It tolerates iron and aluminium oxides and works across a wide pH range.
For your plant, that means lower scaling risk, fewer membrane cleanings, less downtime and longer RO membrane life. It also removes the need to dose hazardous acids into the feed. Small units can soften the make-up water instead, but on larger systems that is very expensive. On those systems, antiscalant can replace the softener filters.
How to dose antiscalant polymer on your RO skid
Inject the antiscalant into the RO feed line after pretreatment: downstream of the multimedia filters and upstream of the cartridge filter. The best point is before the static mixer or the cartridge filter housing.
A typical dose is 1 to 3 mg/L. Your exact dose depends on your feed water: calcium hardness, iron, TDS, alkalinity, pH and silica. Send us a recent feed water analysis and we will recommend a dose for your system. Our earlier antiscalant polymer supply page lists the same product for buyers across Oman.
You can inject the product neat or diluted. If you dilute it, use RO permeate or DI water, and do not dilute it below 10 %.
Wear gloves and goggles when handling the concentrate, and keep the container closed.
Which RO systems and membranes it suits
The product is for brackish water, seawater and wastewater reclamation RO. It suits polyamide and cellulose acetate membranes and works with almost all RO membranes. If you are setting up the full treatment line, our industrial and water treatment chemical range covers the other chemicals your plant uses.
It is designed for feed water without a heavy colloid or silt load, such as groundwater. If your feed carries a lot of silt, fix the pretreatment first. Antiscalant controls scale, not particle fouling.
Membrane already scaled? Clean first, then dose
Antiscalant prevents scale. It does not clean a membrane that is already fouled. If your gauges already show the warning signs, clean the membrane with an RXSOL membrane cleaner first. Then start antiscalant dosing to keep it clean.
Acidic membrane cleaners target iron, silica and calcium carbonate deposits. Alkaline cleaners target organics, biofilm and silt, and run as stage 1 before the acid stage. Tell us what deposit you are seeing and we will quote the right cleaner together with the antiscalant.
Antiscalant polymer at a glance
| Item | Detail |
|---|---|
| Part number | RXSOL-33-3302-020 |
| Product type | Liquid, highly concentrated, polymer-based super-threshold antiscalant and antifoulant |
| Controls | Calcium carbonate, calcium sulphate, barium sulphate, strontium sulphate, calcium fluoride, silica, iron |
| Application | Brackish water, seawater and wastewater reclamation RO |
| Membranes | Polyamide and cellulose acetate; works with almost all RO membranes |
| Dosing point | RO feed line, downstream of the multimedia filters, upstream of the cartridge filter |
| Dosage | 1 to 3 mg/L typical; exact dose depends on your feed water |
| Dilution | Neat, or diluted with RO permeate or DI water, no weaker than 10 % |
| Handling | Gloves and goggles when handling the concentrate; keep the container closed |
| Packing | Confirmed with your quote |
Where to buy antiscalant polymer in Muscat and Oman
Oman Chem (Muscat & Barka for Business Trading) supplies RXSOL Antiscalant Polymer from Barka Industrial Area, Sultanate of Oman. Call +968 77333599, message us on WhatsApp or email muscatchem@gmail.com.
For deliveries to Muscat port and the city, the same product is listed as Antiscalant Polymer on Muscat Chemical. Buyers at Sohar port and in the Sohar industrial area can order it from Antiscalant Polymer on Sohar Chemical. If you also need caustic, acids or other drum chemicals for the same site, see our full product list.
Frequently asked questions
What does antiscalant polymer do in an RO system?
It keeps hardness salts such as calcium carbonate, the sulphates, calcium fluoride, silica and iron in solution as they concentrate along the membrane. The salts leave with the reject water instead of forming scale on the membrane.
How much RO antiscalant should I dose?
A typical dose is 1 to 3 mg/L. The exact dose is site-specific and depends on your feed water: calcium hardness, iron, TDS, alkalinity, pH and silica. Send us your feed water analysis and we will recommend a dose.
Where do I inject the antiscalant on my RO skid?
Inject it into the RO feed line after pretreatment, downstream of the multimedia filters and upstream of the cartridge filter. The best point is before the static mixer or the cartridge filter housing.
Can antiscalant clean a membrane that has already scaled?
No. Antiscalant prevents scale but does not remove it. Clean the scaled membrane first with an RXSOL membrane cleaner, then start antiscalant dosing to keep it clean.
Can I dilute the antiscalant before dosing?
Yes. You can dose it neat or diluted. If you dilute it, use RO permeate or DI water, and do not dilute it below 10 %.