Desalination & RO · seawater and brackish water

A reverse-osmosis plant needs chemicals for four jobs: pretreatment, scale control, dechlorination and membrane cleaning. Oman Chemical supplies antiscalants, sodium metabisulphite, membrane cleaners, RO biocides, acids and caustic soda for seawater and brackish-water RO plants across Oman, from its warehouse in Barka.

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  • Trading since 1995
  • Warehouse in Barka
  • About 7,000 products
  • MSDS on request
Reverse-osmosis membrane racks and pumps in a water treatment plant

What each stage of an RO plant needs

Oman makes much of its drinking water from the sea, and many hotels, camps, factories and farms run their own RO units on seawater or brackish well water. Warm, salty feed water makes scaling and biofouling the main reasons RO plants lose output.

  1. Pretreatment

    Suspended solids, organics and living organisms in the intake foul filters and membranes.

    Chemical typesChlorination of the intake with sodium hypochlorite; coagulants such as ferric chloride and flocculants ahead of media filters.

  2. Dechlorination

    Most RO membranes are polyamide thin-film composites, which free chlorine damages permanently.

    Chemical typesSodium metabisulphite (SMBS) dosed before the cartridge filters or membranes; activated carbon on small units. Many plants watch ORP to confirm no chlorine reaches the membranes.

  3. Scale control

    As water passes through the membranes the salts concentrate, and calcium carbonate, calcium sulphate, barium or strontium sulphate and silica can deposit on the last elements.

    Chemical typesAntiscalants dosed continuously; acid (sulphuric or hydrochloric) to lower feed pH where carbonate scale limits recovery. The dose is set from the feed analysis with projection software.

  4. Membrane cleaning

    Even a well-run plant needs periodic cleaning when normalised flow drops or pressure drop rises.

    Chemical typesLow-pH cleaners (citric acid, hydrochloric acid) for carbonate scale and metal oxides; high-pH alkaline cleaners for biofilm, organics and silt. Work within the membrane maker's pH and temperature limits.

  5. Biofouling control

    Bacteria form slime on membrane surfaces, raising pressure drop and lowering flow.

    Chemical typesMembrane-compatible non-oxidising RO biocides dosed intermittently, plus regular alkaline cleaning.

  6. Post-treatment and polishing

    RO permeate is low in hardness and alkalinity, so it corrodes pipes, and it must be disinfected before storage.

    Chemical typespH correction and remineralisation; sodium or calcium hypochlorite for disinfection; mixed-bed ion exchange resin where demineralised water is needed for boilers or labs.

RO chemicals buyers order most

Ordered by our own sales records: the products customers in Oman reorder most come first.

Also supplied for this work

Part numbers are RXSOL codes; quote them when you order. See this industry in the catalogue

RO and water product categories

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RO and desalination chemicals: questions buyers ask

What chemicals does an RO plant need?

Typically chlorine and a coagulant for pretreatment, sodium metabisulphite to remove chlorine before the membranes, an antiscalant dosed continuously, an RO biocide, and acid and alkaline cleaners for membrane cleaning. Post-treatment adds pH correction and disinfection.

Why must chlorine be removed before RO membranes?

Polyamide thin-film membranes are oxidised by free chlorine and lose salt rejection permanently. Sodium metabisulphite, or activated carbon on small units, removes residual chlorine before the water reaches them.

How much antiscalant should be dosed?

It depends on the feed water analysis, the recovery and the antiscalant chemistry, so the dose is calculated with projection software. Send us your feed analysis and recovery and we will propose a product.

When should RO membranes be cleaned?

A common rule is to clean when normalised permeate flow falls by 10 to 15 percent, or when normalised pressure drop or salt passage rises by 10 to 15 percent, compared with the start-up baseline. Waiting longer makes the fouling harder to remove.

Should the acid or the alkaline clean go first?

Where biofilm, organics or silt are present, the alkaline clean usually goes first, followed by the acid clean for scale. If the deposit is scale only, an acid clean alone may be enough. Follow the membrane maker's cleaning guidelines.

Do you supply chemicals for small hotel and camp RO units?

Yes. Small units use the same chemistry: dechlorination, antiscalant and cleaning chemicals. Tell us the unit size and feed water and we suggest the products and pack sizes.

Buying guides

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