RO Antiscalant

The Reverse Osmosis [RO] membrane should be considered to be at the heart of any reverse osmosis plant system, and damage to it will cause reduced output, poor water quality and increased production costs. The membrane, or rejecting layer, allows the passage of pure water but holds back the dissolved salts.It contains some means of upstream scale inhibition, RO membranes and their flow passages will foul due to scale, the precipitation of sparingly soluble salts. Common examples of scale are calcium carbonate (CaCO3), calcium sulfate (CASO4), barium sulfate (BaSO4), and strontium sulfate (SrSO4). Less common but equally problematic are silica (SiO2) and calcium fluoride (CaF) scales.

Dew formulates a range of liquid antiscalant/dispersants for membrane separation systems. These formulations are designed to inhibit scale while also dispersing colloidal particles. The inhibition and dispersant properties help extend RO system run times, reduce cleaning frequencies and increase the overall productive life of the RO elements. The application of DEWTREAT ® Antiscalants may also eliminate the need for acid addition while maintaining desired recovery rates in some cases.

Water analysis data is unique to each treatment site so we have developed the DEWTRACK-ROTM advisor software program. Cations and anions of a water source as well as general system data are entered into the program which then recommends an appropriate DEWTRACK-ROTM product and dosage specific to that facility.

DEWTREAT formulations are certified under ANSI/NSF 60 for use in systems producing drinking water.

Dew Reverse Osmosis Chemicals Benefits

  • Safe to handle and safe in use
  • Membrane compatibility with all leading manufacturer
  • Improved performance on regular use
  • Stable and effective for long period of time
  • Compatibility with all other products
  • Cost effective
  • Environment Friendly
  • Restores and prolongs membrane life
  • Maintains system performance
  • Reduces down time
  • Protects membranes from oxidizing agents
  • Eliminates and Reduce dosing of acid
  • Reduce cleaning frequency

Recovery rates Reverse osmosis plant recovery rates vary from as low as 10% in the case of sea water to 90% with some low salinity brackish waters. As the water passes along the membrane surface the salt concentration increases and some sparingly soluble salts exceed their solubility products. These salts can precipitate on the membrane surface causing fouling which may reduce output and increase the product water conductivity. The two most troubleŽsome salts are calcium carbonate, calcium sulphate and Silica their prevention is essential if the membrane is to work efficiently. Calcium sulphate scale can be eliminated by lowering the recovery rate, which reduces the calcium and sulphate ion concentration in the water. Reducing the recovery rate is not always the best option as it means running the plant at lower efficiency. The best way to maintain cost effective production is to operate with recovery rates as high as possible whilst at the same time preventing membrane scaling.

Antiscalants are surface active materials that interfere with precipitation reactions in three primary ways:

Threshold inhibition

Ability of an antiscalant to keep supersaturated solutions of sparingly soluble salts.

Crystal modification

Antiscalant distort crystal shapes, resulting in soft non adherent scale. (As a crystal begin to form at the submicroscopic level, negative groups located on the antiscalant molecule attack the positive charges on scale nuclei interrupting the electronic balance necessary to propagate the crystal growth. When treated with crystal modifiers, scale crystals appear distorted, generally more oval in shape, and less compact.)

Dispersion

Ability of antiscalants to adsorb on crystals or colloidal particles and impart a high anionic charge, which tends to keep the crystals separated.

The DEWFLOCTM pretreatment program is designed to eliminate fouling in membrane systems,regardless of the feed water source.

RO Antiscalant
PRODUCT COMPATIBILITY

ALL MEMBRANES

NSF

DEWTREAT-800E

Yes

DEWTREAT-800

Yes

DEWTREAT-801

Yes

Yes

DEWTREAT-802

Yes

Yes

DEWTREAT-803

Yes

DEWTREAT-804

Yes

DEWTREAT-805

Yes

Product Technical Data Sheets for particular properties and application notes for each product.

The DEWTRACK-RO software is also available to allow you to calculate your required antiscalant dose.

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