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Reverse Osmosis (RO) Antiscalant Introduction

Why We Need Antiscalant?

In the Let's Talk About Water Hardness of water treatment industry related technical article. It is introduced that scale is the combination of calcium ions and magnesium ions in water with bicarbonate ions to form CaCO3, MgCO3 and other insoluble solid precipitates.

Therefore, it is very important to stop the generation of scale, adding scale inhibitors to stop the generation of insoluble salts, as one of the most convenient and economical methods, more and more widely used by all walks of life.

Before and after contrast of the RO membrane is clogged by the scale.

RO membrane scale clogging phenomenon in water treatment field

Heating kettle is full of scale.

Heating kettle scale clogging phenomenon in life field

Working Principle

Scale inhibitors are chemicals that make it difficult for calcium ions and magnesium ions in water to agglomerate and achieve scale inhibition. The principle of scale inhibitor can be summarized as chelating solubilization, coalescence & dispersion, and lattice distortion in three categories. And in the laboratory evaluation test, dispersion is the remedy for chelating solubilization, and lattice distortion is the remedy for dispersion.

Dosage Calculation

The amount of reverse osmosis scale inhibitors is affected by a variety of factors. Too much is not only a waste of resources that will cause water pollution, too little is not the effect of scale inhibition, so the amount of scale inhibitors is very important. The recommended concentration of reverse osmosis scale inhibitor is 2 ppm – 8 ppm, that is, 2 mg – 8 mg per liter of water, and the flow rate of scale inhibitor is calculated as follows:

Antiscalant dosage calculation

For example:

If Qf = 700,000 gpd; S = 3 ppm; C = 40%, then, Q =700,000 × 3 ÷ 40% ÷ 10-6 = 5.25 gpd.

If you want to calculate the flow frequency of dosing pump: Antiscalant flow rate ÷ Dosing pump rated flow (in case of equal units), in order to save your time, antiscalant dosage calculator can not only select the units you need but also quickly calculate the value you need.

Main Influencing Factors

Langelier Saturation Index (LSI), also known as the saturation index, is an index for determining whether water is in equilibrium, named after inventor Dr. Wilfred Langelier, who was used to determine whether water is erosive or scaling, an equilibrium index, LSI calculation formula:

Langelier saturation index (LSI) calculation formula

In perfect equilibrium LSI = 0, the acceptable range is -0.3 to 0.3. In this equilibrium range, water is neither scaleable nor corrosive. If LSI > 0.3 or higher, CaCO3 will precipitate in the water and form scale; when LSI < -0.3 or lower, the water becomes corrosive.

Where pHs is the pH value when the solution is saturated with CaCO3 and is related to temperature, TDS, Ca2+ concentration and HCO3- concentration, you can directly use the LSI calculator to calculate the final LSI value.

Description of the situation where scaling or corrosion will occur