Membrane Antiscalants

Membrane Antiscalants are chemicals used in Reverse Osmosis (RO), Nanofiltration (NF), and Ultrafiltration (UF ) systems to prevent scaling on the membrane surface. This scale is usually formed due to the deposition of inorganic salts such as calcium carbonate (CaCO₃), calcium sulfate (CaSO₄), barium sulfate (BaSO₄), strontium sulfate (SrSO₄), and silica (SiO₂).

Here's a more complete explanation 👇

Main Function

Antiscalant works by inhibiting crystal growth or keeping ions dissolved in water, so they do not form deposits that can cover membrane pores. That way:

• Longer membrane life.

• Filtration efficiency increases.

• Operating costs and frequency of washing (CIP - Cleaning in Place) decrease.

How Antiscalant Works

There are three main mechanisms:

1. Threshold inhibition - prevents saturated ions from forming crystal nuclei.

2. Crystal distortion - disrupts the shape and size of crystals so they cannot stick to the membrane.

3. Dispersing action - keeps fine particles suspended so that they can be easily carried away by water flow.

Types of Antiscalants

1. Phosphonate-based - effective for carbonate and sulfate scale.

2. Polymer-based (Polyacrylate, Polymaleate, etc.) - more environmentally friendly, stable at high pH.

3. Blend-based - a combination for improved performance over a wide range of raw water conditions.

Dosage and Usage

• Typical dosage: 1-10 mg/L (depending on feed water quality and membrane type).

• The correct dosage is determined based on scaling potential analysis using RO design software or laboratory tests.

• Antiscalant is usually dissolved and injected into the feed water stream before entering the RO unit.

Example of Commercial Products

• Avista® Vitec series

• Nalco® PermaTreat

• Genesys® Antiscalant

• Kurita®, Hydrex®, or local products such as Antiscalant RO-100/RO-200