What are the harms of scaling

First, we know the meaning of scaling, as it means the deposition of inorganic or mineral dirt particles on the surface of the membranes. Which leads to clogging the pores of the membrane. The sedimentation process is the deposition of low-soluble salts on the surface of the membrane and calcification is the accumulation of suspended solids and microorganisms on the surface of the membrane. Scaling in reverse osmosis systems is a natural phenomenon and can be controlled through filtering, appropriate filtration, and chemical washing when needed.

What is anti-scaling?

The term anti-scaling is a functional substance in industrial systems to reduce deposit formation or, in technical terms, anti-scaling, in industrial equipment such as reverse osmosis (RO) systems many manufacturers have heard of.

Scaling damage

• Chemical scaling is caused by soluble mineral compounds in water such as sodium carbonate, calcium sulfate, silica, silicon dioxide, and barium sulfate.
• It can limit the efficiency of membrane filtration and membrane filter systems.
• Pressure increases and therefore energy consumption and associated costs increase.
• Reduces water quality.
• Reduces frequent washes and malfunctions.
• It is worth noting that the useful life of the membrane filter may be reduced due to the phenomenon of chemical scaling.

The stages of scaling

Precipitate formation begins when the salt concentration exceeds its solubility under solution conditions. Primary crystal cores play a catalytic role in the formation of larger salt crystals. These salt crystals come out of the suspended state and begin to precipitate as long as they reach the required size and mass. The sedimentation process will continue until the ions that make up the salt are saturated in the solution.

The reason for the formation of deposits on the membrane filter:

There are several reasons that lead to the formation of sediments on the surface of the reverse osmosis membrane, the most important of which are:

• Increasing the concentration of minerals of the solution in the water entering the membranes.
• pH increase.
• Creating and increasing the surfaces required for deposition (which will multiply with the continuous chemical scaling of mineral deposits to this required level).
• Increase the water temperature.

Benefits of using an anti-scaling

Scale inhibitor is used as an additive in the primary treatment process in reverse osmosis systems. Anti-scaling is used as an active ingredient for sedimentation control in reverse osmosis membranes. Before transferring the water to reverse osmosis, an anti-scaling with the appropriate concentration is injected into the water feed flow.

The chemicals used in the composition of anti-calc prevent the formation of types of mineral deposits on the surface of the membranes. Injection of appropriate concentrations of anti-scaling leads to controlling the formation of types of mineral deposits such as calcium carbonate, calcium sulfate, iron deposits, and others on the surface of the membrane.

The use of anti-scaling in reverse osmosis systems may reduce costs related to the repair and maintenance of water purification systems. By continuous injection of anti-scaling in the reverse osmosis system, the scaling current will decrease rapidly. The amount of scale inhibitor used as a descaling agent depends on the concentration of soluble salts in the feedwater or the place of application.

Due to the presence of inorganic and mineral salts of the solution for the incoming water to the reverse osmosis water treatment system and water desalination machine, blockage and deposition in the polyamide or cellulose micropores of the reverse osmosis membranes, the phenomenon of calcification occurs.

Precipitates on polyamide films include calcium carbonate, calcium sulfate, barium sulfate, and strontium sulfate. Silica and calcium fluoride deposits are less common but are a problem. To prevent these soluble salts on the membrane, they are injected into the water entering the anti-hull reverse osmosis system.

You can also read more about the importance of using anti-scaling here.

Mechanism of action of anti-scaling

Disruption of the reactions of the production of mineral deposits, or in other words, this substance by some substance in its structure can reduce the rate of reaction of the alkaline compound with all mineral ions in water, in this case during the passage of water through the polyamide membrane. The possibility of sediment formation is eliminated.

Calcium carbonate, calcium sulfate, strontium sulfate, and … are among the minerals that are deposited on the membrane.

In general, all systems in which membrane technology is used for water treatment are subject to membrane pore blockage, the most important of which are reverse osmosis desalination systems.

Problems caused by not using anti-scaling:

The problems that occur mostly due to chemical scaling in membrane filters are the following:

• Decreased flow quality and quantity of flowing water
• Increasing low pressure required pressure, energy consumption, and cost.
• Frequent washing with fewer intervals to optimize processes that reduce the useful life of films and increase costs.
• Frequent and long-term malfunctions.
• Membrane dispersion upon collision with mineral deposition crystals
• One of the useful ways to prevent the occurrence of the problems mentioned is the use of anti-scaling.

Disadvantages of using a poor type of anti-scaling

Increases the need to wash the membrane filter which is not good at all for water purifiers. In addition, the poor material causes the membrane filter to be replaced quickly, which leads to a shortening of the useful life of the filter and, soon after, causes total damage to the device. The useful life of the pumps is also affected by this inferior product and is reduced.

More importantly, this ideal material, if not of good quality. It is also harmful to water and reduces the yield and quality of pure water. As a result, low-quality antiscalants cause many problems, conversely, the higher the quality of the antiscalant, the higher the quality of the treated water.

Sedimentation and blockage of the membranes lead to a decrease in the effective area between the materials and it reduces the turbulence of the flow and may result in a concentration polarization on the surface of the membrane.

The higher the concentration of the solution on the surface of the membrane, the greater the percentage of solute it will pass through. When the effective membrane level decreases, the turbulence will decrease and the cleaning process of the membrane surface will be difficult because the possibility of sending the chemical solution to the surfaces blocked by solid materials will be reduced. It is possible to prevent precipitation by using the correct efficiency of the system and the injection of chemicals.

How does anti-scaling work?

Anti-scaling materials slow down the sedimentation process by preventing the growth of mineral salt crystals. These substances form on the surface of the salt crystal and adsorb on the surface of the polyamide film. By preventing further adsorption of supersaturated salts on the crystal surfaces. They reduce the rate of expansion of the salt crystals.

So that the primary crystal cores do not reach a sufficient size or concentration for precipitation. Most inhibitors have dispersal properties. The properties of suspension or dispersion occur by trapping suspended particles of salt, iron, or solid organic matter. Causing them to be repelled by other anions in solution. This process prevents particles from accumulating and forming larger particles that can precipitate.

Benefits of using anti-scaling when treating seawater

One of the most important points in seawater treatment is that the probability of the presence of boron in this type of feed water is high. It must be separated at a higher pH (in the range of 9-11) with increasing pH. The probability of sediment formation on the surface of the membrane is higher. Since the pH should not change much, adding acid is not helpful at all and the only solution would be to inject an anti-scaling.

Most antiscalants are oxidized by strong oxidants such as chlorine and bromine. Not only lose their properties but also cause bio-contamination by destroying the molecular structure. Therefore, these oxidizers must be removed in the pretreatment system prior to the injection site (e.g. a carbon filter at the start of the line that absorbs chlorine).

The chemical structure of the anti-scaling molecule cannot pass through the membrane. Therefore, no concentrations of this solution enter into the water produced by reverse osmosis. But in terms of the environmental effects. It is necessary to verify the exit of the solution from the discharge stream. In this context, the amount of injection must be controlled in the line. With the need to be injected, the lowest possible percentage of injection is injected.

Finally: You must use an antiscalant that is of good quality in order to be able to save money by:

• Preventing the need to replace expensive membranes prematurely.
• Maintaining efficient plant operation at the highest possible recovery.
• Eliminating or reducing the use of hazardous acids.
• Reducing water consumption by safely operating at high recovery rates.
• Using fewer chemicals.
• Producing less concentrate, and allowing for the better environmental acceptance of that concentrate.
• Reducing energy costs.
• Reducing the downtime caused by frequent membrane cleanings.