8 Questions Need To Be Focused On During The Process Of Using Water Treatment Resin

Resins are widely used in water treatment processes. In water supply treatment, it can be used for water softening and desalination to produce softened water, pure water and ultrapure water; in wastewater treatment, some harmful substances in wastewater can be removed, and valuable chemicals, heavy metals and rare elements can be recovered, In chemical industry, biopharmaceuticals, etc., it can effectively carry out separation, concentration, purification, etc.

I believe that many  friends in water treatment field knew or have used water treatment resins. Today we will talk about water treatment resins in details.

01 What is "resin"?

Resin: high molecular polymer spherical particles with three-dimensional mesh structure and adsorption selection characteristics.

Water treatment resin is divided into cation resin and anion resin, cation resin is further subdivided into sodium type and hydrogen type, sodium type resin exchanges calcium and magnesium ions in water into sodium ions to soften the water. Hydrogen resin is to exchange calcium and magnesium ions in water into hydrogen ions to soften the water. Anion resin contains replaceable hydroxide ions, which can replace acid ions in water. At the same time, the use of anion resin and hydrogen cation resin can make the water soften. Water becomes pure water.

In the water treatment industry, ion exchange is the reaction of the ions in the water and the ions on the ion exchange resin with an equi-charged molar amount.

02 Problems that may occur in the use of resin

1. Backwash loss  

 If the backwash flow is too large or the backwash operation is abnormal, resin loss will occur, and a large amount of resin is often found in the trenches and waste water pools.

2. The flow-through part is damaged  

Resin leaks out of the equipment and enters the post-equipment or water supply system, causing difficulty in the operation of the post-equipment and deterioration of the effluent quality.

3. The resin layering is not clear  For example, mixed bed requires two resins to be well layered, otherwise the water production and effluent quality will be reduced. In severe cases, the effluent will fail to meet the required indicators.

4. Contamination of cation resin by turbidity 

 The turbidity of the influent water exceeds the requirement or the precipitation phenomenon occurs in the direct-current coagulation. When more suspended solids enter the first-stage ion exchanger, the phenomenon of resin pollution will occur. These suspensions often contain coagulants, typically salts of high-valent metal ions.

5. Calcium sulfate precipitation 

When sulfuric acid is used to regenerate cationic resin, if the concentration of sulfuric acid is too high and the flow rate is too slow, calcium sulfate will deposit on the surface of the resin particles, resulting in hardness of the effluent. At this time, it can be regenerated with hydrochloric acid once to dissolve the deposited sulfuric acid, or rinsed with a large amount of water in time.

6. Iron pollution

 Both cation and anion resins have the problem of being polluted, but the mechanism of iron pollution of these two resins is different. In the primary desalination equipment, the cation resin contacts the raw water with iron ions, iron agglomerated products and corrosion products. After the iron ions in the water are absorbed by the cationic resin, it is difficult to regenerate, and the corrosion products become iron ions during regeneration. Iron ion pollution will make the color darker, accelerate oxidative degradation, gradually reduce performance, and deteriorate the quality of effluent. Silicon, organic matter, etc. combine together to form a complex material form to contaminate the anion resin, and this contamination is cumulative.

7. Colloidal silica

Gelled silica is a phenomenon caused by improper regeneration of strong base anion resins. When the ratio of silica and strong acid anions in the raw water is large or there is a weak base anion resin absorbing strong acid in the water, the phenomenon of colloidal silica may occur in the regeneration of the anion resin. This phenomenon is more likely to occur when the lye concentration is high and the temperature and flow rate are low.

8. Organic pollution 

Organic contamination of resins is a major problem in water treatment. As the pollution of natural water becomes more and more serious, the pollution of resin has brought a great threat to water treatment. The stronger the alkalinity of the resin, the more serious the degree of organic pollution.