Pretreatment process strategy to cope with colloid membrane contamination

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Colloidal contamination is a common and troublesome problem in water treatment, especially for ultrafiltration membranes and reverse osmosis membrane systems. Colloidal contamination is mainly caused by the water containing tiny particles between 1 nanometer and 1 micron in size, which are often charged, making them remain dispersed in the water and difficult to remove through natural sedimentation.

Pretreatment process strategy to cope with colloid membrane contamination

As a common physical filtration technology, the surface of ultrafiltration membrane is easily contaminated by colloidal particles. When the content of iron, manganese and silicon in the water exceeds a specific threshold, these substances will also form fouling on the reverse osmosis membrane, seriously affecting the performance and life of the membrane. Therefore, controlling the content of these pollutants in the water is particularly critical.

Pretreatment process strategy to cope with colloid membrane contamination

In order to effectively remove colloidal substances from water, specific pretreatment processes are required. Here are some common methods:

Coagulation method: By adding positively charged coagulants to the wastewater, such as aluminum sulfate, ferrous sulfate, alum, ferric chloride, etc., it can neutralize the negative charge on the surface of colloidal particles, so as to eliminate the electrostatic repulsion between them, so that the colloidal particles coalesce and form larger particles, which is convenient for subsequent treatment.

Flocculation method: The polymer coagulant is added to the wastewater, which will form a polymer after dissolution. These polymers have a linear structure that acts like a bridge between two colloidal particles that are far apart, allowing them to come together to form flocculates of large particles. This flocculate has a large volume and density and is easy to remove by precipitation or filtration.

Electric flocculation method: agglomeration of colloidal particles occurs through the action of electric field. Under the action of an electric field, the charged colloidal particles will move towards the electrode and form a sedimentary layer on the electrode surface. This method is particularly effective for removing charged colloidal particles.

Air floatation: Passing air or other gases into waste water to create tiny bubbles. These bubbles attach to the surface of colloidal particles, causing them to float to the surface to form a scum layer, which is then removed by a slag scraper or other device.

When selecting the pretreatment process, it needs to be determined according to the specific water quality and treatment requirements. At the same time, in order to ensure the pretreatment effect, it is also necessary to strictly monitor and manage the treatment process to ensure that the dosage of the drug and the dosing time and other parameters are precisely controlled. The effect of colloid contamination on the ultrafiltration membrane and reverse osmosis membrane system can be significantly reduced by using appropriate pretreatment technology, and the water treatment effect and operation stability can be improved.

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