Water Quality Requirements for Ultrafiltration Membranes

As water treatment technology becomes increasingly advanced, the filtering performance of ultrafiltration membranes is constantly improving and has great potential for progress. Almost every industry is related to water treatment. 

Ultrafiltration membranes automatically separate pollutants, bacteria, suspended impurities, concentration, and other substances in raw water, all of which are related to water quality.

What are the requirements for water quality for ultrafiltration membranes?

Ultrafiltration uf membranes have a pore size of fewer than 0.01 microns, which makes separating and comparing gel-like substances in filtered solutions difficult. There are many substances that can be filtered through the pores, and some may stick to the surface of the membrane, which can cause a decrease in the water permeability of the ultrafiltration membrane and affect the filtering process, resulting in poor water quality. 

There are certain standards for the inlet water temperature, pH value, and concentration, and if any one of these standards is not met, it will have an impact on the ultrafiltration water quality. So, what are the requirements of ultrafiltration for inlet water quality?

9.the Characteristics of the Ultrafiltration System

1. Temperature

The performance of ultrafiltration membranes is greatly affected by the temperature of the incoming water, as the optimal efficiency of membrane permeability is at 25°C. As the water temperature increases, the permeability also increases, but if the temperature is too high, it can affect the performance of the membrane. Therefore, measures should be taken to lower the water temperature when it is too high.

2. pH Value

Different ultrafiltration membrane materials have different pH value requirements. For PAN or PVDF materials, the pH value requirement is around 2-12, while for cellulose acetate materials, the pH value requirement is around 4-6.

Figure 11 Checking the pH value

3. Microbial Removal

The addition of NaC10,03 oxidant at a concentration of 1-5mg/L can help remove some of the remaining microorganisms and bacteria in the membrane system. If not treated, bacteria can multiply and cause clogging of the ultrafiltration micro-pores, and in severe cases, it can completely block the inside of the hollow fiber. Therefore, it is important to remove bacteria from the incoming water.

4. Turbidity

Turbidity should be below 5 degrees. When suspended solids, microorganisms, and other impurities are mixed in the incoming water, it can cause the water to become turbid. This turbidity is generally set at below 5 degrees.

5. Suspended Solids and Colloids

Although ultrafiltration membranes are effective in removing fine particles and colloids, some colloids with specific charges can be harmful to hollow fiber ultrafiltration membranes. Coagulants are high molecular weight polymers that can form hydrogen bonds to improve colloids, but they cannot be completely removed. By combining several methods, such as adding pH adjusters, bleach, lime, sodium carbonate, and oxidizing agents such as chlorine, coagulation efficiency can be effectively improved.

Each of these requirements must be strictly adhered to; otherwise, the performance of the ultrafiltration membrane will not reach its normal level, affecting water quality. Therefore, it is necessary to adjust the incoming water temperature to a suitable level that meets the requirements of the ultrafiltration membrane to effectively extend its lifespan. For more information about ultrafiltration membranes, please consult NEWater.

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