Ultrafiltration Membranes:Water Quality Requirements

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. So what are the water quality requirements for ultrafiltration membranes?

 

9.the Characteristics of the Ultrafiltration System

1. What are Ultrafiltration Membranes?

Ultrafiltration membrane is a semi-permeable membrane with a pore size of 0.002 to 0.1um. It can effectively remove microorganisms, colloids, diatoms, and other substances that cause turbidity. Advantages include good hydrophilicity, long life, high fouling resistance, and high water output. In addition, beneficial minerals can be retained.
At present, ultrafiltration membranes are playing an increasingly important role in the field of drinking water treatment and industrial wastewater reuse.

UF Filter

2. What are the Requirements for Water Quality for UF 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?

Ultrafiltration Membrane Flow chart

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.

3. What is the Quality of the Water Produced by the UF Membrane?

No. Water quality index Ultrafiltration water production effect
1 SDI ≤1
2 Turbidity (NTU) ≤0.2
3 ss(mg/L) <0.2
4 Microorganism, bacteria, E. coli, pathogen removal rate 0.9999

4. Ultrafiltration vs Reverse Osmosis: What is the Difference?

The difference between ultrafiltration and reverse osmosis membranes lies mainly in the filtration precision.

The pore size of the ultrafiltration membrane: 0.01 to 0.1 micron or so. Can filter sediment, rust, bacteria, and most viruses, the disadvantage is that it can not filter heavy metals.
The pore size of reverse osmosis membrane: 0.0001 to 0.001 micron or so. Capable of filtering bacteria, heavy metals, organic matter, residual chlorine, colloidal matter, and other harmful substances in the water.

Ultrafiltration Membrane Flow chart

Ultrafiltration filter or reverse osmosis filter?

Ultrafiltration water purifier does not need electricity in the process of use. Energy saving and environmental protection and low cost. The disadvantage is that the filtration precision is not high. Can not filter calcium and magnesium ions various heavy metals and other harmful substances. Can not remove the scale.

Reverse osmosis water purifier has high filtration precision and water safety is guaranteed. It can filter bacteria, viruses, metal ions, and other substances other than water. It has a long service life, but it produces wastewater, and the later cartridge consumables are on the expensive side.

The choice of ultrafiltration membrane or reverse osmosis membrane needs to be decided according to the budget and the needs of water quality treatment.

6.Ultrafiltration System Membrane

5. Where Can Ultrafiltration Membrane be Used?

Ultrafiltration membrane filtration capacity is not as good as reverse osmosis membrane, but it is also a widely used filter material in the field of water purification equipment manufacturing. The use of ultrafiltration membrane filtration of the original liquid at the same time will retain the trace substances in the water. Ultrafiltration membranes are often used in the following areas:

  • Industrial wastewater purification.
  • Reverse osmosis pretreatment.
  • Water reuse.
  • Clarification and purification of fruit juice and dairy products.
  • Purification of daily drinking water.
  • Wastewater treatment for electric power and chemical plants.

Figure 1 How the pure water treatment equipment used in Food and Beverage Industry

6. Can Ultrafiltration Membranes be Cleaned and Reused?

Yes. Cleaning ultrafiltration membranes maintains membrane permeability and longevity. The correct cleaning method saves time and reduces damage to the membrane elements during the cleaning process. However, as a consumable, UF membranes need to be replaced after a period of time to ensure consistent water quality.

In addition, different cleaning methods can be used for different membrane modules. Tubular modules can be mechanically cleaned with sponge balls, and hollow fiber modules can be backwashed. For the food industry membranes also need to be sterilized (with NaOH and H2O2, etc.).

Figure 10 Importance of RO membrane cleaning.

7. Final Words

NEWater is a reliable ultrafiltration membrane supplier. I offer you the best UF membrane price. In addition to ultrafiltration membranes, you can also find the best UF filter cartridges, mf membranes, and nanofiltration membranes here. In addition, we can customize the ultrafiltration water system according to your water treatment needs. Turnkey projects reduce your time costs. For more information about ultrafiltration membranes, please consult NEWater.

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