The commonly used filtration technologies for industrial filters cover multiple types, each suitable for different water quality conditions and treatment needs. The following is a detailed introduction to several common technologies, their characteristics, and application scenarios:

1、 Membrane filtration technology

Using specially manufactured semi permeable membranes to separate particles, colloids, dissolved substances, etc. in water, they can be classified into the following categories based on pore size:

1. Microfiltration (MF)

Principle: Separate suspended particles, bacteria, colloids, etc. by intercepting a physical barrier with a pore size of 0.1-10 microns.

Features: Low operating pressure (0.01~0.2 MPa), large processing flow rate, but low filtration accuracy.

Application: Remove large particle impurities such as suspended solids and algae in wastewater during the pretreatment stage.

2. Ultrafiltration (UF)

Principle: With a pore size of approximately 0.001~0.1 microns, it can separate large organic molecules, colloids, bacteria, and viruses.

Features: It can intercept substances with a molecular weight of 5 to 1 million, without the need for chemical agents, and operates under moderate pressure (0.1~0.5 MPa).

Application: Removing proteins, oils, and microorganisms in wastewater treatment, or as a pretreatment for reverse osmosis.

3. Nanofiltration (NF)

Principle: With a pore size of 0.001~0.01 microns, it can intercept small organic molecules, divalent ions (such as calcium and magnesium ions), and some heavy metals.

Features: Low retention rate for monovalent ions, capable of softening and desalination, with high operating pressure (0.5-1.5 MPa).

Application: Desalination of industrial wastewater, heavy metal recovery, organic matter separation (such as dyes and pesticides).

4. Reverse Osmosis (RO)

Principle: With a pore size of less than 0.0001 microns, it can intercept almost all dissolved salts, organic matter, and microorganisms under high pressure (1-10 MPa).

Features: The desalination rate is over 99%, but the energy consumption is high, and regular cleaning of membrane surface pollutants is required.

Application: High purity water treatment (such as boiler water), wastewater reuse, seawater desalination, etc.

2、 Pressure filtration technology

By applying pressure to pass sewage through filter media, impurities are intercepted. Common types include:

1. Frame filtering

Principle: Composed of filter cloth, filter plate, and filter frame, the sludge is dehydrated by pressure to separate solid impurities.

Features: High filtration accuracy, suitable for high concentration suspensions (such as industrial sludge), but with a long operating cycle and the need for manual slag discharge.

Application: Sludge dewatering in chemical, metallurgical, and food processing industries.

2. Centrifugal filtration

Principle: Using centrifugal force to separate suspended particles, the larger the particle size and the greater the density difference, the better the separation effect.

Features: Large processing capacity, high degree of automation, but poor effect on small particles (<5 microns).

Application: Removing high-density impurities such as sand and slag in sewage treatment, or used for sludge concentration.

3. Vacuum filtration

Principle: Under negative pressure conditions, sewage is passed through a filter cloth to trap solid particles.

Features: Low energy consumption, suitable for processing viscous materials (such as electroplating sludge), but slow filtration speed.

Application: Solid liquid separation in the light industry and pharmaceutical industry.

3、 Adsorption filtration technology

Using the adsorption capacity of porous materials to remove organic matter, heavy metals, pigments, etc. from water, typical methods include:

1. Activated carbon adsorption

Principle: Relying on the huge specific surface area (500~1500 m ²/g) and microporous structure of activated carbon to adsorb pollutants.

Characteristics: Significant removal effect on volatile organic compounds (VOCs), color, and odor, but requires regular regeneration or replacement.

Application: decolorization of chemical wastewater, deodorization of drinking water, treatment of organic waste gas (gas-phase adsorption).

2. Resin adsorption

Principle: Utilize the functional groups of ion exchange resin or macroporous adsorption resin to undergo ion exchange or physical adsorption with pollutants.

Features: It can selectively remove specific ions (such as heavy metals and precious metals), and can be reused after regeneration.

Application: Treatment of heavy metal wastewater (such as wastewater containing nickel and copper), purification of radioactive wastewater.

3. Magnetic adsorption

Principle: Combine magnetic materials (such as iron oxides) with pollutants and separate the adsorbed particles through a magnetic field.

Features: Fast separation speed, suitable for the recovery of micron sized magnetic particles, and can be combined with other processes.

Application: Iron removal from steel processing wastewater and rare earth element recovery.

4、 Membrane bioreactor (MBR)

Composite technology combining membrane filtration and biological treatment:

Principle: Microorganisms degrade organic matter in the reactor, while membrane components intercept activated sludge and large molecular substances, achieving sludge water separation.

Features: High processing efficiency, good effluent quality (can be directly reused), low sludge production, but the membrane is prone to fouling and needs to be cleaned regularly.

Application: Treatment of high concentration organic wastewater such as municipal sewage treatment, food processing wastewater, and pharmaceutical wastewater.

5、 Other filtering technologies

1. Electrodialysis (ED)

Principle: Under the action of an electric field, cations and anions in water are separated by an ion exchange membrane.

Features: Low energy consumption, suitable for desalination of saltwater or low concentration wastewater, requiring regular cleaning of the membrane stack.

Application: Desalination of circulating water in power plants and recovery of useful ions from chemical wastewater.

2. Sand filtration/multi-media filtration

Principle: Suspended solids are intercepted through multiple layers of media such as quartz sand, smokeless coal, and manganese sand, relying on physical screening and adsorption.

Features: Low cost, simple operation, commonly used for preprocessing, but limited filtration accuracy (generally>5 microns).

Application: Pre treatment of water plants, primary filtration of industrial wastewater.

3. Precision filtration (security filtration)

Principle: Use a filter membrane or filter element with a pore size of 0.1-5 microns (such as PP melt blown filter element) to trap small particles.

Features: As a pre protection for terminal filtration or membrane processes, it prevents large particles from clogging the membrane components.

Application: Pre treatment of reverse osmosis, preparation of high-purity water for the electronics industry.

Key points for technology selection

1. Water quality characteristics: Select technology based on suspended solids concentration, pollutant type (organic/inorganic), and particle size.   

-High suspended solids: priority sand filtration, plate and frame filtration;   

-Dissolved pollutants: Choose membrane technology, adsorption, or ion exchange.   

2. Processing objective: When there is a high demand for reuse, RO or MBR should be used; Priority should be given to electrodialysis or nanofiltration for desalination needs.   

3. Cost and maintenance: Membrane technology has a high initial investment but occupies a small area, adsorption technology requires regular regeneration, and pressure filtration needs to consider energy consumption.   

By combining multiple technologies such as "pretreatment+membrane treatment+adsorption", efficient purification and resource recovery of industrial wastewater can be achieved.