9 Different Types of Filtration Methods Explained

If you are in the manufacturing, water treatment or pharmaceuticals sector, you will need to know about types of filtration. A process in which unwanted particles are removed from a liquid or a gas is called filtration of water or gas filtration . This guide shows you exactly what types of filtration are. You will be taught 9 techniques that are used in actual industries. You will find out which one is best for you.

Mechanical/Straining Filtration

When physical barriers are required to collect debris, you are employing types of mechanical filtration with different strainer types . The simplest method of trapping particles larger than the filter’s pores is by physical blocking. Imagine it is a sieve, large particles remain, small particles pass through. The pore size varies from 10 to 100 microns, depending on the type of filtration you need.

This is seen in aquariums, wastewater treatment plants and food processing plants. The method is simple, and does not involve complicated equipment or chemicals. The water passes through the filter and the particles become trapped on the surface or in the thin layers of the filter.

It is convenient to use and low cost. Easy to install and does not require special training. But you can’t remove dissolved chemicals or tiny bacteria with this method alone. Most factories employ mechanical water filters as a pre-treatment step and then go to finer filtration steps.

The filter media may be sand, gravel, mesh or synthetic. These will need to be cleaned or replaced periodically as they can get clogged up. Flow rate is maintained at a high rate until the filter is clogged.

Biological Filtration

You use types of biological filtration to break down organic matter using natural bacteria. The beneficial bacteria on your filter media break down the ammonia into less harmful substances in a biological process. This is a natural treatment system that doesn’t use chemicals.

This is commonly observed in aquaria and wastewater treatment systems all over the world. You don’t have to lift a finger, the bacteria do it all for you! No chemicals are required because it is done by natural decomposition. This biological stage is crucial in the wastewater treatment process for secondary treatment.

It takes 4-6 weeks for bacteria to settle in the system. No matter how much you want results quicker, you can’t rush this process. Once you have it configured, though, you can rest assured of consistent performance at minimal maintenance costs. Bacteria colonies grow to maturity and the system becomes self-sustaining.

Bacteria require surface area to grow on your filter. Gravel, plastic media or special biofilm carriers are suitable materials. You test ammonia and nitrite to make sure that the bacteria are doing their job. System crashes are avoided by regular maintenance.

Chemical Filtration (Adsorption)

Activated carbon filters remove dissolved chemicals completely that mechanical filtration does not remove. Types of filtration in chemistry labs use this method extensively.  What occurs in chemical filtration is carbon attracts and holds impurities on its surface through molecular attraction. You are in essence doing chemistry at the molecular level for the purpose of cleaning water or other liquids.

Chemical filtration is used for the removal of chlorine, odors and organics from water. Carbon contains millions of tiny holes which give rise to very large surface area. Chemical filtration is most effective if mechanical filtration is done first to remove the larger particles. This helps to keep carbon from becoming blocked with debris.

The carbon will be replaced periodically when it is full of contaminants. When it is full, it cannot function and will release chemicals into water. The cost of replacement of carbon is a cost, but for high purity applications the result is worth the cost. Regular monitoring will alert you to replace. In chemical filtration systems, metal filter cartridges keep the activated carbon filters alive and running for longer.

Water has to flow through carbon media for the filtration process to occur. As impurities are added to the carbon, the flow rate will decrease. The higher the pressure drop, the more material is clogged. Some carbon types can be regenerated by heating but typically, activated carbon is replaced.

4. Surface Filtration

Surface filtration is used when the particles are large and can be easily filtered out. Simple sieving action traps everything on the outside of the filter. Your solid particles never penetrate deep into the media when pore sizes are small enough. Sintered titanium discs are good surface filtration products for municipal water systems where clean filtration of water and food processing are needed.

For this method to be effective, thin filter media are required. They vary in size from 1-100 microns, depending on the particle size. The efficiency will depend on the quality and uniformity of your filter material. For municipal water systems requiring clean filtration of water and food processing, surface filtration is best.

Surface filtration is used at first to achieve high flow rates. Water flows rapidly through the filter before it becomes clogged. However, if you have a high debris load, you can’t do it without clogging. Filters should be replaced or cleaned regularly to keep flow rate. Easy, but ongoing commitment to maintenance.

The filter medium is typically thin, just a few millimeters thick. Particles can be placed on the surface similar to leaves on a screen. No particles go any further. If the surface becomes clogged, the water will not flow through any longer.

5. Depth Filtration

Among types of water filtration, depth filters are used for heavy particle loads that would fill up surface filters quickly. Your particles are caught across the whole depth of the filter, resulting in multiple layers of filtering. This is not just a superficial clean up, it’s distributed throughout the media.

Industrial depth filter systems use sintered filter discs for their durability and corrosion resistance.

Underground sand filter systems are naturally designed to protect the groundwater from contaminating by applying the principle of depth filtration. The layers of sand are thick, often several meters. Depending on the size of the particles, they are trapped at different depths. This offers very good filtration.

More dirt holding capacity than surface filtration. The frequency of filter changes is less than in surface filtration methods. You will lose flow rate for increased filtration, however. It is a good compromise in industrial applications where reliability is paramount.

The filter media is dense and forms a maze for particles. Torturous path of particles in the media. Small particles go deeper than large particles. This forms a stratified filtration, where the coarser material is on top and the finer material is below.

6. Centrifugal Filtration

When you are looking to separate in a short time that gravity filtration cannot do, you use centrifugal filtration. Particles are pushed outwards by the spinning force and liquid flows through the middle of the machine. This technique is quicker than gravity systems by several hours, usually.

This is used on a regular basis in industrial labs for samples that require quick processing. You don’t have to wait hours or days for your particles to separate from the liquid. It consumes a lot of energy, but it is useful in critical applications. Adjustable speed provides you with accurate separation rates.

The centrifugal systems are typically used in research laboratories to prepare a sample. They are used in industrial applications for high value products, where time is money. The equipment is more expensive up front, but runs efficiently. This process is not a substitute for gravity filtration; it’s an alternative for processes that require faster processing.

The centrifugal force produced by the spinning is a factor that will cause the settling of the particles to be accelerated a lot. The denser the particles the faster they move outwards, leaving the liquid in the middle. Separation is achieved by differences in density. The force intensity and separation rate depends on the speed. Many industrial centrifugal systems are used in conjunction with a sintered filter element in order to achieve more than one separation stage.

7. Entanglement Filtration

Entanglement filtration is used with particles that become entangled in fibers to form a complex filtration network. Your filter media forms a “web” that traps debris in several layers. Particles are not only stuck on the surface, but also stuck inside the fibers at various depths.

This is found in HEPA filters and industrial air systems guarding equipment. The fiber entanglement and random contact with particles makes your air ultra-clean. Even particles smaller than the pores are trapped by random contact with the fibers, by diffusion. This is a good way to protect sensitive equipment and processes that require ultra-clean air.

Entanglement filtration can be seen in cleanroom environments to guard critical manufacturing. This technology is used in electronics manufacturing for contamination control. It’s more effective than simple mechanical filtration at removing submicron particles. Professional maintenance ensures systems are optimized and that there is no bypass.

The fibres are randomly and tortuously arranged. The motion of the particles in the media is irregular. Particles are removed from the air by fibers by three mechanisms – interception, impaction, and diffusion. The higher the density of fibers and the lower the flow rate, the more efficient it is.

Membrane Filtration

Membranes are used for high precision filtration at molecular level. Pressure-driven processes are used to separate membranes according to molecular size. Titanium anodes are used in electroplating applications in conjunction with membrane systems to provide optimal conditions at all times. There are four major types of filtration systems, depending on your needs and purity requirements.

●       Microfiltration (0.1-10 microns): Filters out bacteria and algae from water or other liquids. In winemaking, it is used for clarification, but not to alter the taste of the wine. This is used in the food processing industry for juice clarification. This is the basic particle removal membrane filtration for entry level. Sintered filter elements are used in high-efficiency water treatment for precise filtration and have reusable pore structure.

●       Ultrafiltration (0.01-0.1 microns): Filters out proteins and oils from solutions with very high accuracy. It is essential for pharmaceutical plants to have sterile production environments. Advanced electrode systems keep optimal conditions during processing. This is used in critical applications in medical device manufacturing.

●       Nanofiltration (0.001-0.01 microns): Separates salt and sugar by selective separation. Separates sugar from water in the manufacture of juice. This is the method that is used for the separation of molecules at the molecular level. It’s costly but necessary for high dollar items.

●       Reverse Osmosis (0.0001 microns): Most accurate method to conduct filtration. Removes nearly everything including dissolved salts. It is used in desalination and pharmaceutical laboratories. The membrane allows only water molecules to pass through it.

Electrostatic Filtration

In sensitive areas, electrostatic filtration is used for air cleaning. Electrostatic force is the force that causes charged particles to attract to a collection surface. This is seen in HVAC systems and industrial cleanrooms that safeguard products. Electrical trapping is the method used to accomplish the work rather than mechanical trapping.

The charged particles are attracted to the oppositely charged collection plates or surfaces. The charge is effective in removing particles from the air stream. Collection surfaces are cleaned/replaced regularly. Regular maintenance keeps bypass and maintains efficiency.

Industrial Applications

Water Treatment Plants

In water treatment plants, you employ types of filtration to clean drinking water. What are industrial filters? They are specialized systems designed for demanding applications requiring precise contamination control and regulatory compliance. There are several different types of water filtration used at each step. Mechanical pre-treatment in the first stage for the removal of large debris. Chemicals are removed in the second stage using activated carbon. The advanced purification is achieved by membrane technology in the final stage. This multi-layered strategy provides safe drinking water. Porous frit materials are used in advanced industrial water treatment for separation and purification.

Electroplating Operations

In electroplating, your water quality is directly related to coating quality. Mechanical filtration and chemical treatment are used together for best results. Electrochemical means are employed in some advanced facilities to keep the electrolyte pure during processing. Investing in good filtration will save you expensive production issues and rework. Quality systems provide uniformity of coating.

Pharmaceutical Engineering

In pharmaceutical manufacturing, your filter sterilization pore size needs to be within very strict standards (0.22 microns minimum). The safety of the product is totally determined by the type of filtration sterilization. Quality filtration systems are essential for FDA compliance. Correct filtration during manufacturing is crucial to patient safety. Quality systems help to prevent contamination and meet regulatory requirements.

Comparison Table – All Filtration Types

Type	Pore Size	Best For	Cost	Maintenance
Mechanical	10-100 microns	Debris	Low	Frequent
Biological	Varies	Organic	Low	Moderate
Chemical	1-10 microns	Chemicals	Low-Mid	Regular
Surface	1-100 microns	Particles	Low	Frequent
Depth	0.5-10 microns	Heavy loads	Mid	Moderate
Centrifugal	Varies	Fast separation	High	Moderate
Entanglement	Varies	Air	Mid	Regular
Microfiltration	0.1-10 microns	Bacteria	Mid	Moderate
Ultrafiltration	0.01-0.1 microns	Proteins	High	Regular
Nanofiltration	0.001-0.01 microns	Salt	High	Regular
Reverse Osmosis	0.0001 microns	Pure water	High	Regular
Electrostatic	Varies	Air	Mid	Moderate

Frequently Asked Questions

What are the number of different types of filters?

There are 9-12 main types of filtration based on classification system. They can be mixed together to get the best results. Most industries employ several different types of filtration techniques in combination, strategically. They each are designed to capture a different size of particles and contaminants.

Name the 3 most common types?

In industry, you will see mechanical, chemical and membrane most frequently. Mechanical is used first for debris removal. Chemical used for dissolved contaminants. Membrane is used for the last level of purity. The three make up 90% of all applications globally.

Is it possible to mix the types of filtration?

It’s a must to mix them together for optimum effect. You start by using a coarse one and then finer. Large particles are removed first, small particles are removed later. This “layered” filtration approach is the norm in water treatment types of filtration. This way, you will get much better results.

How frequently do you change filters?

They are replaced monthly to yearly depending on type used. Pressure is monitored to determine when it needs to be replaced. You replace them periodically before they fail. Mechanical filters require regular change weekly or monthly. Membrane filters have a longer life but the initial cost is higher.

Which is the most economical over time?

A mechanical water filter is an initial low cost investment. Little expense down the road for operation and maintenance. It saves you money in the long-term, although it may cost little at first. In industrial systems, low cost mechanical systems are frequently used in combination with high cost membrane systems in a strategic way.

How to select the proper type?

You consider five important questions regarding particles, volume, budget, standards and maintenance. You match your particular requirements with the proper type of filtration. You do research on equipment suppliers that have knowledge about your industry. You test systems prior to full scale implementation.

What factors influence the rate of filtration?

All three (particle size, pressure and temperature) have a significant effect on factors affecting rate of filtration. These factors can be controlled to determine your type of filtration process. Keep an eye on these parameters regularly for optimum performance.

Conclusion

You are now familiar with all types of filtration and their uses. The different types of filtering have various uses in different industries. The various types of water filtration and treatment methods need to be used in conjunction. The appropriate types of filtration equipment can be selected for the needs. It is important to get professional advice to prevent expensive errors. Long-term reliability and efficiency is guaranteed by advanced solutions.

Contact qualified filtration experts today to create the best filtration solution for your particular industrial application, operational needs, and regulatory compliance requirements.