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Membrane filtration
Although the variants of membrane filtration filter different particles, micro organisms and other macro molecules from liquids, all variants use the same membrane filtration method. Membrane filtration is, as the name suggests, based on the presence of a water membrane. Membrane filters are a sort of selective partition; various substances, particles and bacteria can pass through the membrane while others are retained. Every membrane has a specific pore size and Moleculair Weight Cut Off (MWCO). All substances, particles, bacteria and viruses that have a larger pore size or MWCO than the membrane are trapped in the membrane. All substances, particles, bacteria and viruses that have a smaller pore size than the membrane can pass through the membrane. On this page you find everything on membrane filtration water treatment.What is membrane filtration?
Membrane filtration is a separation method that can be used to remove harmful substances from liquids. Various variants of membrane filtration water treatment are used to purify waste water, drinking water and process water, among other things. Membrane filtration is a collective name for various separation processes such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Although we work with all these membrane filtration methods, PB mainly uses in its water filters to remove micro organisms, TSS, Turbidity and macro molecules from our water in this way. With the help of membrane filters, PB ensures safe and clean drinking water.
Membrane filters by PB
Membrane filtration water treatment is often used as a separation method in water purification systems. Membrane filters can, for instance, prevent the formation and spread of bacteria and viruses, but also remove particles like TSS, turbidity and sediment from water. In the most countries it is mandatory to filter safe drinking water. For instance: according to the Dutch Drinking Water Act, only KIWA-certified membrane filters may be used in water treatment. If membrane filters, gatekeeper systems and water filters meet these requirements, they will receive a KIWA BRL K14010-1 certification. All PB products have this certification, which means that they comply with the laws and regulations of KIWA Netherlands.
Our experience is that a KIWA certification abroad is often sufficient to comply with local laws and regulations and meet the WHO standards for Pathogenic Micro-organisms Turbidity and TSS.
Membrane filtration method
At PB, membrane filtration method is used in the treatment of waste water, drinking water, process water, rain water and groundwater. There are various aspects that are of great importance when designing a water purification system based on the membrane filtration method. Aspects that can optimize the effect of membrane filtration are:
- The right choice for the type of water membrane
Depending on the current quality of the liquid and the desired final quality, you can choose the best fitting type of filtration. The filtration experts at PB are happy to help you with the choice of the right membrane. After a careful investigation by our advisors, we can tell you whether you should opt for a micro, ultrafiltration, nano or hyper filtration process.
- Attention for pre- and after-treatment of the purification system and its membranes.
To prevent the water membranes from being damaged or blocked by sharp or hard (sand) particles, the liquid must first be pre-treated. In this way the membrane is protected. The liquid is passed through a fine sieve so that the large parts are removed in advance. There is no standard pre-treatment recipe – after all, every liquid is different. Optimal pre-treatment is determined after an investigation by the experts of PB.
- A correct cleaning method with a frequent rinse and use of the right chemicals.
It is possible that the membrane filters become contaminated during the membrane filtration method. If a membrane is contaminated, its effect will be less. It is therefore of great importance to regularly flush the membranes. With the help of a frequent flush, all collected substances, particles, bacteria and viruses can be removed. Correct rinsing is necessary for any form of water filtration.
Cross flow membrane filtration vs. dead end membrane filtration
Membrane filtration can be either cross flow filtration or dead end filtration. Cross flow filtration has built-in advantages over dead end filtration. This happens because the liquids flow continuously through the membrane. This limits the risk of fouling or an uneven flow. Perfect for automated filtration processes with a high quality end product. At PB we mainly apply cross flow filtration in showers.
Dead end membrane filtration differs from cross flow filtration because there’s no continuous flow. Dead end filtration is a batch process in which the liquid is forced through the membrane filter.
The products of PB are in most settings dead end filtration. But by applying a timer with flush valve, the filter does actually flush frequently. This does give some waste water, but also ensures a longer lifespan of the filter. If combined with yearly maintenance, the lifespan of a membrane filter by PB will be up to 5 years.
Membrane filtration water treatment
There are four commonly accepted methods of membrane filtration water treatment. These methods are defined on the size of the material that needs to be separated from the liquid. The four Membrane filtration water treatment methods are commonly know as microfiltration, ultrafiltration, nanofiltration and reverse osmosis.
Microfiltration
Microfiltration is a membrane filtration method where a membrane filter is placed with a pore size of 0.10 to 1.0 micron. The effect of microfiltration at PB is based on a pressure difference. This pressure difference occurs between the liquid that contains all harmful particles, substances and bacteria, and the filtered liquid. With a required pressure of 0.1 to 2.5 bar, the contaminated liquid is pressed through the membrane. Thanks to the pore size of the membrane, all undissolved substances, particles and bacteria (with a pore size greater than 0.10 microns) will be removed from the liquid. A microfiltration membrane filter is often used as pre filter for ultrafiltration.
Ultrafiltration
Ultrafiltration removes substances in a liquid with the aid of a pressure difference. Where microfiltration is only able to reduce bacteria from liquids, an ultrafiltration membrane can also reduce unresolved viruses from liquids. The membrane filter of ultrafiltration contains pores with a size of 0.01 to 0.10 microns. With a required pressure of 0.5 to 2.5 bar, the contaminated liquid is pressed through the membrane. Ultrafiltration gives PB the ability to reduce the bacteria to LOG 6 and viruses to LOG 4 from drinking water with membrane filtration, without the risk of growth.
Nanofiltration
If nanofiltration is used as a filtration method, not only undissolved substances, but also dissolved substances like chalk and PFAS can be removed. Micropollutants and polyvalent ions are removed from the liquid using a membrane with a pore size of 0.01 to 0.001 micron and a required pressure of 5 to 15 bar. PB delivers nanofiltration as well, contact one of our specialists for more information on nanofiltration.
Reverse Osmosis
With reverse osmosis, we hardly speak of membrane filtration anymore. Reverse Osmosis is very similar to distillation. The reverse osmosis membrane filter has a pore size of less than 0.001 microns. This pore size is very small, so that a separation based on diffusion takes place. With a required pressure of 10 to 70 bar, both micro-impurities, polyvalent ions (dissolved substances) and single ions (dissolved salts) are removed from the liquid. Only gases and low-molecular substances can (partially) pass through the membrane filter of reverse osmosis.
Advantages of membrane filtration
There are many advantages of membrane filtration used in the industry where the following advantages are crucial considerations:
- Flexibility
The wide scope of diverse filtrations methods ensures that the best solution for your separation challenge is available in the industry.
- Lower costs
One of the biggest advantages of membrane filtration is that this method is often less expensive than other technologies. This is because of the lower installation- and energy costs. In addition, membrane filters do not result in a filter cake, therefore there are no costs for removal or disposal of the residue.
- High quality of end product
This separation method perform on the basis of molecular size. This results in a high quality of the end product liquid. Membrane filtration makes it easy to make your end product comply with the strict requirements from the authorities.
- Physical barrier
With Ultrafiltration you always have a physical barrier, even when the power is off. This ensures the safety of water in any conditions and lowers the downtime during maintenance.
Do you want to know more about membrane filtration?
Do you want to know more about the different filtration processes of PB? Or are you looking for specific information about micro-, ultra-, nanofiltration or reverse osmosis? Contact one of our advisers by calling 0314 – 621 465 or by emailing to info@pb-international.com. You can expect a suitable answer within a few working days!
