3 Knowledge about each water purifier that you must know

There are many brands in the water purification industry, and the water treatment methods are complicated. Today, from a technical point of view, you are very clear about various water purification technologies, configurations, advantages and disadvantages.

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1.    Principles of household and commercial water purifiers

According to the accuracy of the filter aperture of the filter membrane and the ability to remove dissolved ions, water purification membranes include four categories: microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. The main filtration methods for direct drinking water are only three categories: ultrafiltration, nanofiltration, and reverse osmosis.

1.1   Ultrafiltration membrane (UF)

Hollow fiber ultrafiltration membrane filament: 0.5-2.0mm, inner diameter 0.3-1.4mm, the hollow fiber tube wall is covered with micropores, the filtration accuracy is 0.5-0.01 microns, and the pore size can intercept the molecular weight of the material from several thousand to several hundred thousand. .

The raw water flows under pressure on the outside of the membrane or the inner cavity to form an external pressure type and an internal pressure type respectively.

Ultrafiltration is a dynamic filtration process. The retained substances can be removed with concentration without clogging the membrane surface, and it can run continuously for a long time.

Ultrafiltration membrane is one of the first polymer separation membranes developed, which can remove bacteria, colloids, organic matter and other impurities larger than 0.01 microns.

1.11   Internal pressure ultrafiltration membrane and principle

1.2    Nanofiltration membrane (NF)

Nanofiltration (Nanofiltration) is a membrane separation technology between ultrafiltration and reverse osmosis.

Its molecular weight cut-off is in the range of 80- and the pore size is 1 nanometer, so it is called nanofiltration.

Nanofiltration technology is a membrane separation technology separated from RO technology, and is the continuation and development branch of ultra-low pressure RO technology.

For a long time in the past, nanofiltration membranes have been called ultra-low pressure reverse osmosis membranes (LPRO: Low Pressure Reverse Osmosis).

Now, nanofiltration technology has been separated from reverse osmosis technology and has become an intermediate between ultrafiltration and reverse osmosis.

The independent separation technology between technologies has been widely used in drinking water preparation, medical water preparation, food industry, environmental protection and many other fields, and has become an important branch of membrane separation technology.

Principle: Like the separation process of ultrafiltration and reverse osmosis membranes, nanofiltration membranes are also membrane separation processes driven by pressure difference, which is an irreversible process.

The separation mechanism can be described using charge models (space charge model and fixed charge model), pore model, and electrostatic repulsion and three-dimensional obstruction models that have only been proposed in recent years.

Advantages: Compared with other membrane separation processes, one advantage of nanofiltration is that it can retain small molecular weight organics and high-valent ions that pass through the ultrafiltration membrane, and it can also dialyze some of the inorganic salts and minerals retained by the reverse osmosis membrane-that is Enables “concentration” and desalination to proceed simultaneously.

It can maximize the removal of all pollutants in the water and retain the proper amount of minerals required by the human body.

1.3   Reverse Osmosis membrane (RO)

RO is the abbreviation of Reverse Osmosis Membrane in English.

The general flow of water is from low concentration to high concentration.

Once the water is pressurized, it will flow from high concentration to low concentration, which is also called reverse osmosis.

Since the pore size of the RO membrane is five millionths (0. micron) of the hair, it is generally invisible to the naked eye, and bacteria and viruses are times that of it.

Therefore, only water molecules can pass through, and any other impurities, ions, and Heavy metals are discharged from the waste water pipe, and the product water is pure water.

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All seawater desalination processes and astronaut wastewater recovery and treatment use this method, so RO membranes are also known as high-tech “artificial kidneys” outside of the body.

At present, domestic and foreign, medical, military and civilian fields use top RO membranes for polymer filtration.

The year-on-year growth rate of reverse osmosis water purification equipment was as high as 77.6%.

In the future, reverse osmosis membrane treatment technology will become the most mainstream product technology.

2.1   PP filter cartridge

The PP cartridge filter element is made of polypropylene (PP) by hot melt, and its precision is 1um to 5um. It is a filter element with high efficiency, low pressure difference, long service life and wide applicability.

Main function: Screening out physical pollutants larger than the diameter of the filter hole through logistics interception. Removal of particulate impurities larger than 5 microns in the water, such as suspended solids, sediment, bloodworms, rust, colloids and other large-volume substances to reduce water The turbidity.

Scope of use: Widely use pure water, food and drinking water pre-filtration treatment; with RO reverse osmosis membrane, nanofiltration membrane, ultrafiltration membrane, etc. as pre-filtration pretreatment.

Replacement cycle: The treated water volume is generally 5 tons, and the replacement cycle is 3-6 months, depending on the source water quality and water consumption.

2.2   Activated carbon

Manufacturing process: Water treatment activated carbon is generally made from high-quality coconut shells, refined through a series of production processes, and has a black appearance.

The advantage is that the pore structure is developed, the specific surface area is large, and the adsorption performance is strong.

The expanded area of the filter pores of 1 gram of coconut shell activated carbon is about square meters.

The reservoir layer has low resistance, stable chemical properties and easy regeneration.

According to needs, it can be made into powder, granule, sintered rod or fiber.

Different water treatment plants are suitable for different activated carbon properties

Main function: Removal of residual chlorine, different colors, odors, heavy metals and other toxic and harmful substances through super adsorption capacity, and can improve the taste of water.

Range of application: It is widely used in the treatment process of pure water, food and drinking water; with nanofiltration membrane, RO reverse osmosis membrane, ultrafiltration membrane, etc. as pre-filtration pretreatment, etc.

2.4   Silicon Phosphorus Crystal

Silicon-phosphorus crystals are glassy pellets made of active ingredients such as soda, phosphoric acid, calcium carbonate, etc., which are fired at -°C with high temperature technology.

It has played a positive role in the anti-corrosion and scale inhibition of the water system and the extension of the service life of the equipment.

2.5   Water softener (high purity sodium chloride)

Soft water salt, also known as ion exchange resin regeneration agent. Its main chemical component is sodium chloride (NaCl), the content is above 99.5%, and the general shape is pellets.

When the resin of the soft water equipment absorbs more and more impurities, its adsorption capacity will gradually decrease. To remove the impurities absorbed by the resin (mainly calcium Ca, magnesium Mg ions), sodium ions (Na) need to be used through backwashing The method is to replace the impurity ions (mainly calcium Ca, magnesium Mg ions) adsorbed by the resin through ion exchange to restore the adsorption capacity of the resin. This process is also called ion exchange resin regeneration.

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Ultrafiltration(UF) is a physical filtration process that uses home water pressure to push water through the semipermeable membrane to get rid of particles larger than membrane pore size in water. The ultrafiltration membrane utilized during the filtration process is a kind of hollow fibers with pore size ranging between 0.01 to 0.1 micron, which is several thousand times smaller than a human hair. While water feeds in, the particles larger than the pore size would be retained on the surface of the membrane, whereas water and beneficial minerals that are smaller than the pore size would pass through and become the drinkable water. One highlight of the ultrafiltration membrane is that it does not remove all the dissolved minerals. This could be considered a pro if the home water TDS is at a good level since a certain amount of the retained minerals are beneficial to our health. Yet, it would be a shortcoming if the source water has a high TDS level, as overmuch TDS would significantly affect the water taste. So, you’d better check your home water TDS level before you buy a UF system. According to an authority review conducted by the United States, Canadian, World Health Organization (WHO) and European Community (EC), the US recommended maximum TDS level is 500 mg/L. If your home water TDS level has already exceeded this value, we suggest you choose a reverse osmosis system that could significantly reduce TDS.

What contaminants does the UF membrane remove?

The UF membrane is very effective in reducing rust, sediment, chlorine taste and odor, benzene, crypto, bacteria; it could also partially reduce algae, chloride, copper, lead, mercury; whereas it has no effect on chemicals and TDS.

Frequently asked questions about the UF membrane

Does Ultrafiltration Need Electricity?

Unlike the reverse osmosis filtration that needs a pump to push water past the membrane by increasing water pressure, ultrafiltration could work well with standard home water pressure. Therefore, most of the ultrafiltration system does not require electricity.

What’s the difference between ultrafiltration and reverse osmosis?

Ultrafiltration and reverse osmosis are all physical filtrations that use pressure to push water through the semipermeable membrane, and block impurities larger than the membrane pore size at the outer surface of the membrane. The main difference between them is filtration accuracy. The ultrafiltration membrane pore size ranges from 0.01 to 0.1 microns, whereas the reverse osmosis membrane has a more fine pore size of 0. microns. Thus the RO membrane could remove impurities that are much finer, such as TDS. Given the difference in pore size, RO systems usually need a pump to increase pressure, while ultrafiltration systems can work well with standard home water pressure. That explains why most RO systems need electricity supply but UF systems don’t need it.

What’s the difference between UF filtration and UV filtration?

UF removes impurities larger than the pore size by filtering them out. UV only works for microorganisms like viruses and bacteria in water by killing them with UV light.

Different types of ultrafiltration systems

There are many kinds of UF filters on the market to meet different customers’ needs, like the whole house filter, which installed at the point of entry where water comes into your home from a municipal supply. As well as point of use filter, like under-sink UF water filter and portable water filter straw.

Whole House Ultrafiltration Systems

The whole house ultrafiltration system is a point-of-entry water filtration system that serves the entire home, including the water tube, faucet, shower head, etc. With the 0.01-micron UF filter, it could eliminate different kinds of impurities and contaminants for the whole home and greatly increase the service life of the tubes, faucets, and any other filters present down-line. But the drawbacks of the whole house systems are that they usually need to be installed when you build the house. Furthermore, they are not comparatively affordable, most of which cost several thousands of dollars. However, point-of-use ultrafiltration systems only take a few hundred dollars or even less.

Under-sink Ultrafiltration System

Under-sink UF membrane filters are very popular for homes and families for the budget-friendly price and excellent filtration performance. Let's take Waterdrop smart under-sink UF system and inline under-sink UF water filter for example.

Smart Under-Sink UF System

The smart under-sink filter smart under-sink ultrafiltration system has a very similar appearance to the RO system. It also takes multi-stage filters and has a smart filter life indicating system on the front panel. It uses polypropylene, activated carbon as pre-filters to remove most of the large eye catchable impurities including colloids, sediments, rust, absorb chlorine taste and odor, fluoride as well as most VOCs in water. After that, the water would be filtered by the UF membrane filters with a pore size of 0.01 micron, where the bacteria, superfine rust and sediments, lead and other heavy metals would be removed. The filtered water then followed by another activated carbon filter to improve the taste and eventually flow to a dedicated faucet for home drinking, cooking, etc. The main difference between the smart UF under-sink system and the modern RO system is the filtration efficiency——the UF filter cannot remove the superfine dissolved minerals in water as discussed above.

Under-Sink Inline Ultrafiltration Water Filter

The inline ultrafiltration water filter is a more compact filtration system compared with the smart UF water filter. It takes an all-in-one design that puts different filter materials like a polyester membrane, activated carbon block, KDF, UF membrane all together in one composite filter to get rid of the harmful substances. Benefit from the all-in-one design, the inline filter takes very little space under the counter and especially fits for small apartments, RVs, etc. Just connect it between the tap water input and output faucet, you will be accessible to refreshing, clean water from the tap at the minute.

Portable Water Filter Straw

Ultrafiltration membranes can also be used in portable water filters for drinking water directly from rivers, lakes, and other water resources outdoors. Also takes an all-in-one design, the portable water filter straw is a four-stage filtration made out of pre-filter fabric, UF membrane, activated carbon filter and post polyester membrane. Though the filter itself has a smart frame, the filtration efficiency is powerful. Most of the harmful substances such as chlorine, rust, colloids, sediments, bacteria and heavy metals could be effectively reduced from the raw water. The compact design allows you to put it in your backpack and takes it everywhere, making it possible for you to access safe water anywhere, anytime.

Takeaway

It is important to understand the working principle of the filtration system before choosing a product. Only in this way, you could understand what kind of filtration works best for your water and whether the system could meet your needs or not. I hope this article would be useful in helping you make the right choice.