Water Filters 101: Water Filtration Technology 净水器入门:水净化技术与材料

Chinese water isn’t known for its purity and freshness. Rivers and lakes are heavily polluted, as well is all tap water (although to a lesser degree) thanks to inadequate water treatment plants and secondary pollution from the aged pipes. Instead of removing chemicals like anti-biotics, pesticides and dissolved solids like metals, the government simply uses incautious amounts of chlorine as a make-shift solution to prevent disease from wreaking havoc among the overpopulated cities.


This means that tap water in China contains multiple pollutants and impurities which are detrimental to your health. To remove these pollutants from the water the only realistic option for most of the families is to install a water filtration solution on your premise. But before you make any decisions you must know the basics of the different technologies in the market, which will help you go through some tricky products or promotion and find the right filters for meeting your families' needs.


Physical Treatments and materials 物理过滤技术和材料

Material: Activated carbon 过滤材料:活性炭

  • Function: Removes particles larger than 0.2μm, pesticides, chlorine as well as other chemicals


  • Precision: >0.2μm


  • Notes: One of the most important filtration materials in the market with many forms like granular and sintered made of different resources like coconut, almond and wood. Coconut is the best.


Material: PP fiber 过滤材料:PP棉

  • Function: Removes visible sediments and invisible water rust as well as other particles


  • Precision: 1μm


  • Notes: One of the most basic filtration materials used in the market for removing large impurities in order to protect the other filters and prolong the longevity of the whole system.


Material: Ultra-filtration membrane 过滤材料:超滤膜

  • Function: Removes particles larger than 0.001μm, bacteria and virus( no chlorine and pesticides)


  • Precision: 0.001~0.01μm


  • Notes: One of the common used membranes(micro filtration, ultra filtration, nano-filtration and reverse osmosis are the 4 type of membranes in the market, micro and nano are not that often used.)


Material: Reverse osmosis membrane 过滤材料:逆渗透膜

  • Function: Removes all rust, bacteria, virus and heavy metals. ( no chlorine and pesticides)


  • Precision: 0.001~0.0001μm


  • Note: Many different RO filters with different production rate including 50G, 75G, 200G, 400G and 800G, etc. The best RO is from US DOW Chemical, famous for their consistency, efficiency and longevity.

备注:RO膜的制水量有多重选择,从50G到75G, 100G,200G, 400G 及800G等。市场上目前公认最好的RO膜来自美国陶氏,其稳定性\过滤效果和使用寿命都是行业领先水平

Material: Silicon Phosphate 过滤材料:硅磷酸

  • Function: Prevents the hard minerals and rust from bonding together and attaching to the dishes, clothes and so on


  • Note: Not a filter, but works for clothes, dishes, kitchen or cooking ware protection. Used quite often for the final stage in Everpure’s commercial systems.


Material: Ion Exchange Resin(salt is often used for its regeneration) 过滤材料:离子交换树脂(通常配合软水盐使树脂再生)

  • Function: Absorbs hard minerals like calcium and magnesium ions, this makes the water softer, protecting clothes and so on.


  • Note: Used often for dish washers, laundry, or softening the whole house water. When resin reaches the absorption limit, the system must be flushed with salt to regenerate the resin.


Material: UV Light 过滤材料:紫外线

  • Function: Kills bacteria and viruses


  • Note: Ozone generation can also be used to the same effect


Chemical Treatments and materials 化学过滤技术和材料

Material: KDF( copper and zinc alloy) 过滤材料:KDF(铜锌合金)

  • Function: Removes chlorine and some heavy metals(some copper and zinc will dissolve into the water)


  • Note: Good for shower filters but not for drinking water as there will be dissolved metals


Material: Vitamin C 过滤材料:维他命C

  • Function: Removes chlorine


  • Note: Dissolves very quickly, although very effective in chlorine removal


Material: Calcium sulfite 过滤材料:亚硫酸钙

  • Function: Removes chlorine and some metals


  • Note: Works efficiently in water at high temperatures


The combo of physical and chemical treatment 物理+化学过滤

Material: Tourmaline(dragon stone) 过滤材料:托玛琳

  • Function: Adds minerals into water, makes the water softer and increases negative ions and total dissolved O2


  • Note: Used quite often for the post stage for RO drinking water purifiers


Pollutants and sizes 污染物尺寸

Pollutants come in various forms and sizes. From visible large sediment like sands, rust, to invisible small particles, such as bacteria and metal ions. The table below outlines the size of common pollutants and the corresponding treatment methods.


Typically for compounds like pesticides and antibiotics, activated carbon is a must in a multi-stage filtration system. Without treatment of carbon filter, the water is not clean enough for drinking and cooking.


How to judge if a filter is good or not? 如何判断净水器是否有效?

Below are some criterion that is used to judge if a filter is good or not.下面是判断滤芯好坏的几个参考标准。

1. What filtration media are used? 滤料的种类是什么?

Any single filter is designed to remove a certain type of pollutant(s), instead of removing all the contaminants. For example, carbon filter is to remove chlorine and chemicals and RO membrane is to remove metals. As a result, if one does not care too much about the brand, it is often recommended to check what filters are used for the water used for different purposes.


2. How many stages are needed? 净水系统有多少级滤芯?

It depends on what the filter is used for. Theoretically, a multi-stage filtration system is better than the single-stage system because the former one will capture various unwanted pollutants while the latter only target at certain type of pollutant(s). But more importantly, it is still subject to what the filter is used for. For example, a single or a double filter with carbon and KDF will be enough for the water used for cleaning while for a multi-stage filtration system with PP, carbon, RO membrane and etc. is needed for water used for drinking and cooking.


3. Are the materials local or imported? 滤芯是进口还是国产好?

For some of the components imported versions will be better, for example reverse osmosis filters from Dow chemical in the USA are much more efficient than local filters.


How to choose a right filter? 如何选择一款净水器?

1.It is often suggested to know your needs before choosing a water filter. Not all water has to make the water as clean as drinking water.


a ) If the water is used for dinking, then all pollutants must be removed, especially chlorine and heavy metals. If you prefer mineral water, then you can look for the RO systems with mineralization filter in the post stage.


b) If the water is used for shower, faucet or laundry, then you have to find a filter that is able to remove chlorine and soften the water.


c) If the water is used for kitchen cleaning, then priority should be given to those with the function to remove or kill bacteria and microorganism.


2. Generally, a multi-stage filter does more jobs than single-stage filter. Check the origin of the filter which may decide its effectiveness. Coconut carbon is better than other types of carbon. RO membrane from Dow/GE is better than other companies.


3. Avoid products that are claimed to be used over 6 or even 1 year with no maintenance. All filters need to be timely maintained to assure their effectiveness. Otherwise, the water quality can be even worse if it is not maintained in time.


Besides the above, some other factors are important too like special kitchen or tap fixtures, the installation service or moving needs. Not all filters will be suitable to install at home and some companies may not last long in the market. So to be cautious.


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