Water purifier and drinking water safety
By Smart Water Tech. Allen Huang 2024-11-09
Water accounts for about 70% of the human body. As an important solvent, water participates in various biochemical reactions in the human body. A healthy person needs to drink about 2L of water per day on average to maintain normal metabolism.
With the intensification of environmental pollution, drinking water sources have been severely damaged, and the types and levels of pollutants have continued to increase; at the same time, with social progress and material abundance, even drinking water that meets the standards may not meet people's requirements for excellence (such as taste, antibiotic residues, etc.).
As a terminal treatment device for drinking water, household water purifiers ensure the safety of our drinking water.
Types of household water purifiers
The mainstream household water purifiers on the market are mainly composed of PP cotton (primary filtration), activated carbon or other composite adsorption materials (secondary filtration), and membrane materials (core filtration) in multiple stages in series, which are composite water purifiers.
Activated carbon materials have extremely high specific surface area and developed internal pores, which can efficiently adsorb organic matter, odor substances, residual chlorine and other chemicals in water. Membrane materials are mainly divided into microfiltration (0.05-5 μm), ultrafiltration (5-100 nm), nanofiltration (1-10 nm), and reverse osmosis (< 2 nm) according to the size of the membrane pore size.
Ultrafiltration can effectively intercept pathogenic microorganisms, and reverse osmosis only allows water molecules and very few ionic minerals to pass through. Therefore, the composite water purifier that connects activated carbon and membrane technology in series can further optimize the quality of drinking water, including reducing color/turbidity, removing organic matter, residual chlorine, and intercepting microorganisms.
Microbial contamination of water purifiers
People are usually sensitive to visible physical and chemical pollution (color/turbidity, smell and taste), and often ignore invisible microbial contamination. Existing scientific studies have shown that the total fine count rate of water treated by household water purifiers exceeds the standard (>100 CFU/mL) by 13.2-87.5%.
Recently, the Yu Xin team of the Institute of Urban Environment, Chinese Academy of Sciences/Xiamen University found that the number of microorganisms attached to the surface of activated carbon and membrane components inside the water purifier can reach 102-106 CFU/g, and the total number of live bacteria is 103-105 copies/mL (PMA-qPCR test). In addition, waterborne pathogens such as Escherichia coli (100-106 copies/g) and Pseudomonas aeruginosa (100-105 copies/g) were also detected to varying degrees (qPCR detection); high-throughput sequencing further revealed the distribution characteristics of Escherichia coli (0-6.26%), Mycobacterium mucogenicum (0.01-3.46%), and Pseudomonas aeruginosa (0-0.16%) in different components of the water purifier.
The activated carbon and membrane components of the composite water purifier can adsorb and intercept microorganisms, consume residual chlorine and other chemicals, and improve the physical and chemical indicators and taste of drinking water. However, it only has a physical effect on microorganisms and does not completely kill them. As the water purifier is used for a longer time or is used in an unscientific way, microorganisms will re-proliferate in the activated carbon and membrane components.
During the sampling survey, it was found that many users have never replaced the filter cartridges of their water purifiers for several years or even more than ten years. The water purifiers are overloaded and have become a "heaven for the accumulation of microorganisms". Once a leak occurs, it will seriously threaten people's health. Therefore, after installing a household water purifier, it is equally important to use and maintain it scientifically and reasonably.
Q1: Does a household water purifier need to replace the filter element?
Are the products on the market that say that the filter element does not need to be replaced reliable?
How often should the water filter be replaced ?
A: Yes. Membrane filtration technology is a physical interception method, and there must be a problem of membrane contamination. In the water treatment process, the performance of the membrane component can be guaranteed by professional cleaning. For household water purifiers, organic membrane components are currently mostly used (a small number of ceramic membranes are used). It is difficult to achieve such a professional behavior as cleaning, so the filter element is replaced to maintain its performance. The replacement cycle of the filter element is related to the water consumption of each household. Users can refer to the manufacturer's recommendations (generally marked on the filter element housing).
Q2: The tap water network is safe, so where do the microorganisms that are filtered out by the water purifier come from?
A: In order to prevent the re-growth of microorganisms in the pipe network, China's "Standard for Drinking Water Hygiene" (GB 5749-2006) stipulates that the residual chlorine limit in factory water and pipe network terminal water is not less than 0.3 mg/L and 0.05 mg/L respectively. Due to the long distance of pipe network transmission or the aging of pipe network in old residential areas, the residual chlorine is consumed, and microorganisms can attach to the inner wall of the pipe network to form biofilm, and may fall off due to hydraulic shear, causing microbial contamination of terminal water. In addition, some bacteria may be resistant to disinfectants and can survive and grow in the pipe network. Therefore, bacteria that fall off the biofilm on the inner wall of the pipe network and bacteria that grow freely in the pipe network may become the source of "deposited" microorganisms filtered by the water purifier.
Q3: Is RO reverse osmosis membrane better than ultrafiltration?
A: The pore size of the RO reverse osmosis membrane is less than 2nm, which can only allow water molecules and very few ionic minerals to pass through. From the perspective of water quality, the water output of the RO membrane is the cleanest. However, its water output is small (more concentrated water is produced), and the minerals in the water are needed by the human body, so we recommend ultrafiltration or nanofiltration technology to meet daily needs.
Q4: If a water purifier is installed, will the water be clean and can it be drunk directly without boiling?
A: Under the premise of reasonable and standardized use of the water purifier, the water safety of the water purifier can be guaranteed to be drunk directly, and boiling it for drinking can further ensure its safety.
About Smart Water Tech
Xiamen Smart Water Tech. focus on
– Instant Hot Water Dispensers
– Under Sink Water Chillers
– Boiling Water Taps
– Chilled Water Taps
– Sparkling Water Taps
– Kitchen Water Taps
– Water Filters
– Water Filter Cartridges
We will continue to devote ourselves to the research of drinking water safety issues and work together with our peers to ensure safe drinking water for residents.
