Choose Water Filter that Meet Your Needs and Budget

The Technology of Home Water Filtration System

Knowing the Difference in Effectiveness

How do we normally choose a home water filtration system? Most of us buy a water filter system is by choosing a brand that we know. Normally we trust a branded product. Or may be because it is introduced by a sales person. But do we really know how effective is the purification system?

Different technology will give different effectiveness and capability to filter certain chemicals i.e. the filter technology. Even the same technology, the effectiveness can be different because of the difference technology in producing the component or media. For example, two reverse osmosis membrane from two manufacturers can have different effectiveness in filtering chemicals, micro-organisms (bacteria, virus, protozoa, spores) and particles.

Without having the knowledge, we may trap by the misleading information given by a water filter company. We may end up paying more than the value of the home water filtration system or even worst, the water filter cannot perform as per claimed when there is a microbial breakout or chemical contamination.

What is a home water filtration system? It also called as drinking water system or home water purifier. The main functions of a drinking water system are to filter or remove all these contaminants:
1. sediments / rust / foreign particles
2. micro-organism and its spores
3. harmful chemicals

The value of a water purifier is on how effective is the system in filtering sediments, rusts, harmful chemicals and water-borne bacteria and other microorganism.

Additional functions of a drinking water filter may be providing the following to the filtered water:

  • energy to the water (pi water)
  • high pH (alkaline water)

Filtration of Particles & Harmful Micro-organisms (Patogens)

Generally, size of soil, sediment, dust, rust and other foreign particles are :
(measurement in micron) (1 micron = 0.001 mm)

  • Clay       : 0.1 – 2
  • Silt        : 2 – 50
  • Sand      : 50 – 2,000
  • Dust       : 5 – 1,000
  • Rust       : 10 – 100
  • Spores    : 3 – 40
  • Asbestos : 0.7 – 90

If you do not own a whole house water filter, you may need a pre-filter for your drinking water system. Most of the drinking water filtration system today come with a pre-filter. A pre-filter is not a water purifier. A pre-filter filters sediments larger than 5 or 10 micron before entering a drinking water filter. This will remove bigger size of contaminant like soil and sand.

First stage of water purification for a drinking water system is called particle filtration. It is to filter particles that bigger than 1 micron including bacteria.

Generally, waterborne bacteria have the size of diameter 0.2-2 micron and length 0.4-14 microns and cannot be filtered through 1 micron filter technology. Therefore, be cautious if there is a claim that a home water filtration system can filter 99.9% of bacteria and chemicals but the water purification system can only filter up to 1 micron.

However, most bacteria that have the size smaller than 0.5 micron are not harmful to our health and they present every where including the air.

Most of the harmful bacteria, protozoa, cysts, etc. have the size bigger than 0.5 micron. Therefore, your drinking water system must be able to filter at, at least, 0.5 micron.
Example : Escherichia coli (diameter 0.8 micron, length 2 micron)
Salmonella typhimurium (diameter 0.5 micron, length 2 micron)
Giardia(diameter 6-8 micron, length 12-15 micron)

Technology for Particle & Micro-organisms Filtration

The filtration effectiveness is different between technologies. Even using same technology, the quality is different too due to various factors. For an example, ceramic filter from company A can be different filtration effectiveness compare to ceramic filter company B.

Instead of using filtration method i.e. physical process, micro-organisms can be killed using ultraviolet treatment, which is used in certain water purifiers. However, some home water filtration systems only apply ultraviolet treatment to reduce amount of certain bacteria in the water and not to kill all the bacteria. Nothing wrong if the system has another technology to safe guard from the pathogen. Moreover, normally it is easier to kill pathogen than other non harmful bacteria.

Filtration of Harmful Chemicals

Technology for Chemical Filtration

  • Filtration through adsorbent medium such as activated carbon and KDF media.
  • Reverse osmosis
  • Distillation
  • Cation exchange

Whatever method of water filtration technology it is, none of them by single method, can filter all the harmful chemicals. Therefore, you need to identify specific contaminants that present in the water and choose the correct water filtration system with the technology that have the capability to filter the dangerous chemicals. Examples of harmful chemical that is commonly present in water are lead and asbestos.

Just like particles filtration, chemical filtration effectiveness is not the same too between different water filter technology and also within the same technology. For example, there are different grade and quality of activated carbon. As we know, carbon is used to filter chlorine. How effective is the chlorine filtration is depends on the carbon quality. The quality is depends on how the activated carbon is being produced or activated.

Different chemical needs different adsorbent medium too. For example, to filter arsenic, it involves several steps. First is to oxides As(III) to As (V). Then, adsorption of As(V) on a medium like iron-coated sand. Another method of filtering arsenic is by coagulation process using different medium of adsorbent.

Therefore, the only way to check the effectiveness on filtering a specific contaminants or chemicals is to run through chemical filtration tests. These tests shall be run by a third party, non profit organization which is recognized for its scientific and technical expertise in the area. The results shall meet the strictest standard established such as NSF/ANSI standards for a home water filtration system i.e. drinking water system.

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