Home water filters come in all kinds of shapes and sizes, and the technology behind them can be quite daunting to understand for the layman. Even so, you can still get a basic understanding of how water filters work without having to acquire a degree in engineering or chemistry. And knowing how the different processes work will mean you can make informed decisions when it comes time to get a filter system installed.
Most people are familiar with the sizes that filters come in, meaning that you can use a jug filter in the fridge, a single-faucet model or a whole-house system. These all refer to how much water you can filter in your home. They don’t really address how that filtration is done. That’s where it gets complicated. Within the realm of most residential water purification systems, there are a handful of different technologies involved:
- Mechanical filtration
- Carbon filtration
- Ion exchange
- Reverse Osmosis
- Ultraviolet (UV) radiation treatment
Each of these will be covered below. Just be aware that many systems will utilized more than one of these techniques, particularly the larger systems that may even use them all.
This just means the basic straining out of large particles from your water. The main purpose for this technique is to remove solid bits of matter, known as sediment. Coarse filters will remove only large particles, but very find micro filters can remove much smaller material that can include some pathogens or bacteria. As the filter spaces are filled with matter, they become less effective and will need to be replaced. Some solid filters (like the ceramic types) can be washed and reused.
Single filters like this are very simplistic but if you were to have a series that ran from coarse to fine, you would find that quite a lot of matter can be strained out. Most filters will have mechanical filters as part of their overall process but they are seldom used on their own because they do not remove any dissolved materials or chemicals. These will only remove dirt, debris, rust particles and other solid materials.
These filter inserts utilize the naturally absorbent nature of carbon to help remove non-particulate chemicals from the water. There are a few different forms of carbon filtration, such as activated carbon or charcoal. This is the type of filter that is excellent at improving the general taste and smell of your water, and even the most inexpensive filter system usually has some form of carbon insert for chemical absorption. Your most effective option is the “activated” carbon because it has been heat-treated to create even more porous surfaces for better filtration. Like the other types of mechanical filters, you can exhaust the abilities of carbon to take in foreign substances and the filters will be need replacing.
This type of filter is ideal for removing many common contaminants, such as chlorine, benzene, radon, pesticide residues, hydrogen sulfide and general bad odors/tastes.
Ion Exchange Systems
Ion Exchange. Image courtesy of FilterWater.com
Now we are getting to the more complex types of treatment systems that will require a little more explanation.
The filter itself is made up of several layers of tiny resin beads that have a special coating on them that reacts with materials it comes in contact with. The principle at work here is that the ions (molecular particles) on the beads will exchange with other ions that are floating freely in the water as it passes through the filter. These filters do not physically trap particles like the other ones do, and you can only remove ions that react correctly with the resin beads.
The beads will release their own coatings of harmless sodium or potassium into the water, while simultaneously removing many other minerals like iron, calcium, manganese, fluoride and sulfates. Because they really only target minerals, this is the ideal type of treatment for mineral-heavy hard water. Many water softener systems use an ion exchange process. It won’t remove any other kinds of toxic chemicals and isn’t usually used on its own when in a purification capacity.
This is the really serious purification technology that good-quality systems will use. If you are looking for very thorough water filtration, you should be looking for a system that has a reverse osmosis component to it. Water to be filtered is held under high pressure in a tank that has a semi-permeable membrane dividing it. The pressure slowly forces water through the membrane, which blocks all the impurities from following. It’s similar to a mechanical filter, but it operates on a much finer molecular scale.
This will block out just about everything but it is a slow working system and it creates approximately 5 gallons of clean water for every 90 that enter the system. You’ll seldom find a system that operates a reverse osmosis process on its own. It usually works in conjunction with a couple of the other systems so that the water being treated at this point is already partially purified.
A reverse osmosis system will remove all types of minerals (calcium, lead, sulfates, aluminum, sodium) as well as fluoride, chlorine, nitrates, solvents and other organic chemical toxins. Pathogens like bacteria or parasites will also be strained out. Overall, it is the best option for removing as many contaminants as possible.
Ultraviolet Light Treatment
Unlike the other processes, this is not really a filter and will not actually remove anything from your water. A large UV light bulb is used to irradiate incoming water to kill off living organisms like bacteria or parasites. It has no further effect on your drinking water. Most municipal systems won’t require this type of treatment but anyone on a private system or well should have one because there is no other chemical treatment involved to kill off the living components in the water.