A filtration system for the water you use at home has many benefits. There are several methods used to filter the water, making it healthier and taste better. Some filters improve the quality of the water you use for washing. If you intend buying a water filter, it would be best to understand how these devices work.
This article is a guide to understanding the different types of water purification methods. What they do and how you may benefit by choosing the right type of water filter for your needs. To provide an idea of what I’m talking about, here’s a list of the water purification methods we’ll be looking into:
All water filters, whether it’s a simple water filter pitcher or a sophisticated multi-stage reverse osmosis filtration system, start with a sediment filter. This is a fairly rudimentary filtration media that blocks sediments, like dirt and rust. They won’t do much to prevent odors, remove contaminants, volatile organic compounds, or bacteria.
Water softeners and remineralization is another aspect of water filtration that can be important to many. Since most of the US is a hard water zone, water softeners are highly sought after. They adjust the PH to provide alkaline or PH neutral water, eliminating the acidic dangers of hard water.
Every water filtration system uses several methods to achieve different results. You may want any combination of these to obtain the perfect water quality for your home.
So let’s take a look at these methods. You’ll be glad you did, as it will enable you to make an informed decision. Some water filters can be really expensive, heading into thousands of dollars, while others can cost less than $30.
Do you really need the most advanced whole house water filter? Perhaps a simpler, inexpensive countertop filter would make better sense. By knowing how the various types of water purifiers work, you will be able to approach these questions with the confidence that comes from having the right information.
Activated Alumina
One of the best ways of removing fluoride, selenium, and arsenic from your household water is to use an activated alumina water filter.
What is Activated Alumina?
Activated alumina is a highly porous filtration medium which is produced by dehydroxylating aluminum hydroxide. This produces aluminum oxide (Al₂O₃).
Microscopic pores in the activated alumina absorb contaminants, trapping them in the filtration media.
How Does an Activated Alumina Water Filter Work?
An activated alumina water filter should be part of a multi-stage water filtration system to be truly effective. It is always best to use a 5-micron prefilter to remove sediment which may block the activated alumina filter.
For the most effective treatment of toxins, like fluoride and arsenic, the water should be less than 8.5 PH. Optimized fluoride removal occurs around 5 – 6 PH. For the best removal of arsenic, the PH should be 7.
This means, when used with a water softener, activated alumina filtration should be done before the water PH is increased to produce alkaline water.
Activated Alumina Precautions
A common question is whether activated alumina releases aluminum into drinking water. The answer is no. Treatment of aluminum hydroxide starts by heating the aluminum to 500°C to remove all impurities. The final product is highly stable and dissolved aluminum cannot occur.
Activated alumina filters are perfectly safe but do require maintenance to prevent toxins from being released into your drinking water.
Activated alumina absorbs toxins and microorganisms, including bacteria. This means that the filter needs to be backwashed and/or replaced before these toxins saturate the filter. Once the filter has reached maximum absorption, toxins may be transferred to the drinking water.
To prevent harm from using these filters, they need to be backwashed according to manufacturer specifications. They also need to be replaced when expired. This will be after a predetermined value according to how many gallons of water have been filtered.
An activated alumina filter reduces water flow and will require adequate pressure to function. A municipal water supply provides sufficient pressure for the filtration media to provide optimum results.
Typically, the water flow, with an active alumina filter at the point of use, is around 1 gallon per minute (GPM) from a municipal water supply. These would normally be under sink water filters. If you’re using a whole house filtration system (point of entry), water flow will increase to about 7 – 10 GPM.
Ceramic Water Filtration
Ceramic is an organic filtration media that is generally used in point of use filtration systems, like under sink and countertop water filters.
What is a Ceramic Filter?
Ceramic filter cartridges, or candles, use porous ceramic to remove impurities in the water. It is an effective means of removing sediment and bacteria from the water.
One of the greatest benefits of using ceramic filtration is that the filters can be cleaned and reused many times. It is one of the most cost-effective filtration methods.
How Does Ceramic Filtration Work?
The pores inside a ceramic filter are around 0.5 micron. They form channels through which the water flows, only allowing particles less than 0.5 micron to pass through. This makes the filter capable of removing up to 99% of bacteria, as most bacteria are more than 1-micron in size.
To improve filtration, the channels turn at sharp angles, restricting the flow of solid materials in the water.
A ceramic filter can be combined with other media, like activated carbon, ion exchange resin, and silver ions.
By using silver ion impregnated ceramic, the removal of bacteria is enhanced, as well as most volatile organic compounds (VOCs), and viruses. Activated carbon will remove toxic chemicals, like chlorine, improving the tase and odor of the water. Ion exchange media will remove heavy metals.
Without these additional filtration media, a ceramic filter will only remove sediment and most bacteria up to 0.5 micron. Hence, a combination of ceramic and other media is the preferred method for complete filtration.
Water Distillation
A water distiller is the best way to produce purified water. Distilled water is free of toxins, metals, and bacteria.
What is a Water Distiller?
A household water distiller is usually a countertop device that uses electricity to heat water and then distill it.
The filter requires no filtration cartridges that need to be replaced. The only cost of operating the distiller is the electricity used. It is one of the most effective water purifying methods, using no chemicals.
How Does a Water Distiller Work?
Water distillation uses the natural process of distilling water. The natural water cycle involves evaporation, the sun heats water in ponds, lakes, rivers, and the ocean. The evaporated water condenses to form clouds, which returns the water to the ground as rain.
A water distiller imitates this process in a controlled environment. The water is heated until it boils and evaporates. It is then condensed, turning the steam back into water which is stored for use.
By heating the water, bacteria, viruses, and VOCs are destroyed. Only water molecules are evaporated, leaving metals and chemicals behind. The end result is water that almost 100% pure.
Without using multiple filtration media, a water distiller will remove chemicals that discolor the water and affect the taste. Metals and sediment are removed, as well as bacteria, and other organic organisms.
Reverse Osmosis
Reverse osmosis (RO) filtration systems are generally under sink or whole house water filters. This usually involves a combination of several filtration methods in organized stages.
Because RO filters are the most complex, they are usually the most expensive. It is the best way to provide large volumes of filtered water. RO systems are often used by large industrial, commercial, and municipal filtration plants.
RO is also the most effective method of desalination, purifying sea water for domestic and industrial use.
What is Reverse Osmosis?
Osmosis is a naturally occurring phenomenon. This is a principle whereby water with a low concentration of salts will flow toward water with a higher concentration. Reverse osmosis is an artificial method of reversing the natural process.
RO requires a semi-permeable (RO) membrane and increased water pressure. Water with a high concentration of dissolved salts is forced through the membrane using water pressure.
Generally, municipal water is pressurized to allow this process to happen without any additional energy being used. In a low pressure system, like gravity feed well water, a pump may be required to provide the pressure needed for the RO process to function properly.
How Does Reverse Osmosis Work?
A reverse osmosis membrane typically consists of 3 layers:
Because of its density and fine filtration (down to 0.2 micron), the RO membrane blocks over 90% of dissolved salts, metals, and bacteria from the feed water. The contaminants that are removed from the water are flushed out, using water pressure. This wastewater is usually disposed of in a drain. It may be recycled by returning the wastewater to the feed.
Due its high density, the RO membrane reduces the water flow. To compensate for the greatly reduced flow, an RO system uses a storage tank.
RO Water Storage
If the RO system did not store filtered water in a tank, the water pressure at the point of supply would be frustratingly slow. To prevent this, a hydro-pneumatic pressure tank is used.
The tank consists of two chambers, one is filled with air and one receives purified water. The two chambers are separated by flexible bladder.
The tank has a control valve that shuts off the feed water when the pressure in the tank is sufficient enough to provide adequate water flow to the home.
As water enters the tank from the RO membrane, the air on one side of the bladder is compressed. This creates the pressure needed to maintain a good flow rate. When you open a faucet, the compressed air forces water into the pipe at the required pressure.
The size of the tank determines how much water can be used before the pressure is reduced and can no longer supply the outlets. A large, whole house RO filter will require a much larger tank than an under sink system which only supplies a single faucet.
When deciding on an RO system for your home, it is important to calculate your average water usage. The RO tank needs to store enough water to meet demand. If it is too small, it will take a long time to repressurize the tank before you have enough pressure in the system to continue using water normally.
Reverse Osmosis Stages
While an RO filter membrane is one of the best ways to remove most contaminants from your water, it is not 100% effective. To improve filtration and filter efficiency, several stages of filtration can be used.
Numerous filtration media can be combined to prolong filter life and remove contaminants that may pass through the RO membrane.
Pre-Filters
Pre-filtration can occur in several stages. The most common pre-filter is a sediment filter. This is a porous membrane that prevents sediment from reaching the RO membrane. By removing these solids from the water, blockages in the RO membrane are reduced. This improves filter efficiency and prolongs the life of the filter.
Sediment Pre-filters can be used in more than one stage. Each stage will remove smaller particles from water. The first sediment filter stage may only restrict particles up to 1-micron. This allows water to flow through faster and reduces blockages in the next stage, which will typically reduce particle size to 0.5 micron. Using two or more sediment pre-filters will improve the efficiency and efficacy of all subsequent stages.
An active carbon pre-filter can also be used to remove chemicals, like chlorine, fluoride, and pesticides. This helps the RO membrane to remove the remaining chemicals more effectively.
Main Filtration Stages
Once the water has passed through the RO membrane some harmful contaminants may remain in small amounts. To ensure the purest water is stored in the RO tank, a number of stages can be used to remove the remaining contaminants and condition the water, like adjusting the PH:
Post Filtration
When the water leaves the tank, several stages can be used to improve water quality and remove any contaminants that may have collected in the storage tank.
What to Consider Before Buying an RO Filter
Reverse osmosis filters are never cheap. They also require installation which has its own complications and adds to the cost. Because of this, deciding on an RO filtration system for your home requires more careful consideration than any other filtration method.
UV Water Purifier
Usually used a post filter in an RO system, UV water purifiers are the best way of ensuring that bacteria and other microorganisms don’t contaminate your drinking water.
Ultraviolet (UV) purifiers are often referred to as water filters. This isn’t entirely correct. UV does not filter the water. Instead, it uses ultraviolet light to kill bacteria and pathogens. This method is also used to ensure that food products are safe for consumption, like treating dairy products, fruit, and animal proteins.
UV purifiers are used to treat the following:
How Does A UV Water Purifier Work?
Using ultraviolet radiation at the correct frequency (254-nm), the DNA of microorganisms is disrupted. This prevents them from reproducing.
A UV lamp is made using mercury vapor. This is sealed inside a glass quartz tube, protecting the electric light from the water. It is surrounded by a casing, through which the water flows. UV radiation penetrates the water, disinfecting it.
Activated Carbon Water Filter
Activated carbon is one of the most common water filtration methods. It used in just about every type of water filter, from water filter pitchers to RO filtration systems.
What is an Activated Carbon Water Filter?
Activated carbon is a filter media used to remove organic chemicals, also known as carbon-based impurities and other common chemicals, like chlorine.
These filters are generally used to filter the following impurities from water:
How Does an Active Carbon Water Filter Work?
Activated carbon or charcoal works by absorbing organic, carbon-based chemicals and some non-organic chemicals. The filter is designed to have the largest surface area to provide maximum exposure to the impurities suspended in the water.
Pieces of charcoal are contained in a filter cartridge. Water is passed through the cartridge, exposing it to the activated carbon media. Impurities are absorbed by the media, improving the clarity, taste, and odor of the water, as well as removing harmful chemicals.
Once the activated carbon media is saturated, it can no longer absorb any more impurities. This means that filter will need to be replaced periodically in order to function properly.
Activated carbon filters are common, making them easy to obtain and are relatively inexpensive.
Ion Exchange Filters
Ion exchange filters are used mostly to soften hard water and can also be used as a deionizer to remove calcium, magnesium, or sodium from the water.
What is an Ion Exchange Filters?
Ion exchange filters use ion-exchange resins, in the form of beads. As water makes contact with the resin media, ions (charged atoms) are exchanged.
The media needs to be re-ionized by removing the ions or cations, that have been exchanged, from the media. This means that ion filters can be reused many times, making them very cost-effective.
How Do Ion Exchange Filters Work?
Ion exchange can be performed in two ways:
Water softening ion exchange filters use a resin that exchanges sodium (Na) ions for calcium (Ca) or magnesium (Mg). Two Na ions are exchanged for each Mg or Ca ion.
A deionization resin can exchange either positive or negative ions, depending on the resin. These beads contain cations or anions.
Cation exchange media is made from divinylbenzene and styrene. They will exchange positive ions, like sodium, calcium, or aluminum suspended in the water for negative hydrogen cations.
Anion filtration beads are made using styrene combined with quaternary ammonium groups. This media exchanges anions in the water, like chlorine, for the hydroxyl ions in the resin beads.
Ion exchange filters can contain combinations of different beads to remove multiple cations and anions, or be more specific, like softeners that remove only magnesium and potassium.