Water Filters

The Three Main Water Filtration Processes Explained

Reverse Osmosis

A Reverse Osmosis (RO) water filter is a type of water purification system that uses a semipermeable membrane to remove various contaminants, impurities, and dissolved solids from water. The process of reverse osmosis involves applying pressure to push water through the membrane, which acts as a selective barrier, allowing only water molecules to pass while blocking larger particles and contaminants.

Here’s a more detailed explanation of how a reverse osmosis water filter works:


    1. Pre-filtration: Before the water enters the RO membrane, it goes through several pre-filtration stages to remove sediment, chlorine, and other large particles. This step is crucial to protect the RO membrane from damage and improve its effectiveness.
    2. Reverse Osmosis: The pre-filtered water is then pressurized and forced through the semipermeable RO membrane. The membrane is designed with extremely tiny pores that allow only water molecules (H2O) to pass through, while blocking the passage of dissolved solids, salts, minerals, and contaminants.
    3. Reject Water: As water is pushed through the RO membrane, a portion of it becomes purified and is collected for use. However, a significant amount of water, typically referred to as “reject water” or “brine,” containing the removed impurities, is discharged and flushed away. This helps to prevent the accumulation of contaminants on the membrane’s surface.
    4. Purified Water: The purified water, also known as “permeate,” passes through the RO membrane and is stored in a clean water tank for consumption. This water is free from a wide range of impurities, including bacteria, viruses, heavy metals, nitrates, fluoride, and other harmful substances.
    5. Post-filtration (Optional): Some RO systems include additional post-filtration stages to enhance the water’s taste and further remove any residual impurities. This may involve using activated carbon filters or other polishing filters.
Granular Activated Carbon

A GAC water filter, also known as a Granular Activated Carbon water filter, is a type of water filtration system that uses a bed of granular activated carbon to remove impurities from water. Granular activated carbon is a highly porous material with a large surface area that can effectively adsorb and trap a wide range of contaminants, including chlorine, bromine, volatile organic compounds (VOCs), bad tastes, odors, and organic chemicals.

Here’s how a GAC water filter works:


  1. Adsorption: When water passes through the granular activated carbon bed, the porous carbon material attracts and retains impurities on its surface. This process is called adsorption, where the contaminants adhere to the surface of the carbon particles.
  2. Contaminant Removal: The GAC water filter can effectively remove various water pollutants, such as chlorine, chloramine, bromine and its by-products, pesticides, industrial chemicals, and organic compounds that contribute to bad tastes and odors in water.
Ion Exchange

The basic principle behind ion exchange water filters revolves around the exchange of ions between the water and a specially designed resin or media inside the filter. The resin typically consists of tiny beads or granules made of a polymer material, which is chemically engineered to attract and trap specific ions.

Here’s how the ion exchange process works in water filters:


  1. Ion Exchange Resin: The filter contains a bed of ion exchange resin with a specific charge, either positively or negatively charged. The resin is chosen based on the target impurities that need to be removed from the water.
  2. Water Flow: When water passes through the ion exchange filter, dissolved ions in the water come into contact with the resin beads.
  3. Ion Attraction: The resin beads have an affinity for certain ions. For example, in a water softener, the resin is negatively charged, and it attracts positively charged calcium (Ca2+) and magnesium (Mg2+) ions, which are the culprits behind hard water.
  4. Ion Exchange: As water flows through the resin bed, the target ions in the water adhere to the resin beads, replacing less desirable ions present on the resin.
  5. Release of Treated Water: The water that passes through the ion exchange filter is now free from the unwanted ions and considered purified or softened.
  6. Regeneration: Over time, the ion exchange resin will become saturated with the unwanted ions it has collected. To refresh the resin and restore its ion-attracting properties, the filter undergoes a process called regeneration.

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