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Ultrafiltration vs reverse osmosis: what are the differences?

Ultrafiltration vs. reverse osmosis? What are the differences and similarities?

Ultrafiltration vs reverse osmosis

Ultrafiltration and reverse osmosis are commonly referred to us as RO and UF.

Both ultrafiltration and reverse osmosis are types of water filtration that rely on home water pressure and use membrane technology to remove contaminants from water.

Ultrafiltration VS reverse osmosis

Reverse osmosis (RO)Ultrafiltration (UF)
Use semipermeable membraneuse hollow fiber membrane
Membrane has a pore size of 0.0001 micronMembrane has a pore size of 0.01 to 0.1 micron.
Removes contaminants such as essential minerals, viruses, copper, cyst, fluoride, lead, nitrates, pharmaceuticals, protozoa, salts, sulfates, TDS, and bacteria.Removes contaminants such as suspended solids (such as sand, sediment &particulate), bacteria, cyst, copper, lead, pharmaceuticals, algae, viruses, and Pathogenic protozoa (such as Giardia lamblia and Cryptosporidium)
Use high water pressure at 50psiuse low water pressure
when water pressure is low you require booster pumpno pump required to increase water pressure
Produce water wastageno water wastage
Filter water slowFilter faster
Requires storage tankNo storage tank
Complex to installEasy to install
Membrane last longerMembrane last less
Intial cost for RO is highintial cost is low
Maintanance cost lowMaintenance cost high
You can additional filter such as carbon and remineralization filterYou can additional filter such as carbon and remineralization filter
  • Membrane type

Reverse osmosis uses a semipermeable membrane, while ultrafiltration uses a hollow fiber membrane.

The difference between semipermeable membrane and hollow fiber membrane is pore size. The pore size is the only thing that determines the type and size of contaminants removed in water.

  • Membrane size

The reverse osmosis membrane has a pore size of 0.0001, while the ultrafiltration hollow fiber membrane has a pore size of 0.01 to 0.1 micron.

  • Contaminants removed

Ultrafiltration hollow fiber membrane has a large pore size compared to RO membrane; therefore, it is capable of removing all suspended large particles.

Ultrafiltration hollow fiber membrane is effective for removing contaminants such as suspended solids (such as sand, sediment &particulate), bacteria, cyst, copper, lead, pharmaceuticals, algae, viruses, and Pathogenic protozoa (such as Giardia lamblia and Cryptosporidium)

Since the RO membrane has small pore sizes, it is capable of removing all dissolved contaminants, including essential minerals such as sodium, magnesium, and calcium. This is the only disadvantage of the RO system, but you can add those lost minerals by adding a remineralization filter. The Ro membrane is also effective for removing contaminants such as viruses, copper, cyst, fluoride, lead, nitrates, pharmaceuticals, protozoa, salts, sulfates, TDS, and bacteria.

  •  Water pressure

As said earlier, both RO and UF rely on home water pressure to push water to the membrane. The RO requires high water pressure that most homes cannot offer, while UF uses low water pressure.

For a RO system to operate effectively and reduce water wastage, it requires a 50psi pressure. In case you are using RO, you need water pressure higher than 50psi. If your home water pressure is lower than the levels, you need to increase pressure by adding a booster pump.

  • Wastewater

Ultrafiltration does not produce any water wastage. All water that passes through the membrane is produced to clean water for drinking.

Reverse osmosis produces wastewater. Once the contaminated water passes through the RO membrane, pure water passes through and becomes safe for drinking, but the water with dissolved contaminants is flushed away to the drain.

RO system requires to be connected to the drain. To alleviate this, you can opt to use a tankless RO system that has a drain ratio of 1:1 rather than a traditional RO system that has a drain ratio of 4:1. Ratio 4:1 means for every gallon the RO system purifies, 4 gallons is converted to wastewater.

  • Filtering speed

Comparing both UF and RO, RO filters water at a slow speed. You require to have a storage tank under your kitchen sink to make pure water available.

UF treats water faster, so you do not require a storage tank the system is installed directly to the faucet.

  • Water storage

UF produces water on demand that goes straight to the dedicated faucet, so it requires no storage tank, and RO requires a storage tank unless you are using a Tankless RO system.

In addition to storage, RO tanks can grow bacteria if not properly cleaned and sanitized. You are required to clean and sanitize the RO tank once per year using a sanitizer.

  • Installation

Both RO and UF are installed directly to the dedicated faucet unless you have a three-way faucet installed.

RO is more complex to install; it has to be hooked to the drain for flushing away contaminated water. 

In case you are using a traditional RO system, require more components to install, such as booster pump, permeate pump, faucet, and storage tank.

Countertop UF systems do not require installation

  • Membrane life span

The reverse osmosis membrane lasts longer than the UF membrane. You require to replace the UF membrane more frequently than the RO membrane.

  • Cost

The initial cost of RO is higher than UF. RO system initial cost ranges about $200-400 and UF about $100-200.

RO requires more components which causes the initial price to be higher but remember the maintenance cost. The UF will cost you more on membrane replacement.

  • Additional filter

Additional filters such as carbon block or remineralization filter can be added to both RO and UF.

A remineralization filter is added to the RO system to add essential minerals that are removed during the filtration process.

Carbon block is added to absorb chlorine taste and odor.

Between RO and UF, which one is best?

If want pure water for drinking, washing fruits, and cooking RO is the best choice.

If you want to retain essential minerals such as calcium and magnesium, UF is the right choice, but still, on the RO system, you can add a post remineralization filter.

The ultrafiltration method is best for tap water because this water is already treated by the municipal and mostly doesn’t contain germs, dissolved particles, and total dissolved salt (TDS) level is within the required limit.

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