What are the differences between ultrafiltration and reverse osmosis?

What are the differences between ultrafiltration and reverse osmosis?

Ultrafiltration and reverse osmosis are commonly referred to 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

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  • Membrane type

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

The difference between a semipermeable membrane and a 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, and particulate), bacteria, cysts, 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, cysts, fluoride, lead, nitrates, pharmaceuticals, protozoa, salts, sulfates, TDS, and bacteria.

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  •  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 50 psi of pressure. If you are using RO, you need a water pressure higher than 50 psi. If your home water pressure is lower than the levels, you need to increase pressure by adding a booster pump.

Shop for the best countertop ultrafiltration water filter system.

  • Wastewater

Ultrafiltration does not produce any water waste. All the water that passes through the membrane is produced as 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 into the drain.

The RO system requires that it 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 are converted to wastewater.

  • Filtering speed

Compared to both UF and RO, RO filters water at a slow speed. You need 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 on 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 into the dedicated faucet unless you have a three-way faucet installed.

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

If you are using a traditional RO system, it requires more components to be installed, such as a 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 will need 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 from about $200-400 and UF from 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.

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

A carbon block is added to absorb the chlorine taste and odor.

Between RO and UF, which one is best?

If you 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.

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

Read further How does ultrafiltration water treatment work?

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