RO Reverse Osmosis Water Filtration System

Introduction

Reverse osmosis is a filtration process where pressure is applied to the side of a semipermeable membrane with a high concentration of solutes, overcoming the natural osmotic pressure. This pressure forces water molecules to move in the opposite direction—from higher to lower concentration—effectively filtering out impurities. Unlike standard filters that trap contaminants, reverse osmosis separates clean water, which passes through the membrane, while contaminants are flushed away in the waste stream.

How RO works: 

1. High pressure is applied to water containing dissolved substances like salts and minerals, forcing it against the semipermeable membrane.

2. This pressure drives water molecules through the membrane, which allows only water to pass while larger molecules and impurities are blocked.

3. Contaminants remain on the pressurized side of the membrane, unable to travel with the water.

4. The purified water that emerges on the other side of the membrane is collected as clean, drinkable water.

5. The remaining concentrated solution of impurities, referred to as brine or wastewater, is then flushed away for disposal or further treatment.

What does reverse osmosis remove? 

Reverse osmosis water system filters out chlorine, salt, PFAS, and dissolved solids like arsenic and fluoride through the RO membrane. Additionally, these systems have sediment and carbon filters that enhance purification capabilities. The carbon filters eliminate chlorine, improve taste, and reduce foul odors, while the sediment filter captures dirt and debris, ensuring a comprehensive reduction of impurities.

Reverse osmosis removes:

• Fluoride

• Salt

• Sediment

• Chlorine

• Arsenic

• VOCs

• PFAS

• Microplastics

• Herbicides and pesticides

• Heavy metals

• Many other contaminants

The contaminants listed are some of the most popular ones treated with an RO system, but the system also removes many other contaminants.

However, a reverse osmosis system does not remove most bacteria and viruses. If your water comes from a city treatment plant, then it should already be microbiologically safe. To remove living organisms and viruses, we recommend UV disinfection.

How does a reverse osmosis water filtration system work?

Reverse osmosis system stages

RO systems feature three, four, or five stages of filtration. Every reverse osmosis water system has a sediment filter, a carbon filter, and the RO membrane. Depending on whether water passes through them before or after the RO membrane, the filters are called pre-filters or post-filters.

Reverse osmosis system process

1. Pre-treatment stage

The process begins with pre-filters, including sediment filters that remove larger particles like sediment, chlorine, and organic matter, which could damage or clog the RO membrane. This initial step ensures that the water is adequately prepared for the more detailed filtration to come.

2. Reverse osmosis filtration

High pressure is applied to the water at this core stage, pushing it through the semipermeable membrane. This membrane, the critical component of the system, features tiny pores (about 0.0001 microns) that allow only water molecules to pass while effectively blocking and removing a significant amount of dissolved salts, chemicals, and microorganisms. The purified water, termed the permeate, is then collected in a storage tank for later use.

3. Wastewater disposal

The concentrated contaminants, which do not pass through the semipermeable membrane, are expelled as wastewater or "brine." This step involves a flow restrictor and drain system that manages water flow through the membrane, maintaining efficiency and preventing the membrane from becoming overwhelmed by pressure. Typically, this process generates about 3-4 gallons of wastewater for every gallon of purified water, which is then properly drained away.

4. Storage and delivery

The processed water is stored in the storage tank until needed. When there is a demand for water, it is delivered through a dedicated faucet, providing clean, safe drinking water on demand. This system ensures that purified water is available instantly whenever required by the user.

5. Post-treatment stage

On demand, water from the tank passes through a post filter on the way to the faucet, providing a fresh pass through carbon to remove any residual taste.