What is a Reverse Osmosis System

The reverse osmosis system is a very simple process used for filtration of water.  It consists of a series of tubes covered with a semi-permeable membrane through which water is passed at high pressure.  For the filtration of water through reverse osmosis the water needs to be pre filtered to remove suspended particles and contaminants such as sediment, chlorine, and other oxides.  At least 90% to 99% of dissolved impurities get removed by this process.

Reverse osmosis is widely used in home and industry

Reverse osmosis was originally used for desalination of water, but today it is widely used for purification and treatment of water in many homes and industries, such as food industry, where it is extensively used for concentrating food liquids and other diary products.  Research has also been done for the concentration of milk to reduce shipping costs.  It is also used in maple syrup production to remove sap from the boiling syrup, however, microbial decontamination and degradation of RO membranes has to be monitored closely.

The reverse osmosis process is also widely used in hydrogen production, waste water management, chemical industries, and for domestic applications. It is also used by reef aquarium keepers, because ordinary tap water may sometimes contain excessive chlorine, chloramines, copper, nitrogen, phosphates, silicates, and many other dissolved chemicals, which are harmful to the sensitive organisms in a reef environment.

The reverse osmosis process

• A sediment filter traps solid particles such as iron rust and calcium carbonate.
• A second sediment filter with smaller pores, which is optional, is used for removing finer particles.
• An activated carbon filter then traps organic chemicals and chlorine.
• A reverse osmosis membrane, i.e., a thin film composite membrane is placed after the pre filters.
• A second carbon filter is installed to capture the chemicals not removed by reverse osmosis, this is optional.
• An optional ultra violet lamp is used to disinfect the water from any microbes that may have managed to get through the other phases of the ro process.

If properly set up, a system requires a 1-hour cleaning cycle once per month or more frequently depending on use and contaminants.  Usually a filter is alarmed through flow rates so exact monitoring is not always necessary.  Sometimes, it may be necessary to install a pump to maintain the osmotic pressure which insures that the system continues to function efficiently but in most cases this is not required.  Reverse osmosis systems last for many years and rarely fail.   Usually they slowly begin leaking more ions until an unacceptable level is reached and then a new membrane is installed.

Types of reverse osmosis systems

There are several types of reverse osmosis systems available for residential use

• 3-stage system
• 4-stage system
• 5-stage system

The 3 stage reverse osmosis systems operate quite efficiently in houses and commercial setups like restaurants, bars, cafes, offices, etc. They are quick and easy to connect and typically have a 5-micron sediment filter and carbon block filter.

A 4-Stage reverse osmosis system may have an additional pre filter rated at 20-microns installed before the 5-micron filter.  This is to remove larger particles  and help to extend the life of the 5-micron filter, which could become plugged quickly if the water has a lot of sediment.  Depending on conditions there could be a second carbon filter installed instead of a second sediment filter.

A 5-stage system has an additional pre-filter, and is effective in removing lead and other heavy metals.  It would also have a second carbon filter also.

Most reverse osmosis systems also have an optional uv lamp.  This lamp is for eliminating bacteria and other organic compounds from the water.

Components of reverse osmosis filters

Many of these machines also have additional components and features that make them more user friendly.

• Auto have auto shut off valves - A great feature for service.
• Compact - For under sink or counter top installation.
• Installation kits - For easy installation.
• User friendly - easy replacement of filter cartridges.

Manufacturers like BEV and GE design systems to suit every need.  Typically a residential system comes with all filters, storage tank, faucet, tubing, installation hardware, installation manual and are suitable for drinking and cooking use.

Most systems are not designed for whole house use.  Designing a system for whole house applications is not worth the cost.  So these systems are not really suitable for shower and laundry use.  A large system can produce about 50 gallons of pure drinking water per day and it is supplied by a separate faucet mounted on your sink near or beside your main faucets.