A Reverse Osmosis System is built of five basic parts:
1) Pressure Vessels & Membranes
Obviously, a Reverse Osmosis System wouldn't get very far without membrane elements. The proteins that make up membrane elements vary depending on the kind of intake water and ending clarity. There are membrane elements for brackish water, seawater, hospital-grade disinfection, and membranes designed to remove specific contaminants to name a few. If there is a water treatment need, you can be sure there is certainly a membrane element for the job. The size of the task (municipal, commercial, or industrial) will determine the size and number of membranes in a system. There can be anywhere from a single two and a half inch membrane (like in an under-sink Reverse Osmosis System) to hundreds of eight inch membranes all working together (a typical reverse osmosis plant).
2) Reverse Osmosis Skid
The best way make your Reverse Osmosis system as durable as possible is with a powder coated, carbon steel frame to mount all of your components on. It's resistant to the elements, designed for the heavy vibration of high-pressure pumps, and  mounts to the ground to ensure that it will last a lifetime.
3) Cartridge Filter
Most Reverse Osmosis Systems come with a cartridge filter to ensure that no particles large enough to damage the membranes come anywhere near them. This cartridge is usually a five micron spun polypropylene filter, but can vary upon request. The cartridge comes in a durable casing that can handle the pressure from the main feed or booster pumps.
4) Reverse Osmosis High Pressure Pump
Without a high-grade pump, the rejection rate for a Reverse Osmosis System isn't viable in most commercial or industrial settings. It is vital to the system to ensure that the pump is matched to the membrane quantity and size appropriately. Usually, the higher the horsepower on the intake pump, the better the rejection and recovery rates of permeate.
5) Control Panel
Lastly, the Reverse Osmosis System has to be controlled by a human operator. At Pure Aqua, we use advanced PLCs or a solid-state microprocessor depending on how advanced the controls need to be. The controls can also be used to manage multiple systems simultaneously, effectively making a one-man water production plant.
Reverse Osmosis Systems can have a number of other components built onto or into them as extra components as well. The entire skid can be built into a containerized system, for example, so your Desalination by RO System is always on the go. There are a number of supplemental skids that can be attached to an RO System as well, for tasks like membrane cleaning, pretreatment, chemical dosing, and a number of other jobs as necessary.