What is Reverse Osmosis?
Osmosis is the passage of water through a semi permeable membrane from a dilute solution to a concentrated solution. Reverse Osmosis is the reverse of the above, but for water to travel in the opposite direction pressure is applied (see Osmotic Pressure). Reverse Osmosis equipment will typically remove most contaminates from water.
Most Reverse Osmosis units now use spiral wound membranes. Due to advances in manufacturing technology these membranes have become the cheapest on the market. Usually an RO system will be between 65% – 85% efficient only rejecting 15% – 35% of the total incoming water to drain. The rejected water from a Reverse Osmosis unit is referred to as the concentrate, whilst the quality water which has passed through the membrane is referred to as the permeate.
Optimisation of Reverse Osmosis units requires us to maximise flux (flow through the membrane) minimise energy expenditure, downtime for membrane cleaning and membrane replacement. The pressure required for Reverse Osmosis membranes used on brackish water is usually upto 20 bar. The pressure required for a Reverse Osmosis membrane used for desalination can reach 80 bar. Developments in membrane technology are reducing these pressures all the time.
The CAD packages provided by the membrane manufactures allow us to optimise the RO design. As RO membranes differ slightly from each manufacture it is prudent to always use the correct CAD package for each membrane type. Temperature of the feed water is a large factor in the sizing of RO equipment. A small increase in water temperature can have large benefits when it comes to maximising plant out put and minimising energy consumption. To view the sizes of Reverse Osmosis equipment available from Derwent Water Systems please view: Reverse Osmosis Plant