Desalination technology involves drawing the sea water into a tank and filtering away the salt and mineral content to be used as drinking water. Desalination prevents the dependence on water sources that have limitation for example rainwater, and snow precipitation. Desalination plants has been built in many regions around the world including Middle East, Arabia, China, Israel, Australia and USA. Several factors are considered when determining whether to establish a desalination plant for example how far is the area from the ocean and other water sources like river, whether the freshwater supplies are being overdrawn, and the cost for building the plant. Usually, the desalination plant is built in a coastal area that is within close proximity to the ocean and the energy fuel sources.

Carlsbad desalination plant is a recently open desalination plant that breaks the record as the biggest desalination plant in the USA. The official name that is given to Carlsbad desalination plant is Claude Bud Lewis Carlsbad. In Carlsbad desalination plant, the water will go through several processes including pre-treatment, desalination and post treatment process. In the pre treatment process, the water that is drawn from the ocean will pass through several filters to get rid of the solids, algae and organic particles. They may add chemicals to allow the solid materials to bond together so that it can easily be filtered away.

The water will pass through carbon filter to remove the bad smell and restore the pH level of the water. In the desalination treatment stage, the water will be pumped through the semi permeable membrane at a high pressure. At this stage, the fresh water is separated from the salt. The semi permeable membrane has tiny holes that measure about 0.002 micros. The measurement of 0.002 micros is about 1/100,000 th the size of human hair.

In the post treatment process, the desalinated water will go through a few types of filters to improve the clarity and taste of the water. The water will pass through the sediment filters to get rid of the remaining fine particles that are not yet filtered away. The water will be disinfected to remove bacteria, and microorganism that is in existent before it is released into the reservoir. Chlorine and sterilizer are added to ensure that the water is clean and safe to use by the communities.

Carlsbad desalination plant uses reverse osmosis (RO) process to produce high quality drinking water. The improvement in the membranes used in reverse osmosis process allow higher salt content to be removed from the water so that the water that is produced is higher in quality. To reduce the consumption of energy, they have made efforts to improve energy recovery for example making use of pressure exchangers in the desalination process. Carlsbad desalination plant is equipped with bigger pumps, membranes and motors than other small scale desalination plants. It aims to expand and increase in size in the next few years to produce more water for the community in San Diego.