Desalination steps

Energy use in ocean water desalination has been heavily studied over the years to help bring the cost of the fresh product water down and comparable to other available water sources. Energy reduction and energy recovery have made huge strides in the since the 1950’s when thermal desalination was the only option. Once reverses osmosis (RO) membranes were developed in the 1960’s, the energy required for ocean water desalination decreased even further. The total energy consumption for a ocean water desalination facility is dependent on the water quality objectives set forth by the Department of Drinking Water and the Department of Public Health. In some parts of the world, less treatment may be necessary and in turn reducing the energy required to produce fresh drinking water.

The latest form of energy savings is with the utilization of energy recovery devices (ERIs) that make sure the energy in the brine stream coming out of the RO at high pressures is recovered and put back into the process. The utilization of these devices reduces the total energy required to power the facility by 35% compared to a facility with no energy recovery. The short YouTube video from the manufacturer describes how these work below.

In addition to recovering energy through ERIs West Basin has tested several other RO membrane manufacturers that claim to provide energy savings as well as optimizing operations during different times of the day and year. Varying operations during the different seasons provides big befits on energy savings especially during red tide or algae events that can clog up the desalination facility and require higher energy costs. All of this research was captured through a Water Research Foundation Grant funded study for West Basin’s Energy Consumption Modeling Toolkit. This energy consumption modeling tool can be utilized to determine how much energy is expended during the desalination process and identify areas to conserve. The tool can be downloaded here.

Energy Comparison by Activity

It’s important to understand and put into perspective the energy requirements of ocean water desalination and compare to other water supply sources and daily use items. Below is a table to understand the amount of energy utilized doing regular activities:

Energy Usage Table

For comparison, ocean water desalination utilizes approximately 4,300 kWh/acre-foot of water produced. West Basin’s proposed local ocean water desalination project is a 20 million gallon a day (MGD) facility and therefore the monthly energy consumption per citizen in our service are (assuming 1 million residents) is 7.8 kWh. Although ocean water desalination is energy intensive, so are several other activities and water supplies. West Basin is committed to lowering the energy consumption of ocean water desalination as low as possible to reduce our impact on the environment. Download here.