Energy recovery for reverse osmosis desalination in Mexico

This paper presents estimates of potential energy savings brought about by the use of energy recovery in small seawater reverse osmosis systems and the implications this could have for Mexico. Energy consumption in well designed reverse osmosis systems around the world without energy recovery ranges from 6-8 kWh/m3. The use of energy recovery can reduce this to 2-3 kWh/m3. The increasing use of reverse osmosis desalination to supply human settlements, agriculture and industry with good quality freshwater in Mexico and today’s record energy prices, highlight the paramount importance of making reverse osmosis installations as efficient as possible. Unfortunately, the associated energy recovery technology is not yet mainstream, and is often neglected, especially in smaller plants due to the comparatively higher capital cost of energy recovery at the small scale. This situation exists in many of seawater systems worldwide and leads to higher running costs and increased environmental impact. This paper also presents an overview of the water and desalination situation in Mexico and it reviews the main desalination technologies and the main energy recovery options for reverse osmosis systems. A case study is also presented where annual energy consumption can be reduced by over 15,000 kWh and potential running cost savings add up to $ 11,000 MXN for a system producing 1 m3/h. The case is then extended to the whole country.