Three pressure retarded osmosis processes

Abstract

Pressure retarded osmosis (PRO) processes can be implemented on a number of water types, using different technologies and achieving various power outcomes. The first one is seawater with river water, necessitating movement at seawater level of huge water volumes with extremely low power losses. The pressure exchanger has to consume significantly less power than it does in RO technology. Pretreatment CAPEX and OPEX expenses have to be considerably lower than those implemented by RO technology, while water quality must be as good as that required for RO. The second one is SWRO brine with wastewater, using already filtered and pressurized brine from an SWRO plant. This option is the most economical, as gauge and osmotic pressure are recovered in the same block of pressure exchangers. The osmotic pressure of the SWRO brine is directly converted to the gauge pressure of the SWRO feed. A proportionally diminishing flow is required from the high pressure pump. The third one is Dead Sea or salt lake with river water, implementing natural exotic resources with extremely high osmotic pressures. The PRO technology in this option requires operation in several stages.