Estimation of the maximum conversion level in reverse osmosis brackish water desalination plants

Abstract

This paper proposes a simple calculation method to estimate the maximum conversion level in reverse osmosis (RO) brackish water desalination plants. The method is based on the scaling potential of different compounds found in the water to be treated. These compounds include silica, calcium carbonate, calcium sulphate, barium sulphate, strontium sulphate and calcium fluoride. Although the method was originally conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water and its pH and temperature. The programmed method then determines the maximum conversion level of the RO system without the risk of scaling of any of the solutes present in the water. The method can be used as an aid in design optimization of RO brackish water desalination plants with acid-free pre-treatment processes and only the use of scale inhibitors.