RO for Brackish Water Desalination

The salinity of brackish water is usually between 2000 and 10 000 mg/L. The World Health Organization (WHO) recommendation for potable water is 500 mg/L, so up to 90 % of the salt must be removed from these feeds. The osmotic pressure of brackish water is approximately 11 psi per 1000 ppm salt, so osmotic pressure effects do not generally limit water recovery significantly. Limitations are generally due to scaling. Typical water recoveries are in the 70–90 % range, which means the brine stream leaving the system is up to 10 times more concentrated in calcium, sulfate and silica ions present in the feed. If scaling occurs, the last modules in the system must be replaced first.