Challenges in Designing an RO System for Tidally Influenced Surface Water

Abstract

Faced with growing populations and maximized freshwater supplies, many US communities are developing higher salinity surface water sources that are tidally influenced, such as the Taunton River (Massachusetts), Hudson River (New York), and Chesapeake, Tampa, and San Francisco bays. These tidally influenced raw water sources can experience salinity changes as great as 10,000 mg/L and temperature changes of more than 25°C. This article investigates reverse osmosis (RO) system design in such wide-ranging conditions, specifically fluctuations in salinity of more than 7,500 mg/L and temperature of more than 26°C in the Hudson River. This case is particularly interesting because the optimum design solution is a crossover between brackish water and seawater membranes. In this crossover range, the effects of wide-ranging temperatures, required salt rejection, and selected operating flux significantly impact membrane selection.