Experimental investigation of the performance of a seawater Reverse Osmosis spiral wound membrane under variable feed water temperature

Desalination is a process to produce fresh water for human consumption, industrial and agricultural purposes, which is increasing worldwide due to climate change. Reverse Osmosis (RO) is today the most utilized method for desalting seawater. Since 2000, RO plants have increased their capacity accounting nowadays approximately 70 % of the total desalination systems. Several parameters influence the performance of RO desalination. Feed water temperature (seawater temperature varies from −2–36 °C) and salt concentration are key parameters for the RO process performance and efficiency. This research presents the response of a seawater RO spiral wound membrane to the variation of the feed water temperature from 5 to 45 ºC. Several experiments were carried out in a small-scale seawater reverse osmosis desalination unit with a capacity of 150 L/h installed at the Agricultural University of Athens. The behaviour of different variables of interest in the desalination process was studied, such as membrane inlet pressure, permeate flow rate, membrane flux, salt rejection, permeate conductivity, power consumption and Specific Energy Consumption (SEC). The results indicated a significant decrease in SEC from 10.5 to 6.7 kWh/m3 as the temperature increased from 5 to 18 ºC. However, in the range between 18 and 45 ºC, SEC varied only between 6 and 6.5 kWh/m3, while the minimum SEC was observed between 28 and 31 ºC. Additionally, membrane flux increased considerably with temperature ranging from 5 to 20 ºC, from about 15.7 to about 17.1 L/m2 h, respectively. In the range of 20–45 ºC, it increased at a lower rate and reached a maximum value of approximately 17.5 L/m2 h.