Impact of Feedwater Salinity on Energy Requirements of a Small-Scale Membrane Filtration System
Many remote communities in both developed and developing countries lack electricity and clean drinking water. One solution, for such communities that rely on brackish groundwater, is a photovoltaic (PV) powered hybrid ultrafiltration (UF) / nanofiltration (NF) or reverse osmosis (RO) membrane filtration system. The system prototype described here can produce between 150 – 280 litres of clean water for each peak sunshine hour, depending on the salinity of the feedwater (1 – 5 g/L of total dissolved solids (TDS)) and membrane choice. The best specific energy consumption (SEC) for achieving drinking water quality with a salinity of less than 0.5 g/L TDS from 1, 2.5 and 5 g/L salinity feedwater was 1.1, 1.8 and 2.6 kWh/m3, respectively. Slightly higher feedwaters (7.5 g/L) can be treated with one of the membranes tested, and as long as sufficient power is available for providing an adequate transmembrane pressure. Higher salinities cannot e treated effectively with the current system due to pressure limitations. Energy recovery would need to be investigated in order to achieve a competitive SEC for such high salinity feedwaters.