The Impact of Solar Intermittency on the Concentration Polarization Factor, Water Quality and Specific Energy Consumption in the Reverse Osmosis Process

Abstract

Water scarcity has prompted the use of desalination technologies such as reverse osmosis (RO) due to its low energy requirement and high production rate. In the present article, the concentration polarization factor (β) was evaluated in RO processes, in batch and continuous systems and with an alternating current (AC) and direct current (DC) to desalinate water with 10,000 mg L−1 of total dissolved solids (TDS). In DC, the power variation and its effect on β was evaluated by simulating intermittent solar photovoltaic radiation. The specific energy consumption (SEC) in kWh m−3, the water quality in mg L−1 of TDS and β were evaluated. In a batch process, 3.98 and 3.85 kWh m−3 were required for AC and DC, respectively. In a continuous process with AC, 3.79 kWh m−3 was required, and for DC, it decreased by 17.93%. The permeate water quality was evaluated with reference to the Mexican standard of 1000 mg L−1 in TDS. A TDS concentration of 1631 mg L−1 was found in batch–AC processes, and a TDS concentration of 747 mg L−1 was found in batch–DC processes. In continuous AC–DC processes, the TDS concentration did not exceed 1000 mg L−1. The permitted β limit was 1.2. The result of the batch process when using DC was 1.007, while for AC, it was 1.022. In continuous processes with AC, the β was 1.008, and in DC, it was 1.012. The results prove that the intermittency due to power variation is an alternative way to reduce the concentration polarization factor, with effects that include a reduction in the specific energy consumption and an improvement in the permeate water quality.