Evaluation of a brackish water desalination pilot system using solar energy

Abstract

Water desalination systems through membrane filtration are efficient in removing salts and have been widely used in different regions of the world. The main objective of this study was to evaluate the quality of water produced from a desalination pilot system with membrane filtration using solar energy and, its operational conditions. The pilot system was installed next to the Water Treatment Plant (WTP) of Praia de Leste, coast of Parana State, Brazil. The feed water for the desalination pilot system was brackish water from the mixture of sea water and fresh water (Pombas river), until total dissolved solids (TDS) concentrations of 3,500 ± 100 mg/L (Experiment 1) and 7,000 ± 100 mg/L (Experiment 2). During the experiments, was evaluated the energy consumption of the pilot system and the production of solar energy by the photovoltaic panels. The brackish water pretreatment using ultrafiltration (UF) was efficient to remove turbidity (95%) and color (100%). The softening system before the reverse osmosis (RO), removed 52.64% of total hardness in the Experiment 1 and 73.36% in the Experiment 2. RO membranes removed 99% of TDS and electrical conductivity, 100% of calcium and 99% of chlorides. The removal efficiency of sulphate from the pilot system was 98%. During the Experiments 1 and 2, the permeation rates presented average values of 22.82 and 22.41 L/h/m. The RO system presented recovery rate of 55.97% (Experiment 1) and 52.65% (Experiment 2). The average osmotic pressure was 10.08 and 13.06 kgf/cm2 for the Experiments 1 and 2, respectively. The average production of solar energy was 84 kWh and 27 kWh (Experiments 1 and 2) and the energy consumption was 199.17 kWh (Experiment 1) and 189.46 kWh (Experiment 2). The treated water from the desalination pilot system presented suitable quality for the required standards in the Brazilian legislation. However, remineralization is necessary for human consumption.