Long-term intermittent operation of a full-scale BWRO desalination plant

Abstract

The use of renewable energy sources (RES) to power reverse osmosis (RO) desalination plants is a promising option for remote communities that face water scarcity. One drawback, however, is that the plants are generally obliged to operate intermittently due to the nature of the RES, which can reduce RO system performance in terms of production, salt rejection and energy consumption. This work analyses the long-term performance of a full-scale brackish water reverse osmosis (BWRO) desalination plant that has been working under intermittent operating conditions for 14 years (similar to 9 h d(-1)). The plant has two stages, a 2:1 arrangement and five spiral wound membrane elements per pressure vessel (Filmtec (TM) BW30-400). The feed water is pumped from a groundwater well. The feed flow and water flux recovery remained practically constant (416 m(3) d(-1) and around 65% respectively) over the 14-year period. The plant uses antiscalant dosing (5 mg L-1) and two cartridge filters in series (25 and 5 mu m) as a pre-treatment. Rinses are carried out before shut-downs. Feedwater conductivity, permeate conductivity, feed pressure, pressure drop, permeate flow, and feed flow operating data were collected. The results show a decrease of about 50% in the average water permeability coefficient and an increase in specific energy consumption from 1.82 to 2.21 kWh m(-3). The results provide useful information about the behavior of BWRO desalination systems under intermittent operating conditions and should be taken into account when designing RES-powered BWRO desalination plants.