Piloting batch reverse osmosis with a flexible bladder for water recovery from scaling-prone brine

A pilot-scale batch reverse osmosis (RO) system with a flexible bladder was designed to recover additional water from RO concentrate. The sulfate-rich, ~6400-ppm concentrate was sourced from the Yuma Desalting Plant (Arizona, USA), which desalinates agricultural drainage water. The pilot produced 4.4 m3/day of permeate with 150 ppm total dissolved solids from the facility’s concentrate stream with a recovery ratio of 82.6%. Despite producing supersaturated brine, there was no performance deterioration due to scaling. Using a bladder for retentate pressurization limited average power to 633 W and the specific energy consumption to 3.3 kWh/m3. The pilot’s energy data informed a model of large-scale batch RO, which has the potential to desalinate the same water for less than 1 kWh/m3. Additionally, a model was developed to predict scaling likelihood in batch RO. This investigation demonstrates that batch RO is a viable technology for low-energy brine concentration beyond saturation limits.