Abstract
This work proposes a plant for zero liquid discharge (ZLD) of a desalination plant waste. The plant uses an electrodialysis unit for salt concentration. In addition, the plant is augmented with an electrolyzer and fuel cell for hydrogen energy production. Several configurations were tested and compared to treat 100 m3/d of seawater fed to the desalination plant. The core operating condition of the ZLD plant is to concentrate 7.3% brine solution up to 12.5%. It is found that the best ZLD configuration can achieve 95% of overall water recovery, 6% liquid waste discharge, and 3,142 kg/d of solid salt production as added value. However, this performance requires a specific energy demand of 900 kWh/m(3). This considerable energy demand is attributed to the electrolyzer which consumes 98% of the total energy requirement. It is found that the energy produced by the fuel cell can cover 80% of the energy required by the electrolyzer. It is also found that attaining full zero waste discharge via recycling the waste liquid back to the process limits the operational range of the process components and may deteriorate the process operation.