Sustainable zero liquid discharge desalination (SZLDD)

•SZLDD can be achieved by using SGSP as sustainable thermal energy source and brine discharge location.•By positioning the DCMD intake in NCZ and its discharge in the LCZ, it assists with improving SGSP performance.•The mass flux model prediction is at an 85% agreement with the experimental data.•The trans-membrane coefficient of the used PTFE membrane is about 0.001kg/m2/Pa/h.•The SZLDD system can deliver 52l/day of fresh water for m2 of membrane coupled with RMIT SGSP. The main purpose of this study is to develop a sustainable zero liquid discharge desalination system. Direct contact membrane distillation unit is connected directly to salinity gradient solar pond (SGSP) to achieve zero liquid discharge desalination. The used system contains a hydrophobic microporous membrane module and a plastic pipe circulating all over the pond water surface to be used as a cooling system. The pipe also used as a wave suppression system as it is floating over the top of the pond water surface. The system is sourced by the hot and high concentrated saline water that is extracted from non-convective zone as a feed solution, then, the brine discharges at the lower convective zone of the solar pond. Therefore, if the saturated brine is used to produce salts, there will not be any brine left over which may lead to zero liquid discharge desalination. The system is modelled theoretically and solved by Matlab simulation program. It has been found that the system has the ability to deliver 52l/day of fresh water for m2 of membrane coupled with SGSP, consuming almost 11kW/m2 of thermal energy. Also, the trans-membrane coefficient of the used membrane is proved to be 0.001kg/m2/Pa/h. The results are analysed and the system performance is evaluated and presented in this paper.