Challenges and potentials of hybrid Membrane-crystallization processes in sustainable zero liquid discharge process and energy cost estimation

This paper focuses various membrane and thermal processes and takes their potentials into account to present the most suitable combined method for a hybrid zero liquid discharge process. The concentration of this study is not only to introduce the most suitable methods, but also to consider the most probable challenges that this process faces during the operation, best exemplified by: concentration polarization, temperature polarization, the effect of various type of salt ions on membrane fouling, the role of antiscalants and membrane wetting. Based on the finding of the research, the proposed hybrid zero liquid discharge process consists of two units. The first unit is the primary desalination, which is composed of two separate stages, i.e., a Nano filtration or reverse osmosis system and a membrane distillation system. For the second unit a crystallization is suggested. Considering the estimation of energy consumption used in a typical greenhouse, village, and city, each of them has its own unique character for fresh water production and energy consumption. Based on calculations, the greenhouse must have its fresh water supplied through underground water at a cost of 0.066 US$ per cubic meter while the village and city fetch theirs from the sea at 0.112 US$. Future research should explore the potential benefits and challenges of implementing zero liquid discharge in the other areas emphasizing various aspects of environmental, economic, and social sustainability.