Strategies for future research and development in desalination – Challenges ahead

Scarcity and value of fresh water has increased use of desalination technologies and alternative water sources globally. This paper briefly discusses the areas that affect the costs and identifies the areas which are believed to have been mainly neglected so far and that require specific attention in terms of future R&D. They are feed water and system characterization, process optimization and concentrate management. R&D and advances in feed water and system characterization is required for determining the fouling potential of the RO modules and as such for establishing a proper pre-treatment system and advancing process optimization as well as concentrate management. This paper highlights the importance of interactive and hydrodynamic effects in water and in system characterization from a fundamental point of view; it discusses the need for developing characterization techniques based on theoretical principles combined with computational and analytical techniques for eventual use by the end-users.

Fresh water is an endangered commodity and as such its scarcity combined with the wide availability saline waters has promoted the global trends towards the use of desalination. Major concern in viability of desalination is its costs. In this paper, seven areas have been identified which affects the costs of desalination and R&D in those areas can be used as cost cutting measures. There has been extensive amount of R&D work in four areas (material and chemical development, pressure recovery devices, co-location of energy and water, and hybrid thermal and membrane processes). The three areas that seriously require R&D work are feedwater and system characterization, process optimization and concentrate recovery/handling. The advancement in feedwater and system characterization is a prerequisite for the advancement in the other two areas and would automatically benefit the other two areas. Furthermore, membrane desalination though a more recent technology than thermal desalination, its use has become more predominant; the total cumulative global membrane desalination capacity has surpassed that of thermal desalination since 1998. Membrane desalination and proper operation of plant is very sensitive to the quality of water entering the RO modules which could get fouled and its operation being hampered in addition to increase in the operation costs. Electric power costs are the major (about 40%) of the operating costs in seawater desalination; electric power costs increases by another 10% from the clean to fouled condition. In addition, there are maintenance and cleaning costs associated to fouling of RO modules. As such feed water and system characterization and proper process design of pre-treatment system is paramount to successful operation of seawater desalination units. Efforts should be directed to establishing proper techniques for feedwater characterization and developing of indices for colloidal fouling and for inorganic fouling and incorporating the interactive and hydrodynamic effects that are usually ignored. Advances in computational techniques and coupling the theoretical principles with advanced experimental analysis certainly would provide that opportunity. As mentioned before once the proper feed characterization method is developed, it would facilitate process optimization for operation as well as for product quality (such as adequate removal of substances of concern such as boron) and for concentrate management.