(401d) Overall Process Synthesis of Seawater Desalination

Population and economic growth, along with climate change, exert an increasing pressure on the availability of adequate water supplies. Today 36% of the global population live under severe water stress with the prediction of reaching 52% by 2050. This rising issue can be alleviated and resolved by undertaking responsible measures such as developing efficient water treatment and management systems [1,2]. Early stage design in water treatment processes, in particular, can provide safe and affordable water by offering maximum design flexibility at lowest system change costs. One promising water treatment process is desalination due to the abundance of the saline water resources on Earth and their sustainable utilization [3]. However, no work has been done so far on the systematic synthesis and optimization, neither in desalination, nor in water and wastewater treatment.

The present work proposes a mathematical framework based on mixed integer non-linear optimization techniques for the systematic synthesis of seawater desalination processes. In the proposed model, two major indicative groups of contaminants are studied, i.e. total suspended and dissolved solids, along with eight candidate technologies targeting the removal of the contaminants. A pre-treatment system of the potential conventional and non-conventional steps is considered [4] before the desalination process which is modelled to accommodate for non-conventional and emerging technology candidates. Optimization of the flowsheet is achieved through increasing the separation efficiencies of the candidate technologies by manipulating their operating conditions within an allowable range [5]. The economic aspects cover operating costs for electricity, chemicals, cleaning, equipment replacement and maintenance. The capital costs account for the capacity of the facility to be designed [6,7,8]. The model is solved for desired water purity to meet drinking water standards with the objective of minimizing the investment and operating costs of the overall process.

The results generally agree with the current world practices in desalination design as a preference towards non-conventional methods is observed, producing water at the lowest price limit. Hence, the developed tool has a significant benefit in reducing the design time, and simultaneously, increasing the cost effectiveness of seawater treatment processes.

Key References

1. WWAP (United Nations World Water Assessment Programme), (2014), The United Nations World Water Development Report 2014: Water and Energy, Paris, UNESCO, vol. 1, pp.1 - 299

2. Veolia Water, (2010), Finding the Blue Path for Sustainable Economy. A White Paper, North America, pp.1-12

3. National Centre of Excellence in Desalination Australia, (2011), Australian Desalination Research Roadmap, Murdoch University, Western Australia, pp.1 - 78

4. Voutchkov, N., (2009), SWRO Pre-treatment Systems: Choosing Between Conventional and Membrane Filtration, Filtration & Separation, vol. 46, pp.5 - 9

5. Koleva, M.N., Polykarpou, E.M. and Papageorgiou, L.G., (2013), An MILP Model for Cost Effective Water Treatment Synthesis, Proceedings from the 20th International Congress on Modelling and Simulation, Adelaide, pp. 2716 - 2722

6. Pickering, K.D. and Wiesner, M.R., (1993), Cost Model for Low-pressure Membrane Filtration. Journal of Environmental Engineering, vol. 119, pp.772 - 797

7. Lu, Y., Hu, Y., Xu, D., and Wu, L., (2006), Optimum Design of Seawater Desalination System Considering Membrane Cleaning and Replacing, Journal of Membrane Science, vol. 282, pp.7 - 13

8. Skiborowski, M., Mhamdi, A., Kraemer, K. and Marquardt, W., (2012), Model-based Structural Optimization of Seawater Desalination Plants, Desalination, vol. 292, pp.30 - 44