Brine management strategies for desalination systems: Decision support system

Rhys Farrall

This thesis explores and evaluates a decision support system (DDS) for the management of desalination brine. The rapid uptake of desalination technologies to meet freshwater demands has led to producing a significant quantity of brine, which is a highly saline solution. Currently, the most popular brine management method in Western Australia (WA) is disposal by surface water discharge (into the ocean), deep-well injection or evaporation ponds. Brine disposal isn’t a long-term sustainable option due to the environmental impacts it can cause, such as salinisation. Brine treatment methods that reduce the liquid volume of brine partially or completely brine is still under development or aren’t currently economically viable. The DDS uses two multi-criteria analysis techniques, interval analytical hierarchy process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) under hybrid information. The use of interval AHP gives decision-makers a reliable method of assigning appropriate weightings to the chosen criteria, using the relative importance between each criterion. The DDS uses TOPSIS to allow for different information types (crisp numbers, interval numbers, fuzzy triangular numbers representing linguistic terms) within the DDS. To showcase the DDS, a case study using 4 emerging brine treatment technologies, membrane distillation (MD), forward osmosis (FO), osmotically-assisted reverse osmosis (OARO) and eutectic freeze crystallisation (EFC) was developed. The results suggest that the most to least appropriate technology are MD. FO, EFC and OARO. Sensitivity analyses using a Monte Carlo simulation determined the influence of varying different criteria weightings on the TOPSIS process. MD was the most dominant appropriate technology with little confusion between FO, which was consistently ranked 2nd. Sensitivity analysis of the entire DDS requires further validation of the interval AHP.

Brine management strategies for desalination systems: Decision support system

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