Pre-feed report on the Pink Lake recovery project

Bradley M Husbands

The Pink Lake Recovery Project is looking at recovering Pink Lake in Esperance to its historical pink colour, as it has been lacking for many decades. The lake's colour is due to the production of Beta-carotene by the salt-loving algae Dunalina Salina as a safety mechanism during photosynthesis when the cell is under significant stress. The stress is caused by high solar irradiance, high salinity (³ 240 g/L) and a lack of nutrients; these conditions cause the production of the red pigment, causing the lake to go pink. The lack of colour in Pink Lake is due to a significant salt reduction due to salt mined from the lake for over 100 years, and an estimated 50% of its original salt quantity was removed (Massenbauer 2020). While Pink Lake is no longer pink, the lake adjacent, Lake Warden, has been going pink since 2012, which led to the belief that by using the water and salt from Lake Warden, Pink Lake can return to its original colour. While also removing the pink colouration from Lake Warden. As the issue has been observed for several years, a feasibility study was conducted on if Pink Lake can be recovered to its original colour. The study concluded that increasing the salt in Pink Lake would recover the pink colouration. Then this thesis looked to prove that concept and find the ideal rate at which salt should be added to recover the lake. The rates were calculated by running small-scale trials to evaluate how the water from Pink Lake would react if just salt were added compared to adding Lake Warden water. While there were no numerical results that backed up the concept that Lake Warden water would be able to recover Pink Lake, there was a change in colour in some of the trials. The trials that just had salt added to them did not have any change over the length of the project; it was the trials that had used Lake Warden water that changed colour significantly. While the trials with only salt added did not show a change, they did help to find that the strain of D.Salina found in both Lake Warden and Pink Lake has a slow growth rate compared to most other strains. Meaning that during the physical trails there was no change to the trials that just had salt added to them, though if given more time they might have changed. Apart from just running the physical trials, a decision-making process was conducted to evaluate the best option for moving salt from Lake Warden to Pink Lake. The process started with brainstorming all possible options to recover the colour of Pink Lake; these were refined to only viable options that would fix the environmental issue. The remaining options were evaluated via a SWOT analysis, and the options with more weaknesses and threats than strengths and opportunities were disregarded again. From there, three options remained; each had a numerical model created, looking at moving the water between Lake Warden and Pink Lake. The MCA was conducted with three main and several secondary criteria, using the models to help evaluate the options further. The MCA evaluated a pumping system as the best option to recover Pink Lake to its historic colour. The biggest takeaways from this report are that this strain of D.Salina has a significantly lower growth rate than other strains. Meaning that any trials going forward will need additional time to be completed, allowing the algae to reproduce. Then for the best options for the recovery, using a pumping system would be the most effective, with the model showing a pumping rate of 200,000 L/hr will take about eight years for Pink Lake to recover by using Lake Warden water. This being a significantly longer than the original time stated in the feasibility study.

Pre-feed report on the Pink Lake recovery project

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