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Recovery of valuable compounds from brines

The theoretical evaluation of several compound recovery strategies have been performed by CTM.

The new brine treatment process proposed in the Life+ ZELDA project is divided in two different stages: electrodialysis metathesis and recovery of valuable compounds.

Abengoa Water and CTM have defined several scenarios that could be used to recover valuable compounds from seawater and brackish water brines with the final aim of reaching a Zero Liquid Discharge desalination process.

Using chemical speciation software, CTM has simulated the different steps of all the scenarios defined, with the final aim to theoretically evaluate the performance of each route: quality of the final effluents, quality and quantity of the obtained solids, reagents used and the required conditions to enhance the precipitation (i.e. pH or temperature).

The software used to reach this purpose has been PHREEQC. PHREEQC is a computer program that has been designed to perform a wide variety of aqueous models. Using this software the speciation and saturation indices calculation for different aqueous solutions can be performed, which is extremely useful to properly and effectively design the compound recovery stage of the new brine treatment process that will be developed in the ZELDA project.

In order to properly simulate the different routes defined, it is highly important to take into account the complexity of the solutions used in the ZELDA project. Brines present a highly content of total dissolved solids, which involves complex interactions and a behavior noticeably different compared with the ideal solutions. That makes quite more difficult to obtain relevant results from brines. In order to adjust as much as possible the theoretical results to reflect the real process, the Pitzer database has been used in all the simulations to compute the activities of the dissolved species. 

The results of the theoretical evaluations performed, will be extremely useful to design some bench scale experiments to validate the most interesting scenarios to recover valuable compounds.

It is expected that at the end of May 2014, the best recovery strategy to be used in Almería’s seawater desalination plant and El Atabal brackish water desalination plant will be defined. Be aware of the news posted at the website to know which has been the scenarios selected!