MIDES Demo Site 1 Journal: How we’ve come this far
Equipment for the first full-scale Microbial Desalination Cell (MDC) pilot plant ever constructed arrived at the MIDES Demonstration Site 1 in Denia, Spain, in October 2019. Before this key arrival, we had been preparing the demonstration site by installing and test-operating the other elements of the MIDES system:
- pre-treatment using ceramic ultrafiltration membranes
- post-treatment using reverse osmosis pilot
The MDC pilot technology was installed at the Demo Site, and connected hydraulically and electrically. The next step was to apply the first SAT tests (Site Acceptance Test) that checked the pump performance, electrical resistance of the MDC, and the hydraulic performance in pipes and tanks.
With the results obtained from the SAT test in hand, some minor adjustment were made, such as changes in the electric cabinet and minor changes in the pilot plant program to better facilitate data management. A second SAT test was then performed with very satisfactory results.
Then we were ready for the first abiotic test. The abiotic test is in the desalination process using the MDC as a electrodialysis system, in which the energy required for desalination is supplied externally to generate the electric potential to favor the ions’ migration through the ion exchange membranes.
In December 2019 and January 2020 a number of further abiotic tests were performed, working with synthetic saline streams based on sodium chloride or sodium bicarbonate starting at 7 mS/cm – and finishing the period when salinity reached 1mS/cm values. This was done to evaluate the correct performance of the desalination process, and to study the performance of the electrodes and membranes, with consideration that the electric current is supplied externally.
The Demonstration Site team – and the consortium – were happy with the news! With the information obtained we could consider that the mechanical and hydraulic design of the system were correct and ready for the next steps.
Moving forward, representatives of MIDES consortium organizations, IMDEA Water and Aqualia collaborated in the selection of the best source of bio-electroactive bacteria, and the most effective procedures of inoculating the bacteria into the MDC cells. IMDEA introduced a Geobacter cell culture, which was inoculated into the anolite tank and then pumped into the MDC cell. Inside the MDC, the bacteria is to attach to the current collectors and develop electroactive biofilm.
We are now in this ongoing process. The encouraging news is that it appears that the bacterial communities in the MDC are developing and consuming organic matter. We look forward to reporting more on these results very soon!
Juan Arévalo of Aqualia has been leading much of the MIDES consortium implementation of this first demonstration site. He contributed information and images for this update, and more data on our MIDES results will be available as the operation in Denia progresses.