A microbial desalination cell (MDC) is used to soften hard water. The MDC achieved more than 90% removal of hardness from several hard water samples, and also effectively removed four heavy metals from a synthetic water sample.
Microbial desalination cells (MDCs) are an emerging concept that uses the bioelectric potential produced from organics via microbial metabolism to accomplish desalination.
MDCs consist of three compartments: the anode, the cathode, and a salt compartment between the anode and the cathode.
This study reports on a bench-scale laboratory experiment to evaluate the effectiveness of using MDC technology to remove hardness from several different hard water samples collected from across the US, ranging in concentrations from 220 to 2080 mg/L as CaCO3.
It was found that the MDC generally removed more than 90% of the hardness from the tested water samples, driven by electron movement in the batch operation. Electricity production was highly related to the conductivity of the hard water samples.
The MDC removed 89% of the arsenic, 97% of the copper, 99% of the mercury, and 95% of the nickel at the testing concentrations in a synthetic solution.
These results provide a proof-of-concept that MDCs can be used to soften hard water that is driven by an electric current.
Further development of the MDC softening process should optimise the reaction configuration, and reduce the volumetric ratio between wastewater and hard water.
