Research shows that microwaving sponges can eradicate most of the bacteria they hold, including E.coli and Salmonella. The university’s professor of environmental engineering, Gabriel Bitton, explains, “Basically, what we find is that we could knock out most bacteria in two minutes … People often put their sponges and scrubbers in the dishwasher, but if they really want to decontaminate them and not just clean them, they should use the microwave,” (via University of Florida)
In the 2006 study, co-authored by Bitton and published in the Journal of Environmental Health, researchers submerged sponges in a treacherous mix of fecal bacteria, E. coli, and bacterial spores, which are difficult to kill. The study found that when the sponges were microwaved for two minutes at full power, 99% of all the germs and bacterial spores were killed. Going a bit further, microwaving the sponges for two more minutes (four minutes total) killed 100% of the bacteria and germs.
If you want to keep your kitchen sponge around longer than 1-2 weeks, which is the recommended replacement time, make sure you lather it up with dish soap and water and place it in the microwave for two minutes to kill off any nasty viruses and bacteria (per The Healthy).