An interesting idea

Your idea, like antibiotics, is something that wipes out a lot of bacteria in mass. The issue is that bad bacteria are often the first to colonize and are the fastest to reproduce. You could end up making things much worse. The tricky part is establishing the correct bacteria in the correct proportion, while keeping the bad ones in low enough proportions.

This is kind of along the lines of an idea I posted a few days ago that I had come up with a couple of years ago. My idea was to clean yourself out with like a prep and then somehow get ultraviolet light up inside to kill off bacteria like ultraviolet light supposedly does in germ areas such as bathrooms. Of course my idea would be much harder to do and you would pretty much have to have a medical professional do it (good luck with that) and with your idea you might not. In any event, I pretty much dismissed my idea for the exact same reason as the responses posted in this thread. I think you are ignoring the assumption that UC is an autoimmune disease where your body is manufacturing antibodies to kill off certain bacteria (probably good bacteria) in your colon, which leads to inflammation and UC symptoms. Merely restoring a microbial population in your gut isn't going to work long term because it doesn't fix the problem of your immune system attacking and killing (good?) bacteria in your gut. Somehow we have to figure out that solution if we ever want a long term cure. This is why immune suppressing drugs are used to treat UC and why most treatments have to be done forever, because it doesn't actually fix the immune system problem. This is also why there are no cures for UC, only long term, life long treatments.

Be careful. Old Mike posted a paper that stated that hydrogen peroxide in the rectal region caused UC. Just in case you were thinking about using that. And who knows what other chemicals might do.

"First do no harm."