Well you can purchase a UV system for you house well that will kill pretty much everything passing by it. For a whole house system there around $400CAN.
I guess it could work!! I know the in water well that have had bacteria (ie. E-coli and coliform) have shown Zero counts of the bacteria after the light was installed and that is will no work done to the well. The only thing you have to watch for is that the liquid must be able to allow the light to past through. A stout would not work due to the opage nature of the brew. An ale would probable be OK, but you would never really know for sure.
It is a good way to kill everything without changing the water chemistry completely. The City water Department uses a UV system on one of the wells here. It can handle about 750 gallon per minute, which may be a bit on the high side for home brewing.