Abstract: Described here are germicidal systems and methods of generating and using them. In some variations, the germicidal systems generally include an anion-exchange resin and a compound configured to non-covalently associate with the anion-exchange resin. The compound typically contains at least one donatable chlorine and at least one exchangeable anion. The compound is also typically configured to undergo resonance stabilization after the at least one donatable chlorine has been donated. Methods of generating hypochlorous acid are also described here. In general, the methods comprise the step of contacting water with a system so as to produce hypochlorous acid. The system typically comprises an anion-exchange resin, and a compound configured to non-covalently associate with the anion-exchange resin. Methods for reducing the quantity of bacteria and viruses in water are also provided here.