Abstract: The present disclosure provides methods of treating water sources, including, but not limited to, dental unit water sources, in order to reduce the titer of bacteria and other pathogens in those water sources and also to inhibit biofilm growth and maintenance in surfaces, such as dental unit water lines, that come into contact with those water sources. The disclosure also provides solid compositions comprising silver citrate which are suitable for use in the disclosed treatment methods, and further provides methods for preparing such solid compositions.