Iodine has been used to disinfect water for a long time. It is used in concentrations between 2.5 ppm to 7 ppm, but there is some controversy regarding the maximum safe dose of iodine because excess of iodine consumption in humans can lead to various diseases(thyroid disorders being very common). I believe this is the reason we have moved towards more safer options like chlorine. 


Besides these two, there is a long list of chemical compounds used as drinking water disinfectants. For the extensive list, you can refer this site : 

http://www.lenntech.com/processes/disinfection/what-is-water-disinfection.htm