Abstract: A method for treatment and disposal of propellant wastewaters, soil washwaters or groundwaters having dissolved perchlorate salts is described, which comprises adding to the contaminated water in an anaerobic reactor a mixed bacterial culture containing a specific bacterium, HAP1, which uses perchlorate as its terminal electron acceptor and thus reduces the perchlorate ion to chloride in the water; maintaining the proper nutrient and environmental conditions for HAP1 to optimally reduce perchlorate in the water and discharging effluent wastewater from the anaerobic reactor to an aerobic reactor and maintaining proper nutrient and environmental conditions for the optimal conversion of soluble organics to carbon dioxide and sludge and reduction of BOD, COD, ammonia and odor in the effluent water.