Method and apparatus for treating contaminants in water under anaerobic conditions is disclosed. The method includes adding to contaminated water a composition including an aqueous mixture of at least one carbohydrate and at least one alcohol and/or bacteriastat. The apparatus includes a source of growing nitrifying bacteria effective for treating contaminants under aerobic conditions, a source of growing bacteria effective for denitrification under anaerobic conditions, and a controller for introducing the growing bacteria in a predetermined amount over a predetermined period of time.