NOVELTY - A water treatment apparatus comprising a source of growing bacteria for treating contaminants, and a controller for introducing the growing bacteria to the contaminants in a predetermined amount over a period of time, is new.    USE - The apparatus is used for treating water contaminants by introducing nutrients for the bacteria and comprising an aqueous solution of a non-flammable, non-explosive carbon source (claimed). It is used in industrial, agricultural, commercial, and residential applications. It can be used for the remediation of waterbodies, e.g. ponds, lakes, agriculture facilities, landfills, industrial wastes, and contaminated sites    ADVANTAGE - The invention maximizes the contact between contaminants from the wastewater and the microbes without the need for a large processing tank or unit, while providing the best conditions for the microbes to grow. It minimizes the size of the system required to output high-quality, environmentally-suitable, water depleted of ammonia nitrites, nitrates, perchlorates, and other contaminants. It is simple, energetically efficient, and effective to reduce to desirable levels the total suspended solids, biological oxygen demand, escherichia-coli, nitrogen-containing compounds, phosphorus-containing compounds, and bacteria of wastewater in a cost-effective manner. It can also deliver microbes and nutrients optimally to enhance the efficiency and performance of the large number of water treatment systems already in operation for nitrification and denitrification without costly reengineering.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) purifying contaminated water comprising introducing a growing bacteria into a contaminated water;    (2) a waste water treatment system comprising a settling tank, the inventive water treatment apparatus; and    (3) an apparatus for introducing bacteria and bacteria nutrients to a wastewater treatment system, comprising a bacteria holding tank for storing the bacteria, a bacteria pump, a nutrient holding tank, a nutrient pump, and a controller for controlling the timing of the pumping of the bacteria and the nutrients.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic illustration of the apparatus.