The ball restricts the amount of oxygen entering the water column so that aerobic organisms grow around the ball and anaerobic organisms grow deep down in the water column. By changing the nutrients in the base of the column, different organisms are encouraged to grow. BART determines presence and activity levels. A color change occurs in the BART tube as a result of the oxygen gradient diffusing from the bottom upward. The change of color indicates a presence of bacteria within that sample.
Interpretation is provided with the kit.
Aerobic growth of bacteria will occur at the surface of the sample between the BART-BALL and the wall of the BART tube. Fifteen mL of water sample is used to bring the BART-BALL up to the correct level. Nutrients will gradually diffuse up the water column to support this bacterial growth. Once the oxygen has been used by the aerobes, this zone becomes free of oxygen and anaerobic growth will dominate. Nutrient medium for growth is provided as a sterile dried pellet on the floor of the tube.