Answer: Bacteria seeded in aeration tank as air is circulated throughout the water- bacteria multiply and eat waste; bacteria settle in clarifier.
Secondary treatment of waste water is the process for utilizing the wastewater that are obtain from sewage or other sources to make it suitable for further use. It utilizes physical phase separation to remove settled solids and uses biological process to remove dissolved and suspended organic components. It utilizes specific bacterial strain which are aerobic in nature. These bacteria are seeded into the waste water and they take up energy from oxygen provided to water by inducing oxygenated air to feed upon the organic components present in water. These bacteria multiply and colonize at the bottom of the clarifier.