The ATS process generally consists of the following phases: • Pre-treatment stage to remove large solids and other undesirable substances. • Aeration stage, where aerobic bacteria digest biological wastes. • Settling stage allows undigested solids to settle. This forms a sludge that must be periodically removed from the system. • Disinfecting stage, where
chlorine or similar
disinfectant is mixed with the water, to produce an antiseptic output. Another option is UV disinfection, where the water is exposed to UV light inside of a UV disinfection unit. The disinfecting stage is optional, and is used where a sterile effluent is required, such as cases where the effluent is distributed above ground. The disinfectant typically used is tablets of
calcium hypochlorite, which are specially made for waste treatment systems. The tablets are intended to break down quickly in sunlight. Stabilized forms of chlorine persist after the effluent is dispersed, and can kill plants in the leach field. Since the ATS contains a living
ecosystem of microbes to digest the waste products in the water, excessive amounts of items such as
bleach or
antibiotics can damage the ATS environment and reduce treatment effectiveness. Non-digestible items should also be avoided, as they will build up in the system and require more frequent sludge removal. ==Types of aerobic treatment systems==