Which type of OSSF relies on mechanical aeration for treatment?

Aerobic treatment units (ATUs) utilize mechanical aeration as part of their treatment process. In these systems, air is pumped into a treatment tank to promote the growth of aerobic microorganisms, which digest organic matter in the wastewater. This aeration is critical because it enhances the biological treatment capabilities of the system, allowing for more efficient breakdown of sewage compared to systems that do not provide mechanical aeration.

The design of aerobic systems often includes a two or three-stage process where solids are settled out, and the aerobic microorganisms are actively aerated to facilitate further treatment. This process is beneficial for sites with limited soil absorption capabilities or where higher treatment levels are required.

Other types of systems, such as conventional systems, do not involve mechanical aeration and typically rely on gravity for wastewater flow and natural decomposition processes. Sand filter systems use a gravel and sand media to filter and treat wastewater but do not employ aeration in the treatment phase. Composting toilets compost waste without the need for a traditional wastewater treatment process, relying instead on aerobic microbes from the environment to break down waste in a different manner. Thus, the reliance on mechanical aeration distinctly characterizes aerobic treatment units.