The tank is shallow, averaging about 3 feet deep, and is constructed with an impermeable lining. This gives the wastewater plenty of exposure to the open air for the diffusion of oxygen, helping prevent anaerobic conditions from occurring. One or more mechanical surface aerators are attached to the side of the ditch. Although surface aerators can vary depending on the design of the system, most resemble a large circular brush. The aerators slowly rotate to introduce oxygen to the wastewater without causing too much turbidity.
Raw sewage is delivered to the ditch where it is slowly mixed by the aerators.
Longer retention time will allow for a greater amount of organic matter within the sewage to be broken down by the aerobic bacteria. After treatment the effluent is then pumped to a settling tank where the sludge and the water are allowed to separate. From here most of the wastewater goes on to other treatment processes. The sludge is removed from the bottom of the settling tank and a portion is returned to the ditch to facilitate microbial activity in the next batch of sewage. Oxidation ditches can be built to accommodate the needs of several thousand people.