Why does treatment of sewage speed up when aeration is improved?

Answer 1

Sewage treatment is accomplished by bacterial action. There are two types, aerobic and anarobic. Aerobic type bacteria is more effetive but requires oxygen. Anarobic is slower and takes no, or less oxygen.

Think of yourself doing exercises. You could lay quietly on your back and tighten muscle groups, and that would give you a little bit of exercise. This is similar to anaerobic activity. Aerobic activity is like a zumba class where you breath heavy and hard and do more fat burning and muscle building faster.

Another example is found in your compost pile. If you pile leaves, grass and yard waste, they will eventually turn to soil, but the process may take years because there is little oxygen at the bottom of the heap. A pitchfork that tosses or turns the pile will allow oxygen to the grass and leaves, and allow oxygen to feed the aerobic bacteria, and the pile may turn to soil in weeks or days.

In sewage treatment, it is important to treat the sewage quickly as there is more raw material headed to the plant with every flush. Oxygen must be added, usually through some spraying and churning, to feed the aerobic bacteria, which eats up that raw sewage must faster then the anaerobic (without oxygen) bacteria can.