The biological portion of the treatment system is commonly referred to as secondary treatment. This involves the removal of suspended solids and oxygen-demanding constituents from the wastewater. This is done by introducing the wastewater into a system of highly concentrated microorganisms (such as bacteria, nematodes, protozoans, etc.), which will consume the solids and oxygen-demanding constituents as food. This process is accomplished by pumping the water from the primary clarification process over the bio-tower. The bio-tower is full of plastic media that has a growth of biological film on it.
A Mixed Liquor of Organisms
From the bio-tower the water is mixed with a concentrated mixed liquor of organisms in the aeration basins. There are eight aeration basins that contain two million gallons of biological organisms or bugs (view photo gallery). The basins are aerated using seven centrifugal blowers that force air through a network of fine bubble diffusers. These basins accomplish the pollutant removal in less than 24 hours. What comes in the plant today will be discharged by tomorrow.