Conventional Activated Sludge Wastewater Treatment Systems

Process Design

Conventional activated sludge systems consist of an aeration tank, in which the wastewater is mixed with oxygen. This process activates microorganisms that digest the wastewater and collide with each other, forming flocs. These flocs have an increased ability to degrade the wastewater’s biological components.

The conventional activated sludge process usually involves these components:

1. Primary screening: This is otherwise known as the grit removal phase. The wastewater is passed through screens of varying sizes to filter out leaves and other solid waste.
2. Equalization (EQ) tank: After the primary screening, the wastewater travels to the primary sedimentation or EQ tank, in which microorganisms naturally decompose the organic waste. Oxygen is injected into the tank to feed and multiply the microorganisms and flocs.
3. Clarifying tank: After going through the EQ tank, the wastewater is sent to the clarifying tank, also known as the “settling tank.” This is where the microorganisms sink to the bottom of the tank, letting the water grow cleaner and reach a state of clarification. The microorganisms are recycled back into the EQ tank to decompose more waste solids.
4. Tertiary filter: While wastewater is often safe enough to be reintroduced into the environment after clarification, this component can be utilized to remove more total suspended solids and produce cleaner effluent. Water that has gone through tertiary filters can often be used for purposes requiring cleaner water.