Organisms | Activated Sludge Process | Wastewater Treatment Plant

 Organisms 

Activated sludge contains a diverse range of living organisms that are responsible for waste decomposition during the activated sludge process. In the activated sludge treatment process, the organisms are the workers. They eat the faeces and use it as an energy source in order to survive and reproduce. 

Organisms that thrive in an oxygen-rich environment decompose waste the most effectively and quickly. Aerobes (or aerobic organisms) are organisms that require the presence of molecular oxygen, O2, to survive. Another type of organism found in activated sludge is facultative organisms, which can use molecular oxygen or oxygen bound in inorganic compounds like nitrate, NO3-.

1. Aerobic organisms are the most common in activated sludge plants. They… 

• Require a sufficient level of dissolved oxygen (molecular oxygen, O2).
• There is little to no odor produced.
• Waste should be oxidized as efficiently as possible.
• Grow fairly quickly.

   2. Organisms that are facultative grow in either an aerobic or anaerobic (no oxygen) environment. They…

• Are less efficient waste-processing organisms than aerobes.
• When oxygen is scarce, produce foul-smelling byproducts of decomposition and incomplete reactions.
• Aerobes grow at a slightly slower rate.

An increase in the supply of food (BOD) stimulates the activity of the organisms and the rate of oxidation. More organisms are produced, which increases activity even more. Because organisms require oxygen to function and survive, an increased food supply creates a demand for more oxygen, which must be supplied by the aeration system. This emphasizes the significance of maintaining a good F/M ratio for the activated sludge process to run smoothly, as well as the ability to alter the aeration rate when the oxygen demand changes.