Activated Sludge

Activated sludge is a wastewater biological treatment process that uses microorganisms (bacteria, protozoa, and other organisms) to decompose organic matter contained in waste. This system is widely used in wastewater treatment plants (WWTP) because it is effective, relatively fast, and produces good quality treated water.

Here is a more detailed explanation:

1. Basic Principles

In an activated sludge system, wastewater is flowed into an aeration tank that is supplied with air or oxygen. This air keeps microorganisms alive and actively decomposes pollutants. The results of decomposition are:

• New biomass (microbial cells)

• CO₂ and water

• Other stable products that are safer for the environment

2. Main Components

• Aeration Tank: A place where biological decomposition takes place with the help of aeration.

• Secondary Clarifier (Secondary Sedimentation): Separates activated sludge (biomass) from clean water.

• Return Activated Sludge (RAS): Part of the sludge is returned to the aeration tank to maintain the microorganism population.

• Waste Activated Sludge (WAS): Excess sludge is disposed of or further treated.

3. Advantages

• Able to remove BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) with high efficiency.

• Can be adjusted to remove nutrients such as nitrogen and phosphorus.

• Relatively fast compared to natural systems such as oxidation ponds.