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Advantages of Aerated Activated Sludge Treatment Processes


Activated sludge is an advanced wastewaster treatment process that utilizes microorganisms to break down sewage and other organic matter into water, CO2 and other inorganic compounds.

The process is as follows:

1. A reactor sized for microorganism growth and wastewater retention time holds the microorganisms and keeps them in suspension via aeration or mechanical mixing. The incoming sewage comes in contact with what is called the floc.

2. After treatment, a clarification step is used to separate the solids from the liquid and allow the treated effluent to exit the system to downstream processes.

3. The settled sludge goes through a recycling system and can be returned to various points in the reaction vessel(s) depending on the type of activated sludge process.

Note: There are many different variations of the process. There could be variations in the aeration method and the fashion in which the sludge goes back to the beginning of the process, but this is the general process for activated sludge treatments.


• Activated sludge treatment systems have been constructed all over the globe using Purestream’s expertise of over 15,000 worldwide installations

• Activated sludge processes are ideal when a high degree of treatment is required, especially when the effluent will be discharged into ecologically and environmentally challenged locations

• Activated sludge processes are available for carbonaceous BOD and TSS removal as well for biological nutrient removal including nitrification, denitrification, and biological phosphorous removal.


The main advantage of activated sludge treatment processes is to provide efficient and effective removal of BOD, COD and other nutrients from wastewater. Another advantage to keep in mind is that the process itself has flexibility and can be modified to fit the specific requirements needed for each system and jurisdiction it is providing treatment for. Activated sludge is widely considered the best recognized form of secondary wastewater treatment and is the most widely used form of secondary wastewater treatment systems.