Deutsch: Aktivschlamm / Español: Lodo activado / Português: Lodo ativado / Français: Boue activée / Italiano: Fanghi attivi /

An Activated Sludge is Product that results when primary effluent is mixed with bacteria-loaden sludge and then agitated and aerated to promote biological treatment, speeding the breakdown of organic matter in raw sewage undergoing secondary waste treatment.


Activated sludge is a biological process used in wastewater treatment to remove organic matter and nutrients from contaminated water. The process involves introducing air into the wastewater to stimulate the growth of microorganisms, which then break down the organic pollutants. The activated sludge system typically consists of aeration tanks where the activated sludge is mixed with the wastewater, settling tanks where the sludge is separated from the treated water, and a return activated sludge (RAS) system to recycle some of the sludge back into the aeration tanks to maintain the population of microorganisms.

The microorganisms in the activated sludge system include bacteria, protozoa, and other organisms that feed on the organic matter in the wastewater. These organisms form flocs that settle out of the treated water in the settling tanks, creating a layer of sludge known as "activated sludge." This sludge can then be further treated through processes such as digestion or dewatering before being disposed of or reused.

Activated sludge is a highly effective and versatile wastewater treatment process that can remove a wide range of pollutants, including organic compounds, nitrogen, and phosphorus. It is commonly used in municipal wastewater treatment plants as well as industrial facilities to meet regulatory standards and protect the environment. The process can be adjusted and optimized to handle fluctuations in flow and pollutant load, making it a flexible solution for treating wastewater in various industries.

Areas of Application

  • Wastewater Treatment: Process in which activated sludge is used to treat sewage and industrial wastewater to remove organic material and pollutants.
  • Contaminated Soil Remediation: Technique where activated sludge is used to break down contaminants in soil, reducing their toxicity.
  • Aquaculture Water Treatment: Application in fish farming to remove excess nutrients and organic matter from water, improving the overall water quality.
  • Landfill Leachate Treatment: Process where activated sludge is utilized to treat leachate from landfills, reducing the concentration of pollutants before discharge.
  • Bioremediation of Oil Spills: Activated sludge can be used to break down oil and other hydrocarbons in marine environments after oil spills, helping to clean up the contaminated area.

Well-Known Examples

  • Wastewater treatment plants: Activated sludge is used in wastewater treatment plants to remove organic pollutants from sewage.
  • Industrial effluent treatment: Activated sludge is utilized in industrial effluent treatment to break down contaminants and purify wastewater.
  • Bioremediation: Activated sludge can be applied to contaminated soil or water to biologically degrade pollutants.
  • Aquaculture: Activated sludge is used in aquaculture systems to help maintain water quality by removing excess nutrients and promoting the growth of beneficial bacteria.

Treatment and Risks

  • Activated Sludge Treatment: The process in which microorganisms are added to wastewater to break down organic matter.
  • Risks of Pathogen Transmission: There is a potential risk of disease transmission if the activated sludge contains harmful pathogens.
  • Chemical Exposure: Exposure to chemicals used in the treatment process can have negative health effects on workers.
  • Odor Emissions: The production of unpleasant odors is a common issue with activated sludge treatment plants.
  • Sludge Disposal: The disposal of excess sludge can be a challenge due to its high organic content.

Similar Terms

  • Microbial Treatment:Use of microorganisms to remove pollutants from wastewater.
  • Biological Aerated Filter (BAF):A method for secondary treatment of wastewater using microorganisms attached to a filter media.
  • Suspension Culture:A process where microorganisms grow and treat wastewater in a suspended state.
  • Biological Nutrient Removal (BNR):A process where microorganisms remove nutrients such as nitrogen and phosphorus from wastewater.
  • Sequential Batch Reactor (SBR):A treatment process where wastewater is treated in batches through a series of cycles.

Examples of Sentences

  • The Activated Sludge plant is working efficiently.
  • The staff members are monitoring the Activated Sludges closely.
  • The quality of water improved significantly after the Activated Sludge's implementation.
  • The process of Activating Sludge is essential for wastewater treatment.



Activated sludge is a widely used wastewater treatment process in environmental engineering. It involves treating wastewater with microorganisms in an aerated tank to break down organic matter. The activated sludge process is effective in removing pollutants such as organic materials, nutrients, and pathogens from water bodies. The microorganisms in the activated sludge feed on the organic matter, converting it into carbon dioxide, water, and biomass. This process helps improve the quality of water before it is discharged back into the environment.


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