Activated Sludge Process

The Activated Sludge Process (ASP) is a sewage treatment process in which air or oxygen is blown into raw, unsettled sewage to smash the solids and develop a biological 'soup' which digests the organic content and pollutants in the sewage. These plants do not have a primary settlement chamber which is the chamber that needs emptying by tanker on a regular basis with most three stage sewage treatment plants.

 In all activated sludge plants, once the sewage has been 'bubbled' long enough, excess sewage liquor is discharged into a clarification chamber where live bacteria settle to the bottom, dead bacteria rise to the top and form a crust with a clear liquid in the middle. This clean water is then discharged into either a watercouse or a soakaway. The live bacteria, called activated bacterial sludge, are returned to the digestion chamber to re-seed the new raw sewage entering the tank and the dead bacterial crust is removed either by the the homeowner or a service engineer on a regular basis. (The Vortex sewage treatment plant can do this automatically itself)

The term "activated" comes from the fact that the particles are actively teeming with beneficial, sewage digesting bacteria, and protozoa.

Activated sludge is different from the smelly anerobic sludge that you have to remove from the primary settlement chambers of other types of sewage treatment plants and septic tanks in that this sludge contains many living organisms which can feed on the incoming wastewater. It is also odourless.

These types of sewage treatment plants have many advantages over other types:

  • Longer emptying intervals
  • Less sludge to remove
  • They tend to be odourless throughout the process
  • They re-seed themselves with beneficial bacteria
  • Very reliable
  • Simple process
  • Inexpensive servicing
  • No moving parts within the plant
  • No need to 'top-up' with extra bacteria

The process is widely used and relied upon by Water Authorites in municipal sewage works. The VORTEX™ is a very good example of an advanced activated sludge sewage treatment plant.