7 Disadvantages of Using an Activated Sludge Process For Your Municipality or Company

7 Disadvantages of Using an Activated Sludge Process For Your Municipality or Company

Biological treatment processes are an important component in many wastewater treatment systems. They are one of the most efficient and effective ways of reducing organic material in wastewater. There are quite a few of them that have been researched and used over several decades. However, one of the most widely used conventional biological treatment process is the activated sludge process (ASP). Many sewage treatment plants use ASP in their secondary treatment steps due to the human and animal organic matter in the inlet waters of wastewater treatment plants.


The term “activated sludge” comes from the fact that the sludge contains live bacteria and protozoa that actively digest and break down sewage. It is different from the sludge solids removed following a settling process in that way, with the addition of being odorless.


The process itself involves pumping the effluent from the primary treatment clarification step into a large tank that contains the activated sludge. The mixture is subjected to aeration, either from submerged or surface aerators. This provides oxygen to the effluent that the bacteria can then use to break down the organic waste material. After a sufficient amount of hydraulic retention time, the resulting slurry is pumped into a clarification system or tank to settle out the remaining solids. The treated water is pumped off from the top to any subsequent polishing filtration and disinfection while the sludge at the bottom is recirculated back to the ASP tank to reseed the leftover activated sludge.


ASP has been proven to obtain decent results in the final quality of the treated water, but it is not without its faults and disadvantages. There are several things to consider before choosing an activated sludge process (ASP) for a municipal, commercial or industrial wastewater treatment application.


We have included 7 potential disadvantages of the conventional activated sludge process to be discussed below....