The extended aeration process offers certain benefits that can be combined with conventional processes to obtain a high quality effluent. In this article I provide the major advantages and disadvantages of this process.
The extended aeration process transforms the popularly used complete mix activated sludge process. This is brought about through an increased hydraulic retention period as well as an increased solid holding period. Sludge digestion units that use an aerobic process are often used when implementing this process. The extended aeration activated sludge process is made use of in places where the influent reception rate in the wastewater treatment plant is below 50,000 gpd or 2 L/s.
Some of the advantages of the extended aeration process are:
This process requires little time for preparing the site as the plants are manufactured as pre-engineered and packaged units. This process proves reliable under sufficient supervision. Initial investment and costs are less. Land area required for setting up the plant is minimal. This process produces the least quantity of sludge among the various processes that utilize activated sludge. The temperature in the wastewater is around 15 degrees C and this enables Nitrification. Hydraulic loading shock at a moderate level can be easily absorbed with a minimal of problems experienced. The end result effluent is of a higher quality than many other processes.
However there are certain disadvantages too. These are:
The packaged plants and its pre-engineered modules may need certain changes to cater to the different regional standards for discharge. At higher temperatures there is de-nitrification which can potentially pave the way for sludge rising. A large variation in the inflow can reduce the efficiency of segregation of suspended solids in wastewater and its BOD. Compared with other wastewater natural treatment systems and land based systems this process consumes more power and has a higher cost of energy requirements. In colder regions the process is susceptible to freezing. Certain nuisance factors associated with this process are the odor produced when treating sludge and the noise from the blower. This process requires a higher quality of skill for operational and maintenance roles.