Sewage treatment plants are categorized under two basic types; Anaerobic and Aerobic sewage treatment. With this blog, we'll be learning all the basics of the aerobic sewage treatment plant.

In the aerobic sewage treatment process, aerobic bacteria digest the pollutants. You also must provide air for the germs to breathe and let them set a bacterial colony. At a sewage treatment plant, the air is always supplied to the Biozone by either of these two processes:

Direct Surface Aeration with Impellers propelled by pumps which whisk the surface of the liquid with the atmosphere, or by
Submerged Diffused Aeration using blowers for air supply via bubble diffusers at the bottom of the tank.

Note: The most prevalent aerobic sewage treatment plants employ natural air currents and do not need electricity. However, these are just used for small scale sewer systems right now.

Aerobic conditions establish an aerobic bacterial colony. These help in reaching complete digestion and oxidation of organic matter and pollutants to Nitrogen, Water, and Carbon Dioxide, thus eliminating the odor and contamination. The effluent generated by this process is non-polluting and may be discharged to a watercourse.

Traditional sewage treatment plants entail only two or three phases, referred to as primary, secondary, and tertiary treatment. Before following these treatments stage-wise, preliminary elimination of rags, cloths, sanitary items, etc. are also carried out in municipal sewer works.

Primary Treatment

Initially, the solids are separated from the collected sewage. They settle out in a main settlement tank's bottom. The sludge is continually reduced in volume with the process, resulting in a vastly reduced mass when compared to the original amount entering the system.

Note: This is usually Anaerobic. The primary settlement tank has the sludge removed as it's about 30% of the tank volume.

Secondary Treatment

That stage is Aerobic. The liquid in the primary treatment comprises biological particulate and dissolved matters. It's then progressively converted to clean water by employing water-borne aerobic micro-organisms and bacteria which digest the pollutants. Generally, this effluent gets clean enough for releasing to rivers or ponds.

Tertiary Treatment

In some instances, the effluent resulting from secondary treatment is not clean enough for discharge. This might be because the flow has rare plants and animals; it's being discharged into is sensitive or is polluted by someone's septic tank. The Environment Agencies may require a higher standard of treatment for the new discharge being more cleaner. It is generally either Phosphorous or even Ammoniacal Nitrogen or both that E.A. desire to be reduced. All this is involved in the tertiary treatment.

Conclusion

Finally, the sludge is removed from the tanker (on a regular interval) and obtained for further processing through aerobic/anaerobic processes. It's then disposed off or re-used. The final treated water may be released into a stream, river, pond, lagoon, bay, or wetland. It can also be utilized for the irrigation of a golf course, green park, or way. It can also be applied for varied purposes such as groundwater recharge if it is appropriately clean.