What happens during secondary sewage treatment? - Leaving Cert Chemistry - Question e - 2003

During secondary sewage treatment, the main process involved is the oxidation or breakdown of organic matter. This step typically involves the use of air (or oxygen) to facilitate the breakdown of waste materials by microorganisms.

Microorganisms, especially bacteria, play a critical role in this treatment stage. They consume organic pollutants and convert them into simpler substances, effectively cleaning the sewage. This biological process can also be supported by activated sludge, which is a mass of microorganisms that aids in the breakdown of waste.

In summary, secondary sewage treatment is primarily characterized by:

• Oxidation of organic materials.
• Breakdown using air or oxygen.
• Utilization of microorganisms (bacteria).
• A biological (or chemical) process facilitated by activated sludge.