Anaerobic treatment is a process where bacteria stabilize organic matter without any free oxygen. This process is especially effective for treating concentrated organic wastes, such as the sludge collected from primary and secondary treatment processes. The complex mechanism of anaerobic digestion can be simplified into a two-stage process:

1. Acid Formation In the first stage, a group of microbes called “acid-forming bacteria” breaks down complex organic materials (like proteins and fats) into simpler organic acids.
2. Methane Formation In the second stage, a different group of microbes, “methane-producing bacteria,” consumes the organic acids and converts them into methane and carbon dioxide. This step stabilizes the waste.

A key advantage of anaerobic treatment is that a low percentage of the organic matter is converted into new biomass compared to aerobic processes. This ability to convert a large fraction of waste into energy-rich gas, rather than new cells, makes anaerobic treatment a cornerstone of sustainable sludge management and high-strength waste stabilization.