What is a common byproduct of aerobic digestion?

Aerobic digestion is a biological process that utilizes microorganisms to break down organic material in the presence of oxygen. During this process, one of the main outcomes is the generation of excess sludge. This excess sludge consists of the microbial biomass that has increased due to the digestion process and can include undigested material as well.

The production of excess sludge is an expected result of aerobic treatment systems, as these systems cultivate beneficial bacteria that help in the breakdown of waste material. Once the organic material is digested, the remaining solids are collected as sludge, which may require further treatment or stabilization before disposal or reuse.

While other byproducts like effluent and biogas can also result from different wastewater treatment processes, they are not typical byproducts of aerobic digestion specifically. Effluent represents the treated liquid that flows out of the treatment system but is not a byproduct in the same sense as excess sludge. Biogas is primarily a product of anaerobic digestion rather than aerobic, and chlorine gas is unrelated to the aerobic digestion process altogether. Therefore, excess sludge is the best answer as a direct byproduct of aerobic digestion.