What process occurs in the stabilization tank during contact-stabilization?

During contact-stabilization in a stabilization tank, the primary process that occurs is the digestion of waste material by microorganisms. This process is integral to wastewater treatment, as it involves the biological breakdown of organic matter present in the wastewater.

In contact-stabilization, raw or partially treated wastewater is mixed with activated sludge, which contains a population of microorganisms. These microorganisms consume the organic waste, leading to the stabilization of the sludge. This breakdown helps reduce the volume of waste and converts it into more inert forms, which can be managed more easily.

The biological activity not only reduces the organic load in the effluent but also helps in the overall treatment process by enhancing the efficiency of subsequent stages in wastewater treatment. This digestion is crucial for achieving acceptable water quality standards before the effluent is released into the environment or further treated.

Other processes, such as chemical treatment or solid-liquid separation, do play roles in wastewater management, but they do not specifically occur in the context of contact-stabilization in a stabilization tank as the digestion of waste by microorganisms does.