The internal circulation reactor (IC reactor) is a form of anaerobic digester. It is primarily designed to treat wastewater

Wastewater

Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

. The IC reactor is an evolution of the UASB and EGSB digestion systems. The digester typically produces biogas

Biogas

Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas...

 with a high concentration methane

Methane

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 (c80%). In essence the IC to improve digestion rates and gas yields. The foot print for the IC reactor is therefore typically smaller however it is taller due to the increased complexity of the reactor.

The IC reactor typically comes as part of a two stage anaerobic digestion system where it is preceded by an acidification

Acidogenesis

Acidogenesis represents the second stage in the four stages of anaerobic digestion:* Hydrolysis: A chemical reaction where particulates are solubilized and large polymers converted into simpler monomers;...

 and hydrolyk tank. Effluent leaving the IC reactor will often require aerobic treatment to reduce biochemical (BOD) and COD

COD

Cod is the common name for fish of the genus Gadus, as well as being used to refer to several other varieties of fish.Cod or COD may also refer to:-Finance and commerce:...

to discharge consent levels.