Imhoff tank: anaerobic biological pretreatment tank
The Imhoff tank is a combined anaerobic biological pretreatment tank. The sedimentation (in the top part) and the anaerobic digestion of the organic material on the bottom take place in the same dual-compartment unit.
The sedimented solids precipitate through communication cracks in the accumulation and digestion compartment, where the organic substances undergo anaerobic fermentation which results in their stabilization and permits their treatment and the easy removal of sludge. The carbon dioxide and methane that develop in the lower compartment do not interfere at all with the sedimentation process that occurs in the upper compartment.
The performance of this system is similar to that of conventional septic tanks, about 50-70% of the total load and 20-30% of the original BOD5.
What is an Imhoff tank?
It is a single Imhoff tank divided into two distinct areas: the sedimentation chamber at the top, and the sludge digestion area at the bottom, which is where the settleable solids accumulate.
Anaerobic bacteria are microorganisms that have a particular quality, and that is that they do not need oxygen to propagate. Therefore, in the Imhoff tank they multiply and help reduce the pool of organic matter through the digestion process.
Imhoff tanks were used during the first half of the 20th century in cities, but were later replaced by other wastewater systems, although they are still used today in small towns as they do not need much space, their operation is simple and does not require a lot of maintenance.
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