4 December 2023

Imhoff tank: efficient solutions for wastewater treatment

vasca imhoff corrugata

The imhoff tanks, also known as imhoff tanks or imhoff wells, represent an effective solution for the primary treatment of wastewater in multiple contexts. This type of septic tank is designed to significantly break down the BOD aliquot, exceeding the performance of a traditional septic tank. The purification of an imhoff pit, in fact, ensures a reduction of more than 30% of BOD5, 30% of COD and more than 50% of suspended solids.

Unlike a traditional septic tank, which includes a series of T-deflectors to prevent the passage of sludge and suspended substances from one chamber to another, the imhoff pit is characterized by a two-chamber design, vertical or horizontal in the case of large tanks (100 or more equivalent inhabitants), which promotes a more complete decantation. For this reason, the imhoff pit is used in the pre-treatment of civil wastewater, ensuring the clarification of biological sewage from different sources, such as housing, schools, boarding schools, restaurants, hotels, factories and offices. This happens before the treated water is conveyed to the sewers, or to a sewage treatment plant for secondary treatment.

Structure and components of an imhoff tank

An imhoff septic tank has two compartments connected by a hydraulic system. Di Camillo manufactures his imhoff tanks mainly in polyethylene, a material that makes the tanks light and resistant, and that added with anti UV agents prevents the development of algae. However, there are different solutions on the market, depending on the size and needs of the customers.

Wastewater enters the sedimentation compartment, or sedimentator. It is a rectangular or round chamber, with a capacity of 25 to 50 litres per inhabitant equivalent, with the walls inclined below, where they converge towards a central crack for the passage of sedimented sludge.

These precipitate in the underlying compartment of storage and digestion, also called digester, from the capacity between 100 to 200 liters per inhabitant equivalent. In the lower compartment, the sludge and the organic substances deposited on the bottom undergo a cold anaerobic fermentation (around 12-15,) for at least 60 days. The discharge of water then takes place in the public sewer, or continues along the sewage plant towards secondary treatments such as degreasers and deoilers.

Maintenance of the imhoff tank

The proper operation of imhoff tanks depends on their periodic maintenance. Some tips can be of simple daily attention, such as avoiding weighing down the area above the pit, and remembering not to throw in the clogging material drains.

For specific cleaning and maintenance, however, the activities should always be carried out by qualified technical personnel.

  • The first control concerns the inlet and outlet of water. In fact, we must make sure that there are no large obstructions that prevent the outflow, and undermine the operation of the imhoff pit.
  • When opening the lid, check that the sludge level in the digestion section does not exceed the bottom of the sedimenter.
  • Part of the sludge contained in the digester must also be periodically taken through the appropriate extraction pipes.
  • Finally, annually (or more often, depending on the number of inhabitants) the tank must be cleaned and emptied by professional cleaning companies.


To find the imhoff pit the size that best suits your needs, and according to the regulations of your region, as well as for all your sewage needs, contact Di Camillo Tanks. Di Camillo has been working for decades in the field of wastewater treatment, with various services to customers, from spare parts assistance to the realization of practices and certifications.