Treating and then reusing sewage will remove the indispensability of employing fresh water. The extent to which the stages of wastewater treatment are costwise viable and provide easy following will give a kick start to recycling and using wastewater. Thus debating the procedures involved in wastewater treatment and their relative merits and demerits, becomes pertinent.

Like tanks using sedimentation, Septic tanks (Imhoff tanks) can play a major role in the process of removing solids from sewage.

Invented by Karl Imhoff of Germany, an Imhoff tank is an improved septic tank in which the inflow of wastewater is not allowed to get blended with the sludge produced. Also, the outflowing effluent is not allowed to carry with it any significant volume of the suspended silt as with a septic tank, featureswise.

**Building and Functional features**

It consists of a 2 chamber tank. The upper chamber is named the deposition of sediment tank or moving in a stream chamber, beyond which sewage flows at a very low velocity; the bottom chamber constitutes the ingestion chamber in which oxygenless or infected disintegration happens.

Solid matters in the wastewater settle to the floor of the sedimentation chamber beyond the slanting lower walls (slope 5 vertical to 4 horizontal). They are made to fall in the digestion chamber through an entrance slot at the bottommost part of the upper chamber. The opening is provided with an airtrap in such a manner that the gaseous fluids produced in the lower chamber cannot make an entrance into the upper chamber.

A gas vent, termed also as, surface skin chamber is fitted in the bottom chamber to remove the vapors going up to the surface. The main gas is methane having a sizeable calorific value and hence may be withdrawn and collected for use. To avert pieces of scum or mud from invading the top chamber, the mire and scum must be kept at a distance of at least forty five centimeters beneath and on top of the openings, sequentially. The clear or zone free of obstructions is called neutral zone.

The bottom chamber comprises 2 to 3 reversed in position cones termed hoppers, with inclined sides (1 : 1) so as to accumulate the sludge at the lowest part of the hopper. The slush is evacuated intermittently using a sludge-pipe, the stream being kept under a fluid pressure of 1.2 to 1.8 m. All of the mud is not withdrawn, only the deepest layers which are fully disintegrated. Some mud is kept behind to maintain the tank seeded with anaerobic bacteria.

To uniformly distribute subsided solids throughout the length of the bottom chamber, so as to make use of the storage capacity to the greatest extent, arrangements for reversing the line of flow at all parts of the tanks, are usually rendered.

**Merits**

Imhoff tanks couple the advantages of both the sedimentation and septic tanks and, therefore find deployment in the case of limited size plants requiring only preliminary treatment. They are more economical and give good results without skilled attention and with minimum problems of getting rid of slush.

**Demerits**

(i) Installing the Imhoff tanks at greater depth spells lack of economy especially where excavation is to be done in rocky terrain or loose sands.

(ii) Imhoff tanks are unsuited to acidity in wastewater

(iii) Full control is not there over their operation. This makes them unsuited for being deployed in large size plants where separate sludge digestion tanks are resorted to.

Author Bio:

Richard J. Runion is the President of Geostar Publishing & Services LLC. Rich loves net research & blogging. His new blog on Wastewater Treatment is fast becoming popular, as it is comprehensive and well-researched.

To learn all about eliminating suspended solids from wastewater, click: http://www.all-about-wastewater-treatment.com .

Keywords: wastewater treatment, recycling wastwater, reusing wastwater, recycling and reusing wastewater, removing solids from wastewater, eliminating suspended solids from wastewater, Imhoff tank, Karl Imhoff

This has also been published as: reusing wastwater on Blogspot