Sludge

:See also oil sludge for automobile engine failures

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:See also sludge metal for the subgenre of doom metal

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Sludge is a solid waste extracted in the process of sewage treatment. When fresh sewage water is added to a settling tank, approximately 50% of the suspended solid matter will settle out in the period of an hour and a half or so. This collection of solids is known as fresh sludge. Such sludge will become actively putrescent in a short time and must be removed from the sedimentation tank before this happens.

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This is commonly accomplished by two different ways. In an Imhoff tank, fresh sludge is passed through a slot to the lower story or digestion chamber where decomposition by anaerobic bacteria takes place resulting in liquefaction and a reduction in the volume of the sludge. After digesting for 6 to 9 months, the result is called "digested" sludge and may be disposed of by drying and then landfilling. It has value as fertilizer, being similar to humus. Alternately, the fresh sludge may be continuously extracted from the tank by mechanical means and passed on to separate sludge digestion tanks which operate at higher temperatures than the lower story of the Imhoff tank and as a result digest much more rapidly and efficiently.

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Oil sludge: Numerous late-model piston engines from many manufacturers have suffered from failures due to oil sludge contamination. These problems happen when fine engine oil passages become clogged with sludge, and often result in catastrophic failure of the engine. 3.3 million Toyota engines were affected, ...

Automobile: An automobile is a wheeled vehicle that carries its own motor. Different types of automobiles include cars, buses, trucks, and vans, with cars being the most popular by far. Earlier terms for automobile include "horseless carriage" and "motor car." An automobile has seats for the driver and, almos...

Engine: An engine is something that produces some effect from a given input. The origin of engineering was the working of engines. There is an overlap in English between two meanings of the word "engineer": 'those who operate engines' and 'those who design and construct new items'....