A] Necessity and process of anaerobic digestion of sludge:-

The aerobic digestion is a process where in the micro organism breakdown the organic matter, when there is no oxygen.

The process is used for both industrial and domestic waste to manage it and also to produce fuel if required.

This process is carried out in some soils or lakes or in oceanic basins, where it is called as "anaerobic activity".

The process of anaerobic digestion:

• It starts with the bacterial hydrolysis of the raw input material.

• The insoluble organic polymer like carbohydrates are broken drawn to soluble derivatives, to make them available to other bacteria.

The acirclogenic bacteria converts the sugar and amino acids into carbon dioxide, hydrogen, ammonia and organic acids.

These bacteria convert the organic acids into acetic acids together with additional ammonia , hydrogen and carbon dioxide.

Finally these methanogenous convert these products into methane and carbon dioxide.

B] Usefulness of anaerobic digestion:-

• It helps to reduce the emission of landfills to the atmosphere.
• It helps to produce the nutrient rich fertilizerrs.
• It needs less capital investment.
• It can be used as a source of renewable energy resources eg biogas having methane.

C] Disposal of solid products of digestion

• Digest tics are the solid material of the original input material which cannot be used by microbes.

• They come in thre different forms i.e. Fibrous, liqour or sludge based combination of the two fractions.

• It has some plastic material.

• These material can be used for making low-grade building products like fiberboard.

• the material also can be used as a feedback for ethanol production.

D] Disposal of the liquid products of digestion:-

• The liquid waste, rich in nutrients can be used as a fertilizer.

• This type of use depend upon the quality of the matter being digested.

• The waste water coming out after dewatering process, has high B.O.D and C.O.D. So , before it is allowed to flow into the surface water.

• It is required to treat it i.e. oxidation process.

E] Disposal of the gaseous product of digestion:-

• The acidogenic bacteria convert the sugar and amino acids into carbon dioxide , hydrogen, ammonia, amd amino acids.

• Finally, the methanogenous convert these product to methane and carbon dioxide gases.

• These gases are used to produce the biogas. It is used directly as a fuel or upgraded to natural gas quality, biomethane. So the gaseous products generated through the process of digestion can be recycled , to produce renewable energy.

• The latest technology of making use of the solid, liquid material as a bioproduct, has not only reduced the cost of the process, but also has solved the problems of disposal of the waste material in various forms.