Aerobic Digestion
by Steve Last
It would be tempting to state that the obvious here and to say that “aerobic digestion” is the opposite of anaerobic digestion and leave it at that, however, within an anaerobic digestion plant, many also operate aerobic digestion as an additional process.
Aerobic digestion is defined as the bacterial process of decomposition or rotting occurring in the presence of oxygen.
It is a process in which, under aerobic conditions, bacteria are used to rapidly consume organic matter and convert it into carbon dioxide.
Aerobic digestion may be used in an AD Plant to further treat:
- the sludge created in anaerobic digestion of wastewater
- the solid fibrous digestate from solid waste anaerobic digestion processes when it is then known usually as the “composting” stage
- the liquid digestate from a solid waste AD plant, which although useful as a fertiliser may for any one of a number of reasons, not be a saleable commodity from that anaerobic digestion plant, and thus require:
- pre-treatment before disposal to a public sewer for onward treatment
- treatment for disposal to a river, where no suitable sewage works is available.
Aerobic digestion is he term most commonly used for the process in which the aerobic digester will decompose the organic matter in the sludge from the anaerobic digestion stage. The organic matter which remains from the Aerobic Digester may then be hauled to a landfill and tipped, or spread on agricultural land.
In the EU and other countries which adhere to the EU legislation regarding restrictions placed on the waste sent to landfills, sludges are defined as liquids, and liquids are no longer permitted to be disposed to Municipal Solid Wastes landfills. It follows that in those countries the above use of aerobic digestion is no longer applicable. However, sludge and cake can also be sent to incineration for disposal.
Why Carry Out Aerobic Digestion?
Aerobic digestion may be employed for stabilisation of the wastewater solids.
Conclusion
Aerobic digestion is used as a final polishing phase in some anaerobic digestion based wastewater treatment processes, and it can also be used to further treat AD Plant sludges.
Sludge generated by this aerobic stage is, in some types of wastewater treatment plants, returned to the anaerobic digester for re-treatment.
Aerobic digestion can be described as a one-step process in which bacteria use oxygen to convert bio-mass into carbon dioxide and water.
Landfill leachate treatment methods can be used at AD Plants which using plants which are similar in principle to the simple plants shown if you click on the ink below:
http:www.leachate,co uk
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