What are the different types of anaerobic digesters?
Anaerobic digesters use anaerobic digestion for a variety of purposes, including the treatment of bio waste, animal manure, sewage, and the generation of biogas.
Anaerobic digesters are classified according to several criteria, including whether the biomass is attached to a surface ("attached growth") or can freely mix with the reactor liquid ("suspended growth"), the organic loading rate (the influent mass rate of chemical oxygen demand per unit volume), and whether they are centralized or decentralized. Most anaerobic digesters in the world are based on wet-type anaerobic digestion, in which biomass (usually animal dung) and water are mixed in equal parts to form a slurry with a total solids (TS) content of about 10-15%.
Solid-state vs. wet-type digesters
Solid-state digesters, as opposed to wet-type digesters, eliminate the need to dilute biomass before use in digestion. Solid-state digesters can handle dry, stackable biomass with a high percentage of solids (up to 40%) and are made up of gas-tight chambers called fermenter boxes that operate in batch mode and are periodically loaded and unloaded with solid biomass and manure. The widely used UASB reactor, for example, is a suspended-growth high-rate digester with biomass clumped into granules that settle relatively easily and typical loading rates ranging from 5 to 10 kg COD/m3/d.
There are many different types of anaerobic digesters, each performing the same basic function in slightly different ways.
Anaerobic digesters include the following:
2: The process of anaerobic contact.
3: Expanded-bed anaerobic reactor.
4: Fluidized anaerobic bed reactor.
5: Anaerobic Lagoon.
7: Anaerobic digester with batch system.
8: The continuous stirred-tank reactor (CSTR).
9: EGSB stands for expanded granular sludge bed digestion.
10: Anaerobic digester with one stage.
11: Anaerobic digester with plug-flow.
12: Anaerobic reactor with submerged media.
13: Solid-state anaerobic digester.
14: Anaerobic digester with two stages.
15: Anaerobic sludge blanket digestion with up flow (UASB).
16: Anaerobic attached growth in both up and down flow.
Digesters are also classified into three types
1: Passive Systems
Biogas recovery is added to an existing treatment component in passive systems.
2: Low-Rate Systems
The main source of methane-forming microorganisms is manure flowing through the digester.
3: High-Rate Systems
To increase efficiency, methane-forming microorganisms are trapped in the digester.
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