Microbes in Human Welfare

Sewage treatment, Biogas production

  • Microorganisms are employed during secondary treatment of sewage treatment plants.
  • After the larger sized particles get settle during primary treatment, aeration is provided in the next step for the excess of the bacterial system.
  • Microorganisms are added to hasten decomposition which happens in an aeration tank and it is well agitated to develop flocs at the surface.
  • Bacteria along with fungi form a mesh-like slimy layer that decreases the BOD (Biological oxygen demand) of the wastewater.
  • Now, the effluent is passed through a sedimentation tank where flocs are allowed to settle down and it is known as activated sludge.
  • The effluent/supernatant is passed onto a river streams etc, or it can be treated with chemicals for further purification.
  • A part of activated sludge is used as inoculum in aeration tank and the rest is passed into anaerobic sludge digester where aerobes are killed and the anaerobes digest the aerobes as well as organic matters into gaseous products (CO2 , CH4 , H2S etc.,) and the spent sludge can be used as manure (or) part of compost.
  • Methane-rich fuel gas produced by digestion of organics with the help of methanogenic bacteria and has a rich composition of methane 50% -70%. ; CO2 – 30% – 40% with N2 , H2S and Hydrogen.
  • After the process is done, the left out residue which is rich in Lignin/minerals could be used as bio-manure.
  • The energy released from biogas is proportional to the amount of methane
  • The calorific value of biogas is 23-28 MJ/m3
  • Biogas / Gobar gas is designed and set up by KVIC and IARI
  • Production involves 3 stages – (i) Solubilization of organics (using Clostridium, Pseudomonas etc.) into monomers / soluble compounds.
  • (ii) Acidogenesis of monomers by fermentative microorganisms such as Acetovibrio, Propionibacterium to form organic acids.
  • Finally, methanogenesis is carried out by methanogenic bacteria to convert organic acids into biogas (methane + CO2).
  • Biogas is a storable form which can be used as both manure and energy.

Part-1: Watch this video for the topic from 21:05 to 38:33

Part-2: Watch this video for the topic from 6:27 to 14:51

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