Sewage Treatment and Biogas

Also called

sewage treatment · sewage treatment plant · STP · primary treatment · secondary treatment · biological treatment · activated sludge · flocs · BOD · biochemical oxygen demand · aeration tank · anaerobic sludge digester · biogas · methanogens · Methanobacterium · gobar gas · मलजल उपचार · बायोगैस · सक्रियित आपंक

Topics

• Sewage, the waste water of towns and cities, is treated in sewage treatment plants (STPs) before release.
• Primary treatment is physical: screens remove floating debris and grit settles out by sedimentation.
• In the primary settling tank the solids sink as primary sludge; the liquid above (the effluent) goes on.
• In the aeration tank air is pumped in and aerobic microbes grow as flocs: bacteria meshed with fungal threads.
• The flocs consume most of the organic matter, so the BOD (the oxygen needed to break it down) falls.
• In the settling tank flocs sink as activated sludge; a small part is pumped back to the aeration tank as inoculum.
• The rest goes to anaerobic sludge digesters, where bacteria break it down and give off methane, H₂S and CO₂.
• This biogas burns; methanogens such as Methanobacterium make it, in digesters and in gobar gas plants.
• The treated effluent, now low in BOD, is let out into rivers and streams.

About this model

A GLB file of about 894 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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