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Aerobic Treatment Processes

Aerobic Treatment Processes. Principles and Dimensioning Eduardo Cleto Pires. Wastewater Treatment Processes. Physical-Chemical Physical separation processes : usually used for pre-treatment and conditioning Chemical coagulation-flocculation followed by physical separation Biological

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Aerobic Treatment Processes

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  1. Aerobic Treatment Processes Principles and Dimensioning Eduardo Cleto Pires

  2. Wastewater Treatment Processes • Physical-Chemical • Physical separation processes: usually used for pre-treatment and conditioning • Chemical coagulation-flocculation followed by physical separation • Biological • Anaerobic processes: no oxygen • Aerobic processes: oxygen

  3. Principles of Aerobic Processes • Higher efficiency than anaerobic • Resistance to chock loads, low temperatures and temperature variations • Great amount of data and sources of information on design and operation

  4. Principles of Aerobic Processes • Depending on the configuration it is possible to apply fine adjustments • simple: aerated ponds – limited control • complex: activated sludge – extensive control • Adequate for low strength (concentration) wastewaters

  5. Principles of Aerobic Processes • Main disadvantage: • High energy consumption • Aeration!!

  6. Principles of Aerobic Processes • Combined processes: anaerobic + aerobic • may result in better removal of recalcitrant compounds (anaerobic) • lower energy consumption • substantial fraction of pollutants are removed at the anaerobic reactor • lower biological sludge generation • resulting from the decreased load at the aerobic reactor

  7. Main Aerobic Systems • Trickling filters • Stabilization ponds (facultative and aerated) • Activated sludge

  8. Aerobic Carbonaceous Matter Removal • Organic matter • soluble • greatest fraction of soluble matter from sanitary sewage is easily degradable • suspended • slow biodegradation • adsorbed by the biomass and converted into soluble matter by means of hydrolysis

  9. Aerobic Carbonaceous Matter Removal • Two phases removal: • oxidation and microorganism synthesis • endogenous respiration (microorganism decay) Metcalf & Eddy. Wastewater Engineering. 4 ed. p.609

  10. Aerobic Carbonaceous Matter Removal • Auto ionization of ammonia in aqueous solution:

  11. Nitrogen Removal • nitrification: two steps conversion of ammonia into nitrate: • oxidation of ammonia into nitrite (NO2−) • oxidation of nitrite into nitrate (NO3−)

  12. Nitrogen Removal • nitrification: two steps conversion of ammonia into nitrate: • total oxidation reaction • oxygen consumption → nitrogen demand

  13. Nitrogen Removal • Denitrification • occurs under anoxic environment (absence of oxygen but presence of nitrates – NO3−) • reduction reaction of nitrates to gaseous nitrogen

  14. Biological Phosphorous Removal • A not well controlled complex process. • Usually occurs by means of absorption and use of phosphorous as a nutrient for microorganism synthesis.

  15. Reference • Tchobanoglous, G.; Burton, F.L. and Stensel, H.D. Wastewater Engineering Treatement and Reuse (Metcalf & Eddy). McGraw Hill, 4th. ed., 2003 (Chap. 7)

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