AERATION PROCESS IN SUBMERGED MEMBRANE BIOREACTORS FOR WASTE - PowerPoint PPT Presentation

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The Initial Bubble Size Required to Aerate Water, to Achieve 95% Transfer of Available Oxygen. Bubble Initially Contains Air 70

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The BOD Curve. (a) Normal Curve for Oxidation of Organic Matter (b) The Influence of Nitrification 73

Translation of Clean to Dirty Water Oxygen Transfer Rates     *   T 20 ( C C ) ( )    20 L OTR ( SOTR )( ) f * C  20 K ( field )   La Where K ( cleanwater ) La C * ( field )   C * ( clean water ) * C   s T * C s 20    P d P w e v   b 20    P d P s w e v 20 and K    T 20 La ( T ) K La ( 20 ) 74

APPLICATION TO PROCESS CONDITIONS   • dC    L OTR V f   dt Pr ocess     * K . a C C V  L f f L  *   K . a ( C C )  OTR  L f f L   f   * SOTR K . a . C  L 20 20 OTE  f SOTE      T 20 * ( C C )   20 L * C  20 75

NOMENCLATURE OTR f Oxygen transfer rate under process (field) conditions [kg / h] SOTR Standard Oxygen Transfer rate at 20 O C, 1 atm and 100% relative humidity [kg/h]  Wastewater Correction factor for oxygen transfer coefficient [-]  Wastewater correction factor for oxygen saturation [-]  Temperature correction factor for oxygen saturation [-]  Pressure correction factor for oxygen saturation [-]  Temperature correction factor for oxygen transfer coefficient [-] C L Bulk liquid phase oxygen concentration [mg / L] * C  Clean water oxygen saturation at diffuser depth submergence and 20 O C [mg/L] 20 76

C * Dissolved oxygen saturation concentration [mg/L] C * Surface saturation concentration at temperature T [mg/L] ST * Surface saturation concentration at temperature 20 o C [9.09 mg / L] C S 20 Absolute temperature [ O K] T Oxygen transfer coefficient [h -1 ] K La Oxygen transfer coefficient at temperature T [h -1 ] K LaT Oxygen transfer coefficient at temperature 20 O C [h -1 ] K La20 P b Barometric Pressure [k Pa] Vapor pressure at temperature 20 O C [k Pa] P V20 P S Standard barometric pressure [101.325 k Pa] d e Effective saturation depth at infinite time [m]  w Specific weight of water [N/m 3 ] 77

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RHEOLOGICAL QUALITIES OF ACTIVATED SLUDGE FROM MCASP • The parameter viscosity is unsuitable for comprehensively describing the flow qualities of activated sludge • The representative viscosity at a shear rate of 23 s -1 is approximately 10 times greater than the representative viscosity at a shear rate of 1,200 s -1 • The activated sludge from MCASP plants show a pseudo plastic behavior 80

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OXYGEN INPUT H   ΔM π . d 2 . k (C C ) . s O B L L U 2 B . .  ΔM M N . B O O 2 2 . 6 . V . k .H   L G (C C ) S L d . U B B . d C  ρ 1 M . M . L w d C O w 2 t d C   K . K . dt K.dt L  (C C B L, W ) s L d C C   K . t L  (C C ) C S L O    C   ln C C K. t L   , L S C O   L 90

OXYGEN INPUT (Contd.)   for C O Oxygen free tank L , O    kt C C [ 1 e ] L S Where :   6 . k   ~  L K Bubble size   B d . U     B B   .   H V ~  G   K Mean velocity of air supply into L , W   V w     the overall area of water tank 91

OXYGEN MASS TRANSFER EFFICIENCY . M •   k O O η g      2 2   O E  kWh    2 • V  w  K . K . (C C ) s , B L W E L • C η  s ( ) . K max  O B . g 2 w • U   B f (one bubble follows the other without any distance) max d B •  1/3  O d 3.236 D (for water at 20 C) B N • Aeration systems using fine bubbles should be considered advantageous (for water). • Systems for the aeration of wastewater must be considered insufficient if they cannot produce a minimum oxygen input per unit time required for wastewater biology, regardless of their respective transfer efficiency. • 92 CONCLUSION The aeration systems used today have a considerable potential for further development from the point of view of increase in the oxygen input in relation to the energy required.

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