AttachedCulture Systems

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Attached-Culture Systems

• Trickling Filter
• Rotating Biological Contactors
• Bio-Towers

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Trickling Filter

• Biofilm or bacterial film or biomass is grown or
  developed on solid medium. Such as rocks, stone
  trieces, synthetic medium etc. This media is
  randomly pocked in reactor. Wastewater is applied
  on the top through a rotating arm and it trickles
  down of the bottom. In its travel to the bottom
  of TF, wastewater is brought into the centure of
  biofilm attached to the medium. The process may
  be depicted as shown below.

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How does it work?

• O2 and Nutrients (BOD etc ) are transferred to
  the fixed film by diffusion
• Oxidized organics are transferred to moving after
  layers by diffusion.

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Continue..How does it work?

• Bacteria metabiological contents of the fixed
  film.
• Biofilm grows or get thickened.
• As its thickness increases, inner layer become
  anaerobic.
•  

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Continue..How does it work?

• Outer biolayer remains aerobic.
• With more thickining of biological layer , cells
  in inner layer die and lyses It causes break in
  the content between film and medias.

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Continue..How does it work?

• Thus, slim layer gets slough off and is being
  carried away by the wastewater.
• In SST, biofilm material (----- half) is
  separated.

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Each area ------- the does at least at 5 min
ntervals.
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Design of Trickling filters

• Generally Empirical Formula
• NRC Formula

S0 Incoming BOD Se Effluent BOD Q Flow
in m3 / min Volume of filter in m3
r Recirculation ratio F Recirculation
Factor,
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For the second stage

• 1.      Volume of media
• 2.      No. of stages
• 3.      Recirculation Ratio

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Eckenfelder Formula

• Account for media characteristics, PFR, First
  order kinetics
• (i) No Ricirculation

K Treatability constant, min-1(0.01 0.1 ) D
Depth, in m Domestic 0.06 at 200c N
Coefficient, characteristic of medium (0.35
0.80) rock 0.408 asbestos 0.75 Q m3 / m2
min KT K20 (1.035) T 20
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• (ii) With Recirculation

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Additional notes on Trickling Filter  
Sludge in Trickling Filter

• Sludge in TF 100 day (long ?c endogeous
  decay, low X, more stablised Sludge)
• Actual Biomass is difficult to analyse
• Overall yield coefficient is 60 80 of AST
  Process
• High rate TF produce more Sludge

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Air Supply in TF

• Natural draft Temperature difference in air
  wastewater
• IIf wastewater temp. lt Ambient temp. downward
  flow of air ,
• If Wastewater Temp. gt Ambient Temp. Upward
  Flow of Air.
• Under drains collecting systems should be
  designed to flow no more than half to allow force
  air passing
• 1 m2 for every 250 m2 of filter area

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Hydraulics of Trickling Filter
  Ø      Rotating arm ½ - 2 rpm Ø     
Peripheral Speed 0.5 3.7 m/min (two arm
system) Ø      Arm length 4.5 70m Ø     
Ports 95mm in dia. Ø      15cm above
media. Ø      Flow velocity in arms gt 0.3 0.6
m/s to prevent deposition of particulates Ø     
Size of parts is generally same.  
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Spacing Step discharge
-----graph--------  
  Ø      Area serviced increases square of the
distance from the center of the filter. For even
distribution of flow over filter
Flow rate in area ------image-------
Ql (flow in pipe at l )
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1.      Draw Q versus l, get spacing 2.     
Determine q for each part h near--- spacing.
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Application of Trickling Filter

• Onsite Treatment
• House Hold