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IV. Wastewater Treatment technologies

Topic IV. 9. Wastewater Treatment Facilities with Suspended Biomass - Aerated Tanks: Kinds, Structures, Basic Technological Parameters

Kinds of Aerated Tanks

I. According to the hydrodynamic conditions Completely mixed reactors Plug flow reactors Diffusion reactors Cell reactors

II. According to the aeration system With pneumatic aeration With surface (mechanical) aeration With combine aeration With pure oxygen supply (oxytanks)

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Kinds of Aerated Tanks

III. According to the activated sludge regeneration Conventional (without activated sludge regeneration) Contact stabilisation (with activated sludge regeneration)

IV. According to activated sludge separation With separate secondary settling tanks With combined aerated tanks/settling compartments With membrane activated sludge separation

V. According to the stages One stage Two stages

VI. According to the structures and distribution Conventional (corridor) Carousel Stepwise wastewater (or air) distribution

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Kinds of Aerated Tanks

Schemesa - without regenerator б - with regenerator

1 - wastewater influent; 2 - aerated tank; 3 - secondary clarifier; 4 - regenerator; 5 - mixed

liquor; 6 - wastewater effluent; 7 - recirculating activated sludge; 8 - waste activated sludge

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Aerated Tanks Structures

Conventional Aerated Tank with Pneumatic Aeration

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Aerated Tanks Structures

Fine Bubbles Pneumatic Aeration System with Distributing Channels and Filtering Plates

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Aerated Tanks Structures

Fine Bubbles Dome-wise

Aerator

Fine Bubbles Disk- wise

Aerator

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Aerated Tanks Structures

Surface (mechanical) Aerator

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Basic Technological ParametersX - activated sludge concentration (SS) in

the aerated tank, g/m3

Rw - aerated tank volume hydraulic load, m3/m2.d

RL - aerated tank organic load, gBOD5/m3.d

RFM - food to micro-organisms ratio (F/M ratio), gBOD5/gSS.d

U - substrate utilisation rate, gBOD5/gVSS.h

x - activated sludge age, d

I - activated sludge index, cm3

r - activated sludge recirculation ratio

EO - specific oxygen demand, gO2/Rw

t - hydraulic retention time, h

Q - wastewater flowrate, m3/h

W - aerated tank volume, m3

Qr - recirculating activated sludge flowrate, m3/h

Xr - recirculating activated sludge concentration, g/m3

QWAS - waste activated sludge flowrate, m3/h

QO2 - oxygen mass rate, g/h

WQRw /

WLQRL /. 0

XWLQRFM ./. 0

WASrx QXXW ./.

rrr XXXQQr /)(/

woO REQ .2