1. 1 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)

2. 2 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

3. 3 Kinds of Aerated Tanks Schemes a - 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

4. 4 Aerated Tanks Structures Conventional Aerated Tank with Pneumatic Aeration

5. 5 Aerated Tanks Structures Fine Bubbles Pneumatic Aeration System with Distributing Channels and Filtering Plates

6. 6 Aerated Tanks Structures Fine Bubbles Dome-wise Aerator Fine Bubbles Disk- wise Aerator

7. 7 Aerated Tanks Structures Surface (mechanical) Aerator

8. 8 Basic Technological Parameters X - activated sludge concentration (SS) in the aerated tank, g/m 3 R w - aerated tank volume hydraulic load, m 3 /m 2.d R L - aerated tank organic load, gBOD 5 /m 3.d R FM - food to micro-organisms ratio (F/M ratio), gBOD 5 /gSS.d U - substrate utilisation rate, gBOD 5 /gVSS.h  x - activated sludge age, d I - activated sludge index, cm 3 r - activated sludge recirculation ratio E O - specific oxygen demand, gO 2 /R w t - hydraulic retention time, h Q - wastewater flowrate, m 3 /h W - aerated tank volume, m 3 Q r - recirculating activated sludge flowrate, m 3 /h X r - recirculating activated sludge concentration, g/m 3 Q WAS - waste activated sludge flowrate, m 3 /h Q O2 - oxygen mass rate, g/h