1. Clarification Dynamics and Limiting Flux Solid Flux analysis for the design of clarifier area requirement in the sludge thickening of wastewater treatment Authors Indrani Dhiman Chakraborty Mentor Professor Suparna Mukherji Subject: ES 639 : Physicochemical Treatment Technologies

2. Learning Objectives After interacting with this Learning Object, you will be able to: analyse Solid Flux for the design of clarifier area requirement in the sludge thickening for wastewater treatment

3. Definitions and Keywords Gravity Flux (N B ° ) - Flux of solids moving downwards due to hindered settling N B ° = C i × v s, where C i is the concentration of solids and v s is the settling velocity Underflow Flux (N u ° ) - Flux of solids due to the bulk flow of recyclable sludge N u ° = C i × u, where u is the underflow velocity Total flux (N s ° ) = Gravity flux + Underflow flux Solid handling Capacity (N L ° ) - Flux of solids at which all the solid particles reach the bottom of clarifier 5 3 2 4 1

4. Definitions and Keywords C f - Solid concentration of clarifier feed C u - Solid concentration of the clarifier underflow Underflow rate is the rate at which sludge is recycled - Q r Overflow rate is the feed rate to the clarifier- Q f 5 3 2 4 1

5. Master Layout 1: Activated Sludge Process 5 3 2 4 1 Stirrer

6. Step 1: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Show light grey liquid filling the aeration tank. Show the fan rotating Show liquid mixing Show liquid moving into the clarifier through pipe. T1: clarifier stirrer

7. Step 2: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Zoom into the clarifier. Show step 3 T1: clarifier stirrer

8. Master Layout 2: Clarifier 5 3 2 4 1 1 1 2 1 2 3 1 2 3 4 1 2 3 4 5 6 FIG 1 FIG 2 FIG 4 FIG 3 FIG 5 FIG 6 This is incorrect: I have discussed with Dhiman please contact him 9920748819

9. Master Layout 3: graph 5 3 2 4 1 1 2 3 4 5 6 CuCu Concentra tion Flux 0 0 1 0.115 2 0.155 3 0.16 4 0.145 5 0.12 6 0.1 7 0.08 8 0.065 9 0.05 10 0.035 11 0.025 12 0.02 13 0.015 14 0.01 15 0.005 16 0.005 17 0.005 Needs to be updated

10. Step 3: 1 5 3 2 4 Description of the action/ interactivity (DT) Text to be displayed (if any) ‏ Show liquid in clarifier as light grey initially (Fig 1 master layout 2) ‏ Show graph starting. As graph reaches 0.06 show clarifier with clear liquid in region 1 and the dirt settling down with a darker grey.(Fig 2 master layout 2) ‏ As graph reaches 0.1 show clarifier with dirt settling further down. (Fig 3 master layout 2) ‏ As graph reaches 0.14 show clarifier with dirt settling further down. (Fig 4 master layout 2) ‏ As graph reaches 0.14 curve show clarifier with dirt settling further down. (Fig 5 master layout 2) ‏ As graph reaches 0.1 down curve show clarifier with dirt settling further down. (Fig 6master layout 2). Show entire graph. DT1 At Ci =0, gravity flux NB°= 0, DT2 As concentration increases, NB° increases to a peak and then decreases as Vs approaches 0 T1: Gravity Flux 1 2 3 4 5 6 CuCu Underflow line should touch Batch flux curve for a critically loaded clarifier

11. Master Layout 4 5 3 2 4 1 Concentra tion Flux 0 0 1 3 2 6 3 9 4 12 5 15 6 18 7 21 8 24 9 27 10 30 11 33 12 36 13 39 14 41 15 44 16 47 17 48 Under flow flux

12. Step 4: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ plot the graph till concentration is 17 mg/l Put Cu lable at 14 mg/l DT1 At Ci =0, underflow flux Nu°= 0, DT2 As concentration increases, Nu° increases proportionately T1: Underflow Flux

13. Master Layout 4 5 3 2 4 1 Concentra tion Flux 00 13.115 26.155 39.16 412.145 515.12 618.1 721.08 824.065 927.05 1030.035 1133.025 1236.02 1339.015 1442.01 1545.005 1648.005 1752.005

14. Step 5: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Show the gravity flux curve and the underflow curve in a single graph. Show total flux coming values in master layout 4 Show only Cu label DT1 Total flux Ns° is the sum of gravity flux and underflow flux T1: Total Flux

15. 1 5 3 2 4 Interactivity option 1: Step No: 6 Interactivi ty type (IO 1/IO 2) ‏ Instruction to learners Question and Options Boundary limits & options Instruction to animators Results and output Chose (one try) ‏ Click on the correct answer Which flux has a larger value? Options: Gravity flux Underflow flux Total flux None of the above ------ Ref to results and output Correct answer is total flux Feedback/ output: ‘ Total flux is the addition of Underflow flux and gravity flux and therefore has a larger value than the others.’

16. Master Layout 5 5 3 2 4 1 A

17. Step 7: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Show all three lines together on one graph. Draw a red dotted line from 0.14 on y axis to 14 mg/l on x axis touching the gravity flux. At 0.14 on y axis label it as NL°. And draw the black line to the underflow flux The lowest point in the sagged portion of total flux line is the limiting flux Tangent drawn to the gravity flux curve from the point on X axis corresponding to Cu if extended to Y axis will meet at NL°. This tangent is the underflow rate line. T1: Underflow rate line

18. Master Layout 7 5 3 2 4 1

19. Step 8: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Draw a black dotted line from C f (10 mg/l) point on x axis to the red line till the green dot. Now show the black dotted line from the green dot to the y axis and Show label N°app. DT1  The point on the underflow rate line corresponding to C f is the state point.  The flux corresponding to state point should be the applied flux N°app T1: Applied flux

20. Step 10: 1 5 3 2 4 Description of the action/ interactivity Audio Narration (if any) ‏ (DT) Text to be displayed (if any) ‏ Draw a blue line from 0 point through the green dot. Show label ORA. DT1 The line connecting 0 to the state point is the overflow rate line T1: Overflow rate line ORA

21. Master Layout 9 5 3 2 4 1 CfCf C u1 CuCu C u4 ORA (Q f2 / A) ‏ ORA1 ( Q f1 / A) ‏ ORA2 ( Q f3 / A) ‏ 1 2 3 Q f1 < Q f2 < Q f3 N 0 APP1 N 0 APP3 N 0 APP2 N L3 0 N L2 0 N L1 0 State point1 State point 2 State point 3 C u2 C u3

22. 1 5 3 2 4 Interactivity option 1: Step No: 11 CfCf C u1 CuCu C u3 ORA (Q f2 / A) ‏ 2 CfCf C u1 CuCu C u4 ORA (Q f2 / A) ‏ ORA1 ( Q f1 / A) ‏ ORA2 ( Q f3 / A) ‏ 1 2 3 Q f1 < Q f2 < Q f3 Graph 1 Graph 2 CuCu C u1 C u2 C u3 C u4 67854 mg/l N 0 APP1 N 0 APP3 N 0 APP2 C u2 C u3 Interactivity type (IO 1/IO 2) ‏ Instruction to learners Boundary limits & options Instruction to animatorsText to be displayed SliderChange the values of C u to see the changes in the applied flux and the overflow rate ------ Show graph 1 with all the labels. If learner reduces C u then show: Refer to graph 2 and shown on graph 1 the C u1 red line with the red dot and dark blue arrow, along with labels (Refer to master layout 8). C u2 is before C u1 line If learner increases C u then show: Next referring to graph 2 shown on graph 1 the C u4 red line with the red dot and blue green arrow, along with labels (Refer to master layout 8). C u3 is before C u4 line Show equation in dark green When concentration changes of clarifier underflow, state point shifts and accordingly N°APP and overflow rate changes. For lower Cu, applied flux is lower and overflow rate is lower For higher Cu, applied flux is higher and overflow rate is higher.

23. 1 5 3 2 4 Interactivity option 1: Step No: 12 CfCf C f3 CuCu C f1 ORA (Q f2 / A) ‏ 2 CfCf CuCu ORA1 ( Q f1 / A) ‏ ORA2 ( Q f3 / A) ‏ Q f3 < Q f2 < Q f1 Graph 1 Graph 2 CfCf C f1 C f2 C f3 C f4 4 5 632 mg/l N 0 APP1 N 0 APP2 N 0 APP C f3 C f1 Interactivity type (IO 1/IO 2) ‏ Instruction to learners Boundary limits & options Instruction to animatorsText to be displayed SliderChange the values of C u to see the changes in the applied flux and the overflow rate ------ Show graph 1 with all the labels. If learner reduces C f then show: Refer to graph 2 and shown on graph 1 the C f1 red line with the red dot and green arrow, along with labels C f2 is before C f1 line If learner increases C f then show: Next referring to graph 2 shown on graph 1 the C f3 red line with the red dot and blue arrow, along with labels C f4 is after C f3 line Show equation in dark green When concentration changes of clarifier feed, state point shifts and accordingly N°APP and overflow rate changes. For lower C f, applied flux is higher and overflow rate is lower For higher C f, applied flux is lower and overflow rate is higher.

24. Questionnaire 1. Which flux has a larger value? Answers: a) Gravity fluxb) Underflow fluxc) Total fluxd)‏ None of the above 2. From which curve’s slope you determine underflow rate? Answers: a) Total flux curveb) Underflow curvec) Gravity flux curved) Limiting flux line 3. State point is the interception point of underflow rate line and which line? Answers: a) Overflow rate lineb) Limiting flux linec) Gravity flux curved)‏ total flux line 1 5 2 4 3

25. Questionnaire 4. What happens overflow rate when underflow concentration decreases? Answers: a) Increasesb) Decreases c) Does not changed)‏ None of the above 5. Applied flux should be lower than Answers: a) Gravity flux b) Underflow flux c) Limiting fluxd)‏ Underflow concentration 1 5 2 4 3

26. Links for further reading Reference websites: Books: 1) Process dynamics in environmental system, Weber, Walter J.,DiGiano, Francis A., New York : John Wiley, 1996 2) Physicochemical processes for water quality control, Weber, Walter J., New York : John Wiley, 1972 3) Wastewater engineering : treatment, disposal, reuse, 2nd ed, Metcalf, Leonard/Eddy, Harrison P., New Delhi : Tata McGraw-Hill, 1979 Research papers:

27. Summary: As concentration increases, NB° (gravity flux) increases to a peak and then decreases as Vs approaches 0. As concentration increases, Nu° (underflow flux) increases proportionately. Total flux Ns° is the sum of gravity flux and underflow flux. The lowest point in the sagged portion of total flux line is the limiting flux. Underflow rate line is a tangent drawn to the gravity flux curve from the point on X axis corresponding to Cu if extended to Y axis and it meets at NL°. The point on the underflow rate line corresponding to C f is the state point. The flux corresponding to state point should be the applied flux N°app. The line connecting 0 to the state point is the overflow rate line. When underflow rate or concentration changes, state point shifts and accordingly NL° and overflow rate changes. For lower Cu, flux is lower and overflow rate is higher. When underflow rate changes, the slope of underflow line changes and thus Cu also changes. This also leads to change in flux and overflow rate