Designing Single-Sludge Bionutrient Removal Systems

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1 Designing Single-Sludge Bionutrient Removal Systems Richard O. Mines, Jr., Ph.D., P.E. Environmental Engineering Mercer University 2001 World Water & Environmental Resources Conference Orlando, FL

2 Activated Sludge Background Activated Sludge Schematic Microbial composition Substrate utilization Solids retention time (SRT) Nitrification stoichiometry May 22, 2001 World Water & Environmental Resources Conferences 2

3 Activated Sludge Background Continued Biokinetic Equations Substrate Biomass Sludge Production Oxygen Requirements May 22, 2001 World Water & Environmental Resources Conferences 3

4 ACTIVATED SLUDGE FLOW SCHEMATIC Q S o Aeration Basin X, V, S e Q + Q r X, S e Secondary Clarifier Q e X e X o S e Q r, X w, S e Return Activated Sludge Waste Activated Sludge Q w, X w May 22, 2001 World Water & Environmental Resources Conferences 4

5 Microbial Composition C 60 H 87 O 23 N 12 P 1 MW = % Nitrogen by Weight 2.3 % Phosphorus by Weight May 22, 2001 World Water & Environmental Resources Conferences 5

6 Substrate Utilization C + O 2 Heterotrophs CO 2 + Energy C + N + P + C 60 H 87 O 23 N 12 P New Biomass C 60 H 87 O 23 N 12 P + CO 2 + NH 3 + PO 4 May 22, 2001 World Water & Environmental Resources Conferences 6

7 Solids Retention Time (SRT) SRT ( days) = Total Biomass Biomass Wasted in System from System May 22, 2001 World Water & Environmental Resources Conferences 7

8 Nitrification (neglecting synthesis) NH + Nitrifiers O 2 NO H + + H 2 O 4.57 kg of oxygen required per kg of NH N oxidized 7.14 kg of alkalinity as CaCO 3 consumed per kg of NH N oxidized. May 22, 2001 World Water & Environmental Resources Conferences 8

9 Effluent Soluble Substrate Concentration S e = K S (1+ b SRT ) SRT ( Y k b) 1 May 22, 2001 World Water & Environmental Resources Conferences 9

10 Biomass Concentration X = Y ( S o S e ) SRT ( 1 + b SRT) θ May 22, 2001 World Water & Environmental Resources Conferences 10

11 Waste Sludge Production P X Y Q ( S S ) = o e 1 + b SRT May 22, 2001 World Water & Environmental Resources Conferences 11

12 O 2 Requirements O 2 = Q ( Y ) ( S o S e ) b XV + NOD NOD = Q ( TKN o ) (4.57) May 22, 2001 World Water & Environmental Resources Conferences 12

13 Biological Nitrogen Removal Schematic Denitrification stoichiometry Pre-anoxic zone sizing Post-anoxic zone sizing May 22, 2001 World Water & Environmental Resources Conferences 13

14 Pre- & Post-Denitrification Systems Mixed Liquor Recycle Influent Mixer Oxic Anoxic Oxic Anoxic Oxic Secondary Clarifier Effluent Return Activated Sludge Waste Activated Sludge May 22, 2001 World Water & Environmental Resources Conferences 14

15 Denitrification 6 NO 3 + 2CH 3 OH 6 NO 2 + 2CO H 2 O 6 NO 2 + 3CH 3 OH 3N 2 + 3CO 2 + 3H 2 O + 6OH 6 NO 3 + 5CH 3 OH Denitrifiers 3N 2 + 5CO H 2 O + 6OH 3.57 kg of alkalinity produced per kg of NO 3 N reduced kg of oxygen available per kg of NO 3 N reduced. May 22, 2001 World Water & Environmental Resources Conferences 15

16 Pre-Anoxic Zone Sizing SDNR 1 = 0.03 ( F M ) ( F M ) = Q S ( X V ) 1 o 1 (Burdick et al., 1982) SDNR 1 = Specific denitrification rate( pre anoxic), days 1 o V ANOXIC = TNOR(1000 g / kg)-0.03( S )(Q)(1.06 ) T (X)(1.06 ) T-20 May 22, 2001 World Water & Environmental Resources Conferences 16

17 Post-Anoxic Zone Sizing SDNR 2 = 0.12 ( ) ( ) ( T C 20 C SRT 1.02 ) Overall (Burdick et al., 1982) SDNR 2 = Specific denitrification rate, d 1 V Anoxic = TNOR ( 1000 g / kg) 2 ( )( ) 2 X SDNR 2 May 22, 2001 World Water & Environmental Resources Conferences 17

18 Enhanced Biological Phosphorus Removal (EBPR) Schematic: anaerobic zone precedes aerobic zone. Acinetobacter phosphorus composition Anaerobic or fermentation zone sizing May 22, 2001 World Water & Environmental Resources Conferences 18

19 Anaerobic/Anoxic/Oxic System Mixed Liquor Recycle Influent Mixer Anaerobic Mixer Anoxic Oxic Effluent Secondary Secondary Clarifier Return Activated Sludge Waste Activated Sludge May 22, 2001 World Water & Environmental Resources Conferences 19

20 Acinetobacter Composition 4 to 8 % Phosphorus by weight May 22, 2001 World Water & Environmental Resources Conferences 20

21 Anaerobic/Fermentation Zone Sizing P Removed = TP o SP P Removed = mg/l of phosphorus removed, TP o = Influent total phosphorus concentration into biological process, mg/l, and SP = Effluent soluble phosphorus from process, mg/l. May 22, 2001 World Water & Environmental Resources Conferences 21

22 Volume of Anaerobic Zone COD:TP ratio = 20:1 to 43:1 1 V = Q Anaerobic 24 [ ( PRemoved ) ] h V anaerobic = Volume of anaerobic zone, m 3 Equation developed from the data developed by Randall et al., May 22, 2001 World Water & Environmental Resources Conferences 22 d

23 Volume of Anerobic Zone COD:TP ratio = 40:1 to 69:1 1 V = Q Anaerobic 24 [ ( PRe moved ) ] h V anaerobic = Volume of anaerobic zone, m 3 Equation developed from the data developed by Randall et al., May 22, 2001 World Water & Environmental Resources Conferences 23 d

24 Design Procedure Size the aerobic zone based on the washout point of Nitrosomonas. Size the pre-anoxic zone using the specific denitrification equation developed by Burdick et al., Size the anaerobic zone using the equations developed by Randall et al., May 22, 2001 World Water & Environmental Resources Conferences 24

25 Heterotrophic Biokinetic Coefficients Heterotrophic Biokinetic Constants at 20E C Y = 0.6 g VSS/g BOD 5 b = 0.06 days -1 k = 5 days -1 K s = 60 mg/l BOD 5 Heterotrophic Biokinetic Constants at 15E C Y = 0.6 g VSS/g BOD 5 b = 0.05 days -1 k = 3.2 days -1 K s = 39 mg/l A temperature correction coefficient (1) of 1.04 was used for correcting b whereas a 1 of 1.09 was used for correcting k and K s. May 22, 2001 World Water & Environmental Resources Conferences 25

26 Autotrophic Biokinetic Coefficients Nitrosomonas Biokinetic Constants at 20EC Y NS = 0.15 g VSS/g NH N b NS = 0.05 days -1 k NS = 3 days -1 K NS = T = 0.74 mg/l Nitrosomonas Biokinetic Constants at 15EC Y NS = 0.15 g VSS/g NH N b NS = 0.04 days -1 k NS = 1.95 days -1 K NS = T = 0.41 mg/l A temperature correction coefficient (1) of 1.04 was used for correcting b whereas a 1 of 1.09 was used for correcting k and K s. May 22, 2001 World Water & Environmental Resources Conferences 26

27 Calculate Nitrosomonas Growth Rate K [ ] ( ) ( T 15) µ ( ) MAX NS = 047. e ph DO DO + DO 1 (SRT ) MIN = ( µ MAX ) ( NH -N ) K +( NH - N ) NS 4 + O NS 4 + O -b NS May 22, 2001 World Water & Environmental Resources Conferences 27

28 Calculate Design & Overall SRTs (SRT ) = (SRT) (SF)(PF) DESIGN MIN (SRT ) =(SRT ) (MF) OVERALL DESIGN May 22, 2001 World Water & Environmental Resources Conferences 28

29 Multiplication Factor (MF) MF = 1 [ 1 A][ 1 B] A = Anaerobic zone fraction of total reactor volume B = Anoxic zone fraction of total reactor volume May 22, 2001 World Water & Environmental Resources Conferences 29

30 Calculate Effluent Substrate Concentration (S e ) S = e [ ] K 1 + b(srt ) s OVERALL [(SRT ) ( Yk -b) - 1] OVERALL May 22, 2001 World Water & Environmental Resources Conferences 30

31 Calculate Effluent NH 4+ - N Concentration ( NH + 4 -N ) = e K NS [1 + b NS (SRT ) DESIGN ] (SRT ) [Y k -b ] -1 DESIGN NS NS NS May 22, 2001 World Water & Environmental Resources Conferences 31

32 Calculate Nitrogen to be Oxidized (NO) NO = TKN o (NH 4+ ) e - N SYN N = SYN Y( S - S ) F [1+b(SRT ) o e N e N OVERALL ] + (X ) F May 22, 2001 World Water & Environmental Resources Conferences 32

33 Calculate Oxic Volume V OXIC = Q(SRT ) X Y ( S - S ) 1 + b(srt ) DESIGN o e DESIGN + X L May 22, 2001 World Water & Environmental Resources Conferences 33

34 Anoxic Zone Calculations N= NO(Q) (MLR+ RAS + Q) N = Effluent & MLR nitrate concentration, mg/l May 22, 2001 World Water & Environmental Resources Conferences 34

35 Mass of Nitrates to be Removed in Anoxic Zone - 3 NO - N = (DO) MLR 0.35 g NO - N g O2 ( - ) 3 EQ (MLR) 1kg 1000g NOR = [( RAS + MLR) N] 1 kg 1000g - TNOR = NOR+( NO -N ) 3 EQ May 22, 2001 World Water & Environmental Resources Conferences 35

36 Calculate Anoxic Volume o V ANOXIC = TNOR(1000 g / kg)-0.03( S )(Q)(1.06 ) T (X)(1.06 ) T-20 May 22, 2001 World Water & Environmental Resources Conferences 36

37 Sludge Production & New Overall SRT P = X ( ) Y So- S 1 + b (SRT ) e OVERALL + X L (Q) 1kg 1000g ( SRT ) OVERALL = X ( V + V + V ) OXIC ANOXIC P X ANAEROBIC May 22, 2001 World Water & Environmental Resources Conferences 37

38 Check SRT values If the new overall SRT is not within 5% of the old overall SRT, the procedure should be repeated. May 22, 2001 World Water & Environmental Resources Conferences 38

39 Oxygen Requirements O 2 = CBOD + NOD - DOC 1kg CBOD = { Q[( Y )( SO Se)] ( b)( X )( VOXIC)} 1000g 1kg NOD = Q( 457. )( NO) 1000g DOC = go Q [ ] gno N NO NO N ( 3 ) e 1000 kgg 3 May 22, 2001 World Water & Environmental Resources Conferences 39

40 Alkalinity Requirements ALK e ( NO) + 3. [ NO N ] = ALK o May 22, 2001 World Water & Environmental Resources Conferences 40

41 Conclusions A step-by-step procedure has been presented for designing a three-stage, nitrogen and phosphorus removal system. Biokinetic equations developed by Lawrence & McCarty (1970) were used for sizing the aerobic zone with Nitrosomonas being the growth limiting microbe. May 22, 2001 World Water & Environmental Resources Conferences 41

42 Conclusions continued The pre-anoxic zone was sized based on the specific denitrification equation developed by Burdick et al., The anaerobic or fermentation zone was sized based on the equations developed from data presented by Randall et al., May 22, 2001 World Water & Environmental Resources Conferences 42

43 Conclusions continued The 4-stage, pre- and post- anoxic BNR system has been validated and presented in the following paper: Mines, R.O.(1997) Design and Modeling of 4-Stage Single- Sludge Systems, Advances in Environmental Research, 1 (3) Plans are to validate the anaerobic equations after collecting data from an A 2 /O facility. May 22, 2001 World Water & Environmental Resources Conferences 43

General Information on Nitrogen

General Information on Nitrogen What is nitrogen? Nitrogen was discovered in 1772 by Daniel Rutherford in Scotland Nitrogen gas makes up nearly 80% of the air we breathe Nitrogen gas is not toxic Nitrogen