Characteristics of Nutrient Removal in Vertical Membrane Bioreactors

Transcription

1 The 2 nd MBR workshop at Hokkaido University Characteristics of Nutrient Removal in Vertical Membrane Bioreactors Prof. Hang-Sik Shin Dept. of Civil and Environmental Engineering Korea Advanced Institute of Science and Technology 1

2 Content Research Background Operating factors for vertical MBR Nutrient removal in vertical MBR Remediation of fouling in vertical MBR Conclusions 2

3 Mechanisms of membrane bioreactors Water Ortho P Water NO 3 T-P Membrane NH 4 -N NO 3 -N N 2 gas Ortho P A I R Anoxic reactor Oxic reactor 3

4 Research Objectives and Scope Operating factors Hydraulic retention time Internal recycle rate C/N ratio Membrane fouling Characterization Dynamic membrane Remediation Nutrient removal Various carbon source EBPR activity Population dynamics Novel MBR (Anoxic/Oxic vertical) Modelling Kinetic study Sludge production EPS accumulation 4

5 Operating factors in vertical MBR 5

6 Objective and Scope Anoxic tank -Denitrification -Phosphorus release Internal recycle Effluent Aerobic tank Aerobic zone -Nitrification -Organic oxidation -Phosphorus uptake Aeration devices Settling tank High MLSS conc. anoxic zone -Liquid/solid separation Influent Distribution devices 6

7 Test phases 7

8 Characteristics of the membrane used 8

9 Summary of Results I.R. (3Q 4Q 5Q): T-N= 68 83%, T-P= 51 8% C/N ratio (4 1): T-N= 55 8%, T-P= 38 76% : Phosphorus removal is more dependent on the content of organics than nitrogen HRT (12 6 hrs): at least 8 hrs HRT was needed Desirable operating conditions; internal recycle rate = 4Q, HRT > 8 hrs Sludge production = 1-6% of the CASP 9

10 Nutrient removal in vertical MBR 1

11 Objective and Scope Scale Reactor Substrate Laboratory MBR1 Sodium acetate Ax (12L) + MBR2 Propionic acid Ox (2L) MBR3 Glucose Scale Pilot Ax (5L) + Ox (833L) Substrate Municipal wastewater 11

12 Materials and Methods Characteristics of laboratory-scale MBRs Item Ax Ox Capacity Internal recycle rate SRT(d) 96 L/day 4% 3 Volume (L) HRT (hr) MLSS (g/l) ORP (mv)

13 Characteristics of synthetic wastewater 13

14 Experimental conditions for lab-scale MBRs 14

15 Characteristics of a pilot-scale MBR 1m Item Ax Ox Capacity Internal recycle rate 4 m 3 /day 4% SRT(d) 6 2.3m Volume (L) HRT (hr) 3 5 MLSS (g/l) ORP (mv)

16 Experimental conditions for a pilot-scale MBR 16

17 Characteristics of municipal wastewater 17

18 Characteristics of external carbon source Food waste Condensate of food waste (CFW) 18

19 Nitrogen removal potential of the CFW 35 3 Nitrate-N concentration (mg/l) Nitrate-N COD COD source: CFW MLVSS: 4.1 g/l COD concentration (mg/l) Time (min) 19

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21 Phosphorus release potential of the CFW NO 3 -N concentration (mg/l) Ortho-P concentration (mg/l) Ortho-P COD Nitrate-N COD source: CFW MLVSS: 4.1 g/l COD concentration (mg/l) Time (min) 21

22 Results and Discussion Effluent quality of lab-scale MBR fed with sodium acetate 5 Phase 1 Phase 2 Phase COD concentration (mg/l) COD T-N T-P T-N concentration (mg/l) T-P concentration (mg/l) Time (day) 22

23 Behaviors of ph and pollutants in the reactor ph Phase 1 Phase 2 Phase 3 COD concentration (mg/l) Phase 1 Phase 2 Phase In Anoxic Oxic Out Stage In Anoxic Oxic Out Stage NH 3 -N concentration (mg/l) Phase 1 Phase 2 Phase NO 3 -N concentration (mg/l) Ortho-P concentration (mg/l) Phase 1 Phase 2 Phase 3 In Anoxic Oxic Out Stage. In Anoxic Oxic Out Stage 23

24 Removal efficiencies of organics and nutrients Sodium acetate Propionic acid Glucose 24

25 Characteristics of EBPR activity with various substrates Experimental conditions for assessment of EBPR activity 25

26 Results of the assessment of EBPR activity with various substrates Batch test P release (mg P/g VSS) Acetate Propionic acid Glucose P uptake (mg P/g VSS) Acetate Propionic acid Glucose

27 Removal efficiencies of nutrients HRT 1 hr 1 hr 8 hr 6 hr 4 hr 8 hr +CFW.43% 8 hr +CFW.86% 27

28 Behaviors of nitrogen and phosphorus in the pilot-scale reactor Ammonia-N concentration (mg/l) Phase 1A Phase 2 Phase Nitrate-N concentration (mg/l) Ortho-P concentration (mg/l) Phase 1A Phase 2 Phase 6 In Anoxic Oxic Out In Anoxic Oxic Out Stage Stage - Phase 1A = 1 hr HRT w/o internal barrier - Phase 2 = 8 hr HRT - Phase 6 = 8 hr HRT + CFW.86% 28

29 Removal efficiencies of nutrients at various temperatures 29

30 Photographs of the formation of dynamic membranes 3

31 The role of dynamic membrane in removal of pollutants Experimental conditions 31

32 Schematic diagram of dynamic membranes 32

33 Reuse potential of the effluent in the pilot-scale vertical MBR 33

34 Comparison of capital costs For a 2,5 m 3 /d treatment plant 135% 125% 1% Normal effluent quality (N=1, P=1 mg/l) Membrane Electrical Stringent effluent quality (N=2.2, P=.15 mg/l + disinfection) Mechanical Civil CASP MBR CASP [Source: The STOWA, 22] 34

35 Summary of Results Condensate of food waste (CFW) great potential as a carbon source for nutrient removal! In the lab-scale vertical MBRs (acetate, propionic acid, glucose), - Average removal efficiency of nitrogen was about 8% - Removal efficiencies of phosphorus decreased in order of acetate (87%), propionic acid (83%), and glucose (78%) at C/N = 1 - Addition of the CFW (5% of COD) improved nitrogen and phosphorus removal efficiencies by 2-4% and 4-11%, respectively. Assessment of EBPR activity (batch test) - P release/uptake activity; acetate > propionic acid > glucose several kinds of PHAs were detected inside the cells 35

36 In the pilot-scale MBR treating municipal wastewater, - Average removal efficiency of total COD, T-N, and T-P 96%, 74%, and 78%, respectively at 8 hr HRT and C/N = As the CFW was supplemented (.86%), T-N and T-P removal efficiencies increased to 81% and 91%, respectively. - At differing temperature (13-25 Nitrification efficiency = 79-81% Phosphorus removal efficiency = 77-81% - Additional removal by the formation of dynamic membranes Organics (8%), nitrification (5%) and denitrification (4%) - The effluent quality could satisfy the current drinking water standards except for ammonia-n. Analysis of population dynamics - As C/N ratio decreased, the number of microbial species decreased - Species of the beta subclass or Proteobacteria are considered to play an important role in EBPR. - When the CFW was added, Geothrix fermentans appeared. 36

37 Remediation of membrane fouling in a vertical MBR 37

38 Objective and Scope Characteristics of membrane fouling Lab-scale (glucose) Ax/Ox vertical MBR Ax/Ox series MBR Pilot-scale (sewage) Ax/Ox vertical MBR 38

39 Ax/Ox series MBR 39

40 Operating conditions: lab-scale MBRs - Organic source = glucose - COD : N : P = 16 : 4 : 6 Operating conditions: pilot-scale vertical MBR 4

41 Results and Discussion Variations of flux and TMP in the series MBR 1 5 Permeate flux (L/m 2 /h) Permeate flux TMP Transmembrane pressure (kpa) Time (day) 41

42 Variations of flux and TMP in the vertical MBR 1 5 Permeate flux (L/m 2 /h) Permeate flux TMP Transmembrane pressure (kpa) Time (day) 42

43 Variations of flux and TMP in the pilot-scale vertical MBR 1 5 Permeate flux (L/m 2 /h) Flux at HRT of 8 hrs TMP at HRT of 8 hrs Transmembrane pressure (kpa) Time (day) 43

44 Effect of EPS concentration on fouling at various HRTs 5 1hrs HRTs 4hrs 5 5 Ra + Rp (x 1 12 m -1 ) Adsorption + Pore blocking Cake layer Total resistance R 2 =.997 Rt = X X Rc (x 1 12 m -1 ) Rt (x 1 12 m -1 ) Total EPS concentration (mg/g VSS) 44

45 Effect of particle size on fouling at various HRTs 5 HRT 1 hrs 4 hrs 5 5 Ra + Rp ( x 1 12 m -1 ) Adsorption + Pore blocking Cake layer Total resistance Y = X (R 2 =.999) Rc ( x 1 12 m -1 ) Rt ( x 1 12 m -1 ) Nominal particle size (µm) 45

46 Schematic diagrams of fouling remediation techniques 46

47 Fouling remediation by outside air supply 2 Designed permeate flux = 18.6 L/m 2 /h 4 Permeate flux (L/m 2 /h) Permeate flux TMP Transmembrane pressure (kpa) Time (day) 47

48 Fouling remediation by inside air supply 18.6 LMH 27.9 LMH 4 4 Permeate flux (L/m 2 /h) Permeate flux TMP Transmembrane pressure (kpa) Time (day) 48

49 Summary of Results 1. Series MBR vs. Vertical MBR (SRT = 3 days) - Vertical-type MBR; relatively low MLSS concentration (EPS and viscosity) reduce membrane fouling! - Cake layer resistance was about 6-7% of the total resistance 2. Lab-scale vs. Pilot-scale vertical MBR - Pilot-scale showed relatively higher values of EPS and viscosity, smaller particle size severe fouling! - In pilot-scale MBR (HRT= hrs); EPS content and particle size increased Cake layer resistance appeared to be the controlling factor of the total resistance 3. Fouling remediation - The inside air supply was more efficient than the outside air supply 49

50 Final Conclusions Internal recycle Effluent Stable and desirable effluent quality Aerobic zone Low sludge production Low membrane fouling Bulking problem ignore! High MLSS conc. anoxic zone High nutrient removal efficiency Influent Distribution devices 5

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52 Enhanced Biological Phosphorus Removal (EBPR) [Source: Smolders et al., 1995] 52