The Effect of Organic Loading on Membrane Fouling in a Submerged Membrane Bioreactor Treating Municipal Wastewater

Transcription

1 The Effect of Organic Loading on Membrane Fouling in a Submerged Membrane Bioreactor Treating Municipal Wastewater R. Shane Trussell, P.E., Rion P. Merlo, Slawomir W. Hermanowicz,, and David Jenkins Department of Civil and Environmental Engineering University of California, Berkeley October 5, 2004

2 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

3 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

4 Membrane Bioreactor (MBR) Modified activated sludge process UF/MF membrane Two configurations External (EMBR) Submerged (SMBR) Introduction

5 Membrane Bioreactor (MBR) Modified activated sludge process UF/MF membrane Two configurations External (EMBR) Submerged (SMBR) Introduction

6 Flow Schemes for the SMBR and Conventional Activated Sludge Process Conventional Aeration Basin Microfiltration Reverse Secondary Osmosis Clarifier Feedwater Backwash Water WASTE Primary Treated Wastewater

7 Flow Schemes for the SMBR and Conventional Activated Sludge Process Conventional Aeration Basin Microfiltration Reverse Secondary Osmosis Clarifier Feedwater Backwash Water WASTE Aeration Basin SMBR Primary Treated Wastewater Reverse Osmosis (Equivalent to a 3 mm screen) Feedwater WASTE

8 Process Limitation CAS Decline in effluent water quality High effluent COD High effluent SS Treatment capacity remains unaffected MBR No decline in effluent water quality Membrane fouling Loss of treatment capacity

9 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

10 Rationale F M = S o " H # X MLVSS The SMBR process is currently limited to an MLSS concentration of 10 g/l The F/M ratio is a key parameter to optimize reactor tank design Small tank (low HRT) Small tank (high F:M)

11 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

12 Equipment and Apparatus Pilot-scale SMBR Treating primary effluent from the City of San Francisco s SEP COD = 325 mg/l TSS = 98 mg/l

13 Membrane Operation and Characteristics Zenon 500C Module Nominal pore size = µm Hydrophilic Membrane flux = 30 L/m 2. h Coarse bubble air = 14 L/s Intermittent aeration 9 min operating cycle followed by 30 sec relax

14 Experimental Methods Initial operating conditions: MCRT = 10 d (F/M = 0.34 gcod/gvss. d) Dissolved oxygen > 2 mg/l Constant MLSS = 8g/L Steady-state data collection began after 3 MCRTs 2 week steady-state data collection period MCRT was steadily decreased (5, 4, 3, 2 d) F/M (0.53, 0.73, 0.84, 1.4 gcod/gvss.d)

15 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

16 Biological Foaming - Nocardioform

17 Illustration of Mechanical Foam Control Foam Liquid ML Recycle Line D = 0.1 m Foam Foam Liquid Coarse Aeration On Membrane Tank Intermittent Aeration (10s on/10s off) ML Recycle Pump Liquid Aeration Tank D = m Foam Liquid Coarse Aeration Off

18 Membrane Performance at 10-d MCRT (F/M=0.34 gcod/gvss. d) Flux Specific Flux Start-up Chemical Clean Large Foam Event Flux, LMH Specific 20 o C, LMH/bar Days of Operation

19 Membrane Performance at 5-d MCRT (F/M=0.53 gcod/gvss. d) Flux Specific Flux Flux, LMH Specific 20 o C, LMH/bar Days of Operation

20 Membrane Performance at 4-d MCRT (F/M=0.73 gcod/gvss. d) Flux Specific Flux 40 Intermittent Coarse Air Failure Foam Event Flux, LMH Specific 20 o C, LMH/bar Days of Operation

21 Membrane Performance at 3-d MCRT (F/M=0.84 gcod/gvss. d) Flux Specific Flux 40 Routine Feed Line Cleaning Routine Feed Line Cleaning Intermittent Coarse Air Failure Flux, LMH Specific 20 o C, LMH/bar Days of Operation

22 Membrane Performance at 2-d MCRT (F/M=1.4 gcod/gvss. d) Flux Specific Flux Foam Event Flux, LMH Specific 20 o C, LMH/bar Days of Operation

23 Effect of F/M on Steady-State Fouling Rate 4.0 MCRT, d Steady-State Fouling 20 o C, LMH/bar. d y = 1.661x R 2 = F/M, g COD/g VSS. d

24 Steady-state Fouling Rate vs scod Soluble COD COD Rejection COD, mg/l scod = 3.8x R 2 = 0.30 COD Rejection = -1.5x R 2 = COD Membrane Rejection, % Steady-state fouling rate, LMH/bar. d

25 Steady-state Fouling Rate vs SMP Protein Carbohydrate Total Total SMP = 7.0x R 2 = 0.77 SMP concentration, mg/l SMP p = 2.8x R 2 = 0.36 SMPc = 4.2x R 2 = Steady-state fouling rate, LMH/bar. d

26 Introduction Rationale Outline Materials and Methods Results Conclusions Acknowledgements

27 Conclusions High organic loading rates (F/M) increased membrane fouling rates Biological foaming was controlled mechanically Increased steady-state membrane fouling rates correlated with SMP, not scod Understanding membrane fouling at high organic loading rates allows engineers to design a compact SMBR without: excessive maintenance costs or failing to meet the design capacity

28 Conclusions Present Worth, $ Capital O&M θ H, time

29 Acknowledgements ZENON Environmental Services Inc. City and County of San Francisco s s Water Pollution Control Department Water Environment Research Foundation

30 The Effect of Organic Loading on Membrane Fouling in a Submerged Membrane Bioreactor Treating Municipal Wastewater R. Shane Trussell, Rion P. Merlo, Slawomir W. Hermanowicz,, David Jenkins Department of Civil and Environmental Engineering University of California, Berkeley October 5, 2004