Development and testing of a fully gravitational submerged anaerobic membrane bioreactor (FG-SAnMBR) for wastewater treatment

Transcription

1 Development and testing of a fully gravitational submerged anaerobic membrane bioreactor (FG-SAnMBR) for wastewater treatment Short Retention Time Anaerobic Digestion Processes for Industrial Wastewater Treatment 11 th December Newcastle, UK Santiago Pacheco-Ruiz* Professor Charles Banks Dr Sonia Heaven s.pacheco-ruiz@soton.ac.uk c.j.banks@soton.ac.uk s.heaven@soton.ac.uk Water and Environmental Engineering Research Group Faculty of Engineering and the Environment

2 Outline Introduction AnMBR for wastewater treatment AnMBR main limitation and research focus Development and testing of a FG-SAnMBR for wastewater treatment Use of a FG-SAnMBR to evaluate the effect of MCRT on membrane fouling, biomass characteristics and overall reactor performance Conclusions 2

3 Introduction Anaerobic membrane bioreactors for wastewater treatment

4 Anaerobic Membrane Bioreactors (AnMBR) AnMBR is an anaerobic treatment process that uses a membrane to provide complete solid-liquid separation total biomass retention increase AD efficiency high effluent quality low sludge production potential net energy production Conventional wastewater treatment plant [a] Conventional anaerobic digester [b] 4

5 AnMBR main limitation and research focus Membrane fouling Cake fouling Pore blocking [c] High energy demand High capital and O&M costs 5

6 AnMBR main limitation and research focus Membrane fouling [1,2,3] Recent AnMBRs reviews stress out that future research should focus on: membrane fouling reduction and cleaning mechanisms improvement Cake fouling Pore blocking [c] link between operational parameters, membrane fouling and treatment performance energy demand reduction High energy demand High capital and O&M costs dissolved methane in effluent low temperature operation nutrient removal 6

7 Membrane type and configuration Type Configuration biogas Flat sheet [d] Submerged feed Hollow fibre biosolids permeate [e] biogas Tubular External feed retentate [f] biosolids permeate 7

8 Membrane type and configuration Type Configuration biogas Flat sheet [d] Submerged feed biosolids permeate Flat sheet - submerged anaerobic membrane bioreactor (SAnMBR) 8

9 Typical flat sheet SAnMBR configuration SAnMBR typical configuration 9

10 Typical flat sheet SAnMBR configuration energy output energy input energy input potential energy loss main energy input energy input SAnMBR typical configuration 10

11 FG-SAnMBR Development and testing

12 Why to develop a fully gravitational SAnMBR? SAnMBRs are usually operated at a constant flux, given by a vacuum pump, where membrane performance is [4] evaluated by changes in TMP due to fouling FG-SAnMBR will draw the permeate with a head difference, providing a constant TMP and where the flux will vary in response to changes in the membrane [4] permeability due to fouling direct information on fouling phenomena direct energy savings, as pumping is avoided no reports on flat sheet FG-SAnMBR 12

13 FG-SAnMBR configuration FG-SAnMBR configuration (front view) FG-SAnMBR gaslift loop (side view) 13

14 Objectives Determine if a flat-sheet SAnMBR can be operated in a fully gravitational configuration Evaluate membrane performance at constant TMP by direct analysis of membrane flux variation due to fouling Assess the overall reactor performance Investigate the establishment of a sustainable membrane flux under different operational conditions Identify proposed system limitations SAnMBR constructed

15 Experimental set-up

16 Experimental design Parameter Operational temperature 36 o C Value Membrane cleaning mechanism Biogas scouring Recirculation rate: 5 L min -1 Reactor working volume Inoculum Test substrate 9.6 L Mesophilic digester treating wastewater biosolids High solids synthetic wastewater Phase Duration (days) Objective TMP (kpa) Start-up 10 Inoculum acclimation and reactor stabilisation 7.0 EP-1 43 First insight into FG-SAnMBR operation 7.0 EP-2 15 Evaluation at High TMP 7.0 EP-3 3 Evaluation with permeate line restriction (valve) 7.0 EP-4 15 Evaluation at low TMP 2.3 EP-5 14 Evaluation at low TMP and a higher OLR 2.3 EP-6 15 Evaluation at low TMP and a higher OLR

17 TMP (kpa) SMP (L CH4 g COD rem.-1) Biogas production (L L-1 react. day-1) J (LMH) MLSS (g L-1) Results Start-up EP-1 EP-2 EP-3 EP-4 EP-5 EP MLSS (g/l) J (LMH) Time (days) 17

18 HRT (hours) OLR (g COD L-1 day-1) COD removal (%) J (LMH) MLSS (g L-1) Results (2) Start-up EP-1 EP-2 EP-3 EP-4 EP-5 EP % 75% 50% 25% 0% 2.0 MLSS (g/l) J (LMH) Time (days) 18

19 Real-time membrane flux monitoring Valve restriction effect on membrane flux

20 Biogas scouring efficiency and fouling formation Failure of biogas recirculation pump for membrane scouring gave an insight of the efficiency of the cleaning mechanism Before running water rinse After running water rinse

21 FG-SAnMBR advantages and disadvantages Membrane performance can be directly analysed by flux Robust, simple and reliable configuration Low TMP required for permeation Potential reduction in membrane cleaning frequency, if sustainable operation is achieved Direct energy savings, up to 5% of total energy demand Self-regulating influent and effluent Constant positive pressure inside the reactor [5]

22 FG-SAnMBR advantages and disadvantages Membrane performance can be directly analysed by flux Robust, simple and reliable configuration Low TMP required for permeation Potential reduction in membrane cleaning frequency, if sustainable operation is achieved Direct energy savings, up to 5% of total energy demand Self-regulating influent and effluent Constant positive pressure inside the reactor Variable flux, during start-up and membrane fouling stabilisation results in fluctuating operation Long flux stabilisation period [5]

23 FG-SAnMBR application Evaluation of the effect of MCRT on membrane fouling, biomass characteristics and overall reactor performance

24 Objectives Evaluate the effect of MCRT on: membrane performance by the direct analysis of membrane flux under a constant TMP overall FG-SAnMBR performance biomass characteristics and its relationship with membrane fouling Experimental Set-up

25 Experimental set-up

26 Experimental design Parameter Value Operational temperature 36 o C Membrane cleaning mechanism Biogas scouring Recirculation rate: 5 L min -1 Reactor working volume 9.6 L Inoculum Test substrate Mesophilic digester treating wastewater biosolids High solids synthetic wastewater Phase Duration (days) Start-up 25 EP-1 25 Objective Inoculum acclimation, reactor stabilisation, and membrane pre-fouling Reactors coupling to establish an evaluation baseline EP-2 95 Evaluation of MCRT effect EP-3 55 Evaluation of MCRT effect EP-4 45 Evaluation of MCRT effect 245 Reactor TMP MCRT OLR (kpa) (days) (g COD L -1 d -1 ) A B A B A B A B A B

27 COD removal (%) HRT (hours) MCRT (days) Flux (LMH) Results Start-up EP-1 EP-2 EP-3 EP % 75% 50% 25% 0% Reactor A Reactor B Reactor A Reactor B Reactor A Reactor B Reactor A Reactor B Time (days) 27

28 CST/MLSS (s g -1 L) MLSS (g TSS L-1) MLVSS (g VSS L-1) Flux (LMH) Results (2) Start-up EP-1 EP-2 EP-3 MCRT (days) Start-up EP-1 EP-2 EP-3 EP-4 Reactor A Reactor B EP Reactor A Reactor B Time (days) Reactor A - MLSS Reactor B - MLSS Reactor A - MLVSS Reactor B - MLVSS Reactor A Reactor B Time (days) 28

29 Dissolved CH 4 (ml L -1 ) BSMP (L CH4 /g-1 COD rem g-1 MLSS) SMP (L CH4 g COD rem -1 ) Results (3) Start-up EP-1 EP-2 EP-3 MCRT (days) Start-up EP-1 EP-2 EP-3 EP-4 Reactor A Reactor B EP E-02 6.E-02 4.E-02 2.E Reactor A Reactor B Maximum Theoretical SMP 0.E Reactor A Reactor A Reactor B Reactor B Time (days) SATURATION CONCENTRATION 29

30 Membrane fouling and biomass characteristics Reactor A (short MCRTs) Reactor B (long MCRT) T=0 T= 1 hr T= 24 hr

31 Conclusions

32 Conclusions The flat-sheet FG-SAnMBR was developed and successfully tested FG-SAnMBRs enabled critical assessment of the membrane performance by direct analysis of the flux at a constant TMP, as well as assessment of specific effects Long term sustainable operation was achieved under different operational parameters with potential energy savings up to 5% Successful evaluation of MCRT effect on membrane fouling, biomass characteristics and overall FG-SAnMBR performance Short MCRT lower membrane fouling, higher biomass filterability Long MCRT higher SMP, lower dissolved methane Still necessary to determine optimum MCRT to reach a balance between membrane flux, methane production and biosolids production

33 Mexican National Council of Science and Technology Thank you

34 Mexican National Council of Science and Technology Questions?

35 References Text Images 1. SMITH, A. L., STADLER, L. B., LOVE, N. G., SKERLOS, S. J. & RASKIN, L Bioresource Technology, 122, STUCKEY, D. C Bioresource Technology, 122, VISVANATHAN, C. & ABEYNAYAKA, A Membrane Water Treatment, 3, WEF, Manual of Practice MARTIN, I., PIDOU, M., SOARES, A., JUDD, S. & JEFFERSON, B Environmental Technology, 32, a. b. c. WEF, Manual of Practice d. e. 35