Lutgarde Raskin Department of Civil and Environmental Engineering University of Michigan

Transcription

1 THE NEED FOR BIOFILM ENHANCED ANAEROBIC MEMBRANE BIOREACTORS Lutgarde Raskin Department of Civil and Environmental Engineering University of Michigan Caroline Van Steendam Julie Fichefet BMG themadag Anaerobe MBR

2 Bench scale study: AnMBR treatment of domestic wastewater at 15 C with submerged flat sheet microfiltration membranes Psychrophilic Inoculum Mesophilic Inoculum days Mesophilic Inoculum 1 Summary of results Wastewater Permeate COD (mg/l) Permeate BOD 5 (mg/l) Synthetic 36 ±21 18 Actual 76 ±10 25 ±3 Biogas sparging was effective at controlling long term fouling Approximately half of methane generated was lost in permeate Psychrotolerant, mesophilic populations dominated in AnMBR Smith, A.L., S.J. Skerlos, and L. Raskin, Psychrophilic anaerobic membrane bioreactor treatment of domestic wastewater. Water Research 47(4),

3 Additional questions need to be answered before AnMBR treatment of domestic wastewater will be implemented 1. Can treatment performance be improved? 2. Can operating temperature be lowered? 275 days 3. How does AnMBR compare to conventional treatment technologies based on cost, energy, and environmental impacts?

4 Additional questions need to be answered before AnMBR treatment of domestic wastewater will be implemented 1. Can treatment performance be improved? 2. Can operating temperature be lowered? 275 days 3. How does AnMBR compare to conventional treatment technologies based on cost, energy, and environmental impacts?

5 New bench scale AnMBR study to evaluate questions generated in initial study P1 P2 P3 Three submerged flat sheet membranes Biogas sparging for fouling control, independently controlled for each membrane Operated initially at high sparging rate for fouling control Psychrophilic temperature (15 o C) Inoculated with mesophilic sludge only 1,000 cm 2 Smith, A.L., S.J. Skerlos, and L. Raskin, Membrane biofilm development improves COD removal in anaerobic membrane bioreactor wastewater treatment. Microbial Biotechnology, 8(5):

6 Poor permeate quality during first 100 days of operation Was limited fouling due to high biogas sparging related to poor performance? Influent 500 COD (mg/l) Effluent Acetate Propionate Days from Startup

7 Can we use biofilm treatment to improve permeate quality? Complex polymers Fermenting bacteria Monomers and oligomers Volatile fatty acids and alcohols (Propionate) Hydrolytic and fermenting bacteria Syntrophic acetate oxidizers Acetate H 2 + CO 2 Acetogens Aceticlastic methanogens Syntrophs CH 4 + CO 2 Hydrogenotrophic methanogens

8 Can we use biofilm treatment to improve permeate quality? Complex polymers Fermenting bacteria Monomers and oligomers Propionate Volatile fatty acids and alcohols (Propionate) Syntrophs Syntrophic acetate oxidizers Acetate H 2 + CO 2 Acetogens Promote Aceticlastic biofilm Hydrogenotrophic methanogens activity? methanogens CH 4 + CO 2 Acetate Hydrolytic and fermenting bacteria e CO 2 CH 4 Permeate

9 Different levels of biofilm development (fouling) on each membrane by varying biogas sparging 0 kpa 27 kpa 45 kpa 0% ~25% ~50% Biogas sparging reduction

10 Biofilm promotion greatly improved permeate quality Low Fouling 160 COD (mg/l) Medium Fouling High Fouling Days from Startup

11 Aceticlastic methanogens and propionate oxidizing bacteria developed over time in biofilm 80 Low Fouling Acetate (mg/l) Bioreactor Medium Fouling High Fouling 0 50 Propionate (mg/l) Days from Startup

12 Methanogenesis in the biofilm impacted the fate of methane 4.0 Methane Oversaturation High Fouling 2.6 ± 0.30 Low Fouling 1.1 ± 0.22 Medium Fouling 1.7 ± Days from Startup 12

13 Are three biofilm communities (fouling layers) different? P1 P2 P3 Microbial community structure DNA DNA extraction of suspended biomass and biofilm biomass Illumina sequencing targeting V4 region of 16S rrna gene of Bacteria and Archaea 1,000 cm 2 Microbial community activity RNA RNA extraction of suspended biomass and biofilm biomass Reverse transcription of RNA cdna IIllumina sequencing targeting V4 region of 16S rrna of Bacteria and Archaea Quantitative PCR of 16S rrna and methyl coenzyme M reductase (mcra) transcript

14 Differences between community structure (DNA) and activity (RNA) and between suspended and biofilm characteristics are substantial Relative Abundance (%) Bacteria unclassified Archaea unclassified Euryarchaeota unclassified Methanomicrobia unclassified Thermoplasmatales unclassified Methanomicrobiales unclassified Methanomicrobiales incertae sedis unclassified Methanobacteriaceae Methanosphaerula Methanosphaera Methanomethylovorans Methanolobus Relative Activity (%) Low Medium Fouling High Fouling Fouling Methanolinea Methanoculleus Methanocorpusculum Methanocalculus Methanobrevibacter Methanobacterium Methanosarcina Methanospirillum Methanoregula Suspended (days from startup) Biofilm (day 138) Methanosaeta

15 Greater mcra gene expression in biofilm than in suspended biomass

16 Syntrophic bacteria most active in high fouling biofilm Relative Abundance of Bacteria (%) Relative Activity of Bacteria (%) Smithella Syntrophus unclassified Syntrophorhabdus unclassified Syntrophomonadaceae Syntrophomonas unclassified Syntrophobacteraceae unclassified Syntrophaceae Low Medium FoulingHigh Fouling Fouling Suspended (days from startup) Biofilm (day 138) 16

17 Additional questions need to be answered before AnMBR treatment of domestic wastewater will be implemented 1. Can treatment performance be improved? 2. Can operating temperature be lowered? 275 days 3. How does AnMBR compare to conventional treatment technologies based on cost, energy, and environmental impacts?

18 Excellent AnMBR performance maintained down to 6 C c 12 c Influent 9 c 6 c 3 c COD (mg/l) Days from Startup

19 Excellent AnMBR performance maintained down to 6 C Biofilm s role in treatment becomes more critical as temperature decreases c 12 c Influent 9 c 6 c 3 c COD (mg/l) Bioreactor Days from Startup

20 Reliance on biofilm for treatment increased dissolved methane oversaturation Smith, A.L., S.J. Skerlos, and L. Raskin, Anaerobic membrane bioreactor treatment of domestic wastewater at psychrophilic temperatures ranging from 15 C to 3 C, Environmental Science: Water Research &Technology, 1(1):

21 Additional questions need to be answered before AnMBR treatment of domestic wastewater will be implemented 1. Can treatment performance be improved? 2. Can operating temperature be lowered? 3. How does 275 AnMBR days compare to conventional treatment technologies based on cost, energy, and environmental impacts? Number of Publications in Peer Reviewed Journals anaerobic MBR AND domestic wastewater Web of Science TM Basic Science search, Oct Smith, A. L., Stadler, L. B., Cao, L., Love, N. G., Raskin, L., and Skerlos, S. J. (2014), Navigating Wastewater Energy Recovery Strategies: A Life Cycle Comparison of Anaerobic Membrane Bioreactor and Conventional Treatment Systems with Anaerobic Digestion, Environmental science & technology, 48 (10):

22 Closing the global warming emission gap will require dissolved methane recovery Medium Strength

23 Conclusions 1. Can AnMBR treatment performance be improved? Biofilm improved permeate quality, but increased dissolved methane Biofilm and suspended microbial communities were distinct 2. Can AnMBR operating temperature be lowered from 15 o C? Permeate quality remained excellent for temperature as low as 6 o C Biofilm becomes more critical as temperature decreases 3. How does AnMBR compare to conventional treatment technologies? Energy demands need to be reduced to compete with conventional technologies Methane release must be avoided to have comparable or lower global warming impacts

24 Goals for ongoing and future AnMBR work 1. Improve treatment performance with a focus on low temperatures and low hydraulic retention times Only possible with substantial biofilm activity new AnMBR designs: expand biofilm activity 2. Avoid methane release to reduce global warming potential Biofilm on membrane results in oversaturation and methane release new AnMBR designs: transfer produced methane from the liquid phase to the gas phase 3. Reduce energy demand to be competitive with conventional technologies Sparging for fouling control has high energy demand new AnMBR designs: alternative membrane designs (e.g., rotating ceramic disk membranes)

25 Acknowledgements Graduate Students: Tanna Borrell Adam Smith Lauren Stadler Caroline Van Steendam Julie Fichefet Steve Skerlos Adam Smith Nancy Love Ilse Smets

26 Publications Anaerobic MBR for Domestic WWT at Low Temperatures Smith, A.L., S.J. Skerlos, and L. Raskin, Membrane biofilm development improves COD removal in anaerobic membrane bioreactor wastewater treatment. Microbial Biotechnology, 8(5): Smith, A.L., S.J. Skerlos, and L. Raskin, Anaerobic membrane bioreactor treatment of domestic wastewater at psychrophilic temperatures ranging from 15 C to 3 C, Environmental Science: Water Research &Technology, 1(1): Smith, A. L., Stadler, L. B., Cao, L., Love, N. G., Raskin, L., and Skerlos, S. J. (2014), Navigating Wastewater Energy Recovery Strategies: A Life Cycle Comparison of Anaerobic Membrane Bioreactor and Conventional Treatment Systems with Anaerobic Digestion, Environmental science & technology, 48 (10): Smith, A.L., S. J. Skerlos, and L. Raskin (2013), Psychrophilic Anaerobic Membrane Bioreactor Treatment of Domestic Wastewater, Water Research, 47(4): Smith, A.L., L. B. Stadler, N.G. Love, S. J. Skerlos, and L. Raskin (2012), Perspectives on Anaerobic Membrane Bioreactor Treatment of Domestic Wastewater: A Critical Review, Bioresource Technology, 122,