Potential Activity of Methanogens in Anaerobic Digesters Study

Investigating the potential activity of methanogens in anaerobic digesters with and without hydrogen addition. The goal is to estimate methane production and compare upgrading potential using a specific assay method. The study involves collecting material from reactors, incubating in specific gas mixtures, and measuring methane production rates over time. Various anaerobic digesters including Viby WWTP are analyzed to understand methane production dynamics and potential limitations.

• Methanogens
• Anaerobic Digesters
• Methane Production
• Reactor Study
• Biogas

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1. Potential activity of methanogens Karoline W. Noer Master student Supervisors: Niels Peter Revsbech and Lars D.M. Ottosen

2. Goals Estimate the potential activity of methanogens from anaerobic digesters Methane production with and without hydrogen addition Develop a method to compare the upgrading potential of different anaerobic digesters

3. Potential activity assay Collect material from anaerobic reactor Gas fast bag with argon, directly from reactor Material is transferred into serum bottles flushed with argon. Headspace is flushed with the specific gas mixture Flasks are incubated in rotor at temperature of the reactor Gas samples from the headspace is collected every 30min for 2h Methane measurements, GC-FID

4. Anaerobic digesters Anaerobic digester Viby WWTP Anaerobic digester by WWTP Anaerobic digester B nlev Biogas Thermophilic 49 C Primary and secondary sludge (bioslam) Mesophilic 38 C Primary and secondary sludge (bioslam) Mesophilic 39 C Different waste and organic material from farms

5. Avoid mass transfer limitations - dilution of material Dilution of the material from the digester with media (Pennings et al. 1998) 1:10 dilution Headspace H2/CO2 in 80:20 ratio N2 in control Methane production over 2h Methane production rate calculated from slope of linear regression Viby WWTP, Methan production 3/12-2015 1.4E-05 H2 rep.1 1.2E-05 H2 rep.2 1.0E-05 Conc. CH4 (mol/L) H2 rep.3 8.0E-06 H2 rep.4 6.0E-06 N2 rep.1 4.0E-06 N2 rep.2 2.0E-06 N2 rep.3 0.0E+00 N2 rep.4 0 50 100 150 -2.0E-06 Time (min) Measurements from Viby WWTP, by WWTP and B nlev Biogas

6. Rates of diluted material Faster production with H2/CO2 Rates far lower than in the reactor Chemical environment? Methane production rate 0.7 0.6 0.5 LCH4/Lmat./day 0.4 0.3 0.2 0.1 0 N2 N2 N2 Reactor Reactor Reactor H2/CO2 84% H2/CO2 12% H2/CO2 77% 5% 100% 4% 100% 8% 100% B nlev by Viby 3-12-15 16-11-15 2-12-15

7. Dilution in 0.5%saline water Same procedure, 0.5% KCl water Dilution series Rates still does not match 10mL material with H2/CO2 headspace shows high rates Dilution in 0.5% saline water, and 10mL pure material 1.00 0.80 LCH4/Lmat./day 0.60 235% 0.40 100% 0.20 119% 53% 42% 0.00 10mL 5mL 1mL N2, 5mL Reactor Viby 15-01-2016 B nlev 14-01-2016 1.00 Viby 15-12-2015 0.80 0.80 0.70 LCH4/Lmat./day 100% 0.60 0.60 LCH4/Lmat./day 0.50 100% 0.40 0.40 143% 0.30 56% 46% 20% 0.20 0.20 9% 0.3% 0.10 0.00 0.00 H2/CO2 N2 Reactor H2/CO2, 1mL N2, 1mLH2/CO2, N2, 10mL Reactor 10mL

8. Test of dilution/undiluted 10mL pure material 1.5bar H2/CO2 or N2/CO2 Final pH*: H2/CO2: ~9.50 N2/CO2: ~ 8.97 *after 3 days incubation Methane production rate, 1.5bar 15 LCH4/Lmat./day 10 5 0 H2/CO2, 10mL N2/CO2, 10mL Reactor B nlev 25-01-16 Methane production Methane production with different amount of material 10mL undiluted material with N2/CO2 closest to reactor levels B nlev 25/1/16 1.5bar B nlev 25/1/16 reactor 0.90 0.80 0.70 LCH4/Lmat./day Viby 0.60 15/12/16 reactor 0.50 0.40 Viby Viby 15/1/16 0.30 15/12/15 Viby 0.20 15/12/15 0.10 0.00 N2, 1mL N2, 5mL N2, 10mL N2/CO2, Reactor, B nlev 100% Reactor, Viby 100% 10mL 105% 9% 43% 47%

9. CO2series CO2 serie 0.25 Buffer with phosphate buffer Minimize the pH effect Same procedure N2/CO2 with different CO2 concentrations Not up to reactor rates Same with 0.02M acetate CO2do not seem to effect rate 0.2 LCH4/Lmat./day 0.15 0.1 0.05 0 0% 1% 12% 27% 66% 100% CO2 serie, with acetate CO2 series, B nlev material 0.5 0.9 0.45 0.8 0.4 100% 0.7 0.35 LCH4/Lmat./day 0.3 0.6 LCH4/Lmat./day 0.25 0.5 CO2 serie 0.2 0.4 0.15 54% 46% 0.3 CO2 serie with acetate 42% 0.1 0.2 25% 0.05 9% 13% 0.1 0 11% 22% 24% 14% 10% 14% 0 Ac., 0% Ac., 1% Ac., 12% Ac., 27% Ac., 66% Ac., 100% Ac., 12% Ac., 27% Ac., 66% 100% Reactor Ac., 0% Ac., 1% Ac.,

10. Next Potential activity assay with 10mL pure material from different anaerobic digesters Test the effect of VS concentration in reactor on the assay