Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Anaerobic digestion of brewing “waste”. L.S. Nkadimeng, S.T.L. Harrison Energy Postgraduate Conference 2013 Background Effluents • Beer • Spent grain • Spent yeast • Wastewater AD (wastewater treatment) Picture from : http://www.sabmiller.in/know-beer_brewing.html University of Cape Town >> 23 May 2017 >> < EPC 2013 > -2- Anaerobic digestion (AD) Steam to brewery Water Carbohydrates sugars Proteins Amino acids Hydrolysis td : Boiler Organic acids, alcohols Acetate, H2, CO2 Biogas (CH4, CO2) H2, CO2, NH4 Fatty acids Lipids CO2 Acidogenesis 30 minutes Acetogenesis 1,4 to 5 days Methanogenesis 2 to 3 days (Mosey 1983; Lawrence & McCarty 1989; Gerber & Span 2008) University of Cape Town >> 23 May 2017 >> < EPC 2013 > -3- Spent grain (Aliyu & Bala, 2011, Mussatto & Teixeira, 2010) Digestibility: Only 15% reduction in COD over 19 days of digestion • Mechanical pre-treatment to promote hydrolysis: grinding 40 Soluble COD (mg-COD/gdBGS) Soluble COD (mg-COD/g-dBGS) 1300 1100 900 700 500 300 University of Cape Town 30 25 20 15 10 5 0 100 -100 0 35 0 50 >> 100 Time (s) 23 May 2017 150 >> 50 200 < EPC 2013 > 100 Time (s) 150 200 -4- Spent yeast: Effect of non-acclimated system on pH 5000 10000 4000 8000 3000 6000 2000 4000 1000 2000 0 COD fed (mg-COD) Reactor COD (mg-COD/L) 12000 TCOD in reactor SCOD in reactor TCOD fed to 1L reactor SCOD fed to 1L reactor 0 0 1 2 3 4 5 6 0 1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 18 Time (days) 7.8 7.6 7.4 pH 7.2 7 6.8 6.6 6.4 6.2 University of Cape Town >> 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (days) 23 May 2017 >> < EPC 2013 > -5- 8000 5000 7000 4500 4000 6000 3500 5000 3000 4000 2500 3000 2000 1500 2000 COD fed (mg-COD) Reactor COD (mg-COD/L) Spent yeast: Slow incremental feeding 1000 1000 TCOD in reactor SCOD in reactor TCOD fed to 1L reactor SCOD fed to 1L reactor 500 0 0 0 5 10 20 Time (days) 25 COD removal rate (mg-COD/L-reactor.day) pH 1200 7.8 15 1000 7.6 30 35 Highest removal rate: 962 mg-COD/L.day 7.4 800 7.2 6007 6.8 400 6.6 200 6.4 6.2 0 0 0 40 500 5 University of Cape Town 10 15 20 25 1000 1500 2000 2500 3000 Time (days) Substrate COD (mg-COD/L-reactor) >> 23 May 2017 >> 30 35 3500 4000 Removal efficiency: 69% in 1 day 97% in 3 days 99% in 9 days • 40 < EPC 2013 > -6- Spent yeast: Continuous feed and draw • 25 day HRT, SCOD/TCOD of feed ~ 60% TCOD in reactor 1 TCOD in reactor 2 TCOD in reactor 2 TCOD if no digestion SCOD in reactor 1 SCOD if no digestion 45000 40000 Reactor COD (mg-COD/L) 35000 30000 25000 20000 15000 10000 5000 0 27 28 29 30 31 32 33 34 Time (day) University of Cape Town >> 23 May 2017 >> < EPC 2013 > -7- Spent yeast: Comparisons to SAB reactor Lab reactors WTP at current op. WTP design spec. HRT Average COD COD reduction reduction rate efficiency Substrate days mg-COD/L.day 25 3390 91% Spent yeast 1.8 1 (min) 1260 4500 (max) 73 - 91% - Wastewater - • Aim to reduce the HRT on lab reactors. • Suggested strategies: recycling and continuous flow. University of Cape Town >> 23 May 2017 >> < EPC 2013 > -8- Conclusions • Degradation efficiency on spent grain was poor and not enhanced by mechanical pre-treatment. Spent grain is not viable as substrate in in the WTP. • Acclimation of the system to yeast feed is important for auto-regulation of pH. • Yeast is promising as substrate in the WTP. Future work • Optimisation of yeast digestion on lab reactors. • Anaerobic digestion experiment to mimic large scale digester (including biogas production measurements) • Possibly, implementation of results on the WTP. University of Cape Town >> 23 May 2017 >> < EPC 2013 > -9- Acknowledgements Prof. S T L Harrison University of Cape Town >> 23 May 2017 >> < EPC 2013 > - 10