1 / 22

Anaerobic Digestion and Biogas

Anaerobic Digestion and Biogas. Terminology and designs. Total Solids, Volatile Solids. Total Solids (TS)= Dry weight of substrate Volatile Solids (VS)= Combustible proportion of TS, organic matter

melinda-chapman
Download Presentation

Anaerobic Digestion and Biogas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Anaerobic Digestion and Biogas Terminology and designs

  2. Total Solids, Volatile Solids • Total Solids (TS)= Dry weight of substrate • Volatile Solids (VS)= Combustible proportion of TS, organic matter • Non-volatile Solids (Ash) = Minerals etc. left over from combustion

  3. Total Solids, Volatile Solids Total Solids Ash

  4. COD/BOD • Chemical/Biochemical Oxygen Demand • Measures amount of oxygen required to degrade a substrate • Used widely in aerobic water treatment • Characterizes wastewaters and organic feedstocks • Estimates energy content of substrate

  5. BMP • Biochemical Methane Potential Assay • Developed as correlative test of BOD in anaerobic systems • Realistic measure of total methane potential of a feestock • Can determine non-biodegradable materials in feedstock

  6. Organic loading rate • Rate at which feedstock is fed to the digester (i.e. g VS / L reactor) • Varies by feedstock, reactor type, temperature, etc. • Too low= too large of reactor • Too high= overload reactor, acidification

  7. Hydraulic Retention Time • How long substrate remains in active volume (i.e. turnover rate) • Optimized for higher biogas/ reactor volume ratio • Too high= Unnecessarily large reactor • Too low= Reduced biogas output, washout microbes

  8. Temperature • Anaerobic metabolism much more sensitive to temperature than aerobic • Methanogens more affected than acidogens • Leads to unbalanced pH at low temps. • Loading rate reduced at low temps.

  9. Mesophilic vs. Thermophilic • Temperature classes for microbes in digester • Mesophilic (30-40°C), Thermophilic (50-60°C) • Different microbial communities operate at each temp. class • Most digesters operate at mesophilic

  10. pH • Very important parameter • Optimum 7.0, acceptable 6.0-8.0 • Methanogens cannot function at low pH. • Ammonia toxicity above 8.0 • Slow recovery after sustained drop in pH.

  11. Different digester types • Batch vs. Continuous • Two phase • CSTR • UASB • Fixed-film

  12. Batch vs. continuously fed • Batch – Digester loaded once, emptied once fully degraded • Continuously fed – Digester regularly loaded (usually daily), effluent produced at each loading

  13. Two phase digestion • Single phase- all in one reactor • Two phase- acidogenesis and methanogenesis separated • Benefits • Increased over-all efficiency (short HRT of acidogenic reactor) • More pH control of methanogenic reactor

  14. Two phase digestion

  15. CSTR • Continuously-Stirred Tank Reactor • Simple but effective design

  16. UASB • Up-flow Anaerobic Sludge Blanket • Frequently used for sewage wastewater

  17. Fixed Film Reactor • Increased substrate-bacteria contact • Utilizes biofilms • Short HRT • Decreased size • Used as DRU

  18. Digesters in developing nations Small scale digester, rural India “Bag digester”, Costa Rica

  19. Digesters in agriculture Covered Lagoon, Tulare, CA Corn sillage digester, Neumunster, Germany

  20. Digesters in industrial settings Lübek mechanical biological treatment plant, Germany Mechanical biological treatment plant, Tel Aviv, Israel

  21. Digesters as architectural features? Appleton Wastewater Treatment Plant, Appleton, Wisconsin Reading Sewage Treatment Works, Reading, United Kingdom

  22. Questions?

More Related