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Biological Treatment

Topic: Ch 7. Biological Treatment. Announcements. HW2 going out today, due next Friday Wiley next Wed March 20 th Field trip w/ Jason Assoiline Email me about DimDim Recordings Tentative Carpool Plan – Time/Location Merced to Clovis is 1hr drive Experiment with mic’s and video.

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Biological Treatment

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  1. Topic: Ch 7 Biological Treatment

  2. Announcements • HW2 going out today, due next Friday • Wiley next Wed • March 20th Field trip w/ Jason Assoiline • Email me about DimDim Recordings • Tentative Carpool Plan – Time/Location • Merced to Clovis is 1hr drive • Experiment with mic’s and video

  3. Roadmap • Background Review - Today • Stoichiometry - Today • Energetics - Wed • Microbial Growth Kinetics - Wed

  4. Background Review

  5. Purpose of Biological Treatment • Capture nonsetteable solids into a biological floc or biofilm • Biomass has specific gravity greater than water • Must remove settled bacteria or won’t reduce BOD • Transform or remove nutrients (N and P) • Oxidize consituents into an acceptable end product

  6. Suspended Growth • Typically aerobic (need aeration… energy!) • Sometimes anaerobic for cases of highly concentrated wastewater • Anaerobic typically used for sludge treatment but this is not usually suspended growth

  7. Bacteria • C5H7O2N • Growth rates double every 10ºC until optimum temp reached • pH optimum 6.5-7.5 • Nutrients may be limited in industrial wastewaters

  8. Metabolism

  9. Bacteria Growth in Batch Reactor • Why does death phase occur? • Draw DO curve? • Draw BOD curve?

  10. Quantifying Biomas • Bacteria Cells = Biomass • Often measured as volatile suspended solids (VSS) • Is VSS entirely biomass? • Other approaches: particulate COD, protein, ,DNA • Biomass yield (Y) = g biomass produced / g substrate consumed • Substrate is typically the constituent in the wastewater that is electron donor (energy source) • What would be the units for the yield for nitrification bacteria (what is the substrate)?

  11. Stoichiometry

  12. Biomass Yield (Y = g cell/g substrate) • Cellular Mass Balance (Stoichiometry) • Assume substrate as glucose • Neglect nutrient other than N • How much substrate leaves system as sludge vs. gas? • What is the yield (Y) based on this stoichiometry?

  13. Biomass Yield (Y = g cell/g substrate) • COD Mass Balance (Stoichiometry) • Assume substrate as glucose • Neglect nutrient other than N • What is the yield (Y) based on this stoichiometry?

  14. COD of Glucose (g O2 / g glucose) • Cellular Mass Balance (Stoichiometry) • Assume substrate as glucose • Neglect nutrient other than N • What is the yield (Y) based on this stoichiometry (change in O2 over change in glucose)?

  15. COD of Glucose (g O2 / g glucose) • Cellular Mass Balance (Stoichiometry) • Assume substrate as glucose • Neglect nutrient other than N • What is the yield (Y) based on this stoichiometry (change in O2 over change in glucose)?

  16. Theoretical Yield [(g cell / g glucose) / (g COD O2 / g glucose)] • Maximum yield… actual yield will be more because not all substrate is converted to cell mass (synthesis) since some is needed for cell maintenance • Solve for the theoretical yield given the following

  17. Theoretical Yield [(g cell / g glucose) / (g COD O2 / g glucose)] • Solve for the theoretical yield

  18. COD of Cell Tissue (g O2/g cell) • Recall that biomass must be removed by settling (as sludge) or effluent will have large BOD • Calculate COD of Cells given,

  19. COD of Cell Tissue (g O2/g cell) • Organics molecules are converted into cellular molecules but still are BOD • Recall that biomass must be removed by settling (as sludge) or effluent will have large BOD • Calculate COD of Cells given,

  20. Example 7-1

  21. Example 7-1 • Draw Schematic?

  22. Example 7-1 • Calculate Observed Yield (g cell / g substrate COD removed) ?

  23. Example 7-1 • Calculate Observed Yield? vs. Theoretical Yield?

  24. Example 7-1 • Oxygen Used per COD removed? • “Oxygen Used”: oxygen consumed by bacteria during synthesis of substrate. • Calculate as difference between CODin and total COD out (substrate COD out + biomass COD out) • “COD removed”: Decrease in substrate COD. Ignores COD of biomass. • Calculate as difference of CODin and CODout

  25. “Oxygen Used”: oxygen consumed by bacteria during synthesis of substrate. • Calculate as difference between CODin and total COD out (substrate COD out + biomass COD out)

  26. Example 7-1 • “COD removed”: Decrease in substrate COD. Ignores COD of biomass. • Calculate as difference of CODin and CODout

  27. Example 7-1 • Oxygen Used per COD removed?

  28. In-Class Problem • Why is theoretical yield less than actual yield? • How was the sound quality today? • Where did you login from? • Did you use best practices? • High speed ethernet (not wireless) • Turn off addon/toolbars on browser • Close other open applications and background internet applications

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