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Understanding Nitrogen and Phosphorus Cycles in Environmental Biotechnology

This lecture explores the intricate nitrogen and phosphorus cycles relevant to environmental biotechnology. It highlights the composition of microbial cells, the importance of limiting nutrients (nitrogen and phosphorus), and the processes involved in nitrogen fixation, ammonification, nitrification, and denitrification. The discussion includes the role of microorganisms like cyanobacteria and Rhizobium, nitrogen removal strategies in wastewater treatment, and methods for phosphorus removal, emphasizing their ecological impact and importance in biogeochemical cycles.

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Understanding Nitrogen and Phosphorus Cycles in Environmental Biotechnology

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  1. CE421/521 Environmental Biotechnology Nitrogen and Phosphorus Cycles Lecture 9-11-08 Tim Ellis

  2. Biogeochemcial Cycles (C, N, P, & S) • composition of b_______ cell (molar formula: C5H7O2N with P 1/5 of the N requirement) • limiting nutrients are _____ and _____

  3. Nitrogen • Atmosphere is _____% nitrogen, yet nitrogen is considered a l__________ n__________ • required in p____________

  4. Nitrogen Cycle Organic nitrogen NO3- NH4+ N2 NO2-

  5. Fixation • 2x108 metric tons/y compared to 2.5x1010 metric tons C/y • cyanobacteria & few others • non-symbiotic – Clostridia • symbiotic – Rhizobium • nitrogenase – requires Mg2+ & ATP (15 to 20 ATP/N2)

  6. Assimilation • NH3 (NH4+) preferred, will use NO3- but has to be reduced to NH4+ • C/N ratio is approximately • 10:1 for aerobes • 150:1 for anaerobes • 50:1 for anaerobes in highly loaded (high rate) system • cell composition is characterized by the empirical formula: ______________ with the P requirement as 1/5 the N requirement (alternatively C60H87O23N12P) • in general cell composition is • 50% C • 20% O • 10-15% N • 8-10% H • 1-3% P • 0.5-1.5

  7. Ammonification • Breakdown of organic N to NH4+ • Examples: • Urea • proteins

  8. Nitrification • Two step process: • requires 4.57 mg O2/mg NH4+- N converted to NO3- – N

  9. Nitrification Kinetics where μmax = maximum specific growth rate, h-1 KS = half saturation coefficient for ammonia, mg/L as NH4-N KO = half saturation coefficient, mg/L as O2 Yield = mg biomass formed/mg ammonia utilized

  10. Nitrification Kinetics

  11. Nitrification Kinetics where μmax = maximum specific growth rate, h-1 KS = half saturation coefficient for ammonia, mg/L as NH4-N KO = half saturation coefficient, mg/L as O2 Yield = mg biomass formed/mg ammonia utilized

  12. Nitrifiers are sensitive to • d____________ o_____________ • t______________ • p___ • i_____________________ where I = concentration of inhibitor, mg/L KI = inhibition coeficient, mg/L

  13. Effects of Temperature • derivation of the • A____________ equation • where k1,2 = reaction rate coefficient at temperature T1,2 • θ = t___________ c__________

  14. Typical Theta Values ln θ ln k Temp (deg C or K)

  15. Calculating Theta • given the following measured data, calculate the theta value

  16. DENITRIFICATION 1. A_____________________ nitrate reduction: NO3- ➔ NH4+ nitrate is incorporated into cell material and reduced inside the cell 2. D___________________ nitrate reduction (denitrification) • NO3- serves as the t____________ e_______________ a_________________ (TEA) in an anoxic (anaerobic) environment nitrate reductase nitrite r. nitric oxide r. nitrous oxide r. NO3- ➔ NO2- ➔ NO ➔ N2O ➔ N2 summarized as: NO3- ➔ NO2- ➔ N2

  17. DENITRIFICATION • requires o______________ m________________(example: methanol) • kinetics for denitrification similar to those for heterotrophic aerobic growth

  18. DENITRIFICATION 6NO3- + 5CH3OH ➔ 3N2 + 5 CO2 + 7 H2O + 6 OH- • calculate COD of methanol: • calculate alkalinity:

  19. Nitrogen Removal in Wastewater Treatment Plants • Total Kjeldahl Nitrogen (TKN) = o___________ n___________ + a______________ • (measured by digesting sample with sulfuric acid to convert all nitrogen to ammonia) • TKN ~ 35 mg/L in influent • p____________ t____________ removes approximately 15% • additional removal with biomass w______________

  20. Methods for Nitrogen Removal • Biological • n_______________ • d________________ • ANAMMOX: ammonium is the electron donor, nitrite is the TEA NH4+ + NO2- ➔ N2 + 2 H2O Suitable for high ammonia loads (typically greater than 400 mg/L) and low organic carbon • Chemical/Physical • air s_______________ • breakpoint c__________________ • ion e_____________________ • reverse o___________________

  21. Concerns for nitrogen discharge: 1. T________________ 2. D________________ of DO 3. E__________________________ 4. Nitrate in d________________ water – causes methemoglobinemia (blue baby) oxidizes hemoglobin to methemoglobin

  22. Phosphorus • limiting n___________________ in algae (at approximately 1/5 the nitrogen requirement) • 15% of population in US discharges to l_________________ • wastewater discharge contains approximately 7- 10 mg/L as P • o__________________ • i______________: orthophosphate

  23. Removal of Phosphorus • Chemical precipitation: • traditional p____________________ reactions Al+3 + PO4-3 ➔ AlPO4 Fe+3 + PO4-3 ➔ FePO4 • as s_______________ (magnesium ammonium phosphate, MAP) Mg+2 + NH4+ + PO4-3 ➔ MgNH4PO4

  24. Struvite as a problem • Scale build-up chokes pipelines, clogs aerators, reduces heat exchange capacity • Canned king crab industry • Kidney stones

  25. Struvite as a Fertilizer • Nonburning and long lasting source of nitrogen and phosphorus • Found in natural fertilizers such as guano • Heavy applications have not burned crops or depressed seed germination (Rothbaum, 1976) • Used for high-value crops For ISU study on removing ammonia from hog waste see: www.public.iastate.edu/~tge/miles_and_ellis_2000.pdf

  26. Sulfur • inorganic: SO4-2 S° H2S • organic: R — O — SO3-2 four key reactions: • H2S o__________________ — can occur aerobically or anaerobically to elemental sulfur (S°) • a___________________ : Thiobaccilus thioparus oxidizes S-2 to S° • S-2 + ½ O2 + 2H+ ➔ S° + H2O • a_______________________: — phototrophs use H2S as electron donor • filamentous sulfur bacteria oxidize H2S to S° in sulfur granules: Beggiatoa, Thiothrix

  27. Sulfur 2. Oxidation of E_______________ Sulfur (Thiobacillus thiooxidans at low pH) 2S° + 3 O2 + 2 H2O ➔ 2 H2SO4 3. A_______________________ sulfate reduction: proteolytic bacteria breakdown organic matter containing sulfur (e.g. amino acids: methionine, cysteine, cystine) 4. D_______________________ sulfate reduction: under anaerobic conditions — s_____________ r________________ b_________________ (SR SO4-2 + Organics ➔ S-2 + H2O + CO2 S-2 + 2H+ ➔ H2S • Desulvibrio and others • Sulfate is used as a TEA & l_____ m____________ w___________ organics serve as the electron donors • Low cell y_______________ • P___________________ of SRB depends on COD:S ratio, particularly readily degradable (e.g., VFA) COD • SRB compete with m_____________________ for substrate: high COD:S favors methanogens, low COD:S favors SRB

  28. Crown Sewer Corrosion

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