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Seminar on Biological Wastewater Treatment Processes Past, Present and Future

Seminar on Biological Wastewater Treatment Processes Past, Present and Future. Dr. Ajit P. Annachhatre Environmental Engineering Program Asian Institute of Technology. Keywords. Wastewater Biological Processes Treatment Processes Applications Ongoing Research Activities.

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Seminar on Biological Wastewater Treatment Processes Past, Present and Future

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  1. Seminar onBiological Wastewater Treatment Processes Past, Present and Future Dr. Ajit P. Annachhatre Environmental Engineering Program Asian Institute of Technology

  2. Keywords • Wastewater • Biological Processes • Treatment Processes • Applications • Ongoing Research Activities

  3. 1.Wastewater • Domestic Wastewater • Industrial Wastewater • Present State of Wastewater

  4. Domestic Wastewater • over 80 % - untreated in Asian mega cities • major components- COD = 250-1000 mg/L Total N = 20-90 mg/L Total P = 4-15 mg/L • effects of discharging into natural receiving bodies • oxygen demand by carbon and nitrogen

  5. Industrial Wastewater... • Eg: Starch industry wastewater • major component- COD = 10,000-20,000 mg/L • effects of discharging into natural receiving bodies - 20 m3/ton of starch - high COD - high suspended solids - cyanide exposure

  6. Industrial Wastewater... • Starch industry wastewater • factory with 300 T/d of starch • wastewater generation 6000m3/d • COD 14,000 mg/L • population equivalent 1000,000

  7. Industrial Wastewater • present treatment method: • Anaerobic ponds • typical loading rates: • 800-1000kg COD /ha/d • area requirement: 100 ha

  8. 2.Biological Processes • aim: any form of life- ‘ survive & multiply ’ • need for energy & organic molecules as building blocks • made of C, H, O, N, S, P and trace elements

  9. Biological Processes... • cell: derives energy from oxidation of reduced food sources (carbohydrate, protein & fats)

  10. Microorganisms Classification: • Heterotrophic- obtain energy from oxidation of organic matter (organic Carbon) • Autotrophic- obtain energy from oxidation of inorganic matter (CO2, NH4, H+ ) • Phototrophic- obtain energy from sunlight

  11. Biochemical Pathways • oxidation of organic molecules inside the cell can occur aerobic or anaerobic manner • generalized pathways for aerobic & anaerobic fermentation

  12. Biochemical Pathways Glucose EPM Pathway Pyruvic Acid ADP ATP Energy Lactic Acid TCA Cycle H+ Respiration H2O CO2 O2

  13. Biochemical Pathways C6H12O6 + 6O2 +38 ADP + 38 Pi 6 CO2 +38 ATP + 44 H2O • aerobic pathways contains- EMP pathways, TCA cycle, respiration • anaerobic pathways contains- EMP pathways • released energy stored as ATP molecules • excess food is stored as Glycogen

  14. Biological growth - exponential growth (batch) - Monod kinetics - Haldane kinetics under toxic conditions

  15. Stationary phase Log growth phase Death phase Lag phase Log No. of Cells Time Biological growth... • exponential growth

  16. µm Max. rate Specific growth rate ( µ) µm/2 ks Substrate Concentration(S) Biological growth... • Monod kinetics

  17. i Specific growth rate ( µ) Substrate Concentration(S) Biological growth... • Haldane kinetics (under toxic conditions)

  18. 3.Applications 1. Carbonaceous removal - aerobic - anaerobic 2. Nitrogen removal - nitrification - denitrification 3. Sulfide removal - anaerobic SO4 reduction - aerobic HS- oxidation

  19. Biological Carbonaceous Removal • aerobic - oxidation bacteria CHONS + O2 + Nutrients CO2 + NH3 + C5H7NO2(organic matter) (new bacterial cells) + other end products - endogenous respiration bacteria C5H7NO2 + 5O2 5CO2 + 2H2O + NH3 + energy (cells)

  20. Biological Carbonaceous Removal • anaerobic Schematic of the Anaerobic Process

  21. Biological Nitrogen Removal • nitrification -energy Nitrosomonas NH4+ + 1.5 O2 NO2- + H2O + 2 H+ + (240-350 kJ) (1) Nitrobacter NO2- + 0.5 O2 NO3- + (65-90 kJ) (2) -assimilation Nitrosomonas 15 CO2 + 13 NH4+ 10 NO2- + 3 C5H7NO2 + 23 H+ +4 H2O (3) Nitrobacter 5 CO2 + NH4+ +10 NO2- +2 H2O 10 NO3- + C5H7NO2 + H+ (4) - overall reaction NH4+ +1.83 O2 + 1.98 H CO3- 0.021 C5H7NO2 + 0.98 NO3- + 1.04 1H2O+ 1.88H2CO3

  22. Biological Nitrogen Removal • factors affecting nitrification * temperature * substrate concentration * dissolved oxygen * pH * toxic and inhibitory substances

  23. Biological Nitrogen Removal • denitrification * assimilatory denitrification - reduction of nitrate to ammonium by microorganism for protein synthesis * dissimilatory denitrification - reduction of nitrate to gaseous nitrogen by microorganism - nitrate is used instead of oxygen as terminal electron acceptor - considered an anoxic process occurring in the presence of nitrate and the absence of molecular oxygen - the process proceeds through a series of four steps

  24. Biological Nitrogen Removal • denitrification * heterotrophic denitrification - denitrifiers require reduced carbon source for energy and cell synthesis - denitrifiers can use variety of organic carbon source - methanol, ethanol and acetic acid

  25. Biological Nitrogen Removal • factors affecting denitrification * temperature * dissolved oxygen * pH

  26. Biological Sulfate Removal * Sulfate removal cycle anaerobic SO4-- HS - S 0(O2 deficient) (O2 excess)

  27. 4.Treatment Processes • pond treatment • activated sludge process • biofilm process

  28. Pond Treatment - no biomass recirculation - high HRT - high land area - O2 transfer limitations - inadequate mixing - excess loading (anaerobic condition-H2S generation)

  29. SW PST AT SST RAS SW Activated Sludge Process F E

  30. Activated Sludge Process... - aerobic - suspended-growth - Design equations

  31. Activated Sludge Process... typical values of cell residence time (c ) - c for C removal ~ 3-10 days - cfor N removal ~ 5-30 days - loading rates ~ 2-3 kg COD/m3/d - drawbacks: O2 requirements, inlet conc.

  32. Biofilm Processes advantages of biofilm processes: - higher process productivity (loading rates) - higher biomass holdup - higher mean cell residence time - no need for biomass recirculation - creates suitable environment for each type of bacteria - sustains toxic loads

  33. Biofilm Processes... • types of biofilms: aerobic, anaerobic, anoxic • process of biofilm formation • - formation of diffuse electrical double layer due to electrostatic forces and thermal motion • - transfer of microorganism to surface • - microbial adhesion • - biofilm formation

  34. Bulk Liquid Liquid Film Biofilm Support Material Y X Y (a) Physical concept Sb X SS Fully Penetrated Substrate Concentration Partially Penetrated (b) Substrate concentration profile Biofilm Processes... • biofilm operation

  35. Biofilm Processes... • biofilm operation • - diffusion resistance • - inadequate supply of nutrients to inner • portions of Biofilm • - limitations on product out diffusion • - attrition of reaction conditions

  36. Biofilm Processes... • biofilm operation • as biofilm thickness increases • effectiveness factor () decreases

  37. Anaerobic biofilm processes

  38. Anaerobic biofilm processes... • importance of H partial pressure • loading rates 10-15 kg COD/m3/d • against 2-5 kg COD/m3/d in • suspended growth processes

  39. Ongoing Research Activities Biological Processes aerobic anoxic anaerobic nitrification denitrification SO42--reduction HS- oxidation detoxification

  40. Ongoing Research Activities aerobic nitrification HS- oxidation inhibition aniline modeling biofilm in ASP degradation processes in SBR Shabbir Jega Sunil & Keshab Savapak Shabbir & Shabbir

  41. Ongoing Research Activities anaerobic SO42--reduction detoxification & modeling & modeling Savapak Amara

  42. Ongoing Research Activities anoxic denitrification toxic chemicals membrane as C source bio reactor Krongtong Tran membrane processes Piyaputr

  43. MODELING OF BIOLOGICAL NITRIFICATION • Study of nitrification process inside a spherical biofloc particle based on biofilm kinetics. • determination of effectiveness factor for substrate consumption and thus the substrate removal rates.

  44. MODELING OF BIOLOGICAL NITRIFICATION • Mathematical model consists of a system of second order differential equations based on steady state material balance and appropriate boundary conditions. • Model is solved numerically using a computer program developed in Macsyma 2.3, which uses 4th order Runge-Kutta method for solving system of ODEs

  45. dr r R DESCRIPTION OF THE PROBLEM Evaluation of concentration profile for the substrates inside a spherical biofloc Assumptions: • Spherical biofloc • Double substrate limited kinetics based on Michaelis - Menten equation • Steady State conditions. • Constant Kinetic and Diffusional parameters, and biomass density inside the floc.

  46. MODEL DESCRIPTION Substrate : Oxygen and Ammonia-nitrogen • Material Balance Equation: Mass transfer limitations due to diffusional resistances and biochemical reactions taking place inside the biofloc are considered.

  47. 1 s2,0 s s1,0 1 0 r 0 • Boundary Conditions: • Depend on, • Degree of penetration • Partial or Full • Limiting Substrate • Substrate-1 (Oxygen) • Substrate-2 (Ammonia) Case : Full Penetration at r = 1.00 , s1 = 1.0, s2 = 1.0 at r = 0, s1 = s1,0, s2 = s2,0, ds1/dr = 0, ds2/dr = 0

  48. RESULTS

  49. Ongoing Research Activities

  50. Ongoing Research Activities UASB for Sulfide Removal Fludized Bed for Sulfide Oxidation Process

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