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AD Applications to Sewage Sludge

AD Applications to Sewage Sludge. Shihwu Sung, Ph.D., PE. Department of Civil, Construction & Environmental Engineering Iowa State University. Anaerobic Treatment Short Course Part 3. Fundamentals * Wastewater Characteristics Analysis * Anaerobic Fundamentals

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AD Applications to Sewage Sludge

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  1. AD Applications to Sewage Sludge Shihwu Sung, Ph.D., PE Department of Civil, Construction & Environmental Engineering Iowa State University Anaerobic Treatment Short Course Part 3

  2. Fundamentals • * Wastewater Characteristics Analysis • * Anaerobic Fundamentals • Anaerobic Treatment Processes • (Traditional vs. High-Rate) • AD Applications to Sewage Sludge • AD Applications to Animal Wastes • AD Applications to Industrial Wastewaters • Beneficial Use of Biosolids & Regulations • AD Bio-refinery Concept

  3. Raw Sewage Bar Rack Grit Chamber Pretreatment Primary Treatment Equalization Basin Pump Secondary Treatment Tertiary Treatment Primary Settling Biological Treatment Secondary Settling Advanced Waste Treatment e.g., Nutrient removal Receiving Water Body

  4. particulate soluble organic 550oC in Temp. inorganic 1μm in size Solid Matrix TS = TSS + TDS ║ ║║ VS = VSS + VDS +++ TFS = FSS + FDS particulate organic soluble organic particulate inorganic soluble inorganic sand, silt salts T : Total S : Solids or Suspended D : Dissolved V : Volatile F : Fixed

  5. Preliminary treatment Primary settling Activated sludge system Secondary settling Screens Grit Chamber Aeration basin Outlet Biogas Anaerobic digester Energy production from biogas Typical Activated Sludge Treatment Plant

  6. Typical Trickling Filter Treatment Plant

  7. Sludge Treatment and Disposal Sludge dewatering

  8. Domestic waste (100) Anaerobic digester (60) Bar screen, Comminutor Grit chamber etc. Preliminary treatment (100) Primary sludge (35) Primary sedimentation (65) Activated sludge, Trickling filter, RBC, etc. Aerobic treatment Oxidized to CO2 (30) Converted to sludge (35) Secondary sludge (25) Secondary sedimentation Effluent (10) Importance of Anaerobic Digestion in Municipal Wastewater Treatment

  9. Sewage Sludge Anaerobic Digester Design Example (using handout)

  10. Importance of solids retention time From Parkin and Owen, 1986)

  11. From Parkin and Owen, 1986)

  12. From Parkin and Owen, 1986)

  13. Volatile Solids (VS/TS) Fixed Solids (FS/TS) % % Untreated Sludge (Xf) 70 30 Digested Sludge (Xd) 50 50 VS Destruction based on Volatility Assume: 1. Fixed solid remain the same 2. Use 1 Kg of dry untreated sludge for calculations 3. X Kg of VS after digestion FS of digested sludge, 50% = [ (0.3 Kg) * 100 ] / (0.3 Kg + X Kg) X = 0.3 Kg => Weight of digested solids = FS + VS = 0.3 + 0.3 = 0.6 Kg

  14. Cont.. Total Solids (TS) Volatile Solids (VS) Fixed Solids (FS) Kg Kg Kg Untreated Sludge 1.0 0.7 0.3 Digested Sludge 0.60.3 0.3 TS destruction, % = (1.0 – 0.6) / 1.0 * 100 = 40% VS destruction, % = (0.7 – 0.3) / 0.7 * 100 = 57.1% VS % Destruction Equations: Xf - Xd0.7 - 0.5 VS, % = ( ---------------- ) x 100 = --------------------- = 57.1% Xf – Xf· Xd 0.7 – 0.7 x 0.5

  15. TEMPERATURE-PHASED ANAEROBIC DIGESTION(TPAD) Application to Sewage Sludge

  16. REGULATORY UPDATE: PATHOGEN REDUCTION Class-A Biosolids: Thermophilic Anaerobic Digestion (55 oC) • Class-A biosolids: • US EPA 40 CFR part 503 • Fecal coliform • < 1,000 MPN/g of TS • Salmonella • < 3 MPN/4 g TS

  17. TPAD: AN ALTERNATIVE HIGH-RATE PROCESS • Improves efficiency and reliability of sludge digestion • Improves characteristics of digested biosolids (Class A) • i.e. pathogen free, dewaterability, odor potential, etc.

  18. Anaerobic Digestion (1) Complex Organics Carbohydrates Proteins Lipids 1. Hydrolysis Simple Organics (2) Volatile Organic Acids Propionate, Butyrate, etc. 2. Acidogenesis Acetate H2 + CO2 (3) 3. Methanogenesis CH4 + CO2

  19. TPAD: THERMO-MESO COMBINATION

  20. ADVANTAGES OF THE TPAD SYSTEM THERMOPHILIC STAGE • Kills pathogens • Hydrolyzes complex organics • Improves volatile solids removal • Reduces foaming MESOPHILIC STAGE • Polishes thermophilic effluent • Converts VFAs to methane • Reduces odors • Improves process stability

  21. FEEDSTOCKS STUDIED • Municipal wastewater sludge OBJECTIVES • Waste stabilization and pollution prevention • Pathogen-free biosolids (Class A) • Energy recovery in the form of methane • Nutrient conservation

  22. TPAD: LABORATORY SETUP Gasmeter Gasmeter H2S scrubber H2S scrubber Feed Tank Thermophilic Mesophilic

  23. STUDIES WITH MUNICIPAL WASTEWATER SLUDGE • Determination of optimal HRT/SRTs and other operating • conditions • Evaluation of performance characteristics at optimal SRTs • Destruction of indicator organisms • Volatile solids removal • Biogas production • Full-scale performance • Data from published sources as well as information collected from the involved treatment plants

  24. CHARACTERISTICS OF PRIMARY AND WASTE ACTIVATED SLUDGES

  25. HRTs & VOLATILE SOLIDS LOADINGS STUDIED CONTROL: Single-Stage 24, 28, 34, 40 days

  26. VS REMOVAL AT VARIOUS HRTs 60 TPAD system A 50 40 30 VS Removal, % Two-Stage System B Single-Stage System 20 10 0 0 10 20 30 40 50 HRT, days

  27. METHANE PRODUCTION FOR DIFFERENT SYSTEMS Reactor Volume = 14 L 10 8 TPAD System A 6 CH4 Production Rate, L/day Single-Stage System 4 TPAD System B 2 0 0 10 20 30 40 50 HRT, days

  28. PATHOGEN DESTRUCTION IN DIFFERENT SYSTEMS 10 Influent 8 6 Log Concentration of F. Coliforms, MPN/g TS 4 1st-Stage of TPAD Single-Stage System 2nd-Stage of TPAD 2 0 0 10 20 30 40 50 HRT, days

  29. VOLATILE FATTY ACIDS IN THE DIFFERENT SYSTEMS 2500 1st-Stage of System B 2000 1500 1st-Stage of System A VFA, mg/L as Acetic Acid 1000 2nd-Stages of Systems A & B Single-Stage System 500 0 0 10 20 30 40 50 HRT, days

  30. OPERATION OF FULL-SCALE TPAD SYSTEMS

  31. CONCLUSION: MUNICIPAL WASTEWATER SLUDGE OPTIMAL SRT: 11-17 days for the system when treating 50:50 mixture of PS:WAS • VS Destruction vs. HRT • Thermophilic Digester: 2/3 system VS destruction • 58 ± 8% w/ HRT 14 ~ 30 (full-scale) 58 ±8% • 49 ± 10% w/ HRT 10 ~ 28 (lab-scale) 49 ±10%

  32. Western Lake Superior Sanitary District

  33. Heat Exchanger Design

  34. Agricultural Market 1 2 3 4

  35. Acknowledgement: • These studies were supported by grants from • Western Lake Superior Sanitary District, Duluth, MN • Black & Veatch Corporations, Kansas, KS • U.S. Department of Agriculture through Iowa • Biotechnology Byproducts Consortium

  36. Question?

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