anaerobic-digestion-process.ppt
- 1. ANAEROBIC SLUDGE DIGESTION PROCESS Prepared By Michigan Department of Environmental Quality Operator Training and Certification Unit
- 2. WASTEWATER Water used to carry waste products away from homes, schools, commercial establishments, and industrial enterprises.
- 4. CHARACTERISTICS OF WASTEWATER Materials Toxic to Biota Metals Ammonia Pesticides Herbicides Chlorine Acids/Bases Human Health Hazards Pathogens Nitrate Toxic Materials
- 5. GOAL – PURPOSE – RESPONSIBILITY Of “Treating” or Stabilizing Wastewater PROTECTION OF NATURAL RESOURCES PROTECTION OF PUBLIC HEALTH
- 7. Wastewater “Treatment” Removes These “Pollutants”
- 8. Wastewater Treatment Processes • Physical / Chemical – screening – sedimentation – filtration – precipitation – chemical destruct • Biological – waste stabilization lagoon – trickling filter – rotating biological contactor – activated sludge
- 9. Treatment Efficiencies Primary (Physical) Treatment 40 - 60 % Suspended Solids 30 - 40 % BOD Secondary (Biological) Treatment 90+ % Suspended Solids 90+ % BOD
- 10. Secondary Organic Inorganic Wastewater Pre Treatment Rock Grit Plastic Etc. Primary Clarifier Settleable Suspended Dissolved Suspended Dissolved Secondary Clarifier Effluent Removal of These “Pollutants” Produces “Residuals” Often called “Sludge” Note: These residuals are sometimes called “Biosolids”, however that term is usually reserved for sludge that has been “stabilized” and meets specific requirements (pathogen reduction, vector attractions, metals concentration)
- 11. SLUDGE The SETTLEABLE solids separated from liquids during processing.
- 12. SLUDGE CHARACTERISTICS •Organic /Inorganic •Oxygen Demand •Odors •Nutrients •Pathogens •Mostly Water
- 13. Purpose of ‘Treatment” •Stabilize Organics •Eliminate Odors •Destroy Pathogens •Reduce Amount of Solids •Enhance De-watering
- 14. Secondary Organic Inorganic Wastewater Pre Treatment Rock Grit Plastic Etc. Primary Clarifier Settleable Suspended Dissolved Suspended Dissolved Secondary Clarifier Effluent Digester Gas Digested Sludge Recycled Water (Supernatant) (Stabilized)
- 15. TYPES of “TREATMENT” Heat and Pressure Heat and Chemical Lime Stabilization Biological Digestion
- 16. Types of Digestion Biological Bacteria Aerobic Anaerobic Use “Free” Oxygen No “Free” Oxygen
- 18. AEROBIC DIGESTION Advantages Effective for “secondary” sludge Simple operation No hazardous gas production Disadvantages Higher operating costs High energy demands No burnable gas Higher organic content
- 20. ANAEROBIC DIGESTION Advantages Low operating costs Proven effectiveness Burnable gas produced Disadvantages Long start-up time Affected by changes in loading and conditions Explosive gas produced
- 22. Anaerobic Digestion Process “TWO-STAGE” Process OR “Two Phase” Process
- 23. Anaerobic Digestion Process “TWO-STAGE” Process This Does Not Mean Two Tanks
- 24. Anaerobic Digestion Process “TWO-STAGE” Process OR “Two Phase” Process Two Types of Bacteria Each Relying On The Other First Stage Second Stage
- 25. Anaerobic Digestion Process First Organic Material Changed By Acid Forming Bacteria To Simple Organic Material Organic Matter Bacteria Organic Acids First Stage +
- 26. Anaerobic Digestion Process First Organic Material Changed By Acid Forming Bacteria To Simple Organic Material Organic Acids Also Called Volatile Acids
- 27. Anaerobic Digestion Process Second Methane-Forming Bacteria Use Organic Acids Produce Carbon Dioxide and Methane Organic Acids + Bacteria CH4 + CO2 Second Stage
- 28. Anaerobic Digestion Process Continuous Process “TWO-STAGE” Process Stabilization Organic Matter Bacteria Organic Acids First Stage Acid Forming CH4 + CO2 Methane Forming Second Stage
- 29. Type of Food Organic Inorganic Soluble Insoluble Anaerobic Digestion Process
- 30. Soluble Organics Cell Membrane Acids Adsorbed Particle Enzymes (Absorption) Typical Acid Forming Bacteria Liquid
- 31. Not All Organic Material Broken Down Type of Food Poor Food Inert Solids -Not Readily Degradable -Plastics, etc. 40 to 60 % of Organics are Reduced
- 32. Anaerobic Digestion Process “TWO-STAGE” Process OR “Two Phase” Process Two Types of Bacteria Each Relying On The Other Must Be In Balance !
- 33. Organic Matter Bacteria Organic Acids First Stage Acid Forming CH4 + CO2 Methane Forming Second Stage Anaerobic Digestion Process Volatile Acids Acid Phase Acids Used at Rate Produced
- 34. Start-up Upset “Sour” “Stuck” Anaerobic Digestion Process Acids Used at Rate Produced If Not Used - Drop in pH Methane Formers Must Be Active
- 35. Anaerobic Digestion Process Methane Formers: Slow Growers Very Sensitive to Changes Loading pH Temperature Digester Operation Depends On Maintaining Proper Environment for METHANE FORMERS BALANCE !
- 36. Anaerobic Digestion Process Products of Digestion 1. Gases Methane (CH4) Carbon Dioxide (CO2) 65 to 70 % 30 to 35 % 7 to 12 cubic feet per pound of volatile destroyed 500 to 600 BTU per cubic foot Can Be Utilized: Heating Digester Heating Buildings Running Engines Electrical Power
- 37. Anaerobic Digestion Process Products of Digestion 2. Scum Lighter Solids Floating from Gas Entrapment Builds Up If MIXING Is Inadequate Not Digested ( Separated from Bacteria) Reduces Digester Capacity Plugs Piping Plugs Vents and Flame Traps
- 38. Anaerobic Digestion Process Products of Digestion 3. Supernatant Liquid That Leaves Digester Two Sources of Water In Digester: Water Pumped In Water Formed During Digestion Recycled Through Treatment Plant High In: Solids BOD Ammonia
- 39. Anaerobic Digestion Process Products of Digestion 3. Supernatant Liquid That Leaves Digester Should Be Removed Frequently in Small Quantities
- 40. Anaerobic Digestion Process Products of Digestion 4. Digested Sludge “Stabilized” Final Product Inorganic Solids Volatile (Organic) Solids - Not Easily Digested
- 41. Well Digested Sludge Characteristics 1. Less Solids 2. Lumpy Appearance 3. Black 4. Less Objectionable Odor 5. Volatile Content Reduced
- 42. Anaerobic Digestion Process Products of Digestion 1. Gases Methane (CH4) Carbon Dioxide (CO2) 2. Scum Lighter Solids 3. Supernatant Liquid Removed 4. Digested Sludge “Stabilized”
- 43. TYPICAL “Two-Stage” ANAEROBIC DIGESTER SYSTEM Transfer Pump Heat Exchanger Hot Water Gas Gas Recirculation Pump Note: Two-Stage System here refers to two separate tanks (One for the treatment process and one for water-solids separation)
- 44. Digestion Factors 1.Bacteria 2. Food 3. Loading 4. Contact 5. Environment
- 45. Digestion Factors 1. BACTERIA Naturally Occurring Must Have Enough Living Organisms Two Different Types BALANCE The Other Factors –Important Because They Affect the Bacteria
- 46. Digestion Factors 1. BACTERIA Balance 2. FOOD Volatile Solids
- 47. Not All Organic Material Broken Down Type of Food Poor Food Inert Solids -Not Readily Degradable -Plastics, etc. 40 to 60 % of Organics are Reduced
- 48. Digestion Factors 1. BACTERIA Balance 2. FOOD Not All Volatile Material None of the Inorganic Volatile Solids
- 49. Digestion Factors 1. BACTERIA Balance 2. FOOD 3. LOADING Volatile Solids
- 50. Digestion Factors 3. LOADING AMOUNT Applied to the Treatment Process Related to the SIZE of the System
- 51. Digestion Factors 1. BACTERIA Balance 2. FOOD 3. LOADING Volatile Solids Amount and Type Concentration of Sludge (% Total Solids) Amount Usable in Sludge (%Volatile) Amount (pounds) of Volatile per Volume Available Volume (gallons) of Sludge per Volume Available
- 52. Digestion Factors 1. BACTERIA Balance 2. FOOD 3. LOADING 4. CONTACT Volatile Solids Amount and Type Mixing
- 53. Digestion Factors 1. CONTACT Bacteria and Food 2. HEAT DISTRIBUTION 3. MINIMIZE SETTLING 4. MINIMIZE SCUM Even Throughout Reduces Available Volume Operational Problems MIXING
- 54. Digestion Factors 1. CONTACT 2. HEAT DISTRIBUTION 3. MINIMIZE SETTLING 4. MINIMIZE SCUM Maximize Digestion Efficiency MIXING
- 55. Digestion Factors 1. BACTERIA Balance 2. FOOD 3. LOADING 4. CONTACT 5. ENVIRONMENT Volatile Solids Amount and Type Mixing Happy Bugs
- 56. Digestion Factors ENVIRONMENT Methane Forming Bacteria Are Very Sensitive to Conditions In the Digester
- 57. Digestion Factors 1. ANAEROBIC 2. TEMPERTURE ENVIRONMENT No Oxygen
- 58. Temperature controls activity of bacteria. Psychrophilic 50 F to 68 F Mesophilic 68 F to 113 F Best 85 F to 100 F Thermophilic Above 113 F Best 120 F to 135 F
- 59. Temperature controls activity of bacteria. Mesophilic 68 F to 113 F Best 85 F to 100 F Within the Range, the Bacteria are Very Sensitive to Temperature CHANGE Most Anaerobic Digesters Are Operated in the Mesophilic Range
- 60. Temperature controls activity of bacteria. Mesophilic 68 F to 113 F Best 85 F to 100 F Temperature Should Not Be Allowed to CHANGE by More Than 1 Degree per Day (After Start-up)
- 61. Digestion Factors 1. ANAEROBIC 2. TEMPERTURE 3. pH 4. VOLATILE ACIDS Mesophilic - Constant Best - 6.8 to 7.2 ENVIRONMENT 5. BUFFERS (Alkalinity) Incoming Sludge and Created No Oxygen Not Excessive
- 62. Digestion Factors 1. ANAEROBIC 2. TEMPERTURE 3. pH 4. VOLATILE ACIDS Mesophilic - Constant Best - 6.8 to 7.2 ENVIRONMENT 5. BUFFERS (Alkalinity) Incoming Sludge and Created No Oxygen Not Excessive ACID Production INCREASED OR ALKALINITY DECREASED Sudden Changes Toxic Materials Start-up
- 63. Digestion Factors 1. ANAEROBIC 2. TEMPERTURE 3. pH 4. VOLATILE ACIDS Mesophilic - Constant Best - 6.8 to 7.2 ENVIRONMENT 5. BUFFERS (Alkalinity) 6. TOXIC MATERIALS Incoming Sludge and Created No Oxygen Not Excessive Inhibit Biological Activity
- 64. OPERATION AND CONTROL BALANCE ! Maintaining Suitable Conditions Maintaining Definite Ranges and Ratios Organic (Solids) Loading Alkalinity Volatile Acids Temperature Mixing
- 65. Digestion Factors 1. BACTERIA 2. FOOD 3. LOADING 4. CONTACT 5. ENVIRONMENT
- 66. OPERATION AND CONTROL 1. BACTERIA Maintain Adequate Quantity Don’t Remove Too Much Don’t Displace Too Much Plan For Re-Start
- 67. OPERATION AND CONTROL 2. FOOD Minimize Amount of Inorganics Entering Eliminate Toxic Material Industrial Discharges Grit Systems
- 68. OPERATION AND CONTROL 3. LOADING AMOUNT Applied to the Treatment Process Related to the SIZE of the System
- 69. 3. LOADING AMOUNT Applied to the Treatment Process Related to the SIZE of the System For An Anaerobic Digestion System – The SIZE Is The VOLUME Available for Digestion (Volume - Cubic Feet OR Gallons)
- 71. h1 Volumecylinder = r2h1 h2 Volumecone = ⅓ r2h2 r r Cylinder Cone
- 72. Digester Volume Example Problem The diameter of a digester is 54 feet. The side water depth (SWD) is 22 feet. The cone depth is 12 feet. Calculate the volume in cubic feet and gallons. Volumecylinder = r2h1 = 3.14 X 27 ft X 27 ft 22 ft X = 50,360 ft3 Volumecone = ⅓ r2h2 = ⅓X 3.14 X 27 ft X 27 ft X 12 ft = 9,156 ft3
- 73. Digester Volume Example Problem Total Volume = 50,360 ft3 + 9,156 ft3 = 59,516 ft3 Total Volume (gallons) = cubic feet X 7.48 gal/ft3 = 59,516 ft3 X 7.48 gal/ft3 = 445,180 gallons = Volumecylinder + Volumecone
- 74. Digester Volume Practice Problems The diameter of a digester is 50 feet. The side water depth (SWD) is 20 feet. The cone depth is 10 feet. Calculate the volume in cubic feet and gallons. Work Calculations on Separate Paper Answers Given on Next Slides 1. 2. Calculate the volume in gallons of a digester 35 feet in diameter, 12 feet SWD and a cone depth of 6 feet.
- 75. Digester Volume Practice Problem The diameter of a digester is 50 feet. The side water depth (SWD) is 20 feet. The cone depth is 10 feet. Calculate the volume in cubic feet and gallons. Volumecylinder = r2h1 = 3.14 X 25 ft X 25 ft 20 ft X = 39,250 ft3 Volumecone = ⅓ r2h2 = ⅓X 3.14 X 25 ft X 25 ft X 10 ft = 6,542 ft3 1.
- 76. Digester Volume Practice Problems The diameter of a digester is 50 feet. The side water depth (SWD) is 20 feet. The cone depth is 10 feet. Calculate the volume in cubic feet and gallons. 1. Total Volume = Volumecylinder + Volumecone = 39,250 ft3 + 6,542 ft3 = 45,792 ft3 Total Volume (gallons) = cubic feet X 7.48 gal/ft3 = 45,792 ft3 X 7.48 gal/ft3 = 342,524 gallons
- 77. Digester Volume Practice Problems 2. Calculate the volume in gallons of a digester 35 feet in diameter, 12 feet SWD and a cone depth of 6 feet. Volumecylinder = r2h1 = 3.14 X 17.5 ftX 17.5 ft 12 ft X = 11,539.5 ft3 Volumecone = ⅓ r2h2 = ⅓X 3.14 X 17.5 ft X 17.5 ft X 6 ft = 1,923 ft3
- 78. Digester Volume Practice Problems Total Volume = Volumecyl + Volumecone = 11,539.5 ft3 +1,923 ft3 = 13,462.5 ft3 Total Volume (gallons) = cubic feet X 7.48 gal/ft3 = 13,462.5 ft3 X 7.48 gal/ft3 = 100,700 gallons 2. Calculate the volume in gallons of a digester 35 feet in diameter, 12 feet SWD and a cone depth of 6 feet.
- 79. “LOADING” Amount Applied to the Treatment Process Related to the SIZE of the System Hydraulic Loading Amount of Sludge Added Volume (gallons) Organic Loading Amount of VOLATILE Solids added Weight (pounds)
- 80. Digester Hydraulic Loading AVERAGE TIME (in Days) that the liquid stays in the digester
- 81. Digester Hydraulic Loading AVERAGE TIME (in Days) that the liquid stays in the digester Proper Digestion Convert Solids Acids to Gas Minimum Time Required: Varies Digester Efficiency Type of Waste Holding Time Increased by Thickening
- 82. Digester Hydraulic Loading Digester Volume Feed Volume Gallons Hydraulic Loading = Hydraulic Loading = Gallons/Day AVERAGE TIME (in Days) that the liquid stays in the digester
- 83. Detention Time EXAMPLE At an average pumping rate of 4,000 gallons per day into a 140,000 gallon digester, the detention time would be: Detention Time Gallons Gallons / Day) = 140,000 gallons 4,000 gallons/day = 35 Days DET. TIME (Days) =
- 84. Detention Time Practice Problems 1. Calculate the Detention Time for a 120,000 gallon digester that receives 3,200 gallons of sludge per day. 2. Calculate the Detention Time for a 260,000 gallon digester that receives 7,200 gallons of sludge per day. 3. Calculate the Detention Time for a 12,000 cubic foot digester that receives 2,500 gallons of sludge per day. Work Calculations on Separate Paper Answers Given on Next Slides
- 85. Detention Time Practice Problems 1. Calculate the Detention Time for a 120,000 gallon digester that receives 3,200 gallons of sludge per day. Detention Time = Digester Volume (Gal) Pumping Rate (Gal/Day) = 120,000 gallons 3,200 gallons/day = 37.5 Days
- 86. Detention Time Practice Problems 2. Calculate the Detention Time for a 260,000 gallon digester that receives 7,200 gallons of sludge per day. Detention Time = Digester Volume (Gal) Pumping Rate (Gal/Day) = 260,000 gallons 7,200 gallons/day = 36.1 Days
- 87. Detention Time Practice Problems Detention Time = Digester Volume (Gal) Pumping Rate (Gal/Day) = 12,000 ft3 2,500 gallons/day = 35.9 Days X 7.48 gal/ft3 = 89,760 gallons 2,500 gal/day 3. Calculate the Detention Time for a 12,000 cubic foot digester that receives 2,500 gallons of sludge per day.
- 88. “LOADING” Amount Applied to the Treatment Process Related to the SIZE of the System Hydraulic Loading Amount of Sludge Added Volume (gallons) Detention Time Digester Volume Feed Volume Gallons Gallons/Day OR
- 89. “LOADING” Amount Applied to the Treatment Process Related to the SIZE of the System Hydraulic Loading Amount of Sludge Added Volume (gallons) Organic Loading Amount of VOLATILE Solids added Weight (pounds)
- 90. PERCENT TOTAL SOLIDS Outline of Solids Analysis Procedure
- 91. SLUDGE SOLIDS PROCEDURE Evaporating Dish Preparation Ignite Cool Weigh Weigh Add Sample Total Solids Analysis Cool Weigh Dry Evaporate
- 92. Percent Total Solids % = Amount in Question Total Amount Possible X 100% % Total Solids = Wt. Of (Dry) Solids Wt. Of (Wet) Sample X 100% % Total Solids = Dry Wet X 100%
- 93. SLUDGE SOLIDS PROCEDURE Evaporating Dish Preparation Ignite Cool Weigh Weigh Add Sample Total Solids Analysis Cool Weigh Dry Evaporate Volatile Solids Analysis Ignite Cool Weigh
- 94. Percent Volatile Solids % = Amount in Question Total Amount Possible X 100% % Volatile Solids = Wt. Of Volatile Solids Wt. Of Dry Solids X 100% % Volatile Solids = Dry - Ash X 100% Dry
- 95. SLUDGE SOLIDS DIAGRAM Sludge Solids 6% 94%Water 100 # 6 # 94 # TOTAL SOLIDS 6 # ASH VOLATILE 70 % 30 % 4.2 # 1.8 #
- 96. TYPICAL RESULTS OF THE DIGESTION PROCESS BEFORE DIGESTION 100,000 Lbs. RAW SLUDGE 75% VOLATILE 25% FIXED 50% VOLATILE 50% FIXED 75,000 Lbs. 25,000 Lbs. 25,000 Lbs. 50,000 Lbs. DIGESTION CONVERTS VOLATILES TO CH4, CO2, AND H2O REMAINING DIGESTED SLUDGE 25,000 Lbs. AFTER DIGESTION CH4, CO2, H2O (Dry Weight)
- 97. “LOADING” Amount Applied to the Treatment Process Related to the SIZE of the System Organic Loading Amount of VOLATILE Solids added Weight (pounds)
- 99. SLUDGE POUNDS CALCULATIONS Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 8,000 GALLONS SOLIDS CONCENTRATION 4.2% VOLATILE SOLIDS 82% LBS DRY SOLIDS = GALS WET X 8.34 LBS GAL X % SOLIDS = 8,000 GAL X 8.34 LBS GAL X 4.2 100 = 8,000 X 8.34 X 0.042 = 2,802 POUNDS DRY SOLIDS
- 100. SLUDGE POUNDS CALCULATIONS Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 8,000 GALLONS SOLIDS CONCENTRATION 4.2% VOLATILE SOLIDS 82% LBS VOLATILE SOLIDS = LBS DRY SOLIDS X % VOLATILE SOLIDS = 2,802 LBS DRY SOLIDS X 82 100 = 2,802 X 0.82 = 2,298 POUNDS VOLATILE SOLIDS
- 101. SLUDGE POUNDS CALCULATIONS 1. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 7,500 GALLONS SOLIDS CONCENTRATION 3.6% VOLATILE SOLIDS 78% 2. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 6,000 GALLONS SOLIDS CONCENTRATION 3.0% VOLATILE SOLIDS 73% Work Calculations on Separate Paper Answers Given on Next Slides
- 102. SLUDGE POUNDS CALCULATIONS 1. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 7,500 GALLONS SOLIDS CONCENTRATION 3.6% VOLATILE SOLIDS 78% LBS DRY SOLIDS = GALS WET X 8.34 LBS GAL X % SOLIDS = 7,500 GAL X 8.34 LBS GAL X 3.6 100 = 7,500 X 8.34 X 0.036 = 2,252 POUNDS DRY SOLIDS
- 103. SLUDGE POUNDS CALCULATIONS 1. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 7,500 GALLONS SOLIDS CONCENTRATION 3.6% VOLATILE SOLIDS 78% LBS VOLATILE SOLIDS = LBS DRY SOLIDS X % VOLATILE SOLIDS = 2,252 LBS DRY SOLIDS X 78 100 = 2,252 X 0.78 = 1,756.6 POUNDS VOLATILE SOLIDS
- 104. SLUDGE POUNDS CALCULATIONS 2. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 6,000 GALLONS SOLIDS CONCENTRATION 3.0% VOLATILE SOLIDS 73% LBS DRY SOLIDS = GALS WET X 8.34 LBS GAL X % SOLIDS = 6,000 GAL X 8.34 LBS GAL X 3.0 100 = 6,000 X 8.34 X 0.030 = 1501 POUNDS DRY SOLIDS
- 105. SLUDGE POUNDS CALCULATIONS 2. Given the following information, calculate the pounds of dry solids and the pounds of volatile solids: VOLUME OF SLUDGE 6,000 GALLONS SOLIDS CONCENTRATION 3.0% VOLATILE SOLIDS 73% LBS VOLATILE SOLIDS = LBS DRY SOLIDS X % VOLATILE SOLIDS = 1,501 LBS DRY SOLIDS X 73 100 = 1,501 X 0.73 = 1,095.7 POUNDS VOLATILE SOLIDS
- 107. Organic (Solids) Loading Rate Amount of Volatile Solids Added per Day Compared to the Size (volume) of the Digester Pounds of Volatile Solids per Day per Cubic Foot 0.02 to 0.10 # Vol. Solids/Day/Ft3 Sometimes as Pounds of Volatile Solids per Day per 1000 Cubic Feet 20 to 100 # Vol. Solids/Day/1000Ft3 Organic Loading Rate Amount of V.S. Volume of Digester =
- 108. Digester Organic Loading AMOUNT of Organic Solids added to a digester related to the SIZE of the digester. Amount of Organic Solids Digester Volume Volatile Solids, pounds /day O.L. = O.L. = Digester Volume, cubic feet
- 109. Digester Organic Loading Data: Digester Volume = 30,000 ft3 Raw sludge pumped = 9,000 gal/day Raw sludge solids concentration = 4.0 % Raw sludge volatile solids = 70.0 % Calculate the organic loading into the digester in lbs of volatile solids per day per ft3 LBS VOLATILE SOLIDS = GAL PUMPED X 8.34 lbs/gal X % Solids (decimal) X % Volatile (decimal) = 9,000 gal/day X 8.34 lbs/gal X 0.04 x 0.70 = 2,102 lbs/day ORGANIC LOADING = 2,102 lbs/day 30,000 ft3 = 0.07 lbs/day/ft3
- 110. Digester Organic Loading 1. Data: Digester Volume = 21,500 ft3 Raw sludge pumped = 5,500 gal/day Raw sludge solids concentration = 3.1 % Raw sludge volatile solids = 76 % Calculate the organic loading into the digester in lbs of volatile solid per day per ft3. Practice Problems 2. Data: Digester Volume = 11,000 ft3 Raw sludge pumped = 4,600 gal/day Raw sludge solids concentration = 3.5 % Raw sludge volatile solids = 74 % Calculate the organic loading into the digester in lbs of volatile solid per day per ft3. Work Calculations on Separate Paper Answers Given on Next Slides
- 111. Digester Organic Loading 1. Data: Digester Volume = 21,500 ft3 Raw sludge pumped = 5,500 gal/day Raw sludge solids concentration = 3.1 % Raw sludge volatile solids = 76 % Calculate the organic loading into the digester in lbs of volatile solid per day per ft3. LBS VOLATILE SOLIDS = GAL PUMPED X 8.34 lbs/gal X % Solids (decimal) X % Volatile (decimal) = 5,500 gal/day X 8.34 lbs/gal X 0.031 x 0.76 = 1,080.7 lbs/day ORGANIC LOADING = 1,080.7 lbs/day 21,500 ft3 = 0.050 lbs/day/ft3 Practice Problems
- 112. Digester Organic Loading 2. Data: Digester Volume = 11,000 ft3 Raw sludge pumped = 4,600 gal/day Raw sludge solids concentration = 3.5 % Raw sludge volatile solids = 74 % Calculate the organic loading into the digester in lbs of volatile solid per day per ft3. LBS VOLATILE SOLIDS = GAL PUMPED X 8.34 lbs/gal X % Solids (decimal) X % Volatile (decimal) = 4,600 gal/day X 8.34 lbs/gal X 0.035 x 0.74 = 993.6 lbs/day ORGANIC LOADING = 993.6 lbs/day 11,000 ft3 = 0.090 lbs/day/ft3 Practice Problems
- 113. Organic (Solids) Loading Rate Amount of Volatile Solids Added per Day Compared to the Size (volume) of the Digester Pounds of Volatile Solids per Day per Cubic Foot 0.02 to 0.10 # Vol. Solids/Day/Ft3 Sometimes as Pounds of Volatile Solids per Day per 1000 Cubic Feet 20 to 100 # Vol. Solids/Day/1000Ft3 Organic Loading Rate Amount of V.S. Volume of Digester (page 28) =
- 114. OPERATION AND CONTROL 3. LOADING Pump Thick Sludge (High % Total Solids) Pump Several Times per Day Uniform Digester Loading Uniform Plant Operations Excess Water Requires More Heat Excess Water Reduces Holding Time Excess Water Removes Bacteria and Buffers
- 115. OPERATION AND CONTROL 3. LOADING % Total Solids % Total Volatile Solids Organic (Solids) Loading Hydraulic Loading
- 116. OPERATION AND CONTROL 1. BACTERIA 2. FOOD 3. LOADING 4. CONTACT
- 117. 1. CONTACT Bacteria and Food 2. HEAT DISTRIBUTION 3. MINIMIZE SETTLING 4. MINIMIZE SCUM Even Throughout Reduces Available Volume Operational Problems CONTACT (MIXING)
- 118. OPERATION AND CONTROL 1. BACTERIA 2. FOOD 3. LOADING 4. CONTACT 5. ENVIRONMENT
- 119. Temperature controls activity of bacteria. Psychrophilic 50 F to 68 F Mesophilic 68 F to 113 F Best 85 F to 100 F Thermophilic Above 113 F Best 120 F to 135 F
- 120. OPERATION AND CONTROL ENVIRONMENT Temperature Control 90 to 950 F Methane Formers Very Sensitive to Changes Good Mixing Essential
- 121. SUMMARY First Stage Second Stage Balance Poor Mixing Over Loading Excess Water Temperature
- 122. SUMMARY First Stage Second Stage Balance Poor Mixing Over Loading Excess Water Temperature
- 123. OPERATION AND CONTROL ENVIRONMENT Volatile Acid/Alkalinity Relationship Ratio Volatile Acids, mg/L Alkalinity, mg/L 140 mg/L 2,800 mg/L = 0.05
- 124. I. Relationship of Volatile Acids to Alkalinity Time Alkalinity Volatile Acids mg/L 2000 1000 600 200 Graph of Digester With Good Buffering Capacity ( Low V.A. at 200 mg/L Compared to Alk. of 2000 mg/L)
- 125. I. Relationship of Volatile Acids to Alkalinity Time Alkalinity Volatile Acids mg/L 2000 1000 600 200 A B C At Time A Something has Happened to Cause the Volatile Acids to Increase Followed by a Decrease in Alkalinity at Time B At Time C the Digester has Become Sour
- 126. II. Volatile Acids / Alkalinity Ratio VA/ALK RATIO 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 Time
- 127. Comparing Graph I to Graph II Time Alkalinity Volatile Acids mg/L 2000 1000 600 200 A B C VA/ALK RATIO 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 B Ratio 0.3 Ratio 0.1 At Time B Measurable Change in Ratio
- 128. % 100 90 80 70 60 50 40 30 20 III. Relationship of Methane and Carbon Dioxide Time CH4 CO2 Sludge Feed At 44% CO2 Will Not Burn
- 129. Time Alkalinity Volatile Acids mg/L 2000 1000 600 200 A B C B % 100 90 80 70 60 50 40 30 20 CH4 CO2 At Time B No Change Comparing Graph I to Graph III
- 130. VA/ALK RATIO 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 % 100 90 80 70 60 50 40 30 20 CH4 CO2 Change At 0.5 Time B No Change At 0.3 Comparing Graph II to Graph III
- 131. IV. Relationship of pH Change 7.0 6.8 6.4 Time
- 132. Time Alkalinity Volatile Acids mg/L 2000 1000 600 200 A B C At Time B No Change 7.0 6.8 6.4 pH Comparing Graph I to Graph IV
- 133. VA/ALK RATIO 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 Change At 0.8 Time B No Change At 0.3 7.0 6.8 6.4 No Change At 0.5 pH Comparing Graph II to Graph IV
- 134. OPERATION AND CONTROL ENVIRONMENT Order of Measurable Changes When A Digester is BECOMING Upset 1. An Increase in VA/Alk. Ratio 2. An Increase in % CO2 3. Inability of Digester Gas to Burn 4. A Decrease in pH
- 135. Volatile Acid/Alkalinity Ratio First Measurable Change Volatile Acids - Low Compared to Alkalinity Best Operation - Ratio Below 0.4 OPERATION AND CONTROL ENVIRONMENT
- 136. Response To Increase Extend Mixing Time Heat More Evenly Decrease Sludge Withdrawal Rate Return Sludge From Secondary Digester *Add Alkalinity (Bicarbonate) Volatile Acid/Alkalinity Ratio OPERATION AND CONTROL ENVIRONMENT
- 137. VOLATILE ACIDS AND TOTAL ALKALINITY Outline of Procedure 1. Separate Solids 2. Measure 50 mL 3. Titrate to pH 4.0 4. Record mL used, Then Titrate to pH 3.3 5. Lightly Boil Sample 3 Min. 6. Cool in Water Bath 7. Titrate from pH 4.0 to 7.0
- 139. % Reduction of Volatile Solids % Reduction of Volatile Solids = %Volatiles In - % Volatiles Out X 100% % Volatile In - ( % Volatile In X % Volatile Out) NOTE: % Must be as Decimals 72% = 72/100 = .72 % Reduction of Volatile Solids = In - Out In - (In X Out) X 100 %
- 140. % Reduction of Volatile Solids % Reduction of Volatile Solids = %Volatiles In - % Volatiles Out X 100% % Volatile In - ( % Volatile In X % Volatile Out) EXAMPLE: Volatile Solids in Raw Sludge = 68% Volatile Solids in Digested Sludge = 45% % Reduction of Volatile Solids = 0.68 – 0.45 0.68 – (0.68 X 0.45) X 100% 0.68 – 0.45 0.68 – 0.31 X 100% = 0.23 0.37 X 100% = 62%
- 141. 1. Calculate the percent reduction of volatile solids in a digester with the following data: 73%Vol. Solids in the raw sludge 51%Vol. Solids in the digested sludge 2. Calculate the percent reduction of volatile solids in a digester with the following data: 73.4%Vol. Solids in the raw sludge 50.5%Vol. Solids in the digested sludge Work Calculations on Separate Paper Answers Given on Next Slides % Reduction of Volatile Solids
- 142. 1. Calculate the percent reduction of volatile solids in a digester with the following data: 73%Vol. Solids in the raw sludge 51%Vol. Solids in the digested sludge % Reduction of Volatile Solids = In - Out In - (In X Out) X 100 % = .73 - .51 .73 - ( .73 X .51) = .73 - .51 .73 - .372 X 100 % X 100 % = .22 .358 X 100 % = 61.5 %
- 143. 2. Calculate the percent reduction of volatile solids in a digester with the following data: 73.4%Vol. Solids in the raw sludge 50.5%Vol. Solids in the digested sludge % Reduction of Volatile Solids = In - Out In - (In X Out) X 100 % = .734 - .505 .734 - ( .734 X .505) = .734 - .505 .734 - .371 X 100 % X 100 % = .229 .363 X 100 % = 63.1 %
- 144. Gas Production Digesters Produce Methane and Carbon Dioxide Normal: 25% to 35% CO2 by Volume As the Bacteria Break Down the Volatile Organics CHANGE - Indicator of Conditions
- 145. Gas Production Digesters Produce Methane and Carbon Dioxide Normal: 65% to 70% Methane by Volume Burns: > 56% Methane Usable as Fuel: > 62% Methane Can Be Used To: Heat the Digester Power Engines Heat Buildings
- 146. Gas Production Digesters Produce Methane and Carbon Dioxide Normal: 65% to 70% Methane by Volume Burns: > 56% Methane Usable as Fuel: > 62% Methane Healthy Digester Should Produce: 7 to 12 cubic feet/pound vol. solids Destroyed
- 147. GAS PRODUCTION CALCULATION Data: Raw sludge pumped in per day = 9,000 gallons Raw sludge solids concentration = 4% Raw sludge volatile solids = 65% % Volatile Solids Reduction = 48% Gas production per day = 8,000 ft3 LBS VOLATILE SOLIDS = GAL PUMPED X 8.34 lbs/gal X % Solids (decimal) X % Volatile (decimal) = 9,000 gal/day X 8.34 lbs/gal X 0.04 x 0.65 = 1,951.6 lbs/day 1,951.6 lbs X .48 = 937 lbs Vol. Solids Destroyed 48% of the Volatile Solids were Destroyed What is the gas production in terms of cubic feet per pound of volatile solids destroyed?
- 148. GAS PRODUCTION CALCULATION Data: Raw sludge pumped in per day = 9,000 gallons Raw sludge solids concentration = 4% Raw sludge volatile solids = 65% % Volatile Solids Reduction = 48% Gas production per day = 8,000 ft3 What is the gas production in terms of cubic feet per pound of volatile solids destroyed? 937 lbs Vol. Solids Destroyed Gas Production, cu.ft. / lb vol. solids Destroyed = 8,000 cu. ft. = 8.5 cu ft / lb vol. solids destroyed
- 149. GAS PRODUCTION 1. Data: Raw sludge pumped in per day = 7,200 gallons Raw sludge solids concentration = 4% Raw sludge volatile solids = 67% % Volatile Solids Reduction = 53% Gas production per day = 7,850 ft3 What is the gas production in terms of cubic feet per pound of volatile solids destroyed? 2. Data: Raw sludge pumped in per day = 2,300 gallons Raw sludge solids concentration = 3.4% Raw sludge volatile solids = 72.6% % Volatile Solids Reduction = 49.3% Gas production per day = 2,800 ft3 What is the gas production in terms of cubic feet per pound of volatile solids destroyed? Work Calculations on Separate Paper Answers Given on Next Slides
- 150. GAS PRODUCTION 1. Data: Raw sludge pumped in per day = 7,200 gallons Raw sludge solids concentration = 4% Raw sludge volatile solids = 67% % Volatile Solids Reduction = 53% Gas production per day = 7,850 ft3 What is the gas production in terms of cubic feet per pound of volatile solids destroyed? Gas Production, cu.ft. / lb vol. solids Destroyed = Cubic Feet Gas % Vol. Slds. Destroyed (decimal) X Lbs. Vol. Slds. In Lbs. Vol. Solids Destroyed = 7,850 ft3 7,200 gal/day X 8.34 lbs/gal X 0.04 x 0.67 .53 X Lbs. Vol. Solids In = 7,850 ft3 852.9 # Vol. Slds. Destroyed = 9.2 ft3/Lb. Vol. Slds. Destroyed
- 151. GAS PRODUCTION 2. Data: Raw sludge pumped in per day = 2,300 gallons Raw sludge solids concentration = 3.4% Raw sludge volatile solids = 72.6% % Volatile Solids Reduction = 49.3% Gas production per day = 2,800 ft3 What is the gas production in terms of cubic feet per pound of volatile solids destroyed? Gas Production, cu.ft. / lb vol. solids Destroyed = Cubic Feet Gas % Vol. Slds. Destroyed (decimal) X Lbs. Vol. Slds. In = 2,800 ft3 .493 X 2,300 gal/day X 8.34 lbs/gal X 0.034 x 0.726 = 2,800 ft3 233.4 # Vol. Slds. Destroyed = 12.0 ft3/Lb. Vol. Slds. Destroyed
- 152. Anaerobic Digestion Process Methane Formers: Slow Growers Very Sensitive to Changes Loading pH Temperature Digester Operation Depends On Maintaining Proper Environment for METHANE FORMERS BALANCE !
- 153. ANAEROBIC SLUDGE DIGESTION PROCESS Prepared By Michigan Department of Environmental Quality Operator Training and Certification Unit