Wqm 207 –lab analysis and data application
- 1. Lab Analysis and Data Application WQM 207 – Activated Sludge Systems
- 2. Lab Data and Analysis Application
- 3. First, lets look at what we have to work with: F/M Ratio Sludge Age SVI MCRT Control Options: Return Activated Sludge Wasting Activated Sludge Aeration Basic Control
- 4. BOD, lbs/day MLVSS, lbs (mg/L BOD)(MGD Flow)(8.34) MLVSS(lbs) (mg/L MLVSSB)(aerator Vol, MG)(8.34) Food/Microorganism Ratio
- 5. AERATION SYSTEMS OPERATIONAL MATHEMATICS Food/Microorganism Ratio: F/M Required Information: mg/l BOD and/or COD concentration in Influent MLVSS (Suspended Solids X % volatile) Aeration tank volume Formula: (BOD or COD) mg/l X 8.34 lbs/gal X MGD____ MLVSS mg/l X Aeration tank volume X 8.34 lbs/gal = F/M
- 6. Example: An activated sludge facility has a flow of 1.2 MGD, Influent BOD= 230 mg/l. The aeration basin is 250,000 gallons and the MLVSS = 2,500 mg/L. 1.2MGD X 230mg/L X 8.34 = 2301.84 Lbs Coming In F= 2,301 lb Aeration SystemVolume 250,000 gal / 1,000,000 =0.25MG 0.25MG X 2500mg/L X 8.34 = 5215 Lbs of Microorganisms under Aeration M = 5,212 lb 2301/5212 = 0.44 F/M Ratio F/M Ratio
- 7. WASTING ACTIVATED SLUDGE OPERATIONAL MATHEMATICS WAS: lbs MLSS Required Information: (FROM MICROSCOPIC ANALYSIS RESULTS) Desired Sludge Age Actual MLSS in system Formula: Desired lbs MLSS = SS lbs being added to system X Desired Sludge Age (days) Where, lbs being added = SS mg/l Aeration Influent X Influent Flow (MGD) X 8.34 lbs/gal + RAS mg/l X RAS Flow (MGD) X 8.34 lbs/gal = lbs of SS added to system Actual lbs in Aeration System = MLSS mg/l X Aeration Volume (MG) X 8.34 lbs/gal Actual MLSS (lbs) – Desired MLSS (lbs) = Excess MLSS (lbs) Convert Excess MLSS (lbs) to volume by: lbs to be wasted 8.34 lbs/gal X MLSS mg/l (actual) = Volume to be wasted
- 8. ACTIVATED SLUDGE SYSTEMS OPERATIONAL MATHEMATICS Solids Retention Time or Mean Cell Residence Time Required Information: MLSS mg/l in Aeration Flow (MGD) Aeration Volume TSS concentration mg/l (Average Secondary Clarifier Core concentration) Secondary Clarifier(s) Volume WAS SS mg/l RAS SS mg/l RAS Flow Rate MGD Secondary Effluent SS mg/l WAS Flow Rate MGD
- 9. ACTIVATED SLUDGE SYSTEMS OPERATIONAL MATHEMATICS Solids Retention Time or Mean Cell Residence Time Formula: Suspended Solids in System (lbs.) Suspended Solids Leaving System (lbs/day) = SRT or MCRT (days) Where: Suspended Solids in System = Aer. MLSS mg/l X Aer Volume (MG) X 8.34 lbs/gal + RAS MLSSX RAS Flow (MGD) X 8.34 lbs/gal = lbs in system And: Suspended Solids leaving System = WAS SS mg/l X WAS Flow (MGD) X 8.34 lbs/gal + Secondary Effluent SS mg/l X Plant Flow (MGD) X 8.34 lbs/gal = lbs leaving/day Thus: lbs in system lbs leaving system/ day = days
- 10. Mathematics dictates A/S system operations
- 11. Sludge Age (days) MLSS (lbs) SS Added (lbs/day) Sludge Age
- 12. Solids RetentionTime is also known as the “mean cell residence time”. It is based on suspended solids leaving the system (sludge age had to do with solids entering the system). Solids DetentionTime (days) = Suspended Solids in System (lbs) Suspended Solids leaving System (lbs/day) Solids Retention Time (days) = Suspended Solids in System (lbs) WAS SS(lbs/day) + Secondary Effluent, (lbs/day) SOLIDS RETENTIONTIME (MCRT)
- 13. An aeration tank has a volume of 450,000 gallons the final clarifier has a volume of 220,000 gallons.The MLSS concentration in the aeration tank is 3,200 mg/L.The WAS is 2,880 lbs SS/day and 650 lbs SS/day are in the secondary effluent. What is the solids retention time for the activated sludge system? Suspended Solids in System (lbs) WAS SS(lbs/day) + Secondary Effluent, (lbs/day) 3,200 mg/L x 0.67 MG x 8.34 = 17,881 lbs 2,880 lbs/day + 650 lbs/day 3,530 lbs/day = 5.1 days SOLIDS RETENTIONTIME
- 14. Following Analysis from Microscopic Examination
- 15. By examining the actual species within an Activated Sludge Process, we can see what is populating the system. Methods of microscopic examination: Gram Stain Neisser Stain India Ink Reverse Stain CrystalViolet Stain Lab Analysis
- 16. Organic Loading MCRT Predominant Groups High Low Flagellates, amoebae and small free swimming ciliates Moderate Moderate High Diversity of organisms, dominated by free-swimming ciliates Low High Stalked ciliates, rotifers and higher invertebrates, especially nematodes With this information it can be seen that Organic Loading and MCRT are directly related. Results
- 17. Activated Sludge Aeration BasinScum Pit Pump Primary Clarifier Secondary Clarifiers Scum and greases WAS Waste Activated Sludge To Digestion and Dewatering RAS Return Activated Sludge To Aeration Basin Influent ACTIVATED SLUDGE CYCLE ANDWASTE SYSTEM
- 18. Terms • Activated sludge: Consists of sludge particles produced in raw or settled wastewater by the growth of organisms in aeration tanks in the presence of dissolved oxygen. • Activated sludge process: a biological wastewater treatment process that uses microorganisms to speed up decomposition of wastes. Secondary Treatment
- 19. Terms (continued) • BNR (Biological Nutrient Removal): Using microorganisms to remove nitrogen and phosphorus from wastewater. • BOD (Biochemical Oxygen Demand): The rate at which organisms use the oxygen in wastewater while stabilizing organic matter under aerobic conditions. • Aerobic: An environment in which atmospheric or dissolved molecular oxygen is present. • Anaerobic: An environment in which atmospheric or dissolved molecular oxygen is NOT present. • Anoxic: An environment in which atmospheric or dissolved molecular oxygen is NOT present, but oxygen combined with nitrogen as nitrate or nitrite exists. Secondary Treatment
- 20. Terms (continued) • RAS (Return Activated Sludge): Settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to reseed the incoming wastewater. • WAS (Waste Activated Sludge): The excess growth of activated sludge that is removed from the microorganism population to maintain balance. • Internal recirculation: Pumping from the end of the aerobic zone to the anoxic zone for de-nitrification. • F/M ratio: Food to microorganism ratio that must be maintained for effective wastewater treatment. Secondary Treatment
- 21. • Secondary treatment Include Biological, chemical, and physical processes • Activated sludge systems • Conventional activated sludge systems • Enhanced (BNR) biological nutrient removal systems • Secondary clarifiers • Disinfection Kills pathogenic organisms. The disinfection process is postponed when secondary effluent is to be processed further in a tertiary treatment process. Secondary Treatment
- 22. • When activated sludge is added to wastewater, the microorganisms feed and grow on waste particles in the wastewater. • As the organisms grow and reproduce, more waste is removed, leaving the wastewater partially cleaned. • The microorganisms need a steady diet of food and oxygen. This is called the (F/M) food to microorganism ratio. Activated Sludge
- 23. • Oxidation is the primary purpose of low-rate activated sludge processes. • The oxidation may be by chemical or biological processes. • The same organisms that oxidize waste also are effective in converting substances to settleable solids if the plant is operated properly. Activated Sludge
- 24. • Oxygen is needed by the living organisms as they oxidize wastes to obtain energy for growth. • An increase in organisms in the aeration tank will require greater amounts of oxygen. More food in the influent encourages more organism activity and more oxidation, therefore more oxygen is required in the aeration tank. Activated Sludge
- 25. • Secondary treatment, in the form of activated sludge processes, are aimed at oxidation and removal of soluble or finely divided suspended materials that were not removed by previous treatment. • The organisms stabilize soluble or finely divided suspended solids by partial oxidation forming carbon dioxide, water and sulfate and nitrate compounds. Activated Sludge
- 26. • The remaining compounds are changed to a form that can be settled and removed as sludge during sedimentation. • After aeration, the wastewater is routed to a secondary sedimentation (clarifier) for separation. • Settled organisms in the final clarifier are in a deteriorated condition due to lack of oxygen and food and should be returned as quickly as possible to the aeration tank. Activated Sludge
- 27. • Settled solids are either returned to the beginning of the activated sludge system (RAS: Return Activated Sludge) or pumped to a sludge stabilizing and thickening facility (WAS: Waste Activated Sludge). • The remaining clarifier effluent is either chlorinated and discharged or undergoes further treatment in an advanced wastewater treatment process. Activated Sludge
- 28. • There are many thought processes about how a BNR system is engineered and operated. BOD removal is relatively simple, but phosphorus and nitrogen removal require a specific zone orientation to meet regulations. • A typical setup: • Zone 1: Anaerobic • Zone 2: Anoxic • Zone 3: Aerobic • Internal recirculation from the end of the anaerobic zone to the beginning of the anoxic zone. Activated Sludge System
- 29. • The first zone is anaerobic to allow for initial release of phosphorus that will later be consumed by microorganisms in the aerobic zone as part of the luxury uptake process. • Luxury uptake occurs when phosphorus accumulating organisms release all of the phosphorus in the anaerobic zone and uptake several times more phosphorus when they reach the aerobic zone. • The second zone is the anoxic zone because the internal recirculation pump feeds aerated sludge from the aeration zone to mix with the incoming sludge. • Denitrification occurs in the anoxic zone as the microorganisms consume the oxygen combined with nitrate and nitrite. The nitrogen molecules combine to form nitrogen gas and is released to atmosphere. BNR Zone Configuration
- 30. • The third zone is the aerobic zone where microorganisms break down BOD, accumulate phosphorus and convert ammonia to nitrate and nitrite. • Dissolved oxygen level control throughout the aerobic zone is critical. •An acceptable environment supports good microorganism metabolism and reproduction while reducing the chance of forming filamentous bacteria. BNR Zone Configuration
- 32. Curtains divide zones and reduce short circuiting.
- 34. Air header with manual valves to control the amount of air to each section of diffusers.
- 35. Dissolved oxygen probe continuously monitors DO and adjusts flow to air header.
- 36. Air Header Automated ControlValve (Controlled by DO probe input set points)
- 38. Clarifier rotating structure. Notice the floor is sloped to the center.
- 39. Sludge enters the clarifier in the center structure and flows outward toward the weir.
- 40. Clarifier arms are turned by a motor. Shear pins and over-torque settings protect the unit from damage if it hangs up on the weir or walls.
- 41. Outfall from weir channel flows into gravity line and to the filter building.
- 42. RAS pumps with suction and discharge valve placement allowing for multiple configurations.
- 43. RAS system suction and discharge piping
- 44. RAS pump meters provide flow control for each of the two discharge headers.
- 45. WAS pumps draw from the discharge of the RAS pumps.
- 46. WAS pumps discharge to a DAFT or directly to a digester.
- 47. Homework Assignment: Read Chapter 3 in your textbooks. WQM 207 - Activated Sludge Systems