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YSI Activated Sludge - 3 Things You Need to Know to Improve Process Control
The document discusses the activated sludge process in wastewater treatment, emphasizing process control through aeration, sludge wasting, and recirculation for improved efficiency. Key concepts include biological treatment parameters such as dissolved oxygen levels, nitrification, denitrification, and the importance of trained personnel. It highlights methods for measuring and controlling various factors to ensure effective biomass management and wastewater treatment outcomes.
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YSI Activated Sludge - 3 Things You Need to Know to Improve Process Control
- 1. Activated Sludge -ThreeThings You Need To Know To Improve Process Efficiency YSI WATER RESOURCE RECOVERY WEBINAR 1
- 2. Activated Sludge ProcessControl Influent Return Activated Sludge (RAS) Mixed liquor Effluent Final settling tank AIR Aeration tank Waste Activated Sludge (WAS) Internal Mixed Liquor Recycle (IMLR)
- 3. Great Inventions ofthe 20th Century 3
- 4. Ardern and LockettPublished 1914 The culmination of years of research and discovery 4 Aeration Growth of ‘humus’ ‘Activation’
- 5. Activated Sludge • (micro-)biological • Aerated • Suspended growth • Hydraulic retention time ≠ Solids retention time • Requires specially trained personnel What all configurations have in common 5
- 6.
- 7. Aeration and the(Bio-Chemical) Environment 7 0 + Nitrification Denitrification Fermentation ‘P’ release ORP, mV OxicAnaerobic Anoxic - BOD removal ‘P’ uptake
- 8. Effect of DOConcentration on Biological Treatment Basis for maintaining DO at or below 2 mg/L setpoint D.O. Reaction 0.75 D.O. : Reaction Control of nitrification also ensures BOD removal cBOD removal Nitrification 0.5 1.0 2.01.5 2.5 3.0 O2 (mg/l) 1/2 vmax vmax Reactionrate 0.3
- 9. Dissolved Oxygen andPerformance Balancing nitrification - denitrification 9 %ofmaxprocessrate Dissolved oxygen Source: Gustaf Olsson, Lund University, Sweden
- 10. Dissolved Oxygen andEnergy 10 Source: Blum, D., High Efficiency Aeration, Clarifier, Illinois WEA, Summer 2013 D.O. 1.5 x > 4 x
- 11. Optical DO Measurement ASTMD888-09 Test Method C • Very stable calibration • Less maintenance • No sulfide interference • Accuracy: +/- 1% • No stirring • No warm-up 11 Continuous Spot sampling
- 12. ORP Ion selective electrode(ISE) Continuous Spot sampling Reference electrode Membrane Junction ISE (mV)
- 13.
- 14. Sludge Wasting ControlsHow Much Biomass Approaches to sludge wasting • Settleability • Constant MLSS • Centrifuge/spin • F/M • Solids Retention Time 14
- 15. Sludge Age, MCRT,SRT, CRT 15 Qe, Xe V, MLSS Qr, Xr Qw, Xr Qi, Xi Biomass in the system Biomass entering / leaving the system÷
- 16. Target SRT COD removalCOD removal + nitrification COD removal + nitrification + denitrification COD removal + nitrfication + denitrification + P removal SRT What are treatment requirements? 16 function
- 17. 0.0 4.0 8.0 12.0 16.0 5 10 1520 25 NitrificationSRT,d Nitrification Design 17 Design SRT; SF=1.5 Operating Range Min. SRT
- 18.
- 19. SRT and Performance 19 EffluentTSS 1year Source: Wahlberg, E. “What makes secondary clarifiers work”, WEFTEC 2013
- 20. Solids Measurement -Optical Reflectance or absorbance • Fast • Simple • Factory calibrated • Low maintenance Continuous Spot sampling
- 21. Sludge Recirculation (RAS andIMLR) 21
- 22. • Constant flow– set RAS flow rate manually (open loop) • Constant percentage – set RAS flow proportional to ww flow (feed forward) Sludge Recirculation for Control of Biomass Distribution RAS is critical to clarifier performance 22
- 23. RAS Flow RateControl Sludge blanket depth approach 23 WW flow RAS flow MLSS Thickening Failure Q + Qras Qras Q MLSS Flux
- 24. RAS Flow RateControl Sludge blanket depth approach 24 WW flow RAS flow MLSS MLSS ↓ Thickening Failure Q + Qras Qras Q MLSS Flux
- 25. RAS Flow RateControl Sludge blanket depth approach 25 WW flow RAS flow MLSS MLSS ↓ Thickening Failure Solids washout Q + Qras Qras Q MLSS Flux
- 26. RAS Flow RateControl Sludge blanket depth approach 26 WW flow RAS flow MLSS Thickening Failure Q + Qras Qras Q MLSS Flux
- 27. RAS Flow RateControl Sludge blanket depth approach 27 WW flow RAS flow Increase RAS MLSS MLSS ↓ Thickening Failure Q + Qras Qras Q MLSS Flux
- 28. Sludge Blanket DepthMeasurement 28 Visual Acoustic (sludge level detector)
- 29. Sludge Recirculation forControl of Denitrification Nitrate is the critical measurement 1) Meet nitrogen limits 2) Maximize use of wastewater COD 3) Minimize external carbon 29 Source: Ingildsen, P, Wendelboe, H., “Improved nutrient removal results using in situ continuous on-line sensors with reduced response time”, WEFTEC 2003
- 30. ISE Ammonium andNitrate Potentiometric (like pH/ORP) • Measuring electrodes: NH4 +, NO3 -, • Compensation electrodes: K+, Cl- • Reagentless • Stable calibration • Replaceable electrodes • Large measuring range Continuous
- 31. ISE Ammonium andNitrate Potentiometric (like pH/ORP) • Measuring electrodes: NH4 +, NO3 -, • Compensation electrodes: K+, Cl- • Reagentless • Stable calibration • Replaceable electrodes • Large measuring range Continuous Spot sampling
- 32. Optical Nitrate Spectral orsingle-wavelength • No electrodes • Factory calibrated (spectral) 32
- 33. Summary and FutureWebinar Topics Process control – it is easier than you think 33 • Aeration to control the environment • Sludge wasting to control the total biomass • Sludge recirculation to control biomass distribution