how to get the best data - preventing fouling of online wastewater sensors
TRANSCRIPT
How to Get the Best Data: Preventing Fouling of Online Wastewater Sensors YSI WASTEWATER WEBINAR SERIES
Today’s Topics
Optical scattered light /absorbance sensors • Measurement principles • Probe Operation & Care • Measurement interferences • Fouling prevention & removal • Demonstration of UltraClean Technology
• Closing Thoughts
Process Monitoring of Wastewater Treatment 2
Solids Detection - Scattered Light
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Scattered light depends on: • Type of particle (absorbance) • Concentration (number of particles) • Size of particles • Shape of particles (absorbance –
reflection) • Wavelength of the light
Not a direct measurement of number or concentration of particles
lamp detector
I0 I
sample
Nitrate, COD Detection – Absorbed Light
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%𝑇𝑇 =𝐼𝐼𝐼𝐼𝐼𝐼
× 100
𝐴𝐴 = log𝐼𝐼𝐼𝐼𝐼𝐼
Probe Operation & Care
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Programming
Measurement Mode – parameter, units, type of factory calibration Signal averaging – number of sensor measurements used to
calculate displayed measurement Automatic Cleaning – type and frequency User Calibration (if needed)
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Maintenance & Verification
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Cleaning Sampling & Reference (lab) Measurement
Maintenance & Verification
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Measurement Interferences
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Causes of Measurement Error
Sample environment properties Aging or drift of the sensor electronics Fouling of the sensor Actual drift of the process
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Causes of Measurement Error
Sample environment properties Fouling of the sensor Actual drift of the process
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Play Ball!
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The difference between accuracy and precision/repeatability
Play Ball!
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Accurate but not precise
Play Ball!
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Precise but not accurate
Play Ball!
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You can always adjust target
Sample Properties
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Air bubbles – accuracy / precision
• Change sensor position
• Increase signal averaging
Interferences by reflections – accuracy / precision
• Especially insertion mounts
• Change sensor position
• User calibration
Demonstration of Signal Averaging
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Fouling
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Organic – biomass, grease Mineral - scale, iron
Automatic cleaning Mechanical wiper Air or water Ultrasonic Combination Manual cleaning Wipe Chemical
Demonstration of UltraClean Technology
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ViSolid® 700IQ Solids Probe
Stainless Steel with sapphire windows Continuous ultrasonic cleaning system No smearing No moving parts No wear parts
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UltraClean Demonstration Video
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Demonstration of UltraClean
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Full-Scale Evaluation
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Pure oxygen activated sludge (sticky) Return activated sludge (concentrated) 3 sensors – 2 x ViSolid with UltraClean; 1 x FDO (no auto clean)
UltraClean ‘On’
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After 10 Days
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UltraClean ‘Off’
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Closing Thoughts
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Summary
Keeping Sensors Clean • Optical sensors are based on light scattering or light absorbance
• IQSN optical probe operation requires programming and cleaning
• Sample environment and fouling are causes of measurement error
• IQSN UltraClean technology extends maintenance intervals
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Example Application – Process Monitoring for Sludge Wasting Control
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Qe, Xe
V, MLSS
Qr, Xr
Qw, Xr
Qi, Xi
List price = $15,195 for monitoring system including probes, controller, output module, power supply module, cables, and mounting equipment
A Tale of Two WRRF
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Plant “A” w/SRT control
Plant “B” Uncontrolled
Plant “B” mimic Plant “A”
SV
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UltraClean is Also Available on IQSN UV and UV/Vis Probes
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CarboVis 70x NitraVis 70x NiCaVis 70x UVT-254 70x NOx 70x
Questions?
Web - www.ysi.com/wastewater Slideshare – www.slideshare.net/YSIinc YouTube – www.youtube.com/YSIinc Phone: 1-800-897-4151 Email: [email protected] or [email protected]
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Now Available from YSI
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IQSN 282 / 284 Controller ProSample P