how to get the best data - preventing fouling of online wastewater sensors

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: info@ysi.com or robert.smith@xyleminc.com

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Now Available from YSI

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IQSN 282 / 284 Controller ProSample P