Fouling is a common cause of measurement error which is preventable by probe design and with proper maintenance. The challenge, as with all types of equipment, is to learn the technology sufficiently to know what steps to take to achieve reliable measurements without excessive effort. This webinar will explain the technology for monitoring important wastewater process parameters with optical sensors and describe best practices for obtaining reliable, trouble-free, long-term ownership of process optical sensors, especially for monitoring solids. The information presented will include benchtop demonstrations of a novel ultrasonic cleaning mechanism and a full-scale demonstration of the effectiveness of UltraClean™ technology incorporated into an IQ SensorNet ViSolid® solids probe. https://www.ysi.com/iqsn2020

1. How to Get the Best Data:
Preventing Fouling of Online
Wastewater Sensors
YSI WASTEWATER WEBINAR SERIES

2. 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

3. Solids Detection - Scattered Light
3
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

4. lamp detector
I0 I
sample
Nitrate, COD Detection – Absorbed Light
4
%𝑇𝑇 =
𝐼𝐼
𝐼𝐼𝐼𝐼
× 100
𝐴𝐴 = log
𝐼𝐼
𝐼𝐼𝐼𝐼

5. Probe Operation & Care
5

6. 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)
6

7. Maintenance & Verification
7
Cleaning
Sampling & Reference (lab) Measurement

8. Maintenance & Verification
8

9. Measurement Interferences
9

10. Causes of Measurement Error
Sample environment properties
Aging or drift of the sensor electronics
Fouling of the sensor
Actual drift of the process
10

11. Causes of Measurement Error
Sample environment properties
Fouling of the sensor
Actual drift of the process
11

12. Play Ball!
12
The difference between accuracy and precision/repeatability

13. Play Ball!
13
Accurate but not precise

14. Play Ball!
14
Precise but not accurate

15. Play Ball!
15
You can always adjust target

16. Sample Properties
16
Air bubbles – accuracy / precision
• Change sensor position
• Increase signal averaging
Interferences by reflections – accuracy / precision
• Especially insertion mounts
• Change sensor position
• User calibration

17. Demonstration of Signal Averaging
17

18. Fouling
18
Organic – biomass, grease
Mineral - scale, iron
Automatic cleaning
Mechanical wiper
Air or water
Ultrasonic
Combination
Manual cleaning
Wipe
Chemical

19. Demonstration of UltraClean
Technology
19

20. ViSolid® 700IQ Solids Probe
Stainless Steel with sapphire
windows
Continuous ultrasonic cleaning
system
No smearing
No moving parts
No wear parts
20

21. UltraClean Demonstration Video
21

22. Demonstration of UltraClean
22

23. Full-Scale Evaluation
23
Pure oxygen activated sludge (sticky)
Return activated sludge (concentrated)
3 sensors – 2 x ViSolid with UltraClean; 1 x FDO (no auto clean)

24. UltraClean ‘On’
24

25. After 10 Days
25

26. UltraClean ‘Off’
26

27. Closing Thoughts
27

28. 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
28

29. Example Application – Process
Monitoring for Sludge Wasting Control
29
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

30. A Tale of Two WRRF
30
Plant “A” w/SRT control
Plant “B” Uncontrolled
Plant “B” mimic Plant “A”
SVI

31. UltraClean is Also Available on IQSN UV
and UV/Vis Probes
31
CarboVis 70x
NitraVis 70x
NiCaVis 70x
UVT-254 70x
NOx 70x

32. 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
32

33. Now Available from YSI
33
IQSN 282 / 284 Controller ProSample P