Process Monitoring of Water and Wastewater Treatment
MWEA 2018 JOINT EXPO AND OPERATORS DAY
February 7, 2018
Functions of a Process Monitoring System
•Compliance / Compliance Assurance
•Early Warning / Upset Detection
•Operational Efficiency / Process Control
2
Dissolved Oxygen (DO)
Wastewater
• Compliance
• Aeration control /
Energy efficiency
Drinking Water
• Taste
• Corrosion control
3
Energy Efficiency
4Source: Blum, D., High Efficiency Aeration, Clarifier, Ilinois WEA, Summer 2013
D.O.
Polarographic DO Sensor
Oxygen diffuses through membrane
Oxygen reduced (consumed) at cathode
Electrons flow = electrical signal (mA)
Oxygen concentration proportional to signal level
O2 H2O
e-
Probe Solution
O2
O2
O2
O2
O2
O2
O2
O2
O2
O2
e-
e-e-
H2OH2O
H2O
H2O
H2O
H2O
H2O
H2O
H2OH2O
H2O
H2O
Anode
Cathode
Membrane
Measuring Dissolved Oxygen using Luminescence
6
The excitation fiber
in the sensor emits
a blue light
causing the sensing element to glow,
or luminesce red.
Measuring Dissolved Oxygen using Luminescence
7
Oxygen is constantly moving through
the Diffusion Layer, affecting the
luminescence of the sensing layer.
The amount of oxygen passing
through the sensing layer is
inversely proportional to the
lifetime of the luminescence in
the sensing layer.
The lifetime of the
luminescence is
measured by the
sensor and compared
against the reference
and a stable dissolved
oxygen concentration is
calculated.
Water Treatment Process Monitoring
8
Physico-chemical treatment
• pH
• Chlorine
• Turbidity
• Alkalinity
• Ortho-phosphate (PO4)
• Total Organic Carbon (TOC)
• Sludge level
• Nitrate
• Dissolved Oxygen (DO)
Wastewater Treatment Process Monitoring
9
Biological and Physico-chemical treatment
• Dissolved Oxygen (DO)
• Total Suspended Solids (TSS)
• Oxidation Reduction Potential (ORP)
• Sludge level
• Ammonia (NH3; N -3 valence)
• Nitrate (NO3-; N +5 valence)
• Ortho-phosphate (PO4)
• Chlorine
• pH
Process Monitoring System Components – Universal Controller
Display
System settings
Power supply
Outputs
10
Process Monitoring System Components – Sensors
Measurement
devices
Signal processing
Instrumental Methods of Analysis / Signal Types
12
Optical
Absorption Emission
Potentiometric Polarographic
Scattering
Electrochemical
Fluorimetry
Ammonia / Ammonium Measurement
Potentiometry – ion selective electrodes (ISE)
Colorimetry (absorption) – cabinet analyzers
13
Potentiometry Sensor Design
14
Reference
electrode
Ion
Selective
Electrode
MembraneJunction
(mV)
Wastewater Ammonia-Based Aeration Control
Ammonia / Ammonium Applications
15
Ortho-Phosphate Detection & Measurement by Colorimetry
reagent
sample
with PO43-
mixing photometeryellow
coloration
=420 nm
Ortho-phosphate Applications
17
Drinking water Wastewater
Control of a Ferric Chloride Dosing Pump (Phosphorus Removal from Wastewater)
light
Turbidity, Total Suspended Solids (TSS) Detection by Light Scattering
19
Backscatter
(digested sludge)
absorbance /
turbidimetry
Nephelometry
(clean water)
< 90°
(mixed liquor)
Turbidity / Total Suspended Solids Applications
20
Drinking Water (compliance)
Water or Wastewater
(non-compliance)
Turbidity Measurement Standards
21
Use of LED 860 (nm)• Weak sensitivity to very small particles
• No influence of colored samples
ISO 7027 LED 860 nm
DIN EN 27027 LED 860 nm
US EPA Method 180.1Tungsten Filament
ASTM D 1889-88 Tungsten Filament
All methods: nephelometric 90°
NTU = FNU = FTU
90°
Tungsten filament• High sensitivity to small particles
• Influence by colored samples
Wastewater Activated Sludge Solids Monitoring System
22
Immersion sensor in mixed liquor Insertion sensor in
return activated sludge
Total Organic Carbon (TOC)
Wastewater
• Surrogate parameter
• Water Reuse
Drinking Water
• Disinfection by-
products
23
Basic Building Blocks of TOC Analysis
Sample
Introduction Oxidation Detection Display
1. Syringe
2. Process/Online
3. Sample loop
4. Autosampler
5. Solids option
1. Combustion
2. Persulfate at 98 °C
3. UV/Persulfate
1. Display
2. Printout
3. Computer
4. Strip Chart Recorder
Carbon
Dioxide
1. NDIR (absorption)
2. Membrane Conductivity (electrochemistry)
TOC Analysis in the Drinking Water Treatment Process
25
Upstream Coagulant Control
26
Downstream DBP Mitigation
27
TOC Analysis – A Different Method
Sample
Introduction Oxidation Detection Display
1. Syringe
2. Process/Online
3. Sample loop
4. Autosampler
5. Solids option
1. Combustion
2. Persulfate at 98 °C
3. UV/Persulfate
1. Display
2. Printout
3. Computer
4. Strip Chart Recorder
Carbon
Dioxide
1. NDIR (absorption)
2. Membrane Conductivity (electrochemistry)
1. UV (absorption)
Direct UV Detection of TOC
TOC Monitoring for (Waste)Water Reuse
30
Control ozone dosage
Monitor treatment
performance (upstream
and downstream
sensors)
Not for compliance
Blanket Level
Wastewater
• Sludge recirculation
(ASP)
• Sludge removal
Drinking Water
• Sludge removal
31
Sludge Blanket Depth Measurement
32Optical Acoustic
Advantages:
• High resolution
• TSS profile
Disadvantages
• Moving parts
• Limited sampling
Advantages:
• Less fouling
• Continuous
• Long-term stability
Disadvantages
• Fluffy sludge /
ambiguous results
Wastewater – Activated Sludge Clarifier
33
Q + Qras
Qras
Q
MLSS
Contact YSI or Systems Specialties
34
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