choosing the right chlorine analyzer for your application ... · pdf fileplay sc digital...
TRANSCRIPT
![Page 1: Choosing The Right Chlorine Analyzer For Your Application ... · PDF fileplay sc digital controller ... New amperometric total chlorine continuous analyzer helped to reveal issues](https://reader031.vdocuments.net/reader031/viewer/2022021509/5a7f9a357f8b9aa24f8bc68c/html5/thumbnails/1.jpg)
Choosing The Right Chlorine Analyzer
For Your Application- DPD Verses
Amperometric
Dr. Vadim B. Malkov, Gary R. Visser,
Terry Engelhardt
Hach Company
Presented by
Kevin Menning
Technical Sales Specialist
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Overview
• Multiple Available Chlorine Monitoring Technologies
– Colorimetric and amperometric have different strengths
– Different applications drive different priorities
• Case Study: Uncovering the Unexpected – Visser
– Amperometric results compared with existing colorimetric
– New technology revealed unexpected variances in the sample
– Using continuous measurement, a treatment issue was discovered
• Case Studies: Multiple issues - Englehardt
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Online Chlorine Monitoring –
Main Characteristics
• Measurement Precision and Accuracy
• Process Control
– Batch analysis
– Continuous analysis
• Influencing Factors
– Cl2 concentration
– Sample pH
– Sample flow = 90% of issues
– Sample temperature
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Accuracy and Precision
• Two words that sound a lot alike, but
very important differences
• Precision is how well you can repeat
the answer over and over• HTTC 10 table iron test
• Accuracy is how close to the true
value your answer is.• How do determine if your answer is accurate?
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Online Chlorine Monitoring –
Major Technologies
Colorimetric:
measuring intensity of color developed by
reaction of chlorine with indicator DPD .
The deeper color, the higher chlorine
concentration. Beers Law chemistry.
Main Differentiators:
• Independent of major sample parameters
(pH, flow, temperature, hardness),
• Established calibration curve
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Colorimetric Chlorine Analyzer -
it automates the lab method
Colorimeter
Pump
Module
KeypadWiring
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CL17 CHLORINE ANALYZERSAMPLE INLET SAMPLE VALVE
UNDER
PRESSURE
LIGHT SOURCE TO WASTE
DETECTORGLASS CELL
MAGNETIC STIRRERPINCHERS
INDICATOR
BUFFER SOLUTION
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Online Chlorine Monitoring –
Major Technologies
Amperometric:
measuring electrical current generated in
a circuitry by reaction of chlorine with
electrodes The larger current value, the
higher chlorine concentration.
Main Differentiators:
• No chemical reagents required
• Fast response to analyte concentration
changes
•Range 0-20
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Online Chlorine Monitoring –
Case Study Setup
Controller
(sc200)
Grab sample
portChlorine
sensor
Optional
pH sensor
Sample
pressure
control kit
Digital controller – local data logging function
Optional pH sensor – additional information about the sample
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Online Chlorine Monitoring –
Technologies Comparison
Colorimetric Amperometric
Pros
• Accuracy (no calibration required)
• Unattended operation (up to 30 days)
• Predictable and simple maintenance
• Results independent of changes in
sample pH, temperature, Cl2concentration, etc.
Pros
• Fast response to changes in Cl2concentration
• Reagentless technology
• No waste stream
Cons
• Reagents and waste stream management
• Clean sample cell
Cons
• Greater interference from sample pH,
temperature, flow, pressure, Cl2concentration, etc.
• Have to calibrate
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DPD Waste Stream Analysis
11
� No federal regulations (RCRA) for this kind of discharge
� The analyses performed in accordance with EPA Methods for
Drinking Water
� Results compared with Maximum Contamination Levels (MCL)
listed for found chemicals
� Chemicals produced by the reagents and analyzer were
identified
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DPD Waste Stream Analysis - Results
12
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Online Chlorine Monitoring –
Applications Overview
Application Type and Regulatory
ExpectationsMain Characteristics
Static Applications: Reportable
(finished water), Sometimes Process
Control
Very stable sample conditions (pH,
Temp, Flow, Cl2 concentration): final
water discharge, distribution systems
Quasi-Stable Applications:
Mainly Process Control, Sometimes
Reportable
Relatively stable sample conditions:
pre-treated water at a DWTP
Dynamic Applications:
Mainly Process Control, Possibly
Reportable
Constantly changing sample
conditions: flash mixers, backwash
loops, disinfection loops, etc.
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Online Chlorine Monitoring –
Keys to Application Success
Steps to choosing your chlorine analyzer:
1. Look at the instrument's major performance specifications to make your
initial decision.
• Chlorine concentration range
• Sample pH range
2. Next, consider each technology's key differentiators to determine which
is preferred for your application.
• Colorimetric
• Amperometric
3. Finally, consider the treatment process details - key to application
success to make sure that your preferred instrument is right for your
application.
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Making a Selection – Step 1
Step 1: Basic Specifications
Colorimetric Amperimetric
Basic Specifications
Chlorine Concentration
Range0 - 5 mg/L 0 - 20 mg/L
Sample pH range NA pH 4 - 9
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Making a Selection – Step 2
Step 2: Technology Key Differentiators
Colorimetric Amperimetric
Key Differentiators
Influence of sample pH,
chlorine concentration,
temperature, flow and/or
pressure changes
No impact on readings
Readings may be impacted.
Adjustment to calibration may be
needed
Calibration Calibration not neededRequired. Frequency based upon
the application.
Routine MaintenanceTubing replacement needed
every 6 months
Membrane and electrolyte
replacement every 3-6 months
ReagentsRoutine reagent replacement
needed every 30 daysNone needed
Reagents in Waste Stream Yes No
Multi-parameter, plug-and-
play sc digital controllerNot available. Compatible with some controllers.
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Calibration and Verification
• Two words that sound a lot alike, but
very important differences
• Calibration is using standards and
following the procedure in the
manual for calibration.
• Verification is comparing to a
standard or another instrument and
making sure it is with-in a certain %
usually 10%.
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Making a Selection – Step 3Step 3: Performance and Applications Specifics
Colorimetric Amperimetric
Additional Instrument Specifications
Response TimeBatch Analysis,
(150 seconds cycle time)
Continuous Analysis,
T CL = 140s
F CL = 100s
Regulatory Method
SM 4500 CL G
40CFR 141.74
EPA Method 334.0
Only EPA Method 334.0
Make sure to read this Method
Keys to application success
Appropriate Applications
(should meet these
requirements)
�Replace reagents
monthly
�A system to manage the
waste stream (if
required).
�Uninterrupted sample flow 1000 O
�Uninterrupted power
�Sample pH should be within ± 0.5 pH unit from
the average value
�Chlorine concentration should be within ± 20%
from the average value
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Online Chlorine Monitoring –
Batch vs. Continuous Analysis
0.75
1
1.25
1.5
1.75
2
2.25
0 50 100 150 200 250 300 350 400 450 500 550
Ch
lori
ne
Co
nce
ntr
ati
on
, p
pm
Time, sec
Response of Amperometric vs. CL17 to Process Chlorine Concentration
Change
Dosage, ppm
CL17, ppm
Amp, ppm
CL17 response time = up to 300 s
depending on sampling
What is the priority – high accuracy or immediate response?
How important is 3 or 5 minutes??
colorimetric
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Online Chlorine Monitoring –
Case Study Setup
Controller
(sc200)
Grab sample
portChlorine
sensor
Optional
pH sensor
Sample
pressure
control kit
Digital controller – local data logging function
Optional pH sensor – additional information about the sample
![Page 21: Choosing The Right Chlorine Analyzer For Your Application ... · PDF fileplay sc digital controller ... New amperometric total chlorine continuous analyzer helped to reveal issues](https://reader031.vdocuments.net/reader031/viewer/2022021509/5a7f9a357f8b9aa24f8bc68c/html5/thumbnails/21.jpg)
Online Chlorine Monitoring –
Case Study Setup
� Both Colorimetric and Amperimetric measuring the same
sample
� Data from both instruments collected to SCADA
� Main goal for implementation of new analyzer – minimize
ongoing maintenance (cost of reagents)
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Online Chlorine Monitoring –
Case Study: SCADA results pre-clearwell
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Online Chlorine Monitoring –
Case Study: Evaluation
1. Good trending between two analyzers
2. Larger variance in amperometric analyzer readings
3. Root cause:
� Process issues?
? Sample flow
? Sample pH
? Sample temperature
� Analyzer malfunctioning?
4. Next steps:
a) Internal data logging
b) Full data evaluation
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Online Chlorine Monitoring –
Case Study: Logged Data
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Online Chlorine Monitoring –
Case Study: Observations
1. Observations:
a) Flow is stable
b) Temperature is stable
c) Substantial pH variations (min = 6.46, max = 9.32)
2. Root cause?
� Not the analyzer (pH independent in this range)
� Process - sample pH effecting chloriamination chemistry
3. Next steps:
a) Verify analyzer performance
b) Determine why pH is unstable
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Online Chlorine Monitoring –
Case Study: Verification
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Online Chlorine Monitoring –
Case Study: Observations
1. Analyzer performs within specifications
2. Water treatment process issues – root cause?
? pH adjustment
? Disinfectants mixing
? Sampling point
3. Next steps:
a) Change sampling point
b) Introduce changes to the chemicals mixing
c) Validate performance
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Online Chlorine Monitoring –
Case Study: Validation
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Case Study –
Results and Conclusions
�New amperometric total chlorine continuous analyzer helped to reveal issues with finished
water
�The unexpected problem uncovered in this case study may be very common for many drinking
water treatment facilities
�Both laboratory and online methods based on batch analysis provide the customers with great
value of accurate results (regulatory reporting aspect)
�An amperometric-based online instrumentation can provide additional benefits due to the
continuous nature of measurement (fast response to process changes)
�Optional pH monitoring and local data-logging features can provide additional benefits:
� Reserved data storage in case of SCADA malfunctioning
� Better understanding of the process (monitoring multiple sample parameters)
� Enhanced troubleshooting
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Finished Water: Final Discharge
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Dynamic Application: Ground Water Station (Aurora,
CO)
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� Stable Finished Water Applications
�Suitable application area for amperometric sensors
�Drift and offset due to pH, flow, etc. should be monitored
� Quasi-Stable Applications
�Some suitable applications for amperometric sensors (redundant)
�Requires more frequent calibration/verification
� Dynamic Applications
�Not the target for amperometric sensor (good redundant analyzer)
�Requires frequent calibration/verification
� Colorimetric instrumentation demonstrated to be suitable for ALL investigated applications
Conclusions
32
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Which one costs more to operate?
Purchase cost
Reagent Cost vs Probe
Time to calibrate an maintain
Which one would I purchase?
F. O. R. D.
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Thank you for your attention!
Questions?
Please contact Kevin Menning at
+1-970-663-1377 x 233