Free Chlorine
description
Transcript of Free Chlorine
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Free Residual Chlorine Measurement
Why measure residual chlorine in drinking water?
?
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Chlorine Chemistry
= HOCl + OCl--
= NH2Cl + NHCl2 + NCl3
= Combined Chlorine +
Free Chlorine
Free Chlorine
Combined Chlorine
Total Chlorine
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Chlorine Chemistry
HOCl + H+ + Cl-
H+ + OCl--
Cl2 + H2O
HOCl
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
% Distribution HOCl vs. pH
7
100
pH4 5 6 8 9 10
% HOCI
90
80
70
60
50
40
30
20
10
0
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Measurement Methods
Colorimetric
Open /Electrode Buffered
Amperometric/Polarographic
High Resolution Redox
pH/ORP Method
Galvanic Sensor
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Colorimetric Systems
Operating Principle
Add buffer and indicator solution to a known volume of water.
After mixing, measure wavelength of light transmitted through sample to determine color change and thus, amount of free residual chlorine in the sample.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Colorimetric Systems
AdvantagesPrice.High pH is not a limiting factor.EPA approved DPD measurement.
DisadvantagesUses reagents.Must use pumps, valves and capillary tubes.Can only generate a new residual reading every 2 1/2 minutes.High maintenance.No pH or temperature output.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Open Electrode/Buffered Systems
Operating PrincipleA known volume of sample water is pumped into a chamber and buffered to a pH of 4.
Two bare electrodes are in contact with the sample inside the chamber and based upon mV readings, a free residual chlorine value is derived.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Open Electrode/Buffered Systems
AdvantagesHigh pH is not a limiting factor.
DisadvantagesUse of buffers.Must use pumps and valves.High maintenance.Difficult start-up.No pH or temperature output.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Amperometric/Polarographic
Membrane Sensor
Operating Principle A sensor consisting of a membrane (which allows HOCL to migrate through it), two dissimilar metal electrodes, and an electrolyte are submersed into the water sample.
A free residual chlorine reading is derived based on mV changes experienced by the sensor.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Amperometric/Polarographic Membrane Sensor
AdvantagesEase of useNo reagents or buffers added
DisadvantagesNo pH or temperature compensation (OPTIONAL)No flow regulationNo pH or temperature output (OPTIONAL)
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
High Resolution Redox
Operating PrincipleCharacterize free residual chlorine demand based upon ORP values of the water sample.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
High Resolution Redox
AdvantagesIn some instances, does a better job of determining residual chlorine demand.
DisadvantagesDoes not measure free residual chlorine directly.Any oxidant present in water sample will be read as an increase in free residual chlorine.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Operating PrincipleWater flows through a Dual Flow Cell consisting of an ORP and a PH sensor.
Microprocessor in the analyzer calculates the free residual chlorine (HOCL+OCL-) concentration by using a polynomial formula. This calculation requires the analyzer to know the measured ORP, PH and temperature values.
IC Controls - pH/ORP Method
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
AdvantagesNo reagents or buffers added.
No moving parts.
pH and temperature compensated.
Easy to set up and calibrate.
Multiple measurement readouts/outputs.
Dedicated relay control for residual chlorine and pH.
DisadvantagesDoes not measure free residual chlorine directly.
Any oxidant present in water sample will be read as an increase in free residual chlorine.
IC Controls - pH/ORP Method
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Operating Principle
A sensor consisting of a membrane (which allows Cl
2 to migrate through it), two
dissimilar metal electrodes, and an electrolyte are submersed into the water sample.
A free residual chlorine reading is derived based on mV changes experienced by the sensor.
Model 875 Galvanic Free Chlorine
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
AdvantagesEase of useNo reagents or buffers addedAbsolute ZeroPretensioned Membrane CapGalvanic Technology
DisadvantagesManual pH compensation (now Available in 876)
Model 875 Galvanic Free Chlorine
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Model 875 Galvanic Free Chlorine
Polarographic vs
IC Controls Galvanic
What's the difference?
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Applied voltage from the Cathode to the Anode.Reaction of Chlorine at Cathode generates a current.Output can go below zero; a value that does not exist.
Therefore, decreased accuracy in calibration and measurement
Polarographic
VO2
O2
O2
O2
Cl2 Cl
2Cl
2
Anode
CathodeMembrane
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
No applied Voltage. Chlorine is the fuel for the battery.Therefore, absolute zero and better accuracy.
Galvanic
O2
O2
O2
O2
Cl2 Cl
2Cl
2
Anode
CathodeMembrane
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Recharging the Sensor
Over time the sensor internal will deplete and the membrane and fill solution will need replacement. Historically, this was a difficult process with creases being formed in the membrane and air bubbles in the fill solution which cause inaccurate readings. At times the process could take up to 1 hour to replace a membrane and put a sensor back on line.
The model 835 sensor provides ease of use which includes fast, reliable and simple maintenance.
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Maintenance is made easywith the Pre-TensionedMembrane cap.
This system ensures thereare no air bubbles or creasesin the membrane cap whichwill cause false inaccuratereadings.
An easy process that allows recharging and re-installationin less than 5 minutes.
MembraneModule
TipRetainer
Pre-Tensioned Membrane Cap
04/05/04
IC Controls 875 Free Available Chlorine System
pH / ORPConductivityDissolved OxygenChlorineStandards
www.iccontrols.com
R1.0 © 2004 IC CONTROLS
Galvanic Technology
Absolute Zero
No Reagents Required
Pre-Tensioned Membrane CapProven Technology
Superior DesignBetter Results
Model 875 Galvanic Free Chlorine