ASTM D7677-16(2023)
(Test Method)Standard Test Method for the Continuous Measurement of Dissolved Ozone in Low Conductivity Water
Standard Test Method for the Continuous Measurement of Dissolved Ozone in Low Conductivity Water
SIGNIFICANCE AND USE
5.1 Dissolved Ozone is useful in many industries for water sanitization, TOC reduction, food preservation, cleaning-in-place of food and beverage systems, and pyrogen destruction. It is often necessary to know how much ozone has entered the water, how much remains, and the degree to which it has been removed before process use.
5.2 Some applications require that contact time, DO3 concentration integrated over time, be calculated, to assure disinfection.
5.3 Continuous observation of trends in these measurements are needed for continuous quality monitoring and the measurement may be used for closed loop control of ozonation.
5.4 In many pure water applications and especially where water quality is regulated by the FDA or similar enforcement agencies, ozone removal must be complete before the water is used. This test method is useful for detecting and determining dissolved ozone levels in water at the trace level as well as at process concentrations where sanitization and chemical reactions occur.
SCOPE
1.1 This test method covers the on-line and in-line determination of dissolved ozone (DO3) in low conductivity water in the range from 0.001 mg/L to 5.0 mg/L DO3 and conductivity 3 is detected by correlating the response of a membrane-covered electrochemical sensor to the dissolved ozone concentration.
1.2 This test method provides a more convenient means for continuous measurement than the colorimetric methods typically used for grab sample measurements.
1.3 This test method has the advantage of high sensitivity as well as durability in the process environment and has few interferences.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7677 − 16 (Reapproved 2023)
Standard Test Method for the
Continuous Measurement of Dissolved Ozone in Low
Conductivity Water
This standard is issued under the fixed designation D7677; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of
1.1 This test method covers the on-line and in-line determi-
Applicable Test Methods of Committee D19 on Water
nation of dissolved ozone (DO ) in low conductivity water in
D3370 Practices for Sampling Water from Flowing Process
the range from 0.001 mg/L to 5.0 mg/L DO and conductivity
Streams
<100 μS/cm, typical of pharmaceutical and microelectronics
pure waters. DO is detected by correlating the response of a
3. Terminology
membrane-covered electrochemical sensor to the dissolved
3.1 Definitions—For definitions of terms used in this
ozone concentration.
standard, refer to Terminology D1129.
1.2 This test method provides a more convenient means for
3.2 Definitions of Terms Specific to This Standard:
continuous measurement than the colorimetric methods typi-
3.2.1 dissolved ozone (DO ), n—Ozone is the tri-atomic
cally used for grab sample measurements.
form of oxygen and, when dissolved in water, is uniformly
1.3 This test method has the advantage of high sensitivity as
dispersed and remains in molecular form.
well as durability in the process environment and has few
interferences.
4. Summary of Test Method
1.4 The values stated in SI units are to be regarded as
4.1 Dissolved ozone measurements are made on a flowing
standard. No other units of measurement are included in this
water sample containing dissolved ozone gas.
standard.
4.2 The sensor flow housing is connected to a process-water
1.5 This standard does not purport to address all of the
sample line or the sensor probe is inserted into a pipe or vessel
safety concerns, if any, associated with its use. It is the
with flowing water.
responsibility of the user of this standard to establish appro-
4.3 The ozone gas permeates the sensor membrane and is
priate safety, health, and environmental practices and deter-
reduced to oxygen and hydroxide ion at the sensor’s cathode at
mine the applicability of regulatory limitations prior to use.
a controlled potential, producing a current flow in direct
1.6 This international standard was developed in accor-
proportion to the partial pressure of ozone in the sample
dance with internationally recognized principles on standard-
outside the membrane.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4.4 The current is correlated with a calibration curve in the
mendations issued by the World Trade Organization Technical
measuring instrument, accounting for temperature effects on
Barriers to Trade (TBT) Committee.
membrane permeation rate and on the solubility of ozone in
water. This correlation provides the conversion from ozone
2. Referenced Documents
partial pressure to concentration.
2.1 ASTM Standards:
4.5 The instrument readout is provided in units of mg/L
D1129 Terminology Relating to Water
(ppm) or μg/L (ppb). For the purposes of this standard, the
1 paired units are considered equivalent.
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.03 on Sampling Water and
5. Significance and Use
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use,
On-Line Water Analysis, and Surveillance of Water.
5.1 Dissolved Ozone is useful in many industries for water
Current edition approved Nov. 1, 2023. Published December 2023. Originally
sanitization, TOC reduction, food preservation, cleaning-in-
approved in 2011. Last previous edition approved in 2016 as D7677 – 16. DOI:
10.1520/D7677-16R23.
place of food and beverage systems, and pyrogen destruction.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
It is often necessary to know how much ozone has entered the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
water, how much remains, and the degree to which it has been
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. removed before process use.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7677 − 16 (2023)
5.2 Some applications require that contact time, DO con- 6.7 Although not a true interference in the measurement
centration integrated over time, be calculated, to assure disin- itself, the rapid decay of ozone to oxygen makes sampling and
fection. calibration especially time dependent. The decay rate is in-
creased greatly at higher temperatures and to some degree at
5.3 Continuous observation of trends in these measurements
higher pH. The half-life of ozone in neutral water is approxi-
are needed for continuous quality monitoring and the measure-
mately 20 minutes at 25 °C.
ment may be used for closed loop control of ozonation.
6.7.1 Sample lines must be short and run at high flow
5.4 In many pure water applications and especially where
velocity to bring a representative sample to the sensor that has
water quality is regulated by the FDA or similar enforcement
not had a significant decrease in ozone concentration.
agencies, ozone removal must be complete before the water is
6.7.2 Where grab samples are taken to establish concentra-
used. This test method is useful for detecting and determining
tion values for calibration, they must be processed quickly to
dissolved ozone levels in water at the trace level as well as at
minimize ozone decay.
process concentrations where sanitization and chemical reac-
7. Apparatus
tions occur.
7.1 Apparatus for Dissolved Ozone Determination—A typi-
cal installation consists of a sampling connection to a process
6. Interferences
line, a sensor with flow housing, a cable connecting the sensor
6.1 This technology is only effective with a flowing sample.
and electronics, and analyzer electronics.
Turbulent flow past the membrane is necessary to continuously
7.1.1 Sampling—The sample can be delivered via a sensor
replenish the ozone that diffuses through the membrane and is
flow housing or cell, or accessed through direct insertion into
consumed in the probe. The replenishment of fresh liquid at the
the process vessel or pipe. Flow through the flow housing must
surface of the membrane ensures representative sampling. The
be continuous during measurements and is typically controlled
required minimum linear velocity is dependent on membrane
by a flow control valve located after the flow housing. A weir
material and thickness and is manufacturer specific. A flow
set up is also acceptable in cases where out-gassing does not
housing designed for the sensor provides the best control of
occur. The weir design requires that the flow control valve be
flow velocity. Follow the manufacturer’s flow rate specifica-
located before the flow housing. Direct insertion probes can be
tions for the flow housing and membrane used.
mounted through a standard T-fitting connection or via an
extraction valve. The valve set up permits the extraction of the
6.2 Interferences are limited to gases which can permeate
probe without interrupting the process flow.
the membrane and react at the cathode or anode. Although
7.1.2 Sensor—The sensor has a body, a membrane, a
many gases can pass through the membrane, only chlorine gas
cathode, an anode, a guard ring electrode (optional), a tem-
has been found to react at the applied potential. However,
perature sensor, and a cable connection to the electronics.
chlorine in high purity water is typically in ionic form which
7.1.2.1 Body—The sensor body should be made of materials
cannot pass through the membrane and so is not usually an
compatible with the process. Common materials of construc-
interference. The exception is that under acidic conditions (pH
tion include PEEK, type 316L stainless steel, and titanium.
<6), chlorinated water can produce dissolved chlorine gas and
7.1.2.2 Membrane—Membranes are composed of a gas
its presence must be minimized to avoid interference.
permeable material that is resistant to process conditions,
6.3 Polarographic ozone sensors must typically be polarized
sometimes reinforced with a fine internal mesh. Common
in the presence of ozone before they can measure reliably and
membrane materials are PFA (PerFluoroAlkoxy), PTFE
be calibrated. The sensor must be connected to the powered
(PolyTetraFluoroEthylene), and Silicone rubber.
measuring instrument to apply the polarization voltage across
7.1.2.3 Cathode—The cathode is the reaction center for
the electrodes while the sensor is in an ozonated sample.
ozone analysis and is exposed to dissolved ozone gas and
Length of time and ozone concentrations needed to achieve full
hydroxyl radicals continuously. The cathode is constructed of
polarization are manufacturer specific.
high purity noble metal such as gold or platinum which resists
6.4 Sample temperature range is dependent on manufacturer ozone degradation.
design and specifications but is generally limited to between 7.1.2.4 Anode—The anode is sacrificial in this method and
requires a metal whose oxidation products will not interfere
0 °C and 50 °C. Temperatures below the freezing point of
water can result in a disturbance of the electrolyte and an with the analysis such as silver which precipitates out of
solution in the presence of halides in the electrolyte.
inability of the sensor to function. Ozone is seldom used in hot
water because the rate of decay to oxygen is too fast to make 7.1.2.5 Guard Ring Electrode—The optional guard ring
electrode surrounding the cathode is charged at the same
it effective.
potential as the cathode and prevents the migration of silver
6.5 Sample pressure must be within manufacturer specifi-
ions back over to the cathode. As the silver passes over the
cations. In some cases varying process pressure can cause
cathode it has a tendency to plate out, causing an increase in
instability.
maintenance frequency as well as a background interference.
6.6 Response time can vary from as little as a few seconds The guard ring electrode can improve stability and response
to a few minutes depending on membrane and sensor design time but does not serve a direct measurement function.
and materials. Time for full response must be allowed, espe- Platinum is typically used since it is resistant to ozone
cially when calibrating. degradation.
D7677 − 16 (2023)
7.1.2.6 Temperature Sensor—Changes in water temperature both the volumetric container and the appropriate quantity of
affect permeation rates through the membrane and require reagent and buffer. In use, the glass ampoule tip is broken off
temperature compensation. Temperature is also used to com- under water in the sample container. The vacuum sucks a
pensate for changing ozone solubility with temperature in the controlled amount of sample into the ampoule where the indigo
conversion of the partial pressure signal to concentration. An and ozone react, producing a color inversely proportional to the
accurate temperature sensor, typically embedded in the head of ozone concentration. Store these ampoules in accordance with
the sensor, is required for proper compensation. manufacturer’s instructions, as they are light, time and heat
7.1.3 Cable—The sensor cable must withstand the environ- sensitive.
mental conditions of the installation and provide continuous 8.3.5 N,N-diethyl-p-phenylenediamine (DPD) Reagent—
high impedance insulation and shielding to carry the low, This reagent is used with other spectrophotometer or colorim-
nanoampere level signal. Installation in dedicated dc signal eter systems and is supplied in manufacturer-specific formula-
conduit is recommended, with proper shielding from electrical tions.
interference. Refer to the manufacturer’s requirements.
8.4 Calibration and Verification Using Air as a
7.1.4 Analyzer Electronics—The measuring circuit applies a
Reference—A certified thermometer and a certified barometer
controlled polarization voltage between the anode and cathode
are used to perform a traceable air calibration.
(and optional guard ring electrode) to promote the ozone
reduction reaction. The sensor’s ozone and temperature signals
9. Hazards
are combined with stored calibration data to compute and
9.1 Ozone gas at high enough concentration is a health
display concentration, as mg/L (ppm) or μg/L (ppb) of DO .
hazard. Areas where dissolved ozone is measured are typically
Data may be accumulated in internal nonvolatile memory, or
near ozone generators and holding tanks that could potentially
exported via analog or digital signals to printer, data acquisi-
leak ozone gas into the ambient atmosphere. Ozone is gener-
tion or control systems.
ally detectable by its characteristic odor at 0.02 to 0.05 ppm by
weight in air although prolonged exposure may cause some
8. Reagents and Materials
desensitization. The OSHA (U.S. Occupational Safety and
8.1 Purity of Water—Reference to water that is used for
Health Administration) limit is 0.1 ppm averaged over 8 hours.
reagent preparation, rinsing or dilution shall be understood to
At least one ambient ozone gas alarm must be on site for safety
mean water that conforms to the quantitative specifications of
of personnel working in the area.
Type II reagent water of Specification D1193.
9.2 Hazardous materials may be used in manufacturer-
8.2 Sensor Electrolyte—A manufacturer-specific electrolyte
recommended sensor maintenance procedures. Sensor and
bathes the anode and cathode to enable the electrochemical
material supplier safety precautions should be observed.
reaction reducing the ozone.
8.3 Calibration and Verification Using a Colorimetric 10. Sampling
Method—Materials or reagents are required for verification or
10.1 Connect the sensor to the sample source in accordance
calibration using a colorimetric method. This method uses a
with Practices D3370 and the instrument manufacturer’s in-
spectrophotometer or colorimeter and either indigo trisulfonate
structions. If any conflict exists in these instructions, give
or N,N-diethyl-p-phenylenediamine (DPD) reagent. Indigo
priority to the manufacture
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