ASTM_D_7677_-_11.pdf

Designation:D767711Standard Test Method for theContinuous Measurement of Dissolved Ozone in LowConductivity Water1This standard is issued under the fixed designation D7677;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the on-line and in-line determi-nation of dissolved ozone(DO3)in low conductivity water inthe range from 0.001 mg/L to 5.0 mg/L DO3and conductivity 100 S/cm,typical of pharmaceutical and microelectronicspure waters.DO3is detected by correlating the response of amembrane-covered electrochemical sensor to the dissolvedozone concentration.1.2 This test method provides a more convenient means forcontinuous measurement than the colorimetric methods typi-cally used for grab sample measurements.1.3 This test method has the advantage of high sensitivity aswell as durability in the process environment and has fewinterferences.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed Conduits3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to.3.2 Definitions of Terms Specific to This Standard:3.2.1 dissolved ozone(DO3),nOzone is the tri-atomicform of oxygen and,when dissolved in water,is uniformlydispersed and remains in molecular form.4.Summary of Test Method4.1 Dissolved ozone measurements are made on a flowingwater sample containing dissolved ozone gas.4.2 The sensor flow housing is connected to a process-watersample line or the sensor probe is inserted into a pipe or vesselwith flowing water.4.3 The ozone gas permeates the sensor membrane and isreduced to oxygen and hydroxide ion at the sensors cathode ata controlled potential of approximately+350 mV,producing acurrent flow in direct proportion to the partial pressure of ozonein the sample outside the membrane.4.4 The current is correlated with a calibration curve in themeasuring instrument,accounting for temperature effects onmembrane permeation rate and on the solubility of ozone inwater.This correlation provides the conversion from ozonepartial pressure to concentration.4.5 The instrument readout is provided in units of mg/L(ppm)or g/L(ppb).For the purposes of this standard,thepaired units are considered equivalent.5.Significance and Use5.1 Dissolved Ozone is useful in many industries for watersanitization,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 thewater,how much remains,and the degree to which it has beenremoved before process use.5.2 Some applications require that contact time,DO3con-centration integrated over time,be calculated,to assure disin-fection.5.3 Continuous observation of trends in these measurementsare needed for continuous quality monitoring and the measure-ment may be used for closed loop control of ozonation.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits.Current edition approved Feb.1,2011.Published March 2011.DOI:10.1520/D767711.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.4 In many pure water applications and especially wherewater quality is regulated by the FDA or similar enforcementagencies,ozone removal must be complete before the water isused.This test method is useful for detecting and determiningdissolved ozone levels in water at the trace level as well as atprocess concentrations where sanitization and chemical reac-tions occur.6.Interferences6.1 This technology is only effective with a flowing sample.Turbulent flow past the membrane is necessary to continuouslyreplenish the ozone that diffuses through the membrane and isconsumed in the probe.The replenishment of fresh liquid at thesurface of the membrane ensures representative sampling.Therequired minimum linear velocity i