bod testing technologies

8/8/2019 BOD Testing Technologies

http://slidepdf.com/reader/full/bod-testing-technologies 1/4

BOD testing

BOD testing technologies

®



BOD testingtechnology

Biochemical oxygendemand, BOD,

measures the amount

o oxygen consumed

by microorganisms

when decomposing

organic matter. BOD

also measures the

chemical oxidation

o inorganic matter

(i.e., the extraction o

oxygen rom water via chemical reaction).

The BOD test used to

measure the amount

o oxygen consumed

by these organisms

can occasionally

give operators some

trouble.

Breiy, the BOD test

consists o an initialand fnal DO reading.

There are several

actors that can aect

accurate initial and

fnal readings. For

greatest success in

your BOD test, ensure

that the probe is cared

or and used properly,

the instrument is

properly calibrated,and gool lab practices

are always ollowed.

Feel ree to visit

www.YSI.com/BOD

to download a Tech

Note entitled How

to Ensure Accurate

and Successful BOD

Measurements .

Vertical proler datadisplay changes in water qualitythroughout the water columnover time. The data at rightshow a stratied water columnand the impacts of an aerationsystem on dissolved oxygen.

Choosing the right sen-sor/technology or mea-

suring dissolved oxygen(BODs) depends mainlyon the preerence o thelaboratory personnel.Optical, luminescenttechnology is gainingwider acceptance overtraditional electrochemi-cal (membrane covered)sensors due to severalactors.

Accuracy: optical sen-

sors are more accuratethan membrane coveredsensors. This beneitis realized with yourblanks. Optical DOsensors have a mg/Laccuracy o +/-0.1mg/L greatly improvingthe chances o blanksnot exceeding the+/-0.2 mg/L thresholdlevel.

Stability: YSI sensorsmeasure the lietime o

the luminescence as it isaected by the presenceo oxygen with a photo-diode in the probe andcompares that readingto a reerence. Whatthis means or you is amore stable DO readingcalculated by the probebased on a highly stablereerence.

Maintenance: optical

technology eliminatesthe need or membranereplacements andanode and cathodemaintenance. Eventhough cap membranesonly take seconds tochange, they can stillcause issues. In addi-tion, since optical sen-sors don’t have anodesor cathodes there is

no sanding or soakingrequired. The optical

sensor only requiresthat its sensor cap bereplaced every 12-18months. The YSI OBODprobe has a protectivesensor guard to preventthe paint layer rombeing scratched whenmoving rom BOD bottleto BOD bottle.

Approval: EPAapproval o changesmade to ASTM D888-0include the addition oTest Method C, whichapproves the use oluminescence-based optcal sensors or dissolvedoxygen measurementor all EPA-regulatedNPDES, BOD andCBOD measurements.

Optical Technology

Sensor Theory - OpticalBriey, this technology utilizes optical, luminescenorder to determine dissolved oxygen values. Te opeld probes and OBODM laboratory BOD probe work in the same manner.

Te optical DO probe measures dissolved oxygeemitting a blue light o the proper wavelength that cthe sensing element to luminesce, or glow red. Oxdissolved in the sample continually passes througdiusion layer to the luminiphore layer, aectin

luminescence in both intensity and lietime. Tesensor measures lietime o the luminescence asaected by the presence o oxygen with a photod(light detector) in the probe and compares that reato a reerence.



8 0 0 7 6 5 4 9 7 4

+ 1 9 3 7 7 6 7 7 2 4 1

w w w . y s i . c o m

Electrochemical Technology

In 1956, Dr. LelandClark invented the irst

polarographic electrodewhile working with YSIscientists to develop theirst DO electrode thatwas protected rom themedium with a mem-brane. In 1963, thistechnology was irst com-mercialized by YSI as aportable DO instrument.

Electrochemical technol-ogy includes both pola-rographic and galvanicsensors.

Accuracy: typicalelectrochemical sensorshave an accuracy speco +/-0.2 mg/L. Be sureto review the system spec i comparing products.Some manuacturersonly state the instrument

spec without the probe/cable.

Stirring: electrochemi-cal sensors require stir-ring o the sample inorder to overcome theconsumption o oxygenat the membrane’s sur-ace. The polarograph-ic BOD probes have abuilt-in stirrer to providesuicient low past themembrane. The opti-cal BOD probe’s havea stirrer to improve theresponse time. Stirringalso ensures a repre-sentative sample in thebottle.

Maintenance: themembrane needsreplaced approximatelyevery 2-8 weeks andthe anode and cathode

Data Troubles

When encountering aproblem with BOD values,most operators blame theinstrument or probe irst.Ater all, it’s what gives youthe values! There can bemany actors leading to theproblem rom dirty BODbottles, DI water, bad seed,bubbles, non-linearity andso on.

Calibration: Regardlesso technology, it is recom-mended to only calibratethe instrument once a daybeore readings are taken.Make sure there are nowater droplets on the probetip beore calibrating andthat the probe is in a 100%water-saturated air environ-ment. A BOD bottle witha little water in the bottom

is all that’s needed. Placethe probe back in this bottlewhen not in use.

Probe Care: Polarographicsensors must have reshelectrolyte and membranesalong with a maintainedanode and cathode or opti-mal perormance. Opticalsensors will need an occa-sional visual check o thepaint layer on the sensor

cap.

Warm-Up Time:Polarographic probesrequire suicient warm-uptime o 5-15 minutes beorecalibrating and using theprobe. Improper warm-uptime can easily lead to datadriting due to an inaccuratecalibration. Optical probesdo not require a warm-upperiod.

need occasional main-tenance (sanding and/

or soaking) in order toprovide optical peror-mance, stability andaccuracy.

Warm-Up Time: theYSI BOD probes usepolarographic sensorsand require a period otime to warm-up beoreusing. In order to savethe working lie o theprobe, it is recommend-ed that the instrument beturned o overnight butthis will require a warm-up time between 5-15minutes in the morningbeore the probe andinstrument can be cali-brated.

Sensor Theory - ElectrochemicalBriely, the electrochemical technology utilizes a gold cathode, silver anode,electrolyte solution, and elon® orPolyetheylene (PE) membrane in order tocreate a potential across the membraneto measure dissolved oxygen. Te oxygenmolecules are consumed at the gold cathodeafer a voltage is applied rom the silveranode. In essence, the diusion rate o oxygen across the membrane is measured.Te amount o oxygen diusing throughthe membrane is proportional to the partialpressure o oxygen outside the membrane.



To order or or moreinormation,

contact YSI.

YSI Inc.+1 937 767 7241800 765 [email protected]

YSI is a global companywith oces world wide.Please eel ree to visitYSI.com/contact-us to locate a local oce.

ProODO and We Know DO aretrademarks o YSI Incorporated.

Tefon is a trademakr od DuPont.

©2010 YSI Incorporated

W70 0910

®

* International probe versions available.

Optical BOD

OptionOrder ProODO Instrument Item #626281 (instrument includes Data Manager desktop sotware and thePro Comm II communications saddle or data transer)

Order Optical BOD Probe Item #626400 (U.S. version with U.S. power supply)orOrder Optical BOD Probe Item #626401 (International version with SAA, EU and BS international out-let adapters and UK BOD unnel adapter)

Polarographic BOD (several options listed below)

Option #1

Order Proessional Plus Instrument Item #6050000 (instrument includes Data Manager desktop sot-ware and the Pro Comm II communications saddle or data transer)

Order ProBOD Polarographic BOD Probe Item #605780 (U.S. or international power supply)

Option #2Order Pro20 Instrument Item #6050020

Order ProBOD Polarographic BOD Probe Item #605780 (U.S. or international power supply)

Option #3Order 5000 Instrument Item #050022 (U.S. version with 115V power supply)

orOrder 5000 Instrument Item #050023 (International version with 230V power supply)

Order Polarographic BOD Probe Item #050102*

Option #4Order 5000 Instrument Item #051004 (U.S. version with 115V power supply)orOrder 5100 Instrument Item #051005 (International version with 230V power supply)

Order Polarographic BOD Probe Item #050102*

BOD Instrument and Probe Ordering Guide

Find our videos at youtube.com/ysiinc

Follow us attwitter.com/YSIinc

Friend us atacebook.com/myYSI

YSI BOD Analyst Pro desktop sotware may beone o the easiest ways to ensure convenient,accurate BOD calculations. Taking human errorout o the BOD calculations increases repeatabil-ity and improves QA/QC assurance.

Order item #625120

bod testing technologies

Documents