BOD/CBOD/COD

BY: LAUREN STEWART AND RACHEL YOUNG

HENRICO COUNTY CENTRAL ENVIRONMENTAL LABORATORY

http://www.controlglobal.com/articles/2

005/496/

OUTLINE

• MEET THE BOD/CBOD ANALYSIS

• BOD/CBOD SETUP

• COD

• PROBES

• SKALAR

OVERVIEW OF BOD ANALYSIS

• BIOCHEMICAL OXYGEN DEMAND; CARBONACEOUS BOD

• MEASURES OXYGEN CONSUMED BY BACTERIA FROM THE DECOMPOSITION OF

ORGANIC MATTER

• DAY 1: DECHLORINATE AND PH ADJUST IF NECESSARY. DETERMINE DILUTION

SERIES. ADD SEED, NITRIFICATION INHIBITOR IF CBOD, AND DILUTION WATER.

MEASURE INITIAL DO. SAMPLES SHOULD HAVE DO 7-9 mg/L

• INCUBATE AT 20°C FOR 5 DAYS

• DAY 5: READ FINAL DO IN mg/L

THE RESULTS

https://boogersonthewall.com/2014/05/08/bully-fish/

• INITIAL DO SHOULD BE 7-9mg/L

• FINAL DO “TAKE 2, LEAVE 1”

• EACH PERMITTED SAMPLE HAS 4 DILUTIONS,

HOPING THAT AT LEAST 2 WILL BE WITHIN

RANGE

• LOOKING AT DIFFERENTIAL BETWEEN INITIAL

AND FINAL DO. CALCULATION ACCOUNTS

FOR SEED AND mLs OF SAMPLE USED.

• WHY SHOULD WE CARE ABOUT BOD

RESULTS?

FIVE DAYS IS THE

LENGTH OF TIME

IT TOOK FOR

WATER IN RIVER

THAMES TO

FLOW FROM

LONDON TO THE

OCEAN

http://meepandwhatnot.wikia.com/wiki/E.T.

BOD/CBOD SETUP

QC AND BATCH SETUP

• DRIFT CHECKS- CHECK PRECISION OF PROBES

• BLANKS- CHECK DILUTION WATER QUALITY

• SEED- 3 BOTTLES TO CALCULATE SCF (SEED CORRECTION FACTOR)

• GGA- CHECKS ACCURACY OF ANALYSIS

• SAMPLES- ONE DUPLICATE PER BATCH

• SEEDED BLANK- RESULT SHOULD BE SIMILAR TO SCF

SOURCE WATER

• REVERSE OSMOSIS UV DISINFECTION DI SYSTEM

• BIANNUAL MAINTENANCE DONE BY VENDOR

• HIGH HPC RESULTS = FLUSH LINES

• FLUSH LINES WITH DILUTE HYDROGEN

PEROXIDE SOLUTION NOT BLEACH

• HOW TO DETERMINE HOW MUCH DILUTION WATER

NEEDED FOR RUN

• # OF BOTTLES X 300 mLs PER BOTTLE + 2000 mLs

FOR RINSING LINES

• PLACE IN INCUBATOR A DAY BEFORE USE

REVERSE OSMOSIS UV DISINFECTION DI SYSTEM

NUTRIENT PILLOWS

• PURCHASE OR MAKE

• USE 1 mL OF NUTRIENTS PER 1 LITER OF

DI WATER TO MAKE DILUTION WATER

• ADD EXTRA NUTRIENT PILLOW PACK

TO 300 mL BOTTLES

DRIFT CHECK BOTTLES

• BOTTLES FILLED WITH DILUTION WATER – 1 BOTTLE PER PROBE

• FILLED AT BEGINNING OF RUN AND READ AT BEGINNING, EVERY 10 SETS OF

BOTTLES AND AT THE END

• WORKS LIKE A CCV – CHECKS TO MAKE SURE PROBES ARE NOT DRIFTING

THROUGHOUT THE RUN BY RETURNING TO THE SAME BOTTLES

• RECOMMENDED ≤0.2 DIFFERENCE IN INITIAL DO READINGS DURING SETUP

AND FINAL DO READINGS DURING READOFF

NITRIFICATION INHIBITORCBOD: INHIBITS CONVERSION OF AMMONIA (NH3) TO NITRATE (NO3-)

• TCMP

• TRICHLOROMETHYL PYRIDINE

• POWDER NITRIFICATION

• 2 SQUIRTS

• DOESN’T DISSOLVE WELL AND MAY STICK

ON PROBE

• PREFERRED IN SM

Fig 1. http://media.wattswater.com/SS-Nitrification_Inhibitor_literature.pdf

• ATU

• ALLYLTHIOUREA

• LIQUID NITRIFICATION:

300 µLs PER SAMPLE

• 1 G 500 mL DI

• SOLUTION IS STABLE FOR 2

WEEKS

• MORE ACCURATE WHEN

DISPENSING

COMMERCIAL SEED PREPARATION

• MAKE DILUTION WATER

• USE 1 CAPSULE PER 500 mLs

DILUTION WATER

• AERATE FOR 1 HOUR

• LET SETTLE FOR 5-15 MINS AND

DECANT SUPERNATANT

http://polyseed.com/main/polyseed.php

SEED PREPARATION

• STOPPED USING COMMERCIAL SEED – LOW GGA RECOVERY

• UNPRESERVED PRIMARY EFFLUENT AND INFLUENT SAMPLE

POURED OFF THE DAY BEFORE USE AND PLACED IN

INCUBATOR – 1 L OF EACH

• POUR OFF PE SUPERNATANT –TURBIDITY 40 ± 1 NTU; AT OUR

LAB MUST BE 40 ± 5 NTU

• IF PE HAS A HIGH TURBIDITY, DILUTE WITH DI WATER

• IF PE HAS A LOW TURBIDITY, ADD REMAINING PE SAMPLE OR

USE INFLUENT SAMPLE TO BRING UP TURBIDITY

• SEED VOLUMES CHANGE SEASONALLY

GGA

• PURCHASE OR MAKE

• MUST BE 198 ± 30.5 mg/L PER METHOD

• 3 BOTTLES FOR PERMITTED SAMPLES – 1 BOTTLE FOR NON-

PERMITTED

COD

• CHEMICAL OXYGEN DEMAND (COD) IS A MEASURE OF THE OXIDIZABLE

ORGANIC MATTER CONTENT OF A WASTEWATER SAMPLE. THE SAMPLE IS

REACTED WITH AN ACIDIC SOLUTION OF POTASSIUM DICHROMATE IN THE

PRESENCE OF A CATALYST (SILVER) AND DIGESTED. OXIDIZABLE ORGANIC

COMPOUNDS REDUCE THE DICHROMATE ION (CR2O72-) TO THE CHROMIC ION

(CR3+). THE AMOUNT OF CHROMIC ION PRODUCED IS MEASURED AND

EXPRESSED AS THE NUMBER OF MILLIGRAMS OF OXYGEN CONSUMED PER

LITER OF SAMPLE.

COD

• WE ARE NOT CERTIFIED – USE COD VALUES TO HELP DETERMINE BOD/CBOD

DILUTIONS

• USE Hg FREE VIALS

• TEST FOR CHLORIDE

COD

• MAKE DILUTIONS OF STRONG

SAMPLES THAT WILL FIT IN THE 50

mg/L TO 1000 mg/L CURVE

• ADD 2 mLs OF EACH SAMPLE TO VIAL

• DIGEST FOR 2 HOURS AT 150°C

• READ ON HACH DR4000 SPEC

BOD/CBOD DILUTIONS

• 4 DILUTIONS FOR PERMITTED

SAMPLES

• 3 DILUTIONS FOR NON-

PERMITTED SAMPLES

COD DILUTIONS TO SKALAR

COD DILUTIONS TO SKALAR

COD DILUTIONS TO SKALAR

COD DILUTIONS TO SKALAR

PROBESMEMBRANE AND LUMINESCENT

MEMBRANE PROBE

FIG 1. YSI HTTPS://WWW.YSI.COM/FILE%20LIBRARY/DOCUMENTS/TECHNICAL%20NOTES/T605-ACCURATE-BOD-MEASUREMENTS-WITH-ELECTROCHEMICAL-AND-OPTICAL-PROBES.PDF

• ELECTROCHEMICAL

• TWO METAL ELECTRODES WITH

SUPPORTING ELECTROLYTE

SEPARATED BY GAS PERMEABLE

MEMBRANE. O2 DIFFUSES AND

REDUCED AT CATHODE BY

VOLTAGE

LUMINESCENT PROBE

• FLUORESCENT FILM SENSITIVE TO

O2. CHANGES IN FLUORESCENCE

ACTIVITY PROPORTIONAL TO O2

CONCENTRATION

• O2 NOT CONSUMED

FIG 2. HACH HTTP://WWW.HACH.COM/POWERLDO

THE LDO PROBE

USES THE SAME

TECHNOLOGY AS

A PULSOX METER

http://meepandwhatnot.wikia.com/wiki/E.T.

CALIBRATING

• RINSE WITH DI, BLOT DRY, WAIT 30 MINUTES. MAKE SURE THERE ARE NO

WATER DROPLETS ON THE MEMBRANE.

• MEMBRANE PROBE NEEDS TIME TO POLARIZE

• NO WARMUP PERIOD FOR LDO

Calibration Verification:

8.83 @ 21.5oC

8.83 x 0.999 = 8.82

ZERO SOLUTION

• IMMERSE THE PROBE IN SODIUM SULFITE SOLUTION OR WATER

THAT HAS INERT GAS (N, AR) BUBBLING THROUGH IT. METER

SHOULD READ <1% DO.

MEMBRANE PROBE MAINTENANCE

• ELECTROLYTE REPLACEMENT: ABOUT 2-4 WEEKS

• MEMBRANE LIFE: AVG REPLACEMENT IS 2-4 WEEKS

• REMOVE MEMBRANE AND RINSE OFF PROBE EVERY 1-3MTH. EACH

CLEANING REMOVES MATERIALS SO AVOID EXCESSIVE CLEANING

• AS NEEDED: SOAK IN 14% AMMONIUM HYDROXIDE 2-3MIN OR

OVERNIGHT IN 3%. RINSE WITH DI WATER, RECHARGE WITH ELECTROLYTE,

AND INSTALL A NEW MEMBRANE.

• AS NEEDED: POLISH DISK FOR DULL FINISHES.

• TURN OFF OVERNIGHT

POLISHING

SILVER ANODE, FROM WHERE CURRENT IS SENT OUT, SHOULD BE SILVER-LOOKING

Silver

Anode

Gold

cathode

YSI https://www.ysi.com/File%20Library/Documents/Technical%20Notes/T605-Accurate-BOD-Measurements-with-Electrochemical-and-Optical-Probes.pdf

LDO MAINTENANCE

• CLEANING SENSOR CAP: USE DI AND KIMWIPE.

RINSE WITH 3% HYDROGEN PEROXIDE TO DISINFECT AND MILD DISH

DETERGENT TO CLEAN AS NEEDED; RINSE WITH DI WATER.

• SENSOR CAP WILL NEED TO BE REPLACED ABOUT ONCE PER YEAR

TROUBLESHOOTING

Issues Membrane LDO

Calibration

difficulty

Wait up to 30 minutes to allow

membrane to polarize

Make sure there aren’t water droplets

Change membrane & solution

Clean probe

Verify calibration coefficients were entered

correctly

Make sure there aren’t water droplets

Clean sensor cap

Rehydrate sensor cap

Replace sensor cap (ensure cavity is dry)

Unstable readings Allow sufficient time for

stabilization (at least 1 min)

Change membrane & solution

Clean probe

Clean sensor cap

Rehydrate sensor cap

Replace sensor cap

Erroneous readings

(jumpy readings,

drifting)

Ensure stir paddle is working correctly

Change membrane & solution

Clean probe

Remove sensor cap and inspect for cracks or

damage

Inspect O-Ring and gasket for damage

Rehydrate sensor cap

Replace sensor cap

SHORT TERM STORAGE

• LDO STORAGE:

• BOD BOTTLE CONTAINING ~ 80 mL OF WATER.

• MEMBRANE STORAGE:

• BOD BOTTLE CONTAINING AT LEAST 1 INCH OF WATER.

LONG TERM STORAGE

MEMBRANE STORAGE:

• REMOVE MEMBRANE CAP, RINSE WITH DI, INSTALL DRY

MEMBRANE (NO ELECTROLYTE SOLUTION)

LDO STORAGE:

• MOISTEN THE SPONGE IN CAP THAT WAS PROVIDED WITH

THE PROBE AND PLACE IT OVER THE SENSOR WITH THE

SENSOR CAP INSTALLED.

• OR PLACE PROBE WITH SENSOR CAP DIRECTLY IN BEAKER

NEW SENSOR CAP. SAVE SPONGE AND SLEEVE.

SKALAR SP1000

MANUAL VS. INSTRUMENT

Manual Instrument

1 probe 1 or more probes

Pour sample, seed, NI, dilution water, GGA Pour samples and GGA – Skalar does the

rest

Wait for each sample to stabilize Instrument has settings to stabilize – analyst

can walk away (can stabilize for up to 3

mins)

Room for error when recording DO values Records DO values directly from probes

Manually record and track changes or

issues throughout the run

Automatically keeps track of changes and

errors throughout the run

SKALAR MAINTENANCE

PROBE MAINTENANCE• DAILY

• RINSE WITH DI AND BLOT DRY

• CALIBRATE WITH 1 POINT CALIBRATION

• QUARTERLY

• VERIFY BAROMETRIC PRESSURE WITH RIC

(AS NEEDED)

• CHECK PROBE ALIGNMENT

• YEARLY

• CALIBRATE TEMPERATURE (AS NEEDED)

• CHANGE SENSOR CAPS

• AS NEEDED

• CLEAN CAPS WITH MILD SOAP

DETERGENT

BAROMETRIC PRESSURE

• BAROMETRIC PRESSURE (ATMOSPHERIC PRESSURE) IS THE PRESSURE EXERTED BY

THE WEIGHT OF THE AIR IN THE ATMOSPHERE OF EARTH

• VARIES WITH ALTITUDE AND MOISTURE

• DECREASES WITH INCREASING ELEVATION

• WEBSITE TO FIND BAROMETRIC PRESSURE AT RIC

• HTTP://VDEM-RICHMONDVA.ALERTEAGLE.COM/HISTORYBAROMETER.ASPX

PUMP MAINTENANCE

• 6 MONTHS

• CHANGE PUMP TUBING

POSITION

• YEARLY

• REPLACE PUMP TUBING

RINSE WELL MAINTENANCE

• DAILY

• EMPTY

• WEEKLY

• CLEAN RINSE WELLS

SEED LINE MAINTENANCE

• DAILY

• RINSE ALL LINES WITH HOT TAP WATER, DI

WATER AND AIR

• 6 MONTHS

• CLEAN SEED LINES WITH 1-2% BLEACH

SOLUTION AND RINSE WITH SODIUM

THIOSULFATE SOLUTION (AS NEEDED)

• YEARLY

• REPLACE LINES (AS NEEDED)

CLEAN SEED LINES

• REMOVE SEED LINES AND PROBES FROM SKALAR

• PREPARE 1-2% BLEACH SOLUTION

• ADD BLEACH SOLUTION TO LINES AND ALLOW TO SIT FOR 15

MINS; REPEAT UNTIL LINES ARE CLEAR

• RINSE LINES WITH DI AND A SODIUM THIOSULFATE SOLUTION

• ATTACH LINES TO SKALAR AND RINSE WITH DI

• CHECK TRC – REPEAT SODIUM THIOSULFATE RINSE AND DI RINSE

UNTIL TRC IS <0.05 mg/L

SYRINGE MAINTENANCE

• DAILY

• VERIFY SYRINGES ARE WORKING

PROPERLY

• YEARLY

• VERIFY SYRINGE DISPENSE VOLUMES

FOR SEED AND ATU

• AS NEEDED

• REPLACE/REPAIR SYRINGES (EX.

GASKET/PLUNGER)

ERROR CODES

• DO1U UNSTABLE DO READING DAY1

• DO5U UNSTABLE DO READING DAY5

• RECHECK CALIBRATION CHECK HAS FAILED THE FIRST TIME

• CALFAIL CALIBRATION CHECK HAS FAILED THE SECOND TIME, ABORTING RUN

• FE FILL ERROR - BOTTLE NOT FULL AFTER ALLOWED TIME.

• SATE SATURATION ERROR, DO>120%

TROUBLESHOOTING

• DO NOT WRITE SEQUENCES

WHILE THE SKALAR IS SETTING UP

A RUN OR READING OFF A RUN

• MAKE TEMPLATES

• KEEP RINSE WELLS CLEAN

• KEEP SEED LINES CLEAN

http://dnr.wi.gov/regulations/labce

rt/BODAbout.html

CALCULATIONS• SEED CORRECTION FACTOR:

INDIVIDUAL SEED CORRECTION FACTOR = ______(INITIAL D.O. – FINAL D.O.)_____

(mL OF SEED IN SEED CORRECTION BOTTLE)

• AVERAGE THE VALUES FROM THE EQUATION ABOVE FOR THE THREE SEED CORRECTION SAMPLES RUN. DETERMINE THE

SEED CORRECTION AS FOLLOWS:

SEED CORRECTION FACTOR = AVERAGE × (mL OF SEED ADDED TO SAMPLE BOTTLES)

• UNSEEDED BLANKS:

BOD5 = INITIAL D.O. – FINAL D.O.

• GGA STANDARD (ASSUMING 6 mL OF GGA USED):

[(INITIAL DO – FINAL DO) – (SEED CORRECTION FACTOR)] X 50 = GGA VALUE

• SEEDED SAMPLES:

BOD5 = ((INITIAL DO – FINAL DO) – SEED CORRECTION FACTOR) X 300

(mL SAMPLE USED)

• IF ANY SAMPLES HAVE A SEED CORRECTED DIFFERENCE <1 mg/L, EXCLUDE THIS RESULT FROM FURTHER CALCULATIONS

FOR NOT MEETING CRITERIA.

REFERENCES

• STANDARD METHODS 5210B-2011

• HENRICO COUNTY SOP #16 BOD-CBOD REV 2.0

• YSI PRO-ODO USER MANUAL

• YSI MEMBRANE PROBE INSTRUCTION MANUAL

• HTTP://WWW.POLYSEED.COM/USERS/APPLICATION_PROCEDURES.PHP

• SKALAR MANUAL

• “A BIRDS-EYE VIEW OF THE BOD TEST” BY PERRY BLAKE, JANUARY 2007

QUESTIONS??

www.examprofessor.com

www.stevehackman.net