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BOD and COD Measurem ent
What is the correlation?
November 15, 2011
Derek Walker, Applications Development ManagerMick Dollenmayer, Regional Sales Manager
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Agenda
1. pp cat ons or an measurement
2. COD and BOD: What are we really measuring?
.
4. Understanding plant baselines and trends
5. Correlation between COD and BOD measurement
6. Question and Answer Session
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Why m easure BOD and COD?
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Why m easure BOD and COD?
Evaluate the efficiency of treatment process and removal
Effluent impact to receiving waters low oxygen demand
For rocess control:
Activated sludge process: do we have enough O2?
Food / Biomass ratios vance rea men processes
Any other reasons?
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What are w e m easur ing w i t h BOD and COD?
BOD (biochemical oxygen demand): a measureof oxygen demand occurring when bacteria
Oxygen depleted by microorganisms (bugs)found in a water sample
reng o e was e s ream
demand of a sample that is susceptible to oxidation by astrong chemical oxidant
xygen ep e e y c em ca ox a on
Organics: carbohydrates (sugars/cellulose), proteins, hydrocarbons
5from waste streams
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How do w e Measure Organ ics?
SAC (UV254)
Mineral Oils
BODCOD TOC
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Are Al l Met hods Equal?
T e Definition Accurac *
BODBio-available organics and other compounds that can be
oxidized through consumption of dissolved oxygen15%
-
CBOD
prevent nitrogen oxidation through consumption ofdissolved oxygen 15%
Chemical ox en demand, measurin the reduction of
COD (Cr) chromium: Cr2O72- (orange-colored) Cr3+ (green-
colored)
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Biggest Issues w i t h Organic Measur ing
BOD: Is there anything that is good about it?
Comparing BOD, TOC, UV, COD: can this be done?
Can it be used to tune the food to microorganism ratio
(F/M)?
Waiting 2 hours or 5 days doesnt allow me to see what is
com ng n o my p an r g now, ow o now ave alarge organic slug?
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BOD & c BOD
Average number of hours/week a typical WW facilityspends on BOD? 15 hours
Average number of bottles set per week for BOD? 21 bottles
Average number of times per week BOD is run? 2 sets
Percent of BOD tests that FAIL to meet StandardMethods Guidelines?
5-10%
Industrial waste streams or slugs can also beproblematic for the BOD test!
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Issues and Root Causes
Failure Key Root Cause(s)
Blank depletion Organic contamination indilution water or bottles
Effluent fails to achieve 2
ppm depletion
Insufficient nutrient or seed
Toxicity
Fail G/GA referenceInaccurate G/GAToxicity
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Tim et he Ac hi l les Heel o f
=
COD = 2-3 Hour Procedure
COD not affected by industrial/toxicsamp es
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Chem ic a l Ox ygen Dem and
COD is a measure of the oxygen demand of asamp e a s suscep e o ox a on y a s rongchemical oxidant
Digestion required: 2 hours @ 150 C
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Com m on Uses o f COD
How do ou use COD??
Food estimate?
Tracking industrial dischargers?
An one char in industrialdischarges based on COD insteadof BOD?
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COD Met hods
Dichromate micro digestion (0.7 15,000 mg/L COD)
Dichromate = strong oxidizer; good digestion
Interference from chlorides occurs > 2,000 mg/L
Mercury waste must be disposed of properly and recycled
Manganese III micro digestion (25 1,000 mg/L COD) ercury ree reagen eas er o spose o
Mn III is not as strong of an organic oxidizer
Chlorides can be removed via precipitation with silver salts,filtered, or centrifuged
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Plant Basel ines, Trends, andCorre la t ions
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Organic s Trend = Load Equal izat ion
400
Inlet of plant
Equalisation to
aeration
200
300
(UV)[m
g/l]
0
100BO
Target: Steady loading to the aeration basin
time [h]
->optimal denitrification and biological phosphorus removal
Solution: - Bypass the primary clarifier during low loading
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Can w e mak e cor re la t ions?
True or False? There is NO general correlation
However:
Correlations can be made on samples with consistent
composition can e use o es ma e eve s
Useful relationships can be made for some samples
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What c or rela t ions are useful?
Standards
Some influent streams, if consistent! Is our influent consistent?
COD: Use to estimate BOD to calculate
required dilutions
,results, and proficiencies
Recommended by Standard Methods!20
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BOD:COD Ex am ple
New Belgium Brewery
BOD removal before dischargingto municipality
Uses COD for daily processcontrol
COD:BOD ratio usually 100:1 for influent, 10:1 effluent
COD #1 parameter used to give operators the big picture
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COD for Rapid Organic Est im at es
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Tak e Hom e Messages
BOD and COD evaluate the efficiency of treatment
COD can be a time saver and is not affected b toxicit
Correlations can be made on samples with consistentcomposition for process control
: ra os can e a grea way o assess resu s oBOD test and proficiency samples!
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An i n ?
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Produc t s for BOD
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LDO fo r BOD
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LDO Met hod Approval
Green: Approved - No data needed
Blue: Approved with Performance Data* - Est. total time 2-8 Lab hrs/ 30-90 days
Orange: Tier 1 Submission
28http://www.hach.com/hqdguide-do
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The COD Prob lem Wast e
EZ COD recycling
Heritage Environmental will pickup and recycle
Mercury Free CODTNTplus packaging
Not EPA approved
Only for low-chloride waters
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Produc t s for COD
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Com parison be t w een
G a n g l in i e n v e r g l e i c h d e r G e r t e T O C T A X u n d U V A S p l u s
a m A b l a u f e i n e r V o r k l r u n g
1 6 0
uv]
m g / l T O C ( T O C T A X ) m g / l D O C u v ( U V A S p lu s )
G a n g l in i e n v e r g l e i c h d e r G e r t e T O C T A X u n d U V A S p l u s
a m A b l a u f e i n e r V o r k l r u n g
1 6 0
uv]
m g / l T O C ( T O C T A X ) m g / l D O C u v ( U V A S p lu s )
6 0
8 0
1 0 0
1 2 0
1 4 0
on[mg/lTOCbzw
.mg/lDOC
6 0
8 0
1 0 0
1 2 0
1 4 0
on[mg/lTOCbzw
.mg/lDOC
SAC / TOC
Primary Effluent
0
2 0
4 0
2 8 . S e p 2 9 . S e p 3 0 . S e p 1 . O k t 2 . O k t 3 . O k t 4 . O k t
Konzentrati
0
2 0
4 0
2 8 . S e p 2 9 . S e p 3 0 . S e p 1 . O k t 2 . O k t 3 . O k t 4 . O k t
Konzentrati
300
400
500
30
40
50
CSB [mg/l] SAK [1/m]
300
400
500
30
40
50
CSB [mg/l] SAK [1/m]
SAC / CODRaw Influent
particulate COD
0
100
200
0 24 48 72 96 120
0
10
20
t [h]0
100
200
0 24 48 72 96 120
0
10
20
t [h]
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