Screening parameters in water analysis
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Transcript of Screening parameters in water analysis
Screening parameters in water analysis
31.08.2015
Ralf Dunsbach
Webinar
The elementargroup – About us
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• The technology leader in
• Elemental Analysis (EA)
• Isotope Ratio Mass Spectrometry (IRMS)
• Offers an unmatched combination of
• innovative technologies,
• tailor-made solutions and
• comprehensive support.
The elementargroup – Key Markets
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AgricultureChemicals EnvironmentalEnergy MaterialsForensics
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Tailor-Made to Customer Needs
• Elemental analyzer optimized for different analytical tasks
• vario Series - Industry-leading versatility in elemental analysis
• rapid Series - Dedicated instruments serving today’s customer needs
• trace Series - Trace-level detection of elements
• TOC Series - Fast and easy determination of total organic carbon
Screening parameters in water analysis
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Water analysis
The main focus within environmental analysis is the subject of water. Our instruments are used to carry out routine analysis of organic impurities in the water industry.
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Introduction
H2O Contains
• Inorganic compounds (salts like NaCl)
• Organic compounds (humic substances + man-made waste)
Only 0,3% of the global water resources is availble as drinking water
Water protection, technology and analysis gain more and more importance!
One of the most important quality criteria for water is Pollution with organic compounds
How to determine organic pollutants
Pollution with organic compounds - how to determine?
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Single compound analysis
by chromatographic methods?
Drawback:
Nearly impossible due to the huge number of possible compounds – applicable only for certain classes of substances (e.g. polycyclic aromatic hydrocarbons)
Screening parameter analysis
for all organic compounds
- BODx - biological oxygen
demand
- COD - chemical oxygen
demand
- TOC -total organic carbon
How to determine organic pollutants
BODx and CSB are indirect methods to determine the amount of
organic carbon by the determination of the biological and chemical oxygen demand during the decomposition of its compounds.
Disadvantage:• slow
• insufficient or wrong oxidation
• depending from biological activity
• heavy metal containing reagents
• no automation
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BOD5 - biological oxygen demand after 5 days
DIN 38 409 H51DIN 38 409 H52
Disadvantage:
particulates are not sufficiently oxidized slow (5 days)
Reference: Fonds der chemischen Industrie - Umweltbereich Wasser
BOD
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DIN 38 409 H41
Disadvantage:
higher or fluctuating results, if dichromate is consumed due to the oxidation of sulfur containing compounds
Reagents:concentrated sulfuric acid H2SO4 – corrosive!potassium dichromate K2Cr2O7 - toxic!mercury substance (masking of chloride) – toxic!
Analysis time: > 2 hours, automation very difficult
Dichromate out of use in EU latest 2017!!
Reference: Fonds der chemischen Industrie - Umweltbereich Wasser
COD
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Recovery rates COD
According to Janicke (WaBoLu report 1/1983):
n-hexane 2% Urea 82%
Cyclohexane 5% benzene 63%
Chloromethane 8% EDTA 78%
Trimethylamine 1% starch 91%
Nicotinic acid 12% stearic acid 60%
Poor recovery for alcanes, amines
False COD readings
• High false readings by chlorides, bromides, iodides, certain sulfur compounds, nitrites and certain metal compounds
• False low readings by chromium (VI)-compounds, nitrates, peroxides
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TOC
EN 1484 - European Standard Water analysis - Guidlines for the determination of the total organic carbon (TOC) and dissolved organic carbon (DOC)
The EN 1484 approves the determination of TOC and DOC as appropriate method to determine the contamination of water with organic compounds.
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R-C + O2 CO2 + H2O + further products
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TC
TC [total Carbon] = TIC [total inorganic carbon] + TOC [total organic carbon]
TOC = POC [purgable organic carbon] + NPOC [non-purgable organic carbon]
TOC + TIC
POC + NPOC
TOC
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TC [total Carbon] Oxidation
Detection
Sample [R-C-R + CO3 2-] + O2 CO2 + H2O + ...
Total carbon can be determined by oxidation and decomposition of the sample and detection of the deriving CO2
How to determine TC
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Detection
Acidified Sample: CO3 2- + 3 H+ CO2 + H3O+
TIC
Total inorganic carbon can be determined by degradation of the carbonates by acid, purging and detection of the deriving CO2
Gas
How to determine TIC
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NPOC [total Carbon] Oxidation
Detection
Acidified and purged Sample [R-C-R ]
Non-Purgable Organic Carbon can be determined by purging the acidified sample in advance to remove TIC and POC, oxidation of the remaining components and detection of the deriving CO2
Oxidation: R-C-R(non vol.) + O2 CO2 + H2O + ...
Purging: [R-C-R (volatile and non volatile) + CO3 2-] + 3 H+ CO2 + H3O+ + R-C-R (vol.)
if POC = 0
NPOC = TOC
How to determine NPOC
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Method Advantages Disadvantages
Differential:
TOC=TC - TIC
includes volatile organic compounds
Less suitable for high TIC concentrations
(TOC << TIC)
long measuring times
Direct: NPOC
Non-purgeable organic carbon = TOC in case no volatile compounds are present
suitable for high TIC concentrations
(TIC >> TOC)
fast results
Does not include volatile organic compounds if
present in the sample
How to determine TOC
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EN 1484 - European Standard
Determination of TOC and DOC by:
• Wet chemical - UV-persulfat method (DOC only)
• Combustion method
How to determine TOC
How to determine TOC
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Wet chemical - UV-persulfat method
Quelle: Deutschen Bundesstiftung Umwelt (DBU)
R-C + O2 CO2 + H2O + further productsUV-light +oxidation agent
Advantage:• large sample volume (up to 20mL)• high sensitivity
Disadvantage:• insufficient oxidation of particulates• not applicable for electrolytes or
chlorine containing samples• not for highly contaminated samples • not for solid samples• not for nitrogen
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Combustion method
R-C + O2 CO2 + H2O + further products
Advantage:• quantitative oxidation of all carbon
containing compounds• low matrix influence• applicable for waste water and solids• applicable for TNb as additional parameter
Disadvantage:• lower injection volume• problematically with salts• lower sensitivity
High temperature in presence of catalyst
How to determine TOC
State-of-the-art TOC analyzer
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The Concept
Easy maintenance
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• Temperatur programmable up to 1100°C
• Matrix separation (patent pending) to keep salt away from the catalyst
• Multiway valve on top of the combustion tube for fast and easy injection
• All maintenance parts easily accessible
Solids analysis
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• Only TOC in water analyzer worldwide with automatic sample feeder for solids
• Sample feeding by reliable ball valve technique
• Sample carousel with 80-120 positions
• Solids expansion kit for carbon amounts up to 20mg C abs.
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Drinking water: 0.5 ppm – 2 ppm TOC
Surface waters: 0.5 ppm – 10 ppm TOC
Waste waters: 5 ppm – 10,000 ppm TOC
Waste and soil: upper ppm to percentage range of TOC
Waters in pharmacy: 0.05 – 0.5 ppm TOC
Waters in power plants: 0.05 – 1 ppm TOC
Waters in semiconductor industries: 0.005 – 0.5 ppm TOC
Typical TOC contents
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Correlation TOC/COD
Oxalic acid
Ethanol
Both compounds have the same TOC (in mol/l), but COD is 5* higher than oxalic acid.
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COD/TOC of certain compounds
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COD/TOC in different samples I
Origin COD/TOC SD
Influent MWWTP <1000 r 3,23 0,42
Influent MWWTP 1000-5000 r 3,16 0,41
Influent MWWTP 5000-10000 r 2,99 0,37
Influent MWWTP 10000-100000 r 2,99 0,37
Influent MWWTP >100000 r 2,92 0,39
Edible oil refinery 3,64 0,70
Fish processing 3,51 0,45
Meat industry 3,26 0,41
Glue production 4,28 1,62
MWWTP: municipal waste water treatment plant
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COD/TOC in different samples II
Origin COD/TOC SD
Ore processing 4,05 0,15
Sugar production 2,92 0,36
Paper production 2,75 0,18
Iron+steel production 3,78 1,02
Textile production 3,05 0,27
Glas and inorganic fiber production 2,62 0,25
Chemical cleaning 3,64 0,24
Waste deposit 3,04 0,2
Oil refineries 3,32 0,25
Source: Verbesserung der Einleiterüberwachung durch die Einführung der Meßgrößen TOC, TNb and Pges., Wasserwirtschaft Forschungsbericht 296-22-322
Summary
• TOC analysis require minimum manpower
• TOC can be measured within 4 minutes
• The only chemicals required for TOC are diluted, non-oxidizing mineral acids
• No special workbench (fume) required for TOC
• Therefore: it needs some work to replace COD by TOC, but it‘s worth it!
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Elementar thanks for your attention!