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Water Analysis
1)Introduction- water for drinking, recreation & others
2) Water quality and standards
3)Analytical Methodologies: Field and laborator
measurement,Pretreatment and Chemical Analysis
4)Special Methods: Automated Analysis, Flow Injectio
Analysis (FIA), and Ion Chromatography (IC)
1) INTRODUCTION
Standard or Reference Values set up by governmen
bodies e.g. EPD, Water Works Department, etc
Analytical methods two types (laboratory and field
methods) REFERENCE:Standard Methods for the
Examination of Water & Waste Water (628.161
S78) jointly issue by
i) American Public Health association
ii) American Water Works Association
iii) Water Environment Federation
Different methods used by different water bodies :
i) Clean water - drinking water, fresh water
ii)Water for recreation-seawater, beach & river water
iii) Dirty water - waste water, water pollution, etc.iv) Processes water - water for industrial use,
consideration for cost, corrosion & fit for purpose.
Some can be very clean such as DI water.
v) Water for specific uses - agriculture/irrigation,
cement/concrete mixing, cooling water, etc.Wastewater, Water, Soil & Sediments Analysis
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2) WATER QUALITY AND STANDARDSStandards
re normally set up by government agents or international
bodies & variable with different water bodies
.1)Drinking water : i) Microbial aspects, ii) Chemical
spects, iii) Radiological aspects, iv) Acceptable aspects
WHO Guideline values
Historically, spread of water borne disease is due to
ontamination of potable water by dirty water (sewage)
with faecal bacteria e.g. London before building deep
underground sewers & surface drainage water debate in
Bombay, India before link of illness to bacteria hasstablishedDevelopment of water supply system for citie
nd associated regulations, practices and control
-1914:U.S. Public Health Service set the standards
for water for bacteria.
-1925 : Cu, Pb & Zn, Pb = 0.1 mg/L (City watersupply by leaded pipeline)
-1946: 7 additional chemical substances
-1962: Pb 0.05 mg/L (availability of method) Current
WHO guideline forPb : 0.01 mg/L
-other chemicals added to water: i) chlorination fordisinfecting water to avoid water borne hyphoid & other
enteric diseases, ii) fluoridation: start in 1945 to reduce
dental cavities. Not too high or too low for best effect.
-Drinking water is metered & used to calculate waste wate
charges in HK.World-wide shortage of water.In Californiaincrease 3x cost to achieve effective water-saving.
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World health Organiszation (WHO): Guidelines for
rinking water quality, Third Edition, 2004.
WHO issues guidelines for quality and standards of
rinking water, risk assessment, monitoring & analysis
methods, sources of pollution, water treatmentDepending on sources of water, water quality varies
reatly in different places, some salty water or hard
water have to be used in drinking. The most important
fit for drinking with no known health hazards
Following parameters specified in WHO guidelines:
Bacteriological quality: Faecal bacteria indicator (E
oli) as general standard (individual bacteria if needed)
) Chemicals of health significance (Guidelines)
a)Inorganic constituents - heavy metals & anions
b)Organic constituents-chlorinated hydrocarbon,
PAH, Nitro-compounds, BTEX (benzene, toluene
ethylbenzene and xylene)
c) Pesticides
d) Disinfectants and disinfectant by-productsi) Radionuclides for alpha and beta emitters
v) Substances that may give rise to complaints- other
metals, hardness, pH, turbidity, dissolved solid, etc.
) Early edition focus on guidelines & standards. From
rd edition (2004), focus is changed to pollution sourceontrol & prevention measures (www.WHO.int)
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Standard based on E.Coli as indicator organismproblem
f mixing up portable water with sewer [connect to the
wrong pipe]
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System survey guidelines for water classification]
Guideline for verification of microbial quality]
Guideline for Bacteriological Quality:
Analytical question : Zero detection limit ??
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G
uidelinesforhe
althsignificant
chemicals(86listedwithguidel
inevalues)
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Guidelines for Radionuclides
-Determination of individual radioactive species requiressophisticated and expensive analysis and their concentrations
are normally very low in water, a screening procedure fortotal
radioactivity present in the form ofalpha and beta radiation
s thus used. The screening levels for drinking water below
which no further action is required are 0.5 Bq/litre for gross
alpha activity and 1 Bq/litre for gross beta activity. [Note : SIunit for radioactivity is Becquerel (Bq), where 1 Bq=1
disintegration per sec.]- To facilitate quick response, HKObservatory hosts the
monitoring network operated by chemists from Government La
- Monitoring air, water and dairy products to check against
potential leakage from nearby Daya Bay nuclear power station
- High background in HKdue to HKgranite (igneous rock)
[HK ~3mCi (100MBq)
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Sv
he sievert (Sv) is the SI unit of equivalent or actual radiation
ose received by receptor (Note: Bq/Ci is energy emitted from
adiation source). Radiation measured in Sv are designed to
present the biological effects of ionization radiation. However,
fferential absorption exhibits by different biological tissue.aking differential absorption into consideration, the unmodified
bsorbed dosage of radiation energy is known as grays (Gy). For
ological impact, further calculations must be performed to
onvert absorbed dose into effective dose, the details of which
epend on biological context, far more complicated than just
multiplying by a weighting factor.From previous
exposure study,
Man-made
radiation
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Guidelines for Aesthetic Qualitynstituent/Characteristics Unit Guideline values Remarks
umintum mg/L 0.2
hloride mg/L 250
hlorobenzenes & chlorophenols - no guldeline value set these compounds may affect taste & odou
olour true colour units (TCU) 15
opper mg/L 1.0
etergents - no guldeline value set no foaming or taste & odour problems
ardness mg/L (as CaCO3) 500
ydrogen sulfide - not detectable to consumers
on mg/L 0.3
anganese mg/L 0.1
xygen-dissolved - no guldeline value set
H - 6.5 - 8.5
odium mg/L 200
olids--tolal dissolved mg/L 1000
ulfate mg/L 400
aste and odour inoffensive to most consumers
emperature-
no guldeline value seturbidity nephelometric turbidity units (NTU 5 preferably
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2.2) Water for recreation (beach & swimming pool)
less stringent as compared to drinking water
Under Water Pollution Control Ordinance, HKis divided
nto 10 water control zones. Water quality varies
depending on different water control zone, with the most
tringent in Tolo Harbour & Channel. The reason is due
o the special regional geography with small mouth for
holding a large volume of water.In HK, 36 gazetted bathing beaches, 11 on HKIsland &
25 in NT & outlying islands.
Beaches are classified by E.Coli count /100 mL as Good610). HKEPD issues regular announcement on beach
waterquality during bathing season. Major water pollution
s due to excess sewage discharged with little treatment.
- Majorproblem
areas :
Typhoon
shelter,
KowloonBay near
Kaitak :
stagnant
water with
littlecirculation
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2.3) Dirty Water
Polluted water- Three types : i) Sewage water (toilet &
itchen), ii) Drainage water (rainwater) & iii) Industrial
ffluent waters
Standards set by HKEPD are different for different water
ones. Allow mixing of sewage & industrial water in old
ndustrial areas. Mix of drainage & sewage water not allow.
Control water zones with different standards for discharge
f wastewater. Most strict at Tolo harbour
parameters includes BOD, COD, grease & oil, metals, etc.
nformation available from HKEPD website
In Holland, COD & BOD are used to charge wastewater.
.4) Processes water: ingredients in finished products,
uoyant transporting
media,coolant,steam
power generation
variable quality by
ifferent industries)
.5) Water for
pecific uses : water
or irrigation, mixingement /concrete &
or cooling water in
ir conditioning
water quality
egulated & regularlymonitored )
T a b le 3 R e c o m m e n d e d v a l u e s f o r w a t e r u s ein m ix i n g c o n c r e t e
S u b s t a n c e Threshold valuefree CO2 25 mg/L
pH approx. 7
sulfide not detectable
sulfate 250 mg/L
chloride 1 500 mg/L
ammonium 100 mg/Lmagnesium 200 mg/L
potassium permanganate 25 mg/L
consumption
humic acids, hydrocarbons not detectable
F o r c o n c r e t e re i n f o r c e d w i t h ir o nchloride 100 mg/Lnitrate 20-50 mg/L
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(3) ANALYTICAL METHODOLOGY
3.1) Field Sampling And Measurement
3.1.1) Sampling and preservation
3.1.2) Direct measurement in field
3.2) Measurement in Laboratory3.2.1) Water quality testing methods
I) Microbiological testing methods
II) Radiological testing methods
III) Chemical testing methods
A) Sample pretreatmentB) Chemical analysis
a) General properties analysis
b) Specific chemical analysis
3.2.2) Automatic Analysis Methods
3.1) Field Sampling and Measurement
3.1.1) Sampling and Preservation
- Surface water : Collection by bucket or sample
container dipped into water in front of vessel
- Drinking water : Running time of 15 to 30 min prioto collection. Sterile glass bottle for bacteria testing
- Waste water: Similar to surface water collection. Fo
QC purpose, use 2-hrs pooled or daily pools samples
-Processes water: Use processes water to wash bottle
- Ground water: Tube wells or shafts with pumps orbuckets
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Table 1 Conservation of substance present in water
Parameter Preservation Method Maximum storage timetrace metals 5 mL HNO3/L several weeks
ammonium, total N2 5 mL HNO3/L few days
mercury 1 mL 10% K2Cr207-
solution/L few days
nitrite no stabilization possible, cooling to 4oC 1 day
cyanides alkali to pH = 11 1 day
iron-II addition of 2,2-bipyridine 1 day
sulfide 2 mL 10% zinc acetate solution/L 1 week
phenols alkali to pH = 12 1 week
Fig.1 Schematic
representation of a
tube well
ampleConservation
Different methods
or different analytes
No HNO3forCOD
No chemical addedorBOD
Sample preservation
an affect analysis
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Domestic Waste Water Sampling
Waste water
from sewer
Screening &
Degritting Remove
solids >
6mm
Primary
SedimentationRemove 50%
suspended
solid as
Primary
Sludge
SecondaryBiological
Treatment (6-8 hrs)
Reduce
ammonia-N and
total nitrogen by
microbes in
activated sludge
Effluent
Discharged
Excess activated
sludge digested,
de-water & landfill Activated Sludge Recycled
Water
Samples
Aeration with
activated sludge
Sedimentation
Tank
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.1.2) DIRECT FIELDMEASUREMENT
- Simple operation and procedure, give immediat
results with no problems associated with sample
storage and transportation
- Specific equipment for each measurement, e.g.glass electrode forpH, Fluoride ISE forF-,
oxygen electrode for dissolved oxygen,
conductivity meter for conductivity measurement
- For spectrophometric measurement, coloured
glass comparators are used for quantitatione.g. use of o-toluidine-HCl for residual chlorine.
Recent development using optical fibre with
computer-attached monochromator
- Parameters includes temperature, weather
conditions, Redox potential, Dissolved oxygen,Active chlorine, conductivity, pH, etc.
- Meter-type instruments with no power
requirement or run by battery power
pHmete
Colorimeter
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Coloured glass
as standard
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3.2) Measurement in Laboratory
3.2.1) Water quality testing methods
I)Microbiological Testing Methods
-Expensive to detect specific pathogen. Thus, use of
indicator organisms are used. Requirements :i) They are always present in contaminated water,
absent when faecal contamination not present,
ii) generally survive longer than pathogens, and
iii) easy to identify.
-If indicator organism absent, water is assumed safe.Total coliform group : defined as all of the aerobic &
anaerobic, Gram-negative, non-spore-form rod-shaped
bacteria which ferment lactose with gas formation
within 48 hours at 35oC given by Standard Methods
for the Examination of Water & Wastewater.Faecal or thermal tolerant coliform (E.coli): the
ncubation temperature is 44.5 0.2C and other
conditions kept constant coliform from human
For individual pathogenic bacteria : tradition
method by colony counts in selective media, or newPCR/DNA techniques for detecting specific bacteria
Method : Pass 100-mL sample through sterile
membrane filtration following by incubation inlactose-peptone solution at 35oC and counting
confirmed colonies (by morphology, colour and
biochemical identification) after 24-48 hours.
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) Radiological Testing Methods Alpha particle: 1)Positivcharged particles,
2) shortest pentration
distance
eta
article: 1)
egatively
hargedarticles
) Longer
enetration
istance
Gamma Ray:1) Lo
abundance
radiation, 2) longe
penetration distancUnstable nucleus decays by emitting
pha particle, beta particle and
amma ray (high energy radiation
g. X-ray)
A) Measurement in field :
Measure beta-particle or gamma radiation due to long distancemeasurement. Alpha particle is too short a distance to measure.
It depends on the penetration power of radiation through given
hickness of Aluminum block to distinguish 241Pu, 129I or 90Sr.
Thus, one can put detector behind a given thickness of Al block
o identify type of radiation. (Qualitative)
The intensity measurement is more a problem for quantitativenalysis, as sources & their distance to the detector are needed.
/ x
neutron
Paper
Thin metal foil Thick Pb block
Heav
water
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I) Scintillation counter measures
onizing radiations. The sensor
onsists of a transparent phosphor,
lastic usually containing
nthracene that fluoresces when
truck by ionizing radiations. A
ensitive PMT measures the light
rom the crystal for counting and
ossibly quantify the amplitude of
he signals from phospor (Moreensitive than GM,semi-quantitive)
I)Geiger Mller (GM) count
Cheap, portable, detect ionizin
radiation, e.g. beta particle &
gamma ray. Special model det
alpha particle. However, low
sensitivity. An inert gas-filled tube (He, Ne orAr with halogen added) briefly conducts electri
city when a particle or high energy radiation
makes the gas conductive. The tube amplifies
this conduction by a cascade effect with outputs
displayed by a needle or lamp and/or audible
sound.(Personal monitor, Yes/No indication)
B) Measurement in the La
I) Liquid scintillation
counting is a standard
laboratory method for
measuring raditaion from
beta-emitting nuclides.(Fixed
demension Quantitative)
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mples are dissolved or suspended in a "cocktail/mixed solution
ntaining an aromatic solvent & small amounts of other fluorescen
ditives (fluors) Beta particles emitted from sample transfer energy
the solvent molecules, which transfer their energy to the fluors. T
cited molecules dissipate energy by emitting light for measuremen
ab procedures : Two common methods for gross alpha & gross
eta activities: 1)Evaporation of known sample volume to drynes
measure activity of residue (as alpha absorbs by solid material,
ot for samples with high total dissolved solid (TDS). 2)adioactive co-precipitation(precipitation on a carrier
recipitateor collector for trace metals. Using a large amount of
nsoluble K salt to co-precipitate radioactive cations):simple,
pecific, but time consuming. Lots of foreign materials added to
ample, producing contamination problem. Applicable to high TDS
amples due to saturated effect. Hard to get 100% recovery.
I) Sealed Xenon Proportional CounterArgon gas-flow proportional counterfor
ccurate determination of & radiation.
quench gas added to prevent proportional
ounter acting as a GM counter.
onization excites inert gas. When coming down to ground state,
mit light which is amplified by cascade electrodes like PMT fo
ulse mode of measurement. 2207/WA/2013/
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2207/WA/2013/II) CHEMICAL TESTING METHODS
) SAMPLE PRETREATMENT (waste & clean water)
urpose of sample pretreatment :a) cleanup major sampl
matrix, b) to remove interference & c) to enhance sensitivity
preconcentration) before GC separation & quantitation
ypes of Pretreatment Methods : i) Preconcentration
vaporation (heat lamp or hot plate): simple, inexpensive,
se for most substances, compatible to most methods, no
hemical added & no contamination. However, time
onsuming, not for volatile compounds, adsorpt-ion loss,
on-specific, high solid content, only for highly solubleompounds. Maximum ~50x .on exchange (cation, anion, chelating): simple, rapid,
nexpen-sive setup,regenerated column, very high pre-
oncentration factor. However, suitable detector, specific
xchanger & solvent needed) Isolation & Phase Separation
recipitation (inorganic & organic reagents):simple,
nexpen-sive & quite specific. However, for low soluble
ompounds with large crystals,lots of foreign ions added &
e-dissolution required.ii) Extracting Trace Pollutants from Liquid Phase
Extract trace levels of pollutants from complicated
matrixes, remove interferences and concentrate analytes
rior to chemical analysis.Commonly used for waste water
Instrument are often used to speed up the extraction andor automation of procedure
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Three major types of extraction from liquid phase : Purge &
Trap, Solid Phase Extraction & Solvent Extraction
) Purge & Trap for Volatile (Purgeable) Organic
ompounds : Two steps, 1st step is to purge organic compounds
ut from aqueous solution by gas and this leads to pre-
oncentration and removal of interferents. Second step is to striprganic compounds out from the adsorbents by carbon
isulphide or by thermal desorption.
Two types : Off-line and on-line Purge & Trap
ff-line Purge & Trap- Removal of moisture by Nafion drier t
duce the effect of water on activated carbon (polymermembrane allowed water to go through but not organic
ompounds, dried by desiccants packed in Drier)
n-line Purge & Trap with cryogenic on-column focusing
apillary column in liquid N2 to trap VOCs) with direct couplin
GC: used to handle a lot of samples at low concentration.
Purge Gas
Activated Carbon
Adsorbent Trap
Aqueous
solution
sample
Nafion
Drier
A hygroscopic ionexchange membran
fabricated in tubula
form and made up
of a co-polymer of
tetra-fluoroethyleneand fluorosulfonyl
monomer
Du Pont Nafion
F2C=C OCC OCCSO3H
nF CF3 F F
F F F F F
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Solid Phase Extraction
using cartridge
Vacuummanifold for
solid phase
extraction of
multiple
cartridges
Pressure
Procedures in SPE
) Solid Phase Extraction(SPE)
Technique involves the use of a solid sorbent selectively
dsorbing the analyte from a large volume of diluted sample
olution, and then eluting by a small volume of strong solvent
Ion Exchange Resin for pre-concentration of trace metals fromqueous low-ionic strength solution, then by hydroxide stripping
-C18SPE (Sorbent)
to preconcentrate
trace non-polar
organic compounds
from aqueousmedium
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) Solvent Extraction
Organic solvent extractionSeparating funnelmore efficient using discrete multiple
xtraction with several small volumes of extractants
Extracting Trace organic pollutants
like-dissolve-like concept for organic compounds with
rinciple based on favourable distribution ratio in the organic
hase. K = Corg /Caq.More complete extraction by multiple extractions using several
ots of smaller volumes than a large solvent volume
Choice of solvent: purity, cost, safety (toxicity & fire hazards)
nd solubility of analyte such as hydrocarbon (hexane) &
hlorinated hydrocarbon solvents (1,1,1-trichloroethylene)Best is CFC on safety & chemical grounds (high purity with
nly C-F bonds & good solubility of organics)
Problem of long extraction timea few hours and CFC isnot
nvironmental friendly
Extraction and Preconcentration of Trace Metals
Chelation of metals by EDTA and other complexes beforeolvent extraction by MIBK(methyl isobutyl ketone) forAAS
rICP determinationremoval of interference by other ionic
ompounds, e.g. phosphate
Substantial number of metals can be extracted by chloride
omplexes in HCl, e.g. Fe (III), Sb(V), Ga(III), Ti(III),
Au(III),Mo(VI), As(III) & Ge(IV)
pH is important for extraction & should be optimized
Chelating resin (Chelex 100) [styrene-divinyl copolymer with
aired iminodiacetate ions as chelating groups to complex with
ansitional metals] to preconcentrate transition metals from high
nic solution and removal of interferents2207/WA/2013/23
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)CHEMICAL ANALYSIS
- Two main types : general and specific analysis
a) General properties of water
i)General observations:colour, odour & appearanc
ii) pH or alkalinity/ acidity (acidic/base capacity)iii) Dissolved and undissolved substances
Total residue dried at 103-105o C (as mg/L):
both dissolved and undissolved solid content
Total suspended matter(as mg/L): undissolved
solid only
Turbidity : cloudiness of solution, related to
suspended solid content except for smaller particles
NTU turbidimeter
is used for measuringnephelometric turbidity
units (NTU) based on
scattered light
measurement with
calibration by a primarystandard for turbidity (an
aqueous suspension of
formazin, an insoluble
polymer formed by
condensation of hydrazine
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ulfate and hexamethylenetetramine)
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Conductivity (as mS): electrical
onductivity is a total parameter for
dissolved and dissociated ionic
ompounds. In seawater, it is related
o salinity. It can be used to calculate
he total ion content in given samples
Dissolved oxygen -important
ndicators for water quality
COD (chemical oxygen demand) &OD (biochemical oxygen demand).
BOD starts as an empirical parameter
o assess water pollution by measuring
he quantity of dissolved oxygen to
xidize organic compounds found in
water with assistance of microorgan-
ms & under defined experimental
onditions. It varies with conditions
uch as temperature, dissolved O2, levels or type of bacteri
& less reproducible compared to COD. However, a lot of
istorical data using BOD for polluted waters, making it an
ssential parameter (To set charges for waste water in EU)
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Grease & Oils: indicate total organic content, measure byissolving organic matters in CFC (now hexane afterCFC
an), evaporate to dryness and weigh
Hydrocarbons: direct FTIRon
olvent extract for total hydrocarbons.
) Specific Chemical Analysis: i) Organic matters includ
Grease & Oil, Hydrocarbons, BOD & COD, Trace organics
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OD - Uptake of oxygen during 5 days or longer by biological
educing system such as activated sludge system. In UK, 5 days
dopted during London sewer construction based on average tim
or water to go through river Thames. ForEU, 7 days is adopted
o meet weekly work schedule.Dissolved Oxygen (DO) measure
y electrode with amperometric detection before and after 5 or 7ays incubation at 20/27oC with or without the seeding of bacter
BOD Empirical parameter covering organic compound
educed substances of nitrogen, sulphur, phosphorus & som
metallic species. (Dl-D2)-(Bl-B2)x f
Pwhere D1 & D2 are DO (mg/L) of diluted sample immediatel
fter preparation and after 5 or 7 days of incubation at 20/27o
espectively; B1 & B2 are DO seed control before and afte
ncubation respectively; P is dilution factor and f is the ratio o
eed in diluted sample in seed control. If no seed is added, th
actor [(B1-B2)xf ] will be zero. Several BOD bottles are used
dilutions + seed) with water filled up to top with no air gap left
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BNC Connector
Anode (silver wire)
Ag/AgCl or Calomel
KCl Electrolyte
Solution
Teflon membrane
ABS Body
oble Metal Cathode
old or Platinum)
Inner glass tubing
BOD(mg O2
/L) =
Oxygen
Electrode
BOD bottleO2 O2 O2
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COD- a few hours measurement
-a wet chemical analytical technique
-refluxing acid-dichromate with a catalyst to carryout chemical oxidation (catalyst: Ag2 (SO4))
-back-titration with ferrous ammonium sulfate
method
COD : oxidation of reduced inorganic species +
carbonaceous matter-oxidise non-carbonaceous compounds such as reduced
states of N & S, some halides, many metals & bound
hydrogen inorganic compounds
-variable oxidation efficiency e.g. pyridine 0.8%
benzene 8%, toluene 22.5%, o-cresol, valine, sodiumstearate >90%
Chemical oxygen demand (COD) is defined as the
amount of oxygen in the form of oxidizing
agent consumed in the oxidation of organic water
components. The degree of oxidation depends upon the
type of substance, pH value, temperature, reaction timeand concentration of oxidizing agent as well as the type
of added accelerators, if any.
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Trace Organics
-Often in complicated matrix require cleanup
-Analytical methods: IR, MS, GC, GC-MS, Florescence
(PAH) and electrochemical techniques- Organic pollutants e.g. phenols, surfactants, etc
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Trace metallic elementsi) AAS : flame & graphite
urnace, ii) ICP-AES (ppm) and ICP-MS (ppb),
i) Electrochemical stripping techniques, useful for tracemetal analysis in seawater.
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Anions (Cl- and SO4=) are monitored in cooling water as
ndicator for corrosion
Active chlorine compounds
residual chlorine determine by amperometric titration
sing standard ferrous sulphate or by colorimetric methods
sing o-toluidine-HCl and coloured glass comparator.
Nutrients in water (PO4=and NO3
-).
Both are limiting nutrients in soiul for algae and plants.
Used as fertilizers to enhance plant growth. Can causeutrophication (excessive algae growth known as algae bloom
present in water at high levels under favourable conditions.
) Inorganic compounds
Hardness of water : total dissolved divalent cations as
measured by EDTA titration.
Anions:requiredppm/ppb determination in acid rain analys
high tech industries. 2 methods i)Ion Selective Electrode
ISE, ii) Suppressed Ion Chromatography Ion Exchange
olumn to separate anions using NaOH as eluent.Suppressoolumn to reduce background conductivity via removing H+
ith OH-to form H2O before conductivity detector
i) Non-suppressed Ion Chromatography (Non-suppressed IC)
Same as (ii) except no suppressed column, Use weak
rganic acid as eluent which absorb UV for indirect UVetection to avoid patent on suppressor (expired now)
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Fig. 2.Fraction of
ammonia and
ammonium ions
a function of pH.
ForNH3-N, Nessler titration
r electrode (ISE) method
Fig. 1, a glass electrodeounted inside a gas-
ermeable membrane toeasure pH) is used. It
easures only NH3.
he ratio between NH3
NH4+ depends on
olution pH (Fig. 2).
It operates at 0-50o
C,orking range:0.01-17000
pm (1.0 to 5x10-7M).
Only operate in aqueous
olution & interfere by oil
grease covering up the
as-permeable membrane.For sample ionic strength
1.0M re uires ad ustment
Fig. 1.
Construction ofammonia electro
Nitrogen Content in Wastewater
otal Nitrogen = Ammonia-nitrogen (NH3-N)+Organic-nitrogen
Org-N)+Nitrate-nitrogen (NO3-N)+ Nitrite-nitrogen (NO2-N)
itrogen is essential for formation of proteins in cell growth and thus
eded to keep activated sludge.However,too much causes algae boom
mmonia is toxic to fish, and nitrates at high enough dosages in the
inking water cause methemoglobinemia in infants as it can convert to
trites in the stomach and interfere with the oxygen-carrying capacity
hemoglobin in blood.Nitrogen exists in NH3,
rganic-N, nitrate & nitrite
waste- water. Under right
onditions, each canonvertible to the others.
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Total Kjeldahl Nitrogen (TKN) is obtained by digesting sample
or two and a half hours in H2SO4and collecting NH3 distilled
or analysis. Result consists of (organic + inorganic) nitrogen plu
H3-N. Thus, organic nitrogen can be calculated by
ubtracting NH3-N and inorganic nitrogen from TKN in the sam
ample.
In field, pH should keep to < 2 by H2SO4 and temp. at 4oC
mmediately after sampling to reduce degradation.
In laboratory, pH adjusted to 9.5 using a borate buffer and
olution distilled into a receiving solution of either boric acid for
Nessler titration or into H2
SO4
for ammonia ISE determination.
Nessler reagent (0.09 mol/L solution ofK2[HgI4] in 2.5 mol/L
KOH) is used to detect small amounts of ammonia. A yellow
oloration indicates the presence of ammonia and at higher
oncentrations, a brown precipitate may form. The sensitivity is
bout 0.3 gNH3in 2 L.
NH4+ + 2[HgI4]
2 + 4OH HgOHg(NH2)I + 7I + 3H2O
O3- & NO2
-Analysis (Inorganic nitrogen, ISE + Cd)
Typically, < 1 % N in form of nitrates (NO3-) or nitrites (NO2
-)
he ratio reflects microbial balance
NO3-
converted to NO2-
by a Cd reduction column or usingydrazine sulfate for the determination ofNO2
-(Total nitrate afte
trate reduction).NO2
- is determined by diazotizing with sulfanilamide and
oupling with N-(1-naphthyl)-ethylenediamine dihydrochloride t
orm a highly colored azo dye which is measured colorimetrically
NO3-= total NO2-(after nitrate reduction)-NO2- (without nitrateduction).
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Injection of phosphatestandards (~100 ug/mL)
and samples
he intermediate product (NH4)3PO4-12MoO3 is a yellow colore
o(VI) complex. When it is treated with ascorbic acid, the bluelored Mo(V) complex formed is detected spectrophotometrical
Phosphorus compound analysis include Total phosphorus,
-phosphate, hydrolyzable phosphate (total inorganic phosphate
& organically bound phosphate in water, wastewater or soil.
Natural total phosphate in water < 0.1 mg/L, normally fixed i
oil and non-toxic. Requires. frequent monitoring in wate
nalysis, leading to use of FIA for automatic determination.
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4) SPECIAL METHODS: A) Automation in Water
Analysis. 4.1)A lot of samples for analysis automatio
different degrees). Normally first for time consuming ste
n sample preparation such as dilution orpHadjustment.
.2) 3 essential elements in automation : brain (decision
making by computer), eye (sensor) & hand (actuator).
.3) The most simple system is automated titration with
ndicator electrode (eye), generator electrode or autopipet
hand), and microprocessor/computer /electronic circuitry
brain) for end-point detection.
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Generator electrodes
-Pt coil- Coulometrically
generate Br2from Br-
) Discrete Automatic titration - electrochemicaltitrant generation and detection
ndicator electrodes
Two Pt flags
Amperometrically
etect
r2/Br-ratio at bothelectrodes
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Operation : i) Conditioning of electrolyte by generating a fixed
amount ofBr2 (indicated by constant current i) ii) Add sample
o reduce current, iii) Generate Br2till current reaches constant
current i again, iv) measure coulomb passed and calculate the
amount ofBr2 generated assuming 100% coulombic efficiency.
Ascorbic acid is back titrated with Br2 generatedby
lectrolysis at anode reaction
Iodine is added as its redox reaction (I-/I ) with ascorbic acid
s more reversible & it can be regenerated by reaction with Br2.
Titration of Ascorbic Acid With Bromine Generated
Ascorbic acid + Br2 2Br- + 2H+ 2207/WA/2013/33
a single-channel TechniconAutoAnalyzer system
Proportional Pump & Manifold
I) Continuous Flow SegmentedAutoanalyser: Commercialutoanalyser incorporating sample preparation & analysis
vailable forCOD, trace metals & nutrients (nitrate, nitrite,
mmonia andphosphorus)
First autoanalyser for water analysis with segmented
ow and air bubbles separating different samples
Dialyzerampler
Note:Bubbles causes disturbance
in detector baseline.Devices added
to remove bubbles before detector
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a) Representation of a simple flow
injection analyser; b) Sample flow
in tube containing a plug of
sample; c) typical response over
time for samples and standards
II) Continuous Flow Non-segmented Analyser
Analyser based on newly deveoped Flow Injection Analysis (FIA
o air bubble to isolate samples. Use only segments of carrier liqui
separate samples.Require accurate control in flowrate & volume
ample injection to achieve repeatable dispersion during each run fo
harp peaks at detector. FIA resemble HPLC with an empty colum
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Note:
Asymmetri
peak with
tailing
Successful development ofHPLC makes suitable valves and low
ressure pump commercially available at affordable price, leading t
e development ofFIA for non-segmented flow auto-analyzer. Du
its flexible design using parts from HPLC, FIA is now largely
placed the dedicated Continuous Flow Segmented Analyzer inutomation for water analysis. The simplest FIA system is using Ion
elective Electrode for continuous flowdirect analyte detection.FIA
ystem with the widest applicationis using UV-Visible detector.
Simple Ion Selective Electrode combination electrode with built-in
ference electrode for monitoring specific ion. As no separation
efore detection, the detector system (Fluoride ISE) must be very
lective towards the analyte to avoid sample matrix interference.
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The flowrate and response time of the ISE orUV
etector affect the sample throughput (no. of analysis perour) of the auto-analyzer.
Symmetrical peak gives the least error in measuring peak
eight for concentration. Asymmetric peak require peak
rea for quantitation, more complicated and less accurate
measurement.The most efficient sample throughput is when the first
eak reaching baseline, the second peak will start with
minimal time between samples. Thus, FIA can handle
undreds of samples everyday. This can be done by
ptimizing the flowrate and mixing rate of the FIAystem.
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NaOH used as eluent
o meet the problem for determination of anions at ppm
vel, Two chemists working at from Dow Chemicals have
atented a suppressor technology in 1975 to enable the use
f conductivity detector to detect non-UV active anions like
hloride and Sulphate after their separation by HPLC using
n Ion Exchange Column. They left Dow Chemicals to set
p a new company (Dionex) to expand the suppressor
chnology to determine anions at ppm level for acid rain
monitoring, taste in food, impurities in DI water and for
arious industrial monitoring, leading to the birth of aillion dollar industry for Ion Chromatography at California
) ION CHROMATOGRAPHY
OH- +H+ H2O Low Background Conductivity
SO4= +H+ H2SO4
Strong acid, high conductivity
(1)
(2)
1) + (2) High Detection Sensitivity
-Patent by DIONEX i
based on suppressor
technology which is
expired in 2005.
Suppressor
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Ion
Chromatogram
using Suppressor
Column for ppm
determination ofanions in water
Fung & Dao, Anal.
Chim Acta, 1995,315, 347.
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Non-suppressed Ion
hromatographyNon-suppressed IC)
Same as IC except
o suppressed column
sed, Use weak
rganic acid as eluentwhich absorb UV for
ndirect UV detection
f non-UV absorbing
nions to avoid patent
n suppressor.
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After suppressor patent is expired, other companies enter
he IC market, producing cheaper & better design with
utomatic/onsite regeneration of suppressor column
1) Running IC Column For Anions
Separation & Quantitation
2)On-column Suppressor Regeneratio
Dual Cycle with one
uppressor in use and
he other regenerated
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013/38
Flowchart For MMS III Membrane Suppressor
To stay ahead in IC
chnology, DIONEXeveloped Membrane
uppressor (patent still
n force) to reduce post-
olumn band broadening,
nable continuous insitu
uppressor regeneration &
chieve ppb detection level.
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Another direction taken by
IONEX is coupling IC
Membrane suppressor
perated by applying +/
oltages across membrane
remove H+ and OH-
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Eluent
(NaOH)
Membrane
Membrane
Regenerant (H2SO
electrolytic H2O)
Regenerant (H2SO4electrolytic H2O)
Sample (NaF,
NaCl, Na2SO4)
reduce thyroi
hormone
production
ii)USEPA
Max level at
1 ppb in drinkin
water in 2002
iii)IC2pp
QL at 100
iv)IC/MS/MSD
4ppt(ng/L) for 99/8
MRM at 100L
v)MRM confirmation for37Cl/35Cl at 0.323 ratio
with MS
detector to
nable ppt
detection of
nion andonfirmation
f anion (ClO4-)
n milk & water
i)High ClO
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SUMMARY
1) For water analysis, it is always under
government control based on standards,
guidelines or objectives.
2) Analytical method should have detection limits
at 10 % or lower of the quantitation limit at
guideline values. Do not need extreme sensitivity.
Method should be fit-for-purpose.3) Cost is always important for water analysis, as
a lot of data are collected on daily basis. There is a
trend towards methods capable of analyzing
multi-parameters.
4) Validity of method is important. Thus, standard
methods are often used with calibration by
reliable standards.
5) High degree ofautomation in analytical
method in water analysis. Future methoddevelopment is towards integration with field
sampling and laboratory analysis, as results
should represent condition in field and many
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