Treatise on Water Science vol III (Aquatic Chemistry and Biology)

456 Pages·2011·28.99 MB·English

by  Peter A. Wilderer

Preface – Aquatic Chemistry and Biology
FHFrimmel, KarlsruheInstituteof Technology, Karlsruhe, Germany
&2011ElsevierB.V.Allrightsreserved.
The World of Aquatic Chemistry and Microbiology challengestosupplysufficientandhygienicallysafewaterfor
human consumption and food production. Severe water
Aquatic chemistry and microbiology do not belong to the shortageandnecessarywaterqualityareissuesthathavearisen
classicalsubjectstaughtinuniversities.Nevertheless,theyare regionallyandarepredictedtointensifydrasticallyduringthe
partofmanycurriculainnaturalsciencesandengineering.Itis followingdecades.Conceptsformultiplewateruseandwater
beyonddoubtthatthefascinationofthemoleculardimension reuse need to be developed, taking advantage of the specific
of water itself and all its constituents, which goes like a red hydrological, climatic, and ecological situations. In addition,
threat through all the aspects of structure, transport, and re- thespecialdemandsofsocialcommunitiessuchasmegacities
actions of and in aquatic systems, attracts so many people. or developing countries have to be considered. Wherever
Due to the broad and fundamental importance of water for possible,theecologicalfunctionsofregionsmustbeprotected
life, including the humans, the molecular water sciences foritismostreasonabletousenatureasaself-sustainedsys-
(MoWaS)havetobetransdisciplinary.Thedisciplineincludes tem also for water cleaning. The protective function of soils
not only physics, chemistry, biology, and geology, but also
and their capability to degrade and eliminate aquatic pollu-
mathematics, engineering, and economics and even parts of
tants make it attractive to use groundwater as a resource for
social sciences. As a consequence, several subjects have de-
drinking water supply, especially when protective zones and
veloped based on fundamental ones but focusing on the
assistingtechnicalmeasuresareestablished.
specialaspectsofwater,examplesofwhichincludelimnology,
Toxicity and hygiene reflecting criteria are, besides the
oceanography, hydrogeology, hydrology, groundwater dy-
technical aspects such as corrosivity, most important for the
namics, drinking water treatment, municipal water manage-
use of water. A meaningful assessment of the use-oriented
ment, industrial water usage, wastewater treatment, and
water quality has also to include parameters which quantify,
hydrothermal usage. Manyof them either are cross-linked or
forexample,biotafriendliness,potentialforbacterialgrowth,
bridgethegaptothefieldsofquantitativewatermanagement.
eutrophication, and disinfection by-product formation. Oc-
The big challenge when dealing with MoWaS can be de-
currence of pathogenic microorganisms and waterborne epi-
duced from the nano- and microscale of the substances in-
demic episodes belong to the most serious events oftenwith
volvedandtheirlowconcentrations.Therelatedbio-response
peaks in wars, natural disasters, and badly managed camps,
canrangefromsubtletoacutetoxiceffects.Methodstoobtain
homes, and companies. Quite often, shortcuts between the
reliable results are still scarce, especially for applications in
systems for drinking water supply and wastewater discharge
naturalenvironment.Here,theinfluencesofmatricesandthe
havebeenidentifiedasreason.
synergeticorantagonisticeffectsinmulticomponent samples
Economic aspects are one of the master driversfor use of
areoftenunclear.
wateranditsmanagement.Ontheonehand,theavailability
It is well accepted that water is the fundamental basis for
of enough water of suitable quality hasbeen discussed as an
ourknownlifeandinitsuniquefunctioncannotbereplaced
issueofhumanrights.Ontheotherhand,waterhasbecomea
by anything else. The physical properties of liquid water are
tradegood,whichissolddirectlyinbottlesorthroughpipes
reflectedinitspropertiesastransportmedium,reactionphase,
or as virtual water in the manifold forms of industrial prod-
andmediatorforhighermolecularstructures.Oneofthemost
ucts. No matter how much profit might be involved in this
impressive properties of the water molecules is the ability to
business, the availability of reasonable resources and eco-
formintermolecularhydrogen(H)-bonds.LinusPaulingonce
said,‘‘ythehydrogenbondisespeciallysuitedtoplayapart nomically feasible treatment technologies will play a funda-
in reactions occurring at normal temperatures, and I believe mental role.The application of cheapenergysources such as
that it will be found that the significance of the hydrogen sun light and the use of homogeneous and heterogeneous
bondforphysiologyisgreaterthanofanyothersinglestruc- catalysis,includingbiocatalysis,leadtomostpromisingwater-
tural feature.’’ In other words,the formation and breaking of treatmentconcepts.
H-bonds in the energy band of our common environmental Intelligent combination and an optimized sequence of
situation deliver the key for understanding life and its sup- treatment steps can further improve the economy of water
porting element – water. It is also obvious that all major plants. Hybrid systems are suited for highly efficient water
changes in water quality and temperature, for example, as a treatmentinfastworkingsmallreactorswiththeadvantageof
result of climate change, must have an influence on the dy- decentralizedapplication.
namics of reactions and on the material balances involved. Keeping these aspects in mind, it becomes obvious that
Thisagainwillinfluencethewatercycleandhencetheaquatic understanding the details of the properties of living and
resources. nonliving water constituents, their reactivities, and transport
Here, water management comes into the focus. Different behavior will help to tailor powerful methods for water-
kindsofwaterusewithdifferentinfluencesonwaterqualityin qualityassessment and to deriveefficient concepts for timely
small- or large scale must be considered. Industrial develop- water-treatment processes. The water cycle is an ideal case
ment and population growth have led to one of the biggest studynotonlyforitsdifferentstagesandhotspots,butalsoas
1
2 Preface – AquaticChemistry andBiology
awholewhichcanteachusthesystematicapproachtocom- screening of estrogen activities, and enzyme-linked immuno-
plex systems and to the solutions of the related man-made tests show the way to modern concepts for conti-
problems. nuous quality control and bioeffect-related assessment. The
Italsoshowsthenecessityoftransdisciplinarythinkingin development and application of standardized methods sup-
the sense of lifelong learning. Starting in the early days of plytoolstoobtainreproducibleandwell-comparableresults.
childhood, we need to lay the foundation for a responsible Forthespecialneedsofwatertreatmentanddistribution,itis
careforwaterasabasisforourlifeandculture. most useful to quantify biodegradability and toxic effects.
Furthermore,weneedtoinvestinthetoolsforasustainable Reactionmechanismsofoxidationanddisinfectionprocesses
watermanagement by developing measures to save the water as well as bioremediation are important not only to under-
cycle in its proper ecological function. This calls for the clas- stand the pathways of technical transformations and natural
sicalcomponentsofteachingandresearchandbeyondthatfor attenuation, but also to optimize treatment strategies. All
innovativeconceptstoservethedailyneedsofwaterusagein thesetopicsareaddressedbyleadingexpertsinthefield.They
aneconomicallyaffordableandsociallyacceptableway. allintendtosupplyfortheinterdisciplinarywatercommunity
To serve this aim, a comprehensive treatise on water is themolecularfactsforameaningfuldiagnosisofthestatusof
presented. Volume 3 of this work includes the chemistry aquatic systems and for efficient technical processes within
and microbiology of MoWaS. The analytical aspects cover the water cycle.
water-specificsumparameters,methodsforthedetermination Astheeditorofthisvolume,Iwouldliketothankallthe
of trace metals and metalloids, as well as radioactive sub- authors for their valuable contributions. Furthermore, I am
stances, and the characterization of natural organic matter gratefultoU.Bilitewski,T.Bu¨nger,G.Donnevert,G.Gauglitz,
(NOM). Emerging contaminants, colloids, and engineered H.Geckeis,B.Hambsch,T.Hofmann,H.Horn,T.P.Knepper,
nanoparticles are presented and data handling is described. D. Knopp, V. Neitzel, R. NieXner, B. Nowack, F. Petry, H.-J.
The identification of bacteria and parasites helps to charac- Pluta, M. Spiteller, and M. Weller for their input by peer-
terize the hygienic status of water. Online monitoring, review.
3.01 Sum Parameters: Potential and Limitations
FHFrimmel andGAbbt-Braun,Karlsruhe InstituteofTechnology, Karlsruhe, Germany
&2011ElsevierB.V.Allrightsreserved.
3.01.1 Introduction 3
3.01.2 GeneralConsiderations andScope 3
3.01.3 DOCandTOC 3
3.01.3.1 Background 3
3.01.3.1.1 Relevance 4
3.01.3.2 Analytical Procedure 4
3.01.3.2.1 Method variations 5
3.01.3.3 Interferences 5
3.01.3.4 Advanced TOC(DOC) Characterization 5
3.01.3.5 Applications 7
3.01.3.5.1 Hydrosphere 7
3.01.3.5.2 Surface water 7
3.01.3.5.3 Water treatment 7
3.01.3.6 Surrogate Parameters 8
3.01.4 Oxygen DemandParameters 8
3.01.4.1 Introduction 8
3.01.4.2 Chemical Oxygen Demand 9
3.01.4.2.1 Background 9
3.01.4.2.2 Analytical procedure 9
3.01.4.2.3 Interferences 10
3.01.4.2.4 Applications 12
3.01.4.3 PMCand Permanganate Index (I ) 12
Mn
3.01.4.3.1 Background 12
3.01.4.3.2 Analytical procedure 13
3.01.4.3.3 Interferences 13
3.01.4.3.4 Applications 13
3.01.4.4 Biochemical OxygenDemand 13
3.01.4.4.1 Background 13
3.01.4.4.2 Analytical procedure 13
3.01.4.4.3 Interferences 14
3.01.4.4.4 Applications 14
3.01.4.4.5 Related parameters (AOC) 14
3.01.4.5 Interdependences 15
3.01.5 UVAandVisible RangeAbsorbance 15
3.01.5.1 Background 15
3.01.5.2 Analytical Procedure 15
3.01.5.3 Interferences 16
3.01.5.4 Applications 16
3.01.6 Organically BoundHalogens AdsorbableonActivatedCarbon(AOX) 18
3.01.6.1 Background 18
3.01.6.2 Analytical Procedure 18
3.01.6.3 Applications 19
3.01.6.4 RelatedParameters 19
3.01.7 AdditionalSum Parameters 19
3.01.7.1 Background 19
3.01.7.2 Examples forEmerging Parameters 20
3.01.7.2.1 Humic substances 20
3.01.7.2.2 NPsandcolloids 21
3.01.7.2.3 Luminescence 22
3.01.7.2.4 Bioeffect quantification 22
3.01.7.3 View 23
References 23
3
4 Sum Parameters:Potential andLimitations
3.01.1 Introduction Methods,2005).Thisputstheapplicationofsumparameters
right into the center of a comprehensive assessment concept
The general assessment of the quality of aquatic systems whichisopenforadynamicbackbondingoftheresultswith
andthejudgmentoftheefficiencyofawater-treatmentfacility theselectionoffurtheranalyticalsteps.Asaconsequence,sum
quite often relies on the application of sum parameters. parameters have found their way into legislation and assess-
Sum parameters are normally based on an integrative quan- ment of environmental protection with all the demands of
tification of a specific group of compounds. However, the dataqualityacceptanceincourtcases.
results obtained are mostly operationally defined and are In this chapter, we discuss in depth the parameters: dis-
often prone to misinterpretation. Therefore, it is essential to solved organic carbon (DOC) and total organic carbon
understandthepowerandatthesametimethelimitationsof (TOC), chemical oxygen demand (COD), permanganate
the parameters applied. Like signposts, they can give first in- consumption (PMC), biochemical oxygen demand (BOD)
formationonassessmentstrategiesandthenecessityofsingle- and assimilable organic carbon (AOC), the color and ultra-
compound analysis. They are also suited for a total balance violet (UV) absorbance (UVA), and on activated carbon ad-
even in the presence of compounds with unknown structure sorbable organically bound halogens (AOX). Most of these
(Frimmel and Abbt-Braun, 2009; Abbt-Braun and Frimmel, parameters refer to the dissolved state of the matter to be
2010). determined.Filtrationthroughmembraneswithnominalpore
All these advantages have led to a prosperous develop- size of 0.45mm is widely used as analytical operation even
ment of water-specific sum parameters and their application though there might be pitfalls from pore blocking, fouling
in legislation, in technical rules, and in environmental rec- layerformation,orscaling.Quiteoften,thewatersamplesare
ommendations. It is beyond doubt that research in and de- analyzedwithoutpretreatment.Thishastobeclearlystatedin
velopment of sum parameters have been significantly the protocol and is normally assigned as total concentration
influenced by the practical aspects of water quality and value, for example, TOC. To close the gap between the dis-
vice versa. The applicability of the corresponding methods solved state and particulate matter, a method for the de-
has also stimulated the development of specific instru- terminationoftheparticle-sizedistributioninthenanometer
mentation (see also Chapter 3.10 Online Monitoring (nm)rangeispresented.
Sensors). Some of the instruments are well suited for con-
tinuous measurements and can be used as online detectors.
This opens the door for the resolution of mixtures by chro-
matography or by other fractionation methods. As a con- 3.01.3 DOC and TOC
sequence, the sum parameter-based detector systems have an
3.01.3.1 Background
important bridging function between unresolved sum par-
ameterquantificationandsinglesubstancedetermination.All The basis for the parameters DOC and TOC is the chemical
these aspects have led on the one hand to a tremendous definitionoforganiccompounds.Theycanbeofbiogeogenic
increase of valuable information, but on the other hand to or anthropogenic origin. Most natural organic substances in
often uncritical interpretation of the results. The aim of this wateraretheleftoversofbiologicalactivitiesandproductsof
chapteris tofocus onsome wellestablished sumparameters a huge variety of naturally occurring physical, chemical, and
and to highlight their characteristics such as biochemical reactions in air, soil, and water. The endless
number of possible substances involved in these processes
1. background,
makes the identification tedious and, from the quantitative
2. principleofthemethod,
pointofview,impossible.Therefore,thetermsnaturalorganic
3. interferencesandlimitations,
matter (NOM) or humic substances (HSs) as the refractory
4. advancedmethod,
partofitareoftenusedforanintegrativedescription,andthe
5. application,and
parametersDOCorTOCforquantification(Thurman,1985;
6. relatedparameters.
Frimmel and Christman, 1988; Perdue and Gjessing, 1990;
Frimmel et al., 2002). Organic compounds of anthropogenic
origincanfindtheirwayintotheaquaticsystemsfromefflu-
3.01.2 General Considerations and Scope ents of wastewater treatment plants and industrial activities,
from chemical wastes and landfills, byaccidents during stor-
Sumparameterssuchassingle-compounddeterminationhave ageandtransportoforganicchemicals,andfromcombustion
to fulfill task-specific minimum requirements concerning andbydeposition fromtheair(Kolpinetal.,2002;Frimmel
exactness.Ithastobedecidedwhethertheprinciple‘asexact and Mu¨ller, 2006; Reemtsma and Jekel, 2006; Ku¨mmerer,
aspossible’ortheapproach‘asexactasnecessary’meetsbest 2008). In the current industrialized environment, it is quite
the requirements of the specific task. Often the desire for a idle to distinguish strictly between the purely natural com-
specific and sensitivemeasurement finds its limitation in the ponents and the anthropogenic ones in many cases. Con-
needsofahighthroughputofsamplesand/oraloweconomic cerning the quantification for C, this might be irrelevant
investment. A reasonable compromise can normally be anyhow. Table 1 gives an overview of the different C species
reached by a sound problem analysis prior to the determin- defined according to their character and/or to the pretreat-
ation itself. In general, classical spectroscopic and electro- ment of the sample prior to elemental C determination. In
chemical methods cover the concentration range in aqueous practical work, the definitions often are only semi-quantita-
samplesfrommgdowntongl(cid:2)1(Skoogetal.,2003;Standard tivelyaccurate.
SumParameters: PotentialandLimitations 5
Table1 Commontermsforproperty-relatedTOCfractions POC) is retained together with the sorbed substances in/on
thefilterandthevolatilecompounds(volatileorganiccarbon,
Synonym Meaning,definition
VOC)arenormallylost:
AOC AssimilableOC(seeSection3.01.4.4.5)
BOC BiodegradableOC(bymicroorganisms) (seeSection TOC¼DOCþPOCkþVOCm ð2Þ
3.01.4.4)
COC ChromatographableOC(byLC,GC,etc.)(seeSection Thismethodhasbeenwidelyaccepted,eventhoughthere
3.01.3.4) are still controversial debates on the influence of the mostly
DOC DissolvedOC(o0.45mm) poorlydefinedfiltercakes,ontheresultsandwhetherthepore
DOM DissolvedOM(E50%DOC) sizeofthefiltershouldbechosentobe0.1mmorevenbelow
NOM NaturalOM(geogenic)
thattobetterreflectthedissolvedstate.Awellacceptableway
POC ParticulateOC(40.45mm)
outoftheseproblemscanbeseeninadetaileddescriptionof
POP Persistentorganicpollutants
theexperimentalprotocolofthemethodapplied.
ROM RefractoryOM(poorlybiodegradable)
VOC VolatileOC(e.g.,boilingpoint(substances)o801C) The occurrence of TOC is a consequence of life on the
Earth. The ubiquity of TOC in aquatic systems has been
OC,organiccarbon;OM,organicmatter. demonstrated in many investigations (Table 1). It is mostly
refractory,thatis,thebiologicallystable partof dissolvedor-
ganicmatter(DOC)whichleadstoakindofsteady-stateTOC
3.01.3.1.1 Relevance
concentration in the different aqueous phases. DOC is often
The relevance of TOC can be deduced from its character as used synonymously with TOC, and other properties of the
universal parameter. Other parameters reflecting specific OMarereflectedinspecificparameters(Table1).
properties of organic matter (OM) such as DOC or AOC or It is obvious that some terms and their definitions must
surrogate parameters such as UVAor COD can preferably be remainvague.Thismeansthattheconcernedparametervalues
relatedtotheTOCvaluetoprovidethebasisforanespecially can have a considerable span of uncertainty. Keeping this in
meaningful comparison of water samples.However, ithas to mind, it seems to be acceptable to use Equation (3) as an
be kept in mind that TOC as sum parameter always remains approximation based on many elemental analyses. Unfortu-
limited in the information it can supply on the chemical nately in literature, the databases are quite often unclear.
structureofthematteritreflects.Theinstrumentaltoolssuited Therefore, experimental data and procedures need to be de-
for continuous TOC determination can be used as detection scribedindetailandunambiguouslytobeuseful:
systemforchromatographic TOCfractionation andbythisit
canhelptoovercomethelimitationofstructuralinformation rðDOMÞE2rðDOCÞ ð3Þ
tosomeextent.
The total carbon (TC)includes all C in inorganic and or-
ganic form (Equation (1)). The total inorganic carbon (TIC)
reflects mainly the carbonate system (CO , HCO (cid:2), and 3.01.3.2 Analytical Procedure
2 3
CO 2(cid:2)),andbydefinitionalsothetracesofCO,CN(cid:2),OCN(cid:2),
3 Due to the high importance of TOC and DOC values in
and SCN(cid:2), which might be of relevance in specific waste-
waterassessment,therearestandardizedinternationalmethods
waters:
for their determination (DIN EN 1484, 1997; Standard
Methods 5310 B, 5310 C, 5310 D, 2005; see also Chapter
TC¼TICþTOC ð1Þ
3.11 StandardizedMethodsforWater-QualityAssessment).
They are mostly based on a quantitative oxidation of the
TOCcomprisesalltheCatomswhicharecovalentlyboundin organicmoleculestoCO whichcanbedeterminedwithavery
2
organic molecules and even particulate matter like carbon lowlimitofdeterminationaround10mgl(cid:2)1.Oxidationisdone
black. either by high-temperature (up to 9501C) combustion in the
In natural aquatic systems and water technology, the car- presenceofacatalyst(e.g.,platinum-groupmetals,cobaltoxide,
bonatesystemisconsideredtobemostrelevantduetoitshigh orbariumchromate)andoxygenoratambienttemperaturein
mass concentrations. TIC can be quantified as CO after solutionusingUVirradiationand/orchemicaloxidantssuchas
2
acidification (pHo2) and purging with an inert gas of high H2O2orpersulfate.InorganicC(IC)hastoberemovedwithin
puritysuchasN orAr.Thepurgingstepwouldalsotransfer a pretreatment step, for example, by acidification with H PO
2 3 4
other volatile substances suchasHCNorsmallorganicmol- andpurgingasCO .Thisseparationstepismostimportantfor
2
ecules suchas methane(CH ),methanol (CH OH),and C - reliableTOCresults,becauseTOCisquantifiedalsoasCO and
4 3 1 2
orC -halogencompoundsfromtheaqueousphasetothegas this value is much smaller than the IC concentration in most
2
phase. Due to the low concentrations of such volatile com- waters.TheCO producedfromtheinorganiccarbonatesystem
2
pounds in most waters, this is often neglected in the mass andfromtheorganicwaterconstituentscanbe(a)quantifiedin
balances,butitcanbeimportantintheassessmentofspecific the gas phase after drying and transfer to a nondispersive in-
situationssuchastheoccurrenceoftoxicsubstances.TheTOC frared(IR)detectoror(b)trappedinalkalineaqueoussolution
includestheorganiccarbon(OC)indissolvedandparticulate withcoulometrictitration.Theprincipleofasystembasedon
matter.ThesetwotypesofCcanbedistinguishedbyfiltration continuousflowinjectionofthesampleisshowninFigure1.
througha0.45-mmpore-sizemembrane,leadingtotheDOC Calibration can be done with defined aqueous potassium
inthefiltrate.Theparticulatepart(particulateorganiccarbon, biphthalate (C H O K) solutions for OC and with sodium
8 5 4
6 Sum Parameters:Potential andLimitations
CO2 analyzer CO2 analyzer Data system
Inorganic CO Organic CO
2 2
Aqueous sample Purger UV reactor Liquid waste
H PO K S O
3 4 2 2 8
CO -free air CO -free N
2 2 2
Figure1 Systemforcontinuous-flowTIC/TOCanalysis.
carbonate (Na CO ) solutions for IC. The different methods
2 3
operateintheconcentrationrange10mgl(cid:2)1or(C)o1gl(cid:2)1. Aqueous
sample
3.01.3.2.1 Method variations
Acid
There is another procedure for continuous-flow injection of
the aqueous sample (Figure 2). After acidification and per-
Oxidant
sulfate addition, the sample is split: one sample flow passes
(K S O )
2 2 8
through the UV reactor, whereas the other one passes to a
delay coil. The CO from each branch is separated by CO -
2 2
selectivemembranesintohigh-puritywater.Theretheincrease
intheelectricalconductivitycanbedirectlyrelatedtotheCO2 Delay coil UV reactor
concentration. The CO2 from the non-UV-irradiated branch 6 min 6 min
represents the TIC, whereas the CO from the irradiated
2
branchrepresentstheTC.TOCresultsfromthedifference.
SampleswithrelativelyhighlevelsofTOC(r(C)4mgl(cid:2)1) Membrane Membrane
and/or suspended OC can be well determined by the high- module module
temperature combustion method. This method is suited for
online measurement. The inorganic carbon can be converted
toCO2byacidification(pHo2)andremovedbypurgingorit CO2 CO2
canbequantified,forexample,inanondispersiveIRdetector. detector (TIC) detector (TC)
In the purged sample, OC can be quantified after high-tem-
peraturecatalyticoxidationasCO (Figure3).
2
AvariationofthemethoddeterminestheTCofthesample
afteritsdirectinjectionintothecombustionchamberwhichis Data treatment
kept at temperatures above 9501C to decompose all carbon- TC − TIC = TOC
ates.TIC and TOCorother carbon fractions can be deduced
Figure2 Membrane-basedprocedureforthecontinuous-flowTIC/TOC
fromtherespectivedifferences.
analysis.
3.01.3.3 Interferences
separate quantification of the concentration of particulate
Special care has to be taken with TOC determination of sus- matterandthatofthedissolvedmatter,forexample,afterap-
pensions. Often the analytical homogeneity and hence the plying filtration through a membrane with defined pore size.
representative character of a sample are endangered by sedi- However, it has to be kept in mind that the filtration can be
mentation and its kinetics. A way out of that dilemma is the influenced by the type of membrane and its bleeding (Khan
SumParameters: PotentialandLimitations 7
Inorganic
CO (TIC)
2
H SO or
2 4
H PO
3 4
Organic CO
Catalytic 2
(OC) (+ H O,
Sample Purging unit combustion 2
chamber HCl …)
Gas (air)
O
CO2 free CO 2free Cooler
2
CO analyzer
2
(non-disp. IR)
Figure3 ExperimentalsetupforthecatalyticcombustionmethodforTIC/TOCdeterminationinaqueoussolutions.
and Pillai, 2007), its surface tension, and age and state of powerfulinstrumentationforquantificationpavedthewayfor
equilibration.Inaddition, undefinedporeblockingandsorp- their advanced analysis. In addition to all, the intelligently
tionprocesseshavetobeconsidered.TheDOCconcentration designedexperimentswhicharecontrolledbyasuiteofTOC
atthebeginningofafiltrationexperimentcanbequitedifferent orDOCmeasurements,aliquidchromatographic(LC)system
to the DOC concentration at the end. For samples with high with online DOC detection has been developed (Huber and
turbidity,filtrationthroughasetoffilterswithdecreasingpore Frimmel,1994)foradvancedOCcharacterization. Especially
sizeanddeterminationofthefractionsobtainedcanbearea- theprincipleofsize-exclusionchromatography(SEC;e.g.,TSK
sonablethoughtime-consumingoption.Anotherpossibilityis HW-50Sor-40Sturnedouttobeusefulfortheassessmentof
thedeterminationofthecolloidalindex(CI,alsoknownassilt DOManditsbehaviorinwater-treatmentprocesses(Heretal.,
density index SI or fouling index FI) for OC characterization 2002b).TheprincipleofthemethodisgiveninFigure4.
(ASTMStandardD4189-07,2007).Theprincipleofthemethod To reach high chromatographic resolution and low de-
istorelatethespecificfiltratevolumeswiththetimeneededto tectionlimits,specialcarehastobetakenforlowbackground
obtainthemasthefiltrationprocessproceeds. levelsofOC.Thismeansthatthephosphatebufferasmobile
Incaseshort-wavelengthUVlampsareusedtoincreasethe phase,theN carriergas,andthephosphoricacidasacidifier
2
amountofOHradicalsforoxidation,carehastobetakenas for the CO purging of the inorganic carbonates have to be
2
theintensityoftheUVlightmaybereducedbyhighlyturbid freeoforganiccontamination.Thesamplecanbeinjectedto
samplesorbyagingofthelightsourceresultinginincomplete either pass the column or bypass it. This leads to the possi-
oxidation.Problemscanalsoarisebychlorideconcentrations bility of determining the amount of chromatographable OC
above0.05wt.%,duetopreferentialoxidationofchloride. andtheTOC.Betweenthecolumnandthespinningthinfilm
AtrelativelylowDOCconcentrationsaspresentinmarine photoreactor, noninvasive online UV/visible (Vis) and fluor-
systems,specialcarehastobetakentoguaranteecorrectresults. escencedetectorscanbeinstalledtogivemulti-dimensionally
Dafner and Wangersky (2002) showed that special attention detectedchromatograms.Inprinciple,theretentiontimes(or
towardthecleannessofthesamplingfacilitiesandprocedureis elution volumes) obtained for SEC columns are reversely
crucial. Sample storage should be short (o2 days) at low correlatedwiththemolecularsizeandingoodapproximation
temperature (o41C) and in the dark. Examples for field pro- withthemolecularweightoftheelutedsubstances.
cedures to collect and preserve freshwater samples for DOC The column elution can be calibrated with polyethylene
analysis were shown by Kaplan (1994), and Zsolnay (2003) glycols and/or polystyrene sulfonates. The exclusion volume
addressed some basic problems and artifacts such as flock (V ) and the permeation volumes (V ) can be determined by
0 P
formation and agglomeration in sampling and preserving dextrane blue and methanol, respectively. However, the mo-
DOM from soil seepage water (see also Chapter 3.06 Sam- lecular size calibration bears some problems because aquatic
pling and Conservation, Chapter 3.07 Measurement Qual- TOCcontainsmanyunknownsubstancesandhencecalibration
ity in Water Analysis). Blank samples should be run to with authentic molecules is impossible (Lankes et al., 2009).
determine background values of equipment, used chemicals, Most common errors come from interfering adsorption and
gases,andfilters(inthecaseofDOCdetermination). ion-exchange effects of the eluted substances in the stationary
phaseofthecolumns.AtypicalchromatogramoftheOMintap
water obtained by UV (l¼254nm), fluorescence (l ¼254
3.01.3.4 AdvancedTOC(DOC) Characterization ex
nm,l ¼450nm),andOCdetectionisgiveninFigure5.
em
The great relevance of TOC and DOC parameters for the as- The OC trace of the chromatograms of the injected water
sessment of aquatic systems together with the available withaTOCconcentrationof0.5mgl(cid:2)1showsadominanceof
8 Sum Parameters:Potential andLimitations
Aqueous
sample Data logging
processing
Eluent Column UV/Vis Fluorescence
(P-buffer) (e.g., SEC) detector detector
Piston Injection IR Inorganic
pump port Phosphoric detector CO
acid pH 2 Peltier 2
con-
UV thin film
Piston denser
pump reactor IR Organic
Carrier
detector CO
gas (N) 2
2
Liquid
waste
Figure4 ExperimentalsetupforthesizeexclusionchromatographiccharacterizationofaquaticOC.
OC
al V0 Vp Fluorescence
n UV
g
si
50)- 1.0
4
e (
c
n
e
c
s
e
or
u
4)-, fl
5 0.5
2
V (
U
C-,
O
e
v
ati
el
R
0
20 40 60 80
Elution volume, V (ml)
e
Figure5 Multi-dimensionalsizeexclusionchromatogramsfortapwater(Karlsruhe,samplingdate07.07.09;r(DOC)¼0.5mgl(cid:2)1;resin:
TSKHW-50S;eluent:phosphatebuffer,26.8mmoll(cid:2)1;injectionvolume2.5ml).
high molecular substances between 40 and 50ml of elution 3.01.3.5 Applications
volume followed by a less large fraction. This material has a
TheDOCmethodsandtheircombinationwithfractionation
relativelystrongUVAanddoesfluoresce.Itisattractivetoas-
methods (e.g., SEC-UV/OC method) are well suited for the
sign these fractions to refractory HSs of higher and lower
advanced characterization and semi-quantitative assessment
molecular size. The relatively sharp chromatographic peak
of environmental processes such as nutrient cyclingand pol-
reflects small organic acids as reported by Brinkmann et al.
lutanttransportaswellastechnicalwater-treatmentprocesses.
(2003a, 2003b) and is followed by gradually eluting un-
(see also Chapter 3.15 Characterization Tools for Differ-
identifiedOC.
entiating Natural Organic Matter from Effluent Organic
Therearesomedetector-specificdifferencesinthefractions
Matter).
andintheirrelativeintensities.Ingeneral,however,themain
fractions look quite similar. As a consequence, the easy-to-
measure UVA is often used as surrogate parameter for OC
determination(Heretal.,2002a,2003).Inthecaseofverylow 3.01.3.5.1 Hydrosphere
backgroundvalues,fractionsofafewtensofngl(cid:2)1OCcanbe Typical ranges for TOC/DOC concentrations of aquatic sys-
quantified. temsaregiveninTable2.
SumParameters: PotentialandLimitations 9
Table2 DOCindifferentaquaticsystems
Aquaticsystems DOCconcentration(mgl(cid:2)1) References
Average Range
Ocean 0.5 0.3–2.0in0–300m; Williams(1971);DuursmaandDawson(1981)
0.2–0.8in4300m
Freshwater
Iceandsnow 0.5 0.1–5.0 Lairdetal.(1988);Frimmeletal.(2002)
Rivers 7 5–9 Malcolm(1985);Sontheimeretal.(1986)
Lakes 2.2 Oligotrophic2–3 Steinberg(2003);McKnightandAiken(1998)
Eutrophic9–16 Aitkenhead-Petersonetal.(2003);BertilssonandJones(2003)
Brownwater 12 10–50 Thurman(1985);FrimmelandAbbt-Braun(1999)
Soilseepagewater 25 19–31 Abbt-Braun(1992);Frimmel(1992)
Rain B1 B0.5upto10 Dinaretal.(2006);GraberandRudich(2006)
Groundwater,CaCO aquifer 0.7 Matthessetal.(1992);Wedepohl(1969)
3
3.01.3.5.2 Surface water 3.01.3.5.3 Water treatment
The SEC-UV/OC method finds a broad application in char- The SEC-OC system can also be used to follow technical
acterizing the OM of rivers. In Figure 6, typical chromato- separation processes such as flocculation, membrane fil-
grams for (a) the river Rhine (Germany) and (b) the river tration,oradsorption.Figure7showstheexampleofboglake
Moskva (Russia) are shown. Although the DOC concen- (brown water) OC as it decreases after (a) addition of ferric
trations are significantly different, the main fractions of the chloride(flocculationwith FeCl )and(b)equilibrationwith
3
OC for both rivers are quite similar, but the small-sized increasing amounts of powdered activated carbon (PAC; ad-
substances are more abundant in the caseof the riverRhine. sorption). It is obvious that in flocculation most of the OM
Both rivers show a small but significant OC fraction around (87%) gets eliminated. Especially, the high-molecular-size
the exclusion volume without any UVA. It could be shown substances get better eliminated than the small ones. Inter-
that these substances are of high molecular carbohydrate esting to note is the high elimination yield of UV-absorbing
type. matter and the relatively, poor elimination yield of AOX
For comparison, the chromatograms for water from a formingprecursors.
brownwater lake (c) and for wastewater (d) are shown. The InthecaseofPACadsorption,therestOCwhichremains
brown water is dominated by a single fraction and it is at- in solution is strongly dependent on the amount of PAC
tractivetoassignittoplant-derivedmatterofhumicstructure. added as expected but it is mainly higher molecular matter
In the case of the wastewater, there are obviously plenty of whichremainsinsolution.Thesefindingscanbeexplainedby
low-molecular-weight organic substances (acids) which get thelimitedavailabilityofporeswithlargersize.
eliminated by biological treatment. As a result of biotreat- All information that can be derived from advanced OC
ment, a large organic fraction with low UVA is generated. characterization does not only supply the basis for a better
Based on the assignment to matter with carbohydrate struc- understanding of the mechanisms which rule the OC distri-
tures, this fraction around the exclusion volume of the SEC bution, but it also opens the door for the development of
column can be used for a rough estimation of the alloch- technically relevant elimination processes and their opti-
thonousandautochthonouspartofaquaticrefractoryOC.In mization(seealsoChapter3.15 CharacterizationToolsfor
large molecular size fractions, there was a predominance of Differentiating Natural Organic Matter from Effluent Or-
polysaccharidematerial.N-Acetylatedpolysaccharidesderived ganic Matter, Chapter 3.16 Chemical Basis for Water
from microbial leftovers. Lignin and tannin derivatives were Technology).
mostabundantintheintermediatesizefraction(Lankesetal.,
2008). However, detailed interpretation has to rely on ad-
3.01.3.6 SurrogateParameters
vancedspectroscopicinformationonmolecularstructure.For
acriticalevaluationofOCassignment,see,forexample,Abbt- Thereareanumberofsumparametersforthedetermination
Braun et al. (2004), Lankes et al. (2008), Reemtsma et al. of OM which have been developed independently or sup-
(2008),andKunenkovetal.(2009).Also,ithastobekeptin plementary to the DOC/TOC methods. Most of them work
mind that photochemical OC detection often does not work simpler and therefore find a broad application as surrogate
quantitatively, for example, up to 70% of certain OC com- parameters for OC. They focus on a specific character of the
pounds were not detected with the organic carbon detection presentorganicsubstancesandcanaddvaluableinformation
system in systematic investigations (Lankes et al., 2009). As- fortheassessmentofwaterquality.Theirspecificinformation
suming that the majority of refractory OM components do canberelatedtothemassunitofOCasauniversalparameter
absorb UV radiation, UVA values are a valuable supplement and which can supply the basis for a sound assessment and
forOCdetection. comparison of different aquatic sources or for following a
10 Sum Parameters:Potential andLimitations
2.0 V V 4 V0 Vp
0 p
OC
4)-signal 1.5 RRihvienre w (WUatVeörrth) 54)-signal 3 RMiovsekr vOUwaVCa (tKeorlomna)
C-, UV (25 1.0 (cid:2)(OC) = 1.7 mg l−1 OC-, UV (2 2 (cid:2)(OC) = 8.5 mg l−1
e O ve
elativ 0.5 Relati 1
R
0.0 0
20 40 60 80 20 30 40 50 60 70 80
(a) Elution volume, Ve (ml) (b) Elution volume, Ve (ml)
2.5 V V
0 p
V V
OC 0 p
UV 4
OC-, UV (254)-signal 12..50 B(cid:2)d(irlOouwtCion)n =w: 1a2:t71e.0r7 HmOg2 l3−1 OC-, UV (254)-signal 23 dW(cid:2)Wb(cid:2)(i(ilOoaOualstsCoCitotgee))nab wi w=c=::: aa a1OU 29tlt: eV4eC3.t9rr.re 9 (ema OmftfgmClgu l)e e−l1n−n1tt, (aOftCer)
Relative 1.0 Relative 1 a
b
0.5 0
20 40 60 80 20 40 60 80
(c) Elution volume, Ve (ml) (d) Elution volume, Ve (ml)
Figure6 SizeexclusionchromatogramdetectedbyOC-andUV(l¼254)-detectionofriverwater((a)riverRhine,(b)riverMoskva),brownwater
((c)Hohlohsee,HO23),andwastewater(dilution1:3)andwastewatertreatmentplanteffluent(d)(resin:TSKHW-50S;eluent:phosphatebuffer,
26.8mmoll(cid:2)1).
complete treatment pathway. Most common surrogate par- biochemical degradation reactions of C-compounds and
ameters and complementary parameters for OC are given in chemicalcombustionsifsufficientO isavailable.
2
Table3.Theyarediscussedinthefollowingsectionsinmore According to the high importance of the load of organic
detail. substances in water, their oxidative transformation into CO
2
hasbecomethebasisforthedevelopmentofsumparameters
for quality assessment (Wagner, 1973). Most of them are
3.01.4 Oxygen Demand Parameters basedonthequantificationoftheoxygennecessaryforamore
orlessquantitativeoxidationofallorganiccompounds.There
3.01.4.1 Introduction are purely chemical methods and there are biochemical
methods,usingamixedbacterialpopulation.
Despite the broad distribution, the stability of the non-
radioactive elements leads to their quite constant total
amounts on earth. However, their appearance in different
3.01.4.2 Chemical OxygenDemand
compounds and phases called speciation makes them dis-
tinguishable according to the chemical bonds in which they 3.01.4.2.1 Background
are engaged (Pauling, 1960). The corresponding oxidation TheaimoftheCODistoobtainacompleteoxidationofall
state of the atoms in their chemical appearance is a typical organiccompoundsofanaqueoussampletoCO .Thisisbest
2
guidefortheirreactivity.Carbonisoneoftheelementswhich reached by wet oxidation with potassium dichromate
covers all the range of eight oxidation state levels from the (K Cr O )inhotacidsolution.Problemscanarisefromother
2 2 7
lowestoneof (cid:2)IVinCH uptothehighestofoneof þIVin waterconstituents,forexample,inorganicones,whichalsoget
4
CO . The elemental form is represented by the graphite and oxidized under the reaction conditions. These disturbances
2
diamond structure. CO is the common end product of all canbetackledbyeliminationofthesubstancesconcernedor
2