United States
Environmental Protection
Agency
Municipal Environmental Researc
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-016 Mar. 1981
Project Summary
Chlorination of Aquatic
Humic Substances
R. F. Christman, J. D. Johnson, D. L Norwood, W. T. Liao, J. R. Hass, F. K.
Pfaender, M. R. Webb, and M. J. Bobenrieth
The overall objective of this research
program was to increase our
understanding of the chemical struc-
tures of aquatic humic material and
their behavior during chemical oxida-
tion, in particular with chlorine.
Experimental methods devised to
isolate humic and fulvic acid fractions
from natural surface waters involved
classical precipitation of humic acids
from large volumes of raw water, fol-
lowed by concentration through
settling and centrifugation. Fulvic acid
materials were concentrated by
adsorption on macroreticular XAD-2
resin followed by base elution. The
controlled oxidation of these samples
with solutions of potassium perman-
ganate (KMnO4) and aqueous chlorine
was followed by solvent extraction,
formation of methyl esters, and
GC/MS analysis. The criteria for
identifying degradation products with
the use of low resolution El, high
resolution El, and Cl mass spectro-
metry are included in appended mate-
rial. Results of the whole-sample
degradation experiments also dictated
how chlorination experiments were
conducted on selected model
compounds.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory, Cincin-
nati. OH 45268, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Aquatic humic material has been
heavily implicated as an important
reaction precursor of trihalomethanes
in natural water systems exposed to
chlorine. It has been assumed that
humic materials are ubiquitously
present in natural waters and have
sufficient chemical similarity in time
and space to account for the observed
property of producing trichloromethane
(CHCIs) when exposed to chlorine.
Further, it has been assumed that the
mechanism of the chlorine (ClzJ-humic
interaction involves the classical halo-
form reaction and that trihalomethanes
are the principal reaction products.
Public and governmental concern over
the presence of CHCIa in drinking water
has focused attention to this
phenomena, and the aforementioned
assumptions have been made because
of inadequacies in our scientific under-
standing of the fundamental chemical
structures present in aquatic humic
materials and, therefore, the reactions
of these structures with chlorine.
The research described in the full
report focuses on the chemical charac-
terization of the reactions of aquatic
humic materials with hypochlorousacid
(HOCI), and the report begins with a
comprehensive literature review. The
experimental approach involved (1)the
chemical degradation of natural aquatic
humic material to gain insight into the
dominant chemical structures in this
natural product material, (2) the reac-
tion of HOCI with model compounds
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having structures similar to the degra-
dation products, and (3) the identifica-
tion of nonvolatile chlorinated and
nonchlorinated degradation products of
natural aquatic humics with HOCI.
Each experimental direction is de-
scribed separately, although the
experimental planning was heavily
influenced by the results of current
work. For instance, early model com-
pound work established that total
trihalomethanes were a minor portion
of the total chlorine demand and,
subsequently, only less volatile reaction
products were emphasized in the actual
humic chlorination experiments. Simi-
larly, the dominance of aromatic
products in the oxidative degradation
mixtures resulted in the exclusion of
aliphatic compounds in the model com-
pound experiments.
The oxidative degradation
experiments reported here have
generated significantly more chemical
structural information on aquatic humic
material than was previously available
in the literature. Controlled oxidation
with KMnOa followed by solvent extrac-
tion, formation of methyl esters, and
GC/MS analysis has established that
the principal identified degradation
products of aquatic humic acid are
aromatic polybasic acids, some of which
are hydroxylated. The degradation
mixture also contains a complex mix-
ture of aliphatic mono- and dibasic acids
in lesser concentrations. Although most
of the chromatographable degradation
products were tentatively identified (low
resolution El, high resolution El, Cl mass
spectrometry), only 20 to 30 wt.% of the
original humic carbon is accounted for
by the identified products. The chemical
data generated in this study do not
provide a fully adequate scientific basis
for modeling humic structures.
However, a hypothetical structure is
presented that would account for the
observed data.
Results and Conclusions
Direct chlorination of both aquatic
humic materials and model compounds
shown to be major component parts of
the aquatic humic and fulvic materials
produced chloroform. Because
dihydroxy aromatic configurations were
significant contributors to the humic
macromolecular structure, the reaction
of resorcinol with HOCI was investi-
gated carefully as a model. A cyclic
chlorinated diketone intermediate was
identified along with other non-CHCIa
reaction products. In addition to chloro-
form, a large number of chlorinated and
nonchlorinated acids, phenols, and
ketones were produced. Ring cleavage
products such as saturated and unsatu-
rated aliphatic mono- and dicarboxylic
acids were major products of model as
well as natural humic materials. Only
small portions (8 to 17 wt.% of total
organic carbon, TOC) of the aquatic
humic material subjected to high pH and
excess chlorine yielded products identi-
fiable by GC/MC (Table 1). Thus,
although hypochlorite (OCI~) is a signifi-
cant degrader of the humic macromole-
cule, it is not as effective as alkaline
KMnO«. The majority of the identified
chlorine degradation products were
nonchlorinated aliphatic acids. The
aromatic acids are primarily polycar-
boxylic, suggesting carbon substituted
on the aromatic rings at three or more
sites in the undegraded macromolecule;
this agrees with the KMnO* data. No
chlorinated aromatic compounds were
identified, however.
Aquatic humic materials are thus
shown to be important precursors of not
only chloroform but also a large number
of other chlorinated and nonchlorinated
organic compounds. Although aromatii
compounds dominate both the KMnO
and HOCI degradation products, theydi
not appear to chlorinate directly. Thi
experimental procedures used in thi
study have shown significant promisi
as a tool for increasing scientific under
standing of fundamental aquatic humi
chemistry. More structural informatioi
can be gained through additions
research on increased oxidative yieli
and extraction and separation effi
ciencies. A method for following thi
changes in macromolecular size/
polarity during the degradation wouli
be extremely useful.
The development of the technique
reported here permits an even wide
range of useful experimentation
Questions to evaluate include (1) di
fulvic acids (most of the TOC) yield quali
tatively and quantitatively simila
results, (2) do the chemical properties o
the humic and fulvic fractions van
seasonally for any source, and (3) wha
chemical variability exists betweei
natural water sources? In addition, thi
effect of oxidant/disinfectants othe
than OCf on humic structures shoul<
be evaluated.
Table 1. Non - Volatile Products of A quatic Humic A cid Chlorination Product Identi
fications and Relative Yields Ether Extract (Methyl Esters)3
Scan. No.
from
Figure 44 Assigned Structure
Ethyl Acetate
Ether Extract* Extract*
Relative Yield % Relative Yield %
Peak Weight (C)/ Peak Weight (C)/
Total Weight C Total Weight C
7 CH3CHzCH(CH3)COOCH3
RCH2COOCH3
1 1 CH3CHCICOOCH3
16 CHCI2COOCH3
22* CCI3COOCH3
22 CI2C=CHCOOCH3
26,37,40 Chlorinated Aliphatic
Methyl Esters
CH3OOCCH2COOCH3
CH3OOCCH=CHCOOCH3
n.d.c
28.4
14.7
9.6
n.d.
3.4
n.d.
0.5
0.2
0.1
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Table 1 . Continued
Ether Extract*
Scan. No. Relative Yield %
from Peak Weight (C)/
Figure 44 Assigned Structure Total Weight C
44
52"
63
-
66
69
77
84
84
88
96
100
115
120.125
151
CHaOOCCHzCHsCOOCH,
^ \COOCH3
CH3OOCCH=CCICOOCH3
CH3OOCCH=CHCOOCH3
CH3OOCCHZCHCICOOCH3
CHzCICHCICOOCH3 or
CHCI2CH2COOCH3
Aliphatic Methyl Ester
CH3OOCCH=CCICOOCH3
CH3OOCC3H3CICOOCH3 +
CH3OOCC2H2CI2COOCH3
Isomer of above compounds
CH3OOCCCI=CCICOOCH3
CH3OOCC3H3CICOOCH3 +
CH3OOCC3H3RCOOCH3
CtHgCOOCHa
«pf0/y,
/ \ CHa
^=*&(OH)3
0.2
4.1
1.6
0.2
0.1
0.3
0.4
4.7
0.1
0.9
0.5
0.1
2.6
2.3
Ethyl Acetate
Extract*
Relative Yield %
Peak Weight (C)/
Total Weight C
0.7
5.2
0.2
2.2
159"
163"
0.9
0.5
3.8
COOCH3
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Table 1. Continued
Scan. No.
from
Figure 44 Assigned Structure
Ether Extract*
Relative Yield %
Peak Weight (C)/
Total Weight C
Ethyl Acetate
Extract"
Relative Yield %
Peak Weight (C)/
Total Weight C
168
187
198
230
255s
COOCH3
COOCH3
CH3OOCCC/=C(COOCH3)2
C6(OCH3)6
COOCH3
rCOOCH3
0.8
2.9
0.5
1.7
5.4
COOCH3
COOCH3
COOCH3
COOCH3
1.0
14.5
2.2
255
265s
265
274
304
321"
330
355
370
408
CeH9OsCI3
COOCH3
HsCOOC COOCr/3
CsHdCH3)(coocHa)a
CeH^CHzCOOCHa)
(COOCH3)3 +
unknown chlorine compound
CeH3(COOCH3)3
COOCHa
0COOCH3
COOCHa
C6Hi(COOCH3)<
CeWCOOCHa)*
C6Hi(COOCH3)*
CBH(COOCH3)5
n.d.
1.9
0.2
0.2
0.3
1.0
0.9
0.4
0.3
0.3
1.6
25.2
15.8
2.1
1.3
'Reaction Conditions: Total Volume=320 ml; Carbon Concentrations=420 mg/l; OCC/C Mole Ratio=X 1.0
Chlorination Time=48 hr.
''For the individual extract.
c=not determined.
"=not detected.
'Confirmed with matching spectra.
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R. F. Christman, J. D. Johnson, D. L. Norwood, W. T. Liao, J. R. Mass, F. K.
Pfaender, M. R. Webb, and M. J. Bobenrieth are with the University of North
Carolina at Chanel Hill. Chanel Hill NC. 7 7.114
Alan A. Stevens is the EPA Project Officer (see below).
me complete report, entitled "L'niormation or aquatic Humic Substances,"
(Order No. PB 81-161 952; Cost: $15.50, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
> U.S GOVERNMENT PRINTING OFFICE. 1M1-757-044/029*
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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