P- t 7/6 ".
CHEMICAL, MICROBIOLOGICAL, AND MUTAGENIC EFFECTS OF USING
ALTERNATIVE DISINFECTANTS FOR DRINKING WATER TREATMENT
by
Benjamin W. Lykins, Jr.
Kathleen M. Schenck
Drinking Water Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Wayne E. Koffskey
Department of Public Works
Jefferson Parish
Jefferson, Louisiana 70121
and
Mark H. Griese
Water Quality and Research
Evansville Water 4 Sewer Utility
Evansville, Indiana 47740
The University of Kansas
42nd Environmental Engineering Conference
Lawrence, Kansas
February 5, 1992
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
CHEMICAL, MICROBIOLOGICAL, AND MUTAGENIC EFFECTS OF USING
ALTERNATIVE DISINFECTANTS FOR DRINKING WATER TREATMENT
Benjamin W. Lykins, Jr.
Chief
Systems and Field Evaluation Branch
Kathleen M. Schenck
Biologist
Systems and Field Evaluation Branch
Drinking Water Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Wayne E. Koffskey
Chief Chemist
Jefferson Parish Department of Public Utilities
Jefferson Parish, Louisiana 70121
and
Mark H. Griese
Manager
Water Quality and Research
Evansville Water And Sewer Utility
• Evansville, Indiana 47740
INTRODUCTION
Future Federal regulations for disinfection/disinfection by-products will
potentially effect most water treatment plants in the United States. In antici-
pation of proposing regulations in June 1993, the U.S. Environmental Protection
Agency is in the process of assessing the performance and potential health risks
of several drinking water disinfectants and their by-products. In order to pro-
vide field data for this assessment and to more thoroughly understand the inter-
actions of disinfection and disinfection by-product control regarding the advan-
tages and disadvantages of a selected direction, studies were done at two drink-
ing water utilities. This paper will discuss some of the results from these stu-
dies which consisted of a pilot plant evaluation at Jefferson Parish, Louisiana
and bench-scale evaluations at Evansville, Indiana.
REGULATIONS
Existing disinfection/disinfection by-product regulations apply only to tri-
halomethanes with a maximum contaminant level (MCL) of 0.10 mg/L. Also, this
regulation only applies to systems serving more than 10,000 people. Possible
-------
future disinfection/disinfection by-product requirements will apply to all public
water systems including non-community systems. Compounds likely to be regulated
with MCLs when these regulations become effective are:
• Trihalomethanes (chloroform, bromodichloromethane,
chlorodibromomethane, bromoform)
• Haloacetic acids (trichloroacetic acid, dichloroacetic acid)
• Chloral hydrate
• Bromate
• Chlorine, chloramines, chlorine dioxide, chlorate, chlorite
Over twenty compounds have been considered for regulation and those excluded
at this time were done so for basically two reasons: (1) insignificant health
risk at levels that occur in drinking water such as haloacetonitriles and chloro-
picrin, and (2) health risks not adequately characterized in time for the reg-
ulation such as the aldehydes. As far as the tri hal omethanes are concerned,
there are several options being considered. One option is to develop an MCL for
each of the four trihalomethanes. Other options include: (1) an MCL for the
total trihalomethanes or, (2) an MCL for each of the trihalomethanes and an MCL
for the total trihalomethanes.
The reasons that these trihalomethane options are being considered are
because the health risks for the individual trihalomethanes are significantly
different, technical feasibility for limiting their formation can vary for each
compound, and hopefully, the trihalomethane regulation can act as a surrogate to
limit other halogenated by-products. Traditionally, drinking water standards for
contaminants are set at the lowest possible number which is technically and eco-
nomically feasible. However, one has to ensure that drinking water is micro-
biologically safe which may mean that a greater risk will have to be accepted
from disinfectants and disinfection by-products than for other contaminants. An
example of this is shown in Figure 1 where risk trade-offs have to be considered
between microbial control and production of disinfection by-products.
ALTERNATIVE DISINFECTANT STUDIES
Jefferson Parish, Louisiana
For this study, raw river water from the Mississippi River was pumped to the
full-scale plant where it was clarified with diallyldimethyl ammonium chloride
or dimethyl amine-type cationic polymers. After fluoridation, but before disin-
fection a portion of the clarified water was filtered through pressure sand fil-.
ters before going to a 10 gallon-per-minute pilot plant. This pilot plant was
operated in a conventional mode with disinfection followed by sand filtration.
Post treatment consisted of granular activated carbon after sand filtration.
Figure 2 shows the flow diagram for this mode of operation.
Each disinfectant contact chamber was 12.75 inches (320 mm) outside diameter
and constructed of stainless steel. The chlorine, chloramine, and chlorine
dioxide contact chambers were 10 feet (3m) in height, producing approximately 30
minutes disinfectant contact time with a flow of 2 gpm (0.13 L/s). The ozone
contact chamber was 11 feet (3.3m). in height, with countercurrent operation
consisting of water entering at the top of the contact chamber and ozone gas
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entering at the bottom. The water and ozone gas influent lines were oriented so
that the influent water would be in contact with the ozone gas stream for
approximately 30 minutes.
Ozone was generated from compressed dry air using an electrically powered
ozone generator with a maximum output capacity of 0.25 Ib/d (0.11 kg/d).
Chloramine was produced by adding hypochlorous acid to the water stream a few
seconds prior to the addition of ammonium hydroxide. Chlorine dioxide was gen-
erated using two solutions, one containing sodium chlorite and sodium hypochlo-
rite and the other containing sulfuric acid. The final pH of the solution was
4. Chlorine was added in the form of hypochlorous acid. Residual concentrations
after disinfection addition were maintained through the contact chambers to be
comparable to those found in many drinking water utilities at the time the study
was initiated. Average residuals were 1.0 mg/L chlorine, 2.1 mg/L monochlora-
mine, 0.5 imj/L chlorine dioxide, and 0.5 mg/L ozone. The nondisinfected process
stream was identical to the disinfected process streams except for elimination
of the contact chamber. The major objectives of this study were to evaluate: (1)
the microbiological effectiveness of the disinfectants, (2) the control of halo-
genated by-products, and (3) potential health effects associated with the use of
these disinfectants.
Microbiological Effectiveness
All of the disinfectants at the dosages used, reduced the col i forms to
acceptable levels. However, with heterotrophic bacteria, all disinfectants
except chloramines reduced the levels to below 100. Other organisms may not have
been as effectively controlled by all disinfectants. For instance, during one
study when MS2 Coliphage was spiked into the pilot plant, chloramines were
ineffective for this virus indicator as shown in Table 1. Future studies at
Jefferson Parish will apply the concentration x time (Ot) concept for
determining disinfectant efficiency. An example of these C»t values that have
been developed for inactivation of various microorganisms by the major disin-
fectants is shown in Table 2.
Ha'logenated By- Product Control
During the one-year operation of the pilot plant, two surrogate parameters
that give an indication of organic concentrations including halogenated by-
products were evaluated: total organic carbon (TOC) and total organic halide
(TOX). The average TOC concentrations in the disinfectant contact chamber
effluents were 3.1, 2.9, 3.2, 3.2 and 3.2 mg/L for the nondisinfected, ozone,
chlorine dioxide, chloramine, and chlorine process streams, respectively. There
was some indication that ozone was reducing the TOC concentration while the
concentration of TOC was fairly constant for the other disinfectants. Further
in the treatment system after the ozone sand column, the TOC was reduced an addi-
tional 0.8 mg/L when compared to the nondisinfected system. Based on the levels
of heterotrophic bacteria in the effluents of the ozone contact chamber and ozone
sand column, the reduction of TOC across the ozone contact chamber appears to
have resulted primarily from oxidation while that across the ozone sand column
can be attributed to biodegradation.
With an average nondisinfected influent concentration of 25 (tg/L, TOX con-
centration increased significantly after 30 minutes of disinfectant contact time
-------
TABLE 1. JEFFERSON PARISH MICROBIOLOGICAL DATA
MS2
RESIDUAL COLIPHAGE COL IFORM HPC
STEAM (mq/U (ml) HOP ml) (ml)
NONDISINFECTANT ' - 400,000 640 43,000
OZONE 0.3 <1 0 14
CHLORINE DIOXIDE 0.5 . 1 0 57
FREE CHLORINE 1.0 <1 0 44
CHLORAMINE 1.9 46,000 0 270
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TABLE 2. SUMMARY OF C«t VALUE RANGES FOR INACTIVATION OF
VARIOUS MICROORGANISMS BY DISINFECTANTS (2'3'4)
Disinfectant
Micro-
oraanism
L. Coli
Polio 1
Rotavirus
Phage f2
G. lamblia
cysts
G... muris
cysts
Free Preformed
Chlorine Chloramine
oH 6 to 7 DH 8 to 9
0.034-0.05
1.1-2.5
0.01-0.05
0.08-0.18
47->150
30-630
Crvptosporidium 7200
-------
for chlorine dioxide, chloramine, and chlorine to 86, 99, and 246 fjg/l, respec-
tively. The same trend seen for TOC was also observed for TOX where an average
reduction of 33 percent occurred in the ozone contact chamber producing an aver-
age effluent concentration of 16 pg/L with a further reduction to 11 fjg/l across
the ozone sand column. Treatment of the sand filtered effluents with free chlo-
rine followed by 5 day storage to simulate the distribution system significantly
increased TOX concentrations for all process streams (557, 540, 339, and 379 vg/L
for nondisinfected, chlorine, ozone, and chlorine dioxide, respectively).
The trihalomethanes (THMs) reacted as expected with no significant concen-
trations (1 fjg/L average) observed in the disinfectant contact chamber and sand
column effluents of the nondisinfected, ozone, and chlorine dioxide process
streams. An average THM concentration of 3 fjg/L occurred in the chloramine dis-
infectant contact chamber and sand column effluents while that in the chlorine
contact chamber effluent averaged 39 /*j/L and increased to 49 /*j/L across the
chlorine sand column. By maintaining a chloramine residual for 5 days, the
terminal THM concentrations increased slightly to an average of 8.5, 3.2, 4.2,
and 9.4 //g/L for the nondisinfected, ozone, chlorine dioxide, and chloramine
process streams, respectively. Similar treatment and storage with free chlorine
produced relatively high terminal THM concentrations for the nondisinfected and
chlorine process streams with average concentrations of 236 and 225 fjg/l. When
compared to the nondisinfected sand column effluent, terminal THMs were 35 and
41 percent less when ozone and chlorine dioxide were used during pretreatment
resulting in average concentrations of 154 and 138 tig/I, respectively. As
expected, granular activated carbon (GAC) reduced all concentrations until the
columns became saturated in 60 to 80 days.
The haloacetic acids followed the same trend as seen with THMs except at a
lower concentration. The highest concentrations were formed using free chlorine
which mainly produced dichloroacetic acid (DCAA), trichloroacetic acid (TCAA),
and bromochloroacetic acid (BCAA). Chloroacetic acid (CAA), bromoacetic acid
(BAA), and dibromoacetic acid (DBAA) were also formed to some extent. Average
instantaneous concentrations for dichloroactic acid were 0.9, 1.7, 3.7, 1.1, and
13 fjg/l for the nondisinfected, chlorine dioxide, chloramine, ozone, and chlorine
process streams after sand filtration, respectively. Five-day terminal values
for the same process streams with free chlorine were 60, 44, 38, and 60 fjg/l for
the nondisinfected, chlorine dioxide, ozone, and chlorine streams, respectively.
Similar treatment of the sand filter effluents with chloramine and a 5 day
storage period resulted in only slightly elevated DCAA concentrations. The
slight concentration Increase is similar to that seen for THMs during similar
treatment with chloramine suggesting that both were formed by free chlorine
during in-s'itu formation of chloramine. GAC adsorption produced continued
removals of 80% or greater of DCAA after steady-state which was about 150 days
of operation. GAC steady-state was reached in about 250 days for DCAA after
storage for five days with a free chlorine residual. After GAC steady-state,
average removals were 48, 73, 53, 46, and 51 percent for the nondisinfected,
ozone, chlorine dioxide, chloramine, and chlorine process streams, respectively.
Similar observations for all unit processes were also seen for TCAA.
Relatively low concentrations of haloacetonitriles were formed across each
process stream with chlorine producing the highest levels which averaged 3.1
total haloacetonitriles. Less than 1 pg/L average of haloacetonitriles was
8
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observed across the other process streams. The predominant haloacetonitrile
(HAN) was dichloroacetonitrile (DCAN) followed by bromochloroacetonitrile (SCAN),
dibromoacetonitrile (OBAN), and trichloroacetonitrile (TCAN). Treatment of the
chlorine sand column effluent with additional free chlorine and subsequent 5-day
storage produced an average concentration of 1.9 pg/L of DCAN which was the same
as that of the sand column effluent suggesting that all DCAN precursors had
reacted. No consistent breakthrough of the HANs was observed through any GAC
column except that of the chlorine process stream, which was still removing over
95% of the influent HANs at the end of the one-year operational period.
Only two haloketones, 1, 1, 1-trichloropropane (TCP) and 1, 1-dichloro-
propane (DCP) were detected with the highest concentration (1 to 2 /*3/L) being
observed in the chlorine process stream. Post chlorination of the sand column
effluents followed by 5-day storage produced similar TCP concentrations in each
process stream with average concentrations of 2.1, 2.5, 4.2, and 2.5 fjg/l for the
nondisinfected, ozone, chlorine dioxide, and chlorine, respectively. Although
consistent breakthroughs of these haloketones were observed across the GAC
columns, removals remained above 85 percent throughout the one-year operational
period.
Chloral hydrate (CH) was formed predominantly in the chlorine process stream
with an average contact chamber effluent concentration of 2.9 fjg/l which in-
creased to 4.5 j/g/L across the sand filter because of an additional 30 minutes
chlorine contact time. The CH concentrations in the effluent of the chloramine
contact chamber and sand column were identical averaging 0.25 //g/L. CH was de-
tected intermittently in the contact chamber and sand column effluents of the
chlorine dioxide, ozone, and nondisinfected process streams at average concen-
trations ranging from 0.01 to 0.07 /*j/L. Post-treatment of the sand column
effluents with free chlorine and storage for 5 days produced relatively similar
CH concentrations averaging 79, 55, 45, and 75 /*}/L for the nondisinfected,
ozone, chlorine dioxide, and chlorine process streams, respectively. Similar
treatment with chloramine produced average concentrations of 0.03 to 0.3 fjg/l.
GAC adsorption removed all of the CH throughout the project in all process
streams.
The concentrations of chloropicrin (CP) in the effluents of the disinfection
contact chambers and the sand columns were the same, averaging 0.004, 0.004,
0.015, 0.038, and 0.43 ijg/l for the nondisinfected, ozone, chlorine dioxide,
chloramine, and chlorine process streams, respectively. Chlorination and 5-day
storage of the sand column effluents produced concentrations averaging 1.3, 7.7,
1.4, and 1.3 ^g/L for the nondisinfected, ozone, chlorine dioxide, and chlorine
process streams, respectively. Pre-ozonation appears to have produced an in-
crease in CP precursors. Only slight increases in CP concentrations were ob-
served after similar chloramine treatment and storage of the sand column efflu-
ents with average concentrations of 0.03, 0.04, 0.11, and 0.09 /xi/L for the non-
disinfected, ozone, chlorine dioxide, and chloramine, respectively. No consis-
tent breakthrough of CP above 0.003 //g/L was observed across the GAC column of
any process throughout the operational period.
-------
MUTAGENICITY STUDIES (Jefferson Parish. Louisiana)
Satnole Disinfection
For the health-related studies at Jefferson Parish, a portion of the clar-
ified water after fluoridation was filtered through pressure sand filters and
split into four process streams as shown in Figure 3. Three of these streams^
were disinfected with either chlorine, chloramine, or ozone while the fourth
stream was not disinfected and served as a control. Chlorine dioxide was not
evaluated at this time because it appeared that chlorine dioxide would not be an
acceptable disinfectant when the disinfection/disinfection by-product regulation
was promulgated. The system used for the three disinfected streams consisted of
a contact chamber followed in series by a sand column and a 55-gallon stainless-
steel drum fitted with a spiral stainless-steel baffle. The modified drum served
as an additional contact chamber. The system for the nondisinfected stream was
similar except that the initial contact chamber was omitted.s The contact time
in the contact chamber was approximately 30 min for each of the disinfected
streams and the empty-bed contact time for the sand column was approximately 20
min. The ozone stream was split after the sand column and post-disinfected with
either chlorine or chloramine. As a result of stream splitting, the flow rate
to the two post-disinfected drums was decreased. Therefore, the contact time for
post-disinfected drums was approximately 150-180 min while the contact time for
the non-ozonated chlorine and chloramine streams and the nondisinfected stream
was approximately 85-100 min. The amount of chlorine and chloramine added to the
two ozonated streams was adjusted so that the residual disinfectant concentration
leaving the drums matched the corresponding final residuals observed for the
chlorinated and chloraminated (non-ozonated) streams (0.5-1.0 ppm C12 and 0.8-1.5
ppm NH2C1).
SAMPLE COLLECTION
Macroreticular resins (Amber!ite XAD-8 and XAD-2) were used to collect and
concentrate the organic compounds from the process streams for chemical and
toxicological testing. The concentration procedure described by Miller et al.
was used with the following modifications. Ethyl acetate was utilized instead
of acetone to elute the organic material from the XAD resins and the ratio of
sample volume to resin volume was decreased from 760:1 to 150:1. The change in
ratio was made to minimize the potential breakthrough of MX, 3-Chloro-4 (dichlor-
omethyl)-5-hydroxy-2(5H)-furanone, and compounds with similar solubilities in
water. The XAD resins were cleaned by Sohxlet extraction with ethyl acetate and
methanol for 24 hr and stored in methanol. Prior to sample collection, each
column pair containing 5 L of XAD-8 and XAD-2 resin was flushed with 200 L of
water to remove the residual methanol. Fifteen hundred liters of each of the
process streams were passed through the column pairs serially at a flow rate of
60 L/min. The pH of the column influent was maintained at pH 2 by the in-line
addition of 9N hydrochloric acid.
Following sample collection, each column was filled with sufficient ethyl
acetate to provide a standing head. The columns were then agitated to completely
wet the resin and allowed to equilibrate for 15 minutes. Each column pair was
then eluted serially with 15 L of ethyl acetate. Residual water was removed from
the ethyl acetate extract by allowing the water to separate and then draining off
the water in a separatory funnel. Each extract was concentrated to <1.5 L under
10
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vacuum at 40°C by rotary evaporation. The samples were each adjusted to exactly
1.5 L with ethyl acetate before storing at 4°C. Immediately prior to chemical
or toxicity testing, aliquots of the 1000X concentrates were further concentrated
by rotary concentration at 40°C.
RESULTS AND DISCUSSION
Three rounds of water sample concentrates were collected during September
1989, March 1990, and July 1990. An examination of the seasonal effects (early
fall-89, early spring-90, and mid summer-90) of finished water quality and surro-
gate parameters for the control stream (non-disinfected + sand) showed that the
early spring sample had the lowest values for: pH (7.3), dissolved solids (184
mg/L), TOC (2.8 mg/L), and TOX (15.7 ug/L). The early spring sample also had the
lowest concentrations for eight volatile organics examined. This latter finding
may simply be a consequence of the lower TOC levels in the spring sample that may
result from a flushing of naturally occurring .organic matter from the source
water over the course of the winter. However, it should be noted that TOX values
observed for the (C12 + sand) and (NH2C1 + sand) samples were highest for the
spring sample. This suggested that the nature of the precursor material was dif-
ferent and that more semivolatile and nonvolatile halogenated compounds were
formed. This idea is supported by the observed increase in the formation of
haloacetic acids.
Significantly lower values were obtained for the spring sample with regard
to brominated compounds (bromodichloromethane, dibromochloromethane, and bromo-
form). The most likely causes being either a decrease in the bromide content in
the source water or an increase in the ammonia level of the source water that
would result in the formation of combined bromine rather than free bromine. As
for the effect of seasonal changes on the formation of halogenated by-products,
the differences appeared to be less well defined. However, the over-all forma-
tion of brominated DBFs was spring < summer < fall.
Many of the halogenated by-products of interest were analyzed for each dis-
infectant stream. <6'r'8> Of special interest was the potential concentration of
these by-products when water is delivered to the customer. This was evaluated
by storing samples for 5 days with a disinfectant residual to simulate concentra-
tions in the distribution system. An example of the effects of using different
disinfection alternatives for the September 1989 sampling is shown in Table 3.
These data show a definite trend. For example, with dichloroacetic acid, when
chlorine is added prior to and after sand filtration about 45 ^g/L, on average,
was detected. If ozone is added prior to sand filtration and chlorine after sand
filtration, this average concentration was reduced to 32 #3/L. If however, mono-
chloramine is used prior to and after sand filtration, the average concentration
is reduced to about 8 fjg/L. Further reductions were seen when ozone was added
before sand filtration and monochleramine after sand filtration (4.6 ^g/L aver-
age). This trend was seen for other prevalent halogenated by-products such as
trichloroacetic acid, bromochloroacetic acid, chloral hydrate, and trichloro-
methane.
A similar trend is seen for mutagenicity studies on samples collected at
Jefferson Parish as shown in Figure 4. From these data, one might conclude that
ozonation prior to sand filtration and chloramination after sand filtration will
12
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TABLE 3. JEFFERSON PARISH DISINFECTION BY-PRODUCT FORMATION
POTENTIAL FOR SELECTED STREAMS (SEPTEMBER 1989)
Concentration in
BY-PRODUCT
Chloroacetic
Acid
Dichloracetic
Acid
Trichloro-
acetic Acid
Bromoacetic
Acid
Dibromoacetic
Acid
Bromochloro-
acetic Acid
Dichloro-
acetonitrile
Trichloro-
acetonitrile
Dibromochloro-
acetonitrile
Bromochloro-
acetonitrile
1,1-Dichloro-
propane
1,1,1-Trichloro-
propane
Chloropicrin
Chloral Hydrate
Trichloromethane
Bromodichloro-
methane
Dibromochloro-
methane
Tribromo-
methane
TOX
NONDIS.
0.
0.5
0.2
0.
0.
0.2
0.1
0.
0.
0.
0.1
0.
0.
0.
1.0
0.4
0.1
0.1
27.
SAND-
C12
16.0
44.9
39.8
1.2
0.8
28.7
1.6
0.1
0.3
0.7
0.1
1.8
0.9
37.5
156.
35.0
8.
0.
505.
OZONE-
SAND -
_CJ2
17.0
32.3
19.0
1.0
1.2
20.2
1.3
0.
0.4
0.7
0.1
1.7
4.2
32.6
121.
29.0
10.0
1.0
328.
NH2C1 -
SAND-
_NH2CJ_ .
0.4
8.2
1.7
0.1
0.1
3.8
0.
0.
0.
0.
0.
0.
0.
0.1
5.3
1.2
0.1
0.
55.
OZONE -
SAND-
NH2C1
0.6
4.6
0.7
0.1
0.1
1.4
0.
0.
0.
o.
0.
0.
0.
0.
1.8
0.5
0.1
0.1
29.
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solve the halogenated by-product problem. This is true but one also has to eval-
uate the total impacts of disinfection. For instance, although ozone shows pro-
mise and may be a viable disinfection alternative, assimilable organic carbon
(AOC) increase in the distribution system has to be controlled. This can be done
by biostabilization of the water during treatment before distribution. An ex-
ample of this is shown in Table 4. In this example, after ozonation, 162 (jg/L
of AOC is present. Sand filtration provides some biostabilization by reducing
the AOC to 38 fjg/l while the GAC effluent is 4 ^g/L; comparable to the AOC con-
centration (3.7 /jg/L) in the chlorine contact chamber effluent. Ozonation by-
products such as aldehydes, ketones, and acids are also a concern. Although
chloramines may be the disinfectant of choice to provide a disinfection residual,
it may not provide the desired disinfection effectiveness and there have been
some health concerns with ingesting chloramines.
EVANSVILLE. INDIANA STUDIES
Another potential disinfectant for controlling halogenated by-products, is
chlorine dioxide which was further evaluated beyond the scope of the Jefferson
Parish project. At a drinking water utility on the Ohio River, a pilot plant was
used to compare chlorine dioxide disinfection with chlorine disinfection' . The
addition of chlorine dioxide to the raw water with delayed chlorination permitted
coagulation/sett!ing/filtration and oxidation to remove trihalomethane precur-
sors, thereby reducing the amount of trihalomethanes formed during post-treatment
chlorination. A comparison of the average trihalomethane concentrations for the
two disinfectant modes showed a reduction of approximately 60 percent when chlo-
rine dioxide was used. Although chlorine dioxide disinfection can reduce tri-
halomethane concentrations, control of the metabolites (chlorite and chlorate)
is essential before chlorine dioxide can be considered a viable disinfection
alternative. Equipment is now available to produce chlorine dioxide that is
virtually free of chlorine and chlorate. Bench-scale studies have recently been
completed which evaluated the reduction of chlorite and chlorine dioxide by a
reducing agent.c>
All of the samples used for these studies were collected from the effluents
of pilot plant secondary settling basins after approximately 200 minutes of chlo-
rine dioxide contact time.( } These grab samples were analyzed immediately for
residual chlorine dioxide (C102), chlorite (C102), and chlorate (C103), treated
with the respective reducing agent for a variety of contact times, and reanalyzed
for the same chlorine dioxide species.
The major reducing agents considered for these studies consisted of sulfur
dioxide, sodium thiosulfate, sodium metabisulfite, and ferrous iron. For sulfur
dioxide, complete reduction of residual chlorine dioxide and chlorite ion was
achieved but a marked increase in chlorate ion concentration was consistently
observed as shown in Figure 5. This same phenomenon occurred with sodium metabi-
sulfite. The degree of C102 reduction with sodium thiosul fate depended on pH and
contact time. Removal of chlorite ion was demonstrated with little or no chlo-
rate formation. However, the dosages required for complete reduction appear to
make this reducing agent impractical. Ferrous iron appears to be an effective
methodology for the removal of chlorine dioxide and chlorite ion residuals. Both
of these undesirable finished water residuals were eliminated in minutes at pH
6.0 to 7.0 and preliminary results indicate that excess reductant may be easily
controlled by pre-filter chlorination.
15
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TABLE 4. AVERAGE AOC CONCENTRATION
AT JEFFERSON PARISH, LA
TREATMENT AOC.uq/L
NON DISINFECT 13.5
03CONTACT CHAMBER 162.
Oj-SAND 38.2
03-SAND-GAC 4.0
C12CONTACT CHAMBER 3.7
C12-SAND-GAC 2.6
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Bacterial mutagenicity was evaluated during a dual pilot plant study using
ferrous iron in one train with chlorine dioxide disinfection and ozone in the
other train (Figure 6). Figure 7 shows the results of these tests using the TA
100 strain. Regardless of whether chlorine dioxide or ozone is used as a
predisinfectant, when GAC is incorporated into the treatment scheme, the muta-
genicity is low when compared to the schemes incorporating dual media filtration.
SUMMARY
Regulations to control contaminants in drinking water in the United States
are expected to become more stringent and more prevalent. Forthcoming disinfec-
tion and disinfection by-product regulations will effect virtually every commun-!
ity water system. There are various ways to control disinfection by-products,
one of which is to use an alternative to chlorine. However, when this is done,
one should consider various aspects of each disinfectant. There appears to be
no single disinfectant that is applicable for all situations.
ACKNOWLEDGEMENTS
The authors acknowledge the assistance of Robert Miller, Paul Ringhand, and
Ron Dressman for their help in sample collection, analyses, and data interpreta-
tion. The authors also thank Sandra Dryer, Pat Underwood, and Steve Wai trip for
helping prepare this paper.
This paper has been reviewed in accordance with the U.S. Environmental,
Protection Agency's peer and administrative review policies and approved for pre-
sentation and publication. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use by the USEPA.
18
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REFERENCES
1. Lykins, Jr. B.W., Koffskey, W.E., and Miller, R.G., "Chemical Products and
Toxicologic Effects of Disinfection", Journal AWWA, 78:11, 66-75, 1986.
2. Hoff, J.C., "Inactivation of Microbial Agents by Chemical Disinfectants",
U.S. EPA, EPA/600/2-86/067, 1986.
3. National Primary Drinking Water Regulations, Final Rule, Federal Register,
40 CFR Parts 141 and 142, Vol. 54, No. 124, Thursday, June 29, 1989.
4. Korich, D.6., Mead, J.R., Madore, M.S., Sinclair, N.A., and Miller, R.G.,
et al, "Results of lexicological Testing of Jefferson Parish Pilot Plant
Samples", Environmental Health Perspectives, Vol. 69, 129-139, 1986.
5. Miller, R.G., et al, "Results of Toxicological Testing of Jefferson Parish
Pilot Plant Samples", Environmental Health Perspectives, Vol. 69, 129-139,
1986,
6. Lykins, Jr., B.W., et al "Ozone for Trace Organic Contaminant Removal",
Proceedings of 1990 International Ozone Association Conference, Shreveport,
Louisiana, March 27-29, 1990.
7. Lykins, Jr. B.W., Moser, R., and DeMarco, J., "Treatment Technology in the
United States: Disinfection and Control of Disinfection By-Products", the
2nd Japan - U.S. Governmental Conference on Drinking Water Quality
Management, Tokyo, Japan, July 24-26, 1990.
8. Lykins, Jr. B.W., "Disinfection of Drinking Water and Control of Disin-
fection By-Products in the United States", U.S./U.S.S.R. Bilateral Project,
Cincinnati, Ohio, October 15, 1990.
9. Lykins, Jr. B.W. and Griese, M.H., "Using Chlorine Dioxide for Trihalo-
methane Control", Journal AWWA, 78:6, 88-93, 1986.
10. "Disinfection Byproduct Control Using Chlorine Dioxide", U.S.' EPA
Cooperative Agreement No. CR-816837, 1990.
11. Griese, M.H., et al., "The Use of Reducing Agents For the Total Elimination
of Chlorine Dioxide and Chlorite Residuals in Drinking Water", Journal
AWWA, 83:5, 56-61, 1991.
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