American Journal of Anal yt ical Chemistry, 2011, 2, 522-532
doi:10.4236/ajac.2011.25062 Published Online September 2011 (http://www.SciRP.org/journal/ajac)
Evolution and Fate of Haloacetic Acids before and
after Chlorination within the Treatment Plant
Using SPE-GC-MS
Sadia Waseem1, Ijaz Ul Mohsin2*
1Institute of Chemistry, University of Punjab, Lahore, Pakistan
2Institute of Chemical Technologies and Analytics, Technical University of Vienna, Austria
Received December 30, 2010; revised March 7, 2011; accepted Mach 18, 2011
Abstract
The previous research on the occurrence of disinfection by-products (DBPs) in drinking water has focused
on trihalomethane (THMs) formation and evolution, in particular within distribution systems. In this study,
the variability of occurrence of haloacetic acids (HAAs) before and after treatment was investigated. The
investigation focused on point–to-point fluctuations of HAAs in different treatment stages within the treat-
ment plant. The research was also carried out to find out the possible sources for the presence of HAAs be-
fore chlorination in the raw water. The results showed that the presence of HAAs from the raw water point
until the filtered water occurred due to industrial waste and sewages. Subsequent formation of HAAs from
treated point until service reservoir due to disinfection. The HAAs concentration was the highest and most
variable in the plant where level of DBP precursor indicators and the chlorine dose were both higher. How-
ever, HAAs level and in particular dichloroacetic acids (DCAA) (the preponderant HAAs species in the wa-
ters under study), trichloroacetic acids (TCAA) decreased dramatically during filtration, very probably be-
cause of the biodegradation within the filter. An ANNOVA test was used to evaluate the level of significance
of HAAs between treated water and service reservoir outlet water.
Keywords: Haloacetic Acids, Disinfection by-Products, Drinking Water
1. Introduction
Chlorination is a widely used disinfection method in
Malaysia because of its properties of odour removal, high
oxidation potential, economy and efficiency. This “tradi-
tional” disinfection process has been recognized as one
of the greatest public health achievement of the millen-
nium. The chlorination of water history begins in the
18th century where John Snow was the first person who
used chlorine to treat the water at Broad Street Pump in
Soho, London after a cholera outbreak in 1850. This
life-saving technology has served the water supply well
for a century providing disease-free tap water to public.
Haloacetic acid (HAA) is one of the important classes of
DBPs formed during chlorination of water. The main
HAA of concern in drinking water which contain chlo-
rinated and brominated species are monochloroacetic acid
(MCAA), dichloroacetic acid (DCCA), trichloroacetic
aicd (TCAA), monobromoacetic acid (MBAA), dibro-
moacetic acid (DBAA), tribomoacetic acid (TBAA),
bromochloroacetic aicd (BCAA), chlorodibromoacetic
acid (CDBAA) and bromodichloroacetic acid (BDCAA).
The presence of HAAs in drinking water supply poses
health risk because HAAs are suspected human carcino-
gens. The drinking water standard of HAAs known as
maximum contaminant level has not yet been regulated
in Malaysia. In USA most utilities remain in compliance
with MCLs for THMs and HAAs; however, many indi-
vidual measurements showed THMs and HAA concen-
trations over the MCL values (1). In essence, the running
annual average compliance monitoring allows utilities to
average sampling sites with low DBP concentrations and
sampling sites with high DBP concentrations to remain
in compliance with the MCLs. Th is discrepancy initiated
and substantially shaped the stage 2 DBP rule [1]. The
stage 2 DBP rule, introduced in USEPA 2006 [2], builds
upon the stage 1 DBP rule to minimize THM and HAA
formation. The USEPA [3] sets maximum contaminant

S. WASEEM ET AL.
523
level goals (MCLGs) and maximum contaminant levels
(MCLs) for HAAs. The MCLs for THMs and HAAs did
not change; however, the compliance monitoring has
been updated to a locational running annual average
(LRAA). The LRAA forces the utilities to identify the
sampling sites in the distribution system with the highest
concentrations THMs and HAAs. These sampling sites
are then used for compliance monitoring; each sampling
site must remain in compliance with MCL. The change
to LRAA compliance monitoring could be problematic
for some utilities that experience the DBP concentration
near the MCL. To maintain the compliance monitoring,
utilities might need to optimize the drinking water disin-
fection practices to minimize the formation of HAAs in
each sampling sites. An optimization process would in-
volve varying the disinfection cond itions and monitoring
the change in HAA formation. Drinking water regulation
and guidelines have been established for HAAs which
are considered to be potential human health hazards [4].
Recent research efforts have led to a better understanding
of the simultaneous formation and spatio-temporal evo-
lution of HAAs at laboratory scale (bench-scale experi-
ments) and full scale (within distribution systems) (5-11).
These studies have demonstrated that so me water quality
and operational characteristic (e.g. pH, chlorine dose)
may affect the preponderance of one or the other group
of chlorinated DBPs. In addition, it has been also estab-
lished that the saptio-temporal behavior of HAAs and
THMs within distribution systems is not comparable
[11-12]. There is very little information available con-
cerning the evolution of HAAs within treatment plants
that use post chlorination only. Garcia-Villanova et al.
[13] documented and modeled the behavior of THMs
within a treatment plant, but no information was gener-
ated for HAAs. As for THMs, it is important to docu-
ment the impacts of the treatment process on HAA evo-
lution within treatment plants. In Malaysia, HAAs has
not been regulated, this is simply due to lack of informa-
tion. Effectively no study as for the levels of HAAs in
Malaysian dri n ki n g wat er has been reported.
This study was performed in order to investigate the
behavior of HAAs within the treatment plant. To gain a
better understanding, the effect of the various treatment
stages on the fate of these compounds and checks out the
trend of HAA concentration before chlorination and after
chlorination. Additionally, this study discusses the effect
of residual chlorine on the formation of HAAs in service
reservoir (SRO) water outlet. An ANOVA test was used
to evaluate the level of significance between treated wa-
ter (TW) and service reservoir outlet (SRO) water. The
main purpose of the testing was to evaluate the reliab ility
of measurements and the differences between treated
water and service reservoir water results.
2. Material and Methods
2.1. Treatment Plant under Study
Sungai Semenyih treatment plant (SSTP) was selected
for this study. This plant is use post chlorination as one
of their treatment stage. This is the most important plant
delivering drinking water to the populations of Selangor
city and Putrajaya. This plant uses surface water fr o m the
Semenyih river water. Pollution sources in the Semenyih
river basin namely: paper, wood industries, landfill, hous-
ing area and livestock farm were monitored monthly.
The plant serves 1000,000 inhabitants. Treatments stages
consist of coagulation-floculation-sedimentation, slow
sand filtration, and post chlorination.
2.2. Data Collection Strategy
To collect the data, four sampling points were estab-
lished in treatment plant. The first point represents raw
water (RW), the second point representing filtered water
(FW) (after coagulation, flocculation and sedimentation),
third point represented treated water (TW); finally the
fourth point was located at the outlet of service reservoir
water (SRO). Sampling was conducted at the four points
for a period of 6 months (f rom March 20 08-august 2008) .
In order to collect data on HAAs and the parameters that
can influence their evolution; pH, temperature, total or-
ganic carbon (TOC), and free residual chlorine. Water
samples were taken twice a week during the period under
study. In total, 51water samples were taken at each point
of the treatment plant, resulting in about 204 samples
collected for the study. Temperature, pH, HAAs and
TOC were measured in samples collected at RW, FW.
Temperature, pH, residual chlorine, HAAs were meas-
ured in samples collected at TW, and SRW. In addition
to the mentioned water quality parameters, data for tur-
bidity and operational parameter (chlorine dose) were
provided by the plant managers.
2.3. Sampling and Analytical Methods
Samples for measuring HAAs were collected in 50 ml
amber glass bottle with ground-glass-stoppers. The bot-
tles had been pre-washed with phosphate-free detergents,
rinsed with deionized water and ultra-pure water and
placed in an oven at 250˚C for 2 hours. Samples for TOC
were measured in the laboratory, whereas pH, tempera-
ture and free residual chlorine were measured in situ.
Bottles for determination of TOC and HAAs were trans-
ported to the laboratory in a container that maintained
water temperature at 4˚C prior to analysis. A surrogate
standard (10 mg/l, 2, 3 dibromobutanioc acid in methyl-
tert-butyl-ether (MTBE), HPLC grade) was added to

S. WASEEM ET AL.
524
sample to monitor method performance. A commercial
(Silicabond SAX) was used as SPE sorben t. Disposable 3
ml SPE cartridges with 300 mg sorbent were employed.
Cartridges were activated and conditioned prior to use
using 10 ml methanol, followed by 10 ml deionised wa-
ter. Once activated, 50 ml of sample solution was passed
through the SPE cartridge without a vacuum system.
HAAs retained were eluted with 3 ml of 10% H2SO4/
MeOH solution. After methylation, 7 ml of Na2SO4 solu-
tion was added to increase the extraction efficiency. The
methyl tertbutyl-ether (MTBE) extracted samples were
placed in amber vial prior to GC-MS analysis. The pH of
water was measured by using an electron pH meter
(Corning 320, Hanning Instruments). Turbidity was
measured with a HACH turbidimeter (2100N model).
Total organic carbon (TOC) was analyzed using TOC
analyzer (Aurora model 1030, O.I analytical)
3. Results and Discussion
3.1. Occurrence of HAAs within the Plant and
Sungai Semenyih Catchment Area
The concentration of HAAs was monitored throughout
the treatment process at one treatment plant inclusive of
different treatment steps. The selected plant, Semenyih
water treatment plant (SWTP), located at Putrajaya. Ma-
laysia has complete treatment process comprising four
steps: raw water subjected to storage, coagulation/floc-
culation, settlement, sand filtration, chlorination and fi-
nally supplied to consumers through service reservoirs.
The mean level of HAAs obtained is given in Figure 1
i.e. the levels of DCAA and TCAA slightly increased
from treated water to service reservoir. This is due to
further reaction of residual chlorine with the HAAs pre-
cursors. After chlorination, lime is introduced in the fil-
tered water and that leads to increase in pH which results
in an increase in DCAA and a decrease in TCAA. As
high pH causes the degradation of TCAA into DCAA,
the reservoir water contains high DCAA rather than
TCAA. The high formation potential of TCAA and
DCAA level was found irrespective of treated water in
the service reservoir due to contact time with the residual
chlorine. The HAAs concentration depends on both the
level of chlorination an d the quality of the water sample.
For this treatment plant, DCAA and TCAA was two en-
riched species of disinfection was found and mixed
halogenated molecules were also observed. In addition to
their occurrence in drinking water, HAAs have also been
observed in swimming pool water and surface waters
[14]. The sources of HAAs in surface waters include
wastewater discharges and the deposition of HAAs
formed in the upper atmosphere from degradation of
chlorinated solven ts [14].
The volatile organochlorines are considered to be one
of the main sources of HAAs in the environment [15].
These organochlorine compounds have been found to be
of either anthropogenic origin, emanating from volca-
noes and oceans or occurring naturally in some plants
and soil fungi. As such, HAAs are distributed in the
various environmental compartments like the hydro-
sphere, air, biosphere and soil. Chemical and pharmaceu-
tical manufacturing processes like the bleaching of wood
pulp by paper mill and cooling water are yet other
Figure 1. Variations of HAAs according to the various treatment stages within the Sungai Semenyih water treatment plant
(SSTP).

S. WASEEM ET AL.
525
sources of HAAs in the environment [16]. The presence
of HAAs in raw or un-treated water is understandable
due to the fact that HAAs are distributed all around the
world in lakes, groundwater, surface water, seawater and
soil [17-18] and their production has been attributed to
both anthropogenic and natural activities. Research con-
ducted in Japan [18] has shown the presence of haloace-
tic acids in coastal seawater. The occurrence and mass
fluxes of MCA, DCA, and TCA were assessed on a re-
gional scale over Switzerland, based on more than 1000
concentration measurements in rain and snow, surface
water, groundwater, and wastewater. Among different
precipitation events, the measured concentrations varied
significantly from < 7100 - 11 ng/l. However, no statis-
tically different average haloacetic acid (HAA) concen-
trations among six precipitation sampling sites located in
various areas in Switzerland were observed (range of
average concentrations: MCA 1430 - 2770 ng/l, DCA
390 - 1370 ng/l, TCA 95 - 380 ng/l, TFA 33 - 220 ng/l).
The similar average HAA concentrations in precipitation
at a remote site close to the free troposphere at an eleva-
tion of 3580 m above sea level (Jungfraujoch) and at a
site that receives precipitation which scavenged the
Earth’s boundary layer (urban site Dübendorf/Zürich)
suggests that HAAs are derived from well-mixed pre-
cursor(s) in the atmosphere (Berg et al. 2000). Whatever
the type of process used, it seems that the HAAs are
clearly formed at the chlorination step, but it is notable
that raw water (untreated water) already contained
DCAA, TCAA, and BCAA. These molecules, whose
presence was confirmed by taking the sample in the Se-
menyih river water from the pollution sources.
The study has been carried out in the whole Semenyih
catchment with nine stations. The nine stations were
covering whole Sungai Semenyih catchment area right
from Sungai Semenyih dam (SS1) down to intake point
(SS9). As shown in Table 2 analysis of water samples
within the Semenyih catchment area showed the pres-
ence of HAAs started from Sungai Saringgit (SS2) and
increased downstream up to the raw water intake point
(SS9). The location of sampling points in Semenyih river
is shown in Figure 2.
Although all water samples were not chlorinated, the
presence of HAAs even at low levels of 0.1 - 2.6 µg/l
indicates other sources of these compounds. The antro-
pogenic inputs could be from the industrial discharges,
agricultural activities or the landfill. The high level of
HAAs at Sungai Rinching (SS5) and Sungai Beranang
(SS7) were indicative of impact of sewage discharges,
paper industry, wood industry and palm oil mill effluent
discharges around the SS5 and the discharge of leachate
from the landfill near the SS7. The discharges were col-
lected from potential pollution sources which have been
determined by early research (19). In this present study,
the presence of DCAA, TCAA, BCAA, in the raw water
was acknowledged due to volatile organic chlorine
compounds and paper mill waste in Sungai Semenyih
catchment area. The results of this study indicate that all
HAAs components present in raw water were signifi-
cantly reduced by the sand filtration except BCAA. The
biodegradation of DCAA, TCAA, BCAA, DBAA,
DBCAA and TBAA in dry season was most probably
due to the highly favorable conditions for microbial ac-
tivity within the sand filter. This could be the reason the
level of HAAs has been decreased after sand filtration.
Conventional filtration always contributes significantly
to the removal of HAAs (20). HAAs are either not de-
tected or are present at very low levels in raw water (RW)
samples, since this water is hardly ever subjected to
chlorination since no pre-chlorination treatment stage is
performed at this plant. After chlorination the major
HAAs found in tr eated water (TW) and service reservoir
outlet (SRO) examined were monochloroacetic acds
(MCAA), dichloroacetic acids (DCAA), trichloroacetic
Table 2. Mean concent rat ions of HAAs (µg/l) withi n the Sungai Semenyih catchment area.
Station Numbers
Compounds Occurrence (%) SS1 SS2 SS3 SS4 SS5 SS6 SS7 SS8 SS9
MCAA 12 - - - - 0.1 - - 0.1 -
DCAA 48 - 0.1 0.7 0.5 3.3 1.0 2.9 3.0 1.8
TCAA 25 - 0.1 0.4 2.6 1.9 0.7 1.6 1.0 0.6
MBAA - - - - - - - - - -
DBAA 15 - - 0.1 0.5 0.7 0.1 0.5 0.5 0.4
TBAA - - - - - - - - - -
BCAA 1 - - - 0.1 1.0 0.1 1.0 1.4 0.5
CDBAA - - - - - - - - -
BDCAA - - - - - - - - - -

S. WASEEM ET AL.
526
acids (TCAA), bromochloroacetic acids (BCAA), di-
bromoacetic acids (DBAA), and dichlorobromoaceic
acids (DCBAA). The impact of chlorination to the pro-
duction of HAAs was clearly shown by the increased
level of HAAs in the treated water and service reservoir
outlet water. Mean levels and total concentrations of
HAAs for raw water, filtered water, treated water and
service reservoir outlet water samples collected at the
treatment plant are listed in Table 3 together with their
maximum contamination level (MCL) and there was a
sharp increase in the total concentration of HAA in
treated water (24.35 µg/l), as compared to raw water (3.3
µg/l), and filtered water (1.2 µg/l). These findings were
in line with the reported levels of trihalomethane (THMs)
in treated water in same treatment plant which were ac-
knowledged due to chlorination process [21].
Figure 2. Location of sampling points in the Sungai Semenyih.
Table 3. Mean concentration of HAAs in various drinking water samples (in µg/l).
RW FW TW SRO Total
Malaysian standards
MCLa µg/l)
MCAA - - 0.47 0.38 0.85 -
DCAA 0.93 0.18 9.8 12.2 23.11 50
TCAA 0.95 0.19 7.9 9.4 18.4 100
BCAA 0.59 0..59 2.2 2.1 5.69 -
DBAA 0.83 0.07 3.2 1.8 5.96 -
DCBAA - - 0.78 0.84 1.62 -
a = maximum contamination le vel

S. WASEEM ET AL.
527
The dominant species of HAA within the treatment
plant was DCAA, followed in decreasing order by
TCAA, BCAA, DBAA and DCBAA. Between treated
water (TW) and service reservoir outlet (SRO), DCAA
and TCAA concentration were not significantly (p < 0.05)
different because low level of free residual chlorine in
the TW contributed to a lesser rise of DCAA and TCAA
levels in SRO (an increase of about 40% and 32% for
TW, 45% and 35% for SRO, respectively). Similarly the
concentrations of BCAA and DBAA decrease from TW
(with an average of 9% and 13% respectively) to SRO
(with an average of 8% and 7% respectively). This could
be ascribed due to the instab ility of b rominated sp ecies at
high pH (Xie 2004). Figure 3 shows the percentage of
each component of the HAAs relative to the total of the
6HAAs, along the treatment process. The results showed
that in TW an d SRO, DCAA was by far the p redominant
species representing on average 40 % and 46% of HAAs
respectively. These results are consistent with most stud-
ies where raw water has been chlorinated experimentally
[13,19]. However, as shown in Figure 3, for both stages
(TW and SRO), the relative dominance of DCAA and
TCAA varied because of contact time. This portrait
changes dramatically in the RW and FW where DCAA
represented on average 28% and 14% of total HAAs for
SSTP, respectively.
In the raw water (RW) and filtered water (FW) the av-
erage percentage of TCAA (29%, 15%), DBAA (25%,
6%) are changed respectively except BCAA. The aver-
age percentage of BCAA is 65% (0.59 µg/l) in filtered
water and 18% (0.59 µg/l) in raw water (RW) which is
almost same in term of concentration within the two
treatment stages (RW, FW). This indicated that BCAA
could not be removed using sand filtration. Average
value of water quality parameters at the sampling points
of the Sungai Semenyih water treatment plant (SSTP) are
Figure 3. Percentages of individual HAAs compared to total HAAs along the treatment stages within Sungai Semenyih water
treatment plant (SS T P).

S. WASEEM ET AL.
528
given in Tabl e 4. Biofiltration is an effective process for
removing biodegradable organic matter and biodegrad-
able HAAs. Sand, anthracite, and garnet are common
media for biological filters. In this treatment plant, sand
is used as media for biological filters. Preliminary studies
conducted by the author’s a research group indicated that
biologically active carbon (BCAA) is an effective proc-
ess for HAAs removal [17]. In this plant, filtration proc-
ess is carried out using sand which is not as efficient as
BAC. This may be the reason why only little concentra-
tion of HAAs species (DCAA, TCAA, and DBAA) is
reduced. The presence of BCAA in filtered water indi-
cated that filtration using sand is not effective for de-
creasing the concentration of BCAA which is still same
as in raw water.
The presence of BCAA in filtered water is added by
the fact that the bromochloroderivatives (BCAA) are not
easily degradated due to their physical and chemical be-
havior. The higher the number of halogen atoms and the
corporation of bromine cause an increase in the biologi-
cal stability of the HAAs. However, studies carried out in
pond waters have shown DCAA to undergo faster deg-
radation compared to that of MCAA and TCAA [18]. A
decrease of DCAA, TCAA and DBAA between raw wa-
ter (RW) and filtered water (FW) were observed. The
degradation of D CAA, TCAA, and DBAA in dry season
was very probably due to the highly favorable conditions
for microbial activity within the filter. In fact, Williams
and Fauntleroy [21] reported that specific type of bacte-
ria (identified as a Bukholderia & Sphingomonas species)
may degrade dihalogenated DBPs in warm water. In
Malaysia, the weather is always warm that biodegrada-
tion could be happened. The temperature would be fa-
vorable conditions for the formation of such biomasses.
3.2. Temporal Variability of HAAs within the
Period of Study
HAAs level in the plant under study varied not only ac-
cording to the sampling locations throughout the treat-
ment processes, but also temporally from the beginning
to the end of sampling period. Figures 4 - 7 show that
monthly variation of HAAs in the four sampling loca-
tions within the plant was considerable and also indi-
cated that the monthly patterns of HAAs in the four sam-
pling locations. For instances, in the month June, all
HAAs species are higher in concentration rather than rest
of months. In fact, this could be due to different level of
TOC, dose of chlorine, and pH (see Table 4). Mono-
chloroacetic acids (MCAA) was found at zero concentra-
tion in SRO but in the TW the concentration of MCAA
was above zero. The loss of MCAA in SRO was proba-
bly due to biodegradation. The observed trend for the
biodegradation of HAAs [18] is as follow: MCAA >
DCAA > TCAA The loss of MCAA in SRO was indi-
cated that MCAA is degradated faster than DCAA and
TCAA, as can be seen in above mentioned trend.
The effect of TOC, pH and Chlorine dose on the for-
mation of HAA6 in TW and SRO is shown in Figure 8
(a), (b), (c). It is observed that the change in HAA6 is
similar to the change in TOC except for the result ob-
tained on June 16. The level of HAA6 in TW and SRO
increased on June 30, probably because of the highest
TOC value (8.9 mg/l), chlorine dose (3.3 mg/l).
4. Conclusions
This study aimed to investigate variations of HAAs
within treatment plant where river water is not pre-chlo-
rinated before subsequent physico-chemical treatment.
Analysis of raw water (RW), filtered water (FW) from
the treatment process of the Sungai Semenyih water
treatment plant showed that the HAAs mainly appeared
at the chlorination step. However it was also possible to
find HAAs species (DCAA, TCAA, BCAA, DBAA)
before treatment in the raw water and filtered water. In
this case, these could not be considered as chlorination
by products, but probably from discharges of paper and
waste, wood based industries and from sewage dis-
charges. In this treatment plant, the results showed that
Table 4. Average values of water quality parameters at the sampling points of the Sungai Semenyih water treatment plant (SSTP).
Parameters RW FW TW SRO
TOC (mg/l) 3.1 0.78 NM NM
pH 6.4 5.9 7.1 7.3
Temperature (˚C) 25.9˚C 25.9˚C 25.9˚C 25.9˚C
Chlorine dose (mg /l) NA NA 2.8 Na
Residual c hl orine (mg/l) NA NA 1.88 1.75
Tu r b i d i ty (N TU ) 26 5 . 6 0. 6 8 0. 6 7 0. 6 2
Total HAAs (µg/l) 3.3 1.2 24.3 26.7
NM = non-m easured, NA = non-a pplicable

S. WASEEM ET AL.
529
Figure 4. Monthly variation of HAAs concentration in raw water.
Figure 5. Monthly variation of HAAs con centration in filtered water.

530 S. WASEEM ET AL.
Figure 6. Monthly variation of HAAs con centration in treated water.
Figure 7. Monthly variation of HAAs con centration in reservoir outlet.

S. WASEEM ET AL.
531
(a) (b)
(c)
Figure 8. Temporal variations of HAA6, TOC (a), Chlorine dose (b), and pH (c) within the SSTP.
the initial formation of HAAs was high er and more vari-
able in the treated water (TW) where level of HAAs
precursor and chlorination dose were both higher and
more variable. In this case, subsequent formation of
HAAs was observed up until service reservoir outlet
(SRO) because of remaining levels of residual chlorine
and HAAs precursors. However, HAAs level were de-
creased dramatically during filtration because of the
biodegradation of DCAA, TCAA, DBAA except BCAA.
Bromochloroacetic acids (BCAA) concentration was
remaining same in the filtered water (FW). The effect o f
filtration on the fate of HAAs w as seasonally dependent,
with the highest degradation in warm water periods and
practically no variation in substance level during cold
season. In Malaysia, just hot season prevail so that tem-
perature (25˚C) is suitable for the biodegradation of
HAAs during sand filtration and it will be favorable con-
ditions for microbial activity within the filter. Results of
this study suggested that treatment plant practicing no
pre-chlorination of raw water and conventional sand fil-
tration process that no dramatic impact on HAAs forma-
tion will be observed. The post-chlorination leads the
formation of HAAs.
5. Acknowledgements
The authors gratefully acknowledge Universiti Kebang-
saan Malaysia for the laboratory facilities. The financial
support under R and D under the MOSTI Grant is grate-
fully acknowledged. We wish to express our thanks to

532 S. WASEEM ET AL.
Konsortium ABASS Sdn, Bhd, for opening their treat-
ment plant for us to carry out t his stu dy.
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