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International Journal of Scientific Research in Environmental Sciences, 2(3), pp. 94-106, 2014
Available online at http://www.ijsrpub.com/ijsres
ISSN: 2322-4983; ©2014 IJSRPUB
http://dx.doi.org/10.12983/ijsres-2014-p0094-0106
94
Review Paper
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
Nurazim Ibrahim, Hamidi Abdul Aziz*
School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
*Corresponding Author: Email: cehamidi@usm.my; Tel: 04-5996215; Fax: 04-5941009
Received 03 January 2013; Accepted 26 February 2014
Abstract. Natural organic matter (NOM) can be defined as a mixture of complex organic compounds that universally present
in natural waters. High NOM content in water strongly impact the water quality and treatment in several ways (e.g. causing
colour and odour, filter fouling and increase coagulant dose). Besides that, NOM also acts as the main precursor to
disinfectant by products (DBPs) produce from the reaction of NOM and disinfectant during water treatment. DBPs are known
to be carcinogenic to human and animals. The formation of DBPs is depending on NOM characteristics. Generally, NOM
characteristics are differ according to the water sources. In order to understand NOM properties, NOM fractionation is required
and therefore different approaches have been proposed for its characterization. Meanwhile several methods of treatment have
been developed to remove or reduce the amount of NOM in drinking water sources to prevent DBPs formation. The aim of this
paper is to review and discuss the properties and available treatment techniques for NOM.
Keywords: Natural Organic Matter, Disinfectant By-products, Fractionation, Treatments
1. INTRODUCTION
Generally, natural organic matter (NOM) is defined as
a mixture of complex organic compounds that
universally present in natural waters (Matilainen et al.,
2010; Parson et al., 2004) as a result of organic matter
decomposition and metabolic reaction (DECWMD,
2011). NOM presence in water can be quantified by
total organic carbon (TOC) or dissolved organic
carbon (DOC) and UV254 measurement. However, the
chemical properties of NOM were obtained through
fractionation process. Typically NOM characteristic is
dependent on the biodegradable dissolved organic
carbon (BDOC) content in water sources. NOM that
originates from decayed of biota living in water
bodies such as macrophites, algae and bacteria’s are
known as autochthonous NOM (Nikolaou, and
Lekkas, 2001). Meanwhile, allocthonous NOM was
referred to NOM from external sources that enter
streams through natural cycle (e.g. soil leaching and
snow melting) or human activities (e.g. Effluent from
wastewater treatment plant) (Hwang et al., 2002;
Crouè et al., 2000).
According to the past studies (Sharp et al., 2006;
Ahmad et al., 2002), NOM characteristic and
properties are differed according to the origin of water
sources. Hence different methods were proposed for
removing or reducing NOM amount in drinking water
sources. Besides NOM treatment, methods for DBPs
removal from drinking water was also developed
(Wang et al., 2013c; Duan et al., 2012; Xie et al.,
2012; Comninellis et al., 2008; Cai et al., 2007).
The presence of NOM has a significant impact to
the quality of drinking water sources (Matilainen et
al., 2010). Therefore, the amount of NOM has been
observed by US authorities to monitor its content in
potable water sources. Primary concern of NOM
presence in water sources is related to the formation
of harmful disinfectant by products (DBPs) from
disinfection process during drinking water treatment
(Yee et al., 2009). The most common DBPs detected
in drinking water are trihalomethanes (THMs) and
haloacetic acids (HAAs) (Krasner et al., 2006).
Furthermore, certain DBPs products such as
Chloroform, Dichlorobromomethane and
Trichloroacetic acid are potentially carcinogen to
human (Nikolaou, and Lekkas, 2001).
Other disadvantages of NOM to drinking water
sources and treatment process are, 1) acting as mobile
carrier to inorganic and organic pollutants (increase
the transportation and distribution) 2) causing yellow/
brown colour to water and cause taste and odour
problems 3) compete with other pollutants for
adsorption sites 4) serve as substrate to undesirable
biological growth in the distribution system 5) control
coagulant and disinfectant dosage which cause an
increase of sludge volumes and DBPs formation 6)
major compounds that cause membrane fouling
Ibrahim and Aziz
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
95
(Huang et al., 2011; Matilainen and Sillanpaa et al.,
2010; Ahmad et al., 2002; Abbt-Braun, and
Frimmel,1999).
A number of studies have been conducted in order
to find the best solution for controlling DBPs
formation by reducing NOM amount in drinking
water sources (Xie et al., 2012; Toor, and Mohseni,
2007; Singer, and Bilyk, 2002). Different approaches
were taken by researchers in developing methods at
different stages of drinking water treatment. This
paper aims to present information on NOM presence
in drinking water sources and its impact to drinking
water in relation to DBPs formation as well as the
possible methods of treatment.
2. NATURAL ORGANIC MATTER
CHARACTERISTICS
The main component of NOM was TOC which
consists of dissolved organic carbon (DOC) and
particulate organic carbon (POC) fraction.
Nevertheless, POC only represents a small amount of
TOC which indicate that DOC is the main fraction of
NOM. In addition, DOC present in natural water was
mainly comprised of hydrophobic and hydrophilic
components whereas hydrophobic component
represents about 50% of DOC while hydrophilic
ranging between 25-40%. The remaining fraction is
transphilic organic matter (Zularisam et al., 2006;
Sharp et al., 2006; Parson et al., 2004).
Moreover, hydrophobic and hydrophilic
components can be further split into three different
classes namely acid, bases, and neutral which have
different chemical groups where hydrophobic classes
is rich with aromatic carbon, phenolic structures and
conjugated double bonds while hydrophilic classes
contains more aliphatic carbon and nitrogenous
compounds (Kim and Yu, 2005; Duan and Gregory,
2003; Nikolaou, and Lekkas, 2001). Humic and fulvic
acids are examples of hydrophobic acid while
carboxylic and polyuronic acids are in hydrophilic
acids group (Bond et al., 2010; Matilainen, 2007).
Figure 1 shows the relationship between NOM
fraction and chemical groups of NOM.
Fig. 1: Relationship between NOM fraction and its chemical groups (Sources: Matilainen 2010; Matilainen, 2007; Crouè et al.,
2000; Marhaba et al., 2000)
International Journal of Scientific Research in Environmental Sciences, 2(3), pp. 94-106, 2014
96
Typically, allochthonous NOM is the major
contributor to hydrophobic fraction while
authotochthonous is the main sources for hydrophilic
fraction (Crouè, et al., 1999). However, NOM
concentration and characteristics in natural water are
not necessarily the same. The concentration may vary
according to many factors such as topography, season,
flood, drought and human activities (Hudson et al.,
2007; Abdullah et al., 2003). This indicated that,
NOM concentration and characteristics is dependent
to water origin and its surrounding (Bond et al., 2012;
Zularisam et al., 2006). Table 1 shows variation in
hydrophobic and hydrophilic concentration in river
water at different places.
Table 1: NOM fraction concentration at different origin
Sources
Hydrophobic
Hydrophilic
Transphilic
Unit
References/ Countries
Ulu Pontian River,
Johor
2.38
2.6
1.7
mg/L
Zularisam, et al., 2006.
Malaysia
Luan or Yellow
River, Beijing
1.35
1.00
1.43
mg/L
Chen et al., 2008. Northern
China
Millstone River,
New Jersey
0.53
2.34
1.63
mg/L
Marhaba, 2000. New Jersey
Harbin Water
Treatment Plant
43.8
15.6
40.6
%
Lu, et al., 2009. Harbin, China
Basically, humic substances in NOM represent a
range of complex organic matter in water and soil that
originates from decayed animals and plants. Main
component of humic substances are fulvic acid (water
soluble at acidic to alkaline pH) and humic acid
(insoluble at acidic pH) (Maurice and Namjesnik-
Dejanovic, 1999) known as hydrophobic acid. In
natural water, hydrophobic acid consists
approximately 90% of fulvic acids and 10% of humic
acids which is opposite to humic substances originate
from soil leaching that mostly consist of humic acids
compared to fulvic acids (Uyak and Toroz, 2006;
Nikolaou, and Lekkas, 2001). Thus, water sources that
received more land based carbon has greater amount
of humic substances.
Beside its hydrophobicity, NOM was also
characterized in accordance to its molecular mass/
weight distribution. According to Ray et al. (2002),
humic acids in water have high molecular mass
(HMM) greater than 2000 Daltons. The suggestion
was in agreement with data obtained by Matilainen et
al. (2005) where NOM molecular mass recorded for
humic substances reach up to 10,000 or larger. Similar
results were also obtained by Sharp et al. (2006). High
molecular mass indicated that the water sources
mostly consist of aromatic carbon UV-absorbing
element.
In freshwater, humic and fulvic acids are the major
causes for colour changes as well as odour and taste.
Additionally, humic substances in natural water at pH
higher than 4 can be regarded as anionic
polyelectrolytes that carry negative surface charge as
a result of carboxyl and phenolic group’s ionization
(Matilainen et al., 2010; Duan and Gregory 2003).
This characteristic allowed NOM to bind particles
with an opposite charges like heavy metals (Wu et al.,
2012) and escalate the rate of transportation and
distribution of pollutants in water sources. Different
intermolecular forces (e.g. electrostatic interaction,
hydrogen bonding, hydrophobic interaction and
multivalent cation formation) are expected to occur
and form aggregates (Maurice and Namjesnik-
Dejanovic, 1999) of NOM with other pollutants.
Meanwhile Wu et al. (2012) has suggested that
molecular weight is one of the factor affecting
sorption behavior between NOM and metals.
Besides humic substances (hydrophobic), NOM
also consists non-humic substances (hydrophilic) that
has low molecular mass (LMM). According to Croué
et al. (1999) hydrophilic fraction isolated from low
humic waters can be consider as a stronger precursor
to THM and HAAs formation compared to
hydrophobic NOM. This fraction has a lower C/O
ratio and specific UV absorbance (SUVA) value
which indicated that less aromatic carbon present
(Croué et al., 1999). Treatment option such as
coagulation, and oxidation process are not effective
for removing this type of fraction (Sarathy et al.,
2011; Bond et al., 2010; Matilainen et al., 2010).
According to Bolto et al. (2002) the best removal
mechanism for this fraction is expected to be an
adsorption. Thus, adsorption process such as magnetic
ion exchange resin (MIEX®) is a better treatment
option (Bond et al., 2010; Mergen et al., 2008) for
hydrophilic fraction.
To date, Malaysia is still using a conventional
treatment method which consist of coagulation,
flocculation sedimentation, filtration and disinfection
processes. However, these treatments are not very
effective in removing NOM in drinking water sources.
The presence of NOM in water sources may disrupt
coagulation process by competing for adsorption site
with other pollutant. Consequently, higher dosage of
coagulant required for the treatment process. High
Ibrahim and Aziz
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
97
coagulant dosage may pose a risk to the consumer
such as Alzheimer’s disease as a consequence of Al
residual in drinking water. However, low dosage of
coagulant causes an incomplete removal of NOM in
water. Residual of NOM will react with disinfectant
during treatment process and formed new products
namely disinfection by products (DBPs) that is
harmful and carcinogenic. Hence, it is important to
understand NOM characteristics before deciding the
suitable method for NOM removal.
2.1. NOM Characterization
Basic characteristics of NOM can be obtained by
determine several parameters such as TOC, DOC,
UV-absorbance and SUVA. However more detail
characterization study required more sophisticated
techniques and equipment. Characterization study
based on bulk parameters (physical characterization)
only offers quantitative information of NOM.
Meanwhile spectroscopic methods (Fluorescence,
UV-vis, FTIR, 1H NMR, 13C NMR, 15N NMR, 2-D
NMR), and chromatographic methods (HP-SEC,
FIFFF, Mass spectrometric methods, FTICR MS, GC-
MS) measured NOM hydrophobicity, molecular
weight or elemental composition which provide
further details on NOM quality in water in term of
chemical characteristics.
2.1.1. Bulk Parameters
Basically the amount of NOM in water can be
determined by three parameters which are TOC/
DOC, UV254 and SUVA. TOC or DOC provides a
total organic carbon concentration in the samples by
measuring level of organic carbon amenable to CO2
oxidation after removing inorganic carbon (Volk et
al., 2002). Meanwhile, UV254 is used to describe UV
absorbance measured by spectrophotometer at 254 nm
and reported in cm-1. SUVA (specific UV absorbance)
value represent the overall concentration of NOM in
water, according to TOC/DOC and UV254 results,
SUVA value can be obtained by dividing the value of
UV254 (cm-1) with TOC/DOC (mg/L) concentration
and multiply with 100 cm/M (USEPA, 2009) as
shown in equation 1.
Moreover, SUVA values also can be used as
indicator to describe hydrophobicity of NOM in
water. SUVA values lesser than 3, indicate that the
sample contains more hydrophilic and low molecular
weight materials while SUVA values more than 4
indicated that water samples mostly consist of
hydrophobic components with high molecular
materials (Wang et al., 2013b). This method was ease
to use but high concentration of nitrate in low DOC
water may interfere with the measurement (Matilainen
et al., 2011).
2.1.2. Fluorescence
A fluorescence technique has been established in the
last 50 years for investigating organic composition in
water (Hudson et al., 2007). Since NOM consist of
heterogeneous compounds, it is difficult to identify
individual fluorescent compounds in water. Thus, the
fluorophores are usually groups into human-like,
fulvic- like and proteins-like (Hudson et al., 2007).
Alternatively, fluorophores can be identified through
individual chemical characteristics whereas
fluorescence spectrophotometric is conducted on
NOM to obtain three spectrums namely emission
spectra, excitation spectra and synchronous spectra
(Ahmad et al., 2002). Marhaba and Lippincott, (2000)
had used fluorescent spectrophotometric scan to
determine six different types of NOM fractions
(hydrophobic acid, hydrophobic base, hydrophobic
neutral, hydrophilic acid, hydrophilic base and
hydrophilic neutral) in water treatment plant. The
fractions were distinguished according to the
difference in excitation and emission wavelength
range. However, the emission wavelength that set
these fractions spectrally apart from each other
(Marhaba, 2000). Table 2 shows an emission
wavelength obtained for NOM fraction derived from
water intake (Raritan and Millstone River as well as
Delaware and Raritan Canal) of Somerset water
treatment plant.
International Journal of Scientific Research in Environmental Sciences, 2(3), pp. 94-106, 2014
98
Table 2: Fluorescence wavelength of NOM fraction (Adopted from Marhaba, 2000)
Fraction
Wavelength, λ (nm)
Hydrophilic Acid
345-357
Hydrophilic Base
357-369
Hydrophilic Neutral
609-621
Hydrophobic Acid
417-429
Hydrophobic Base
369-381
Hydrophobic Neutral
309-321
Further development allowed fluorescence
technology to advance whereas the rapid detection (<1
min) of three dimensional excitation emission
matrices (EEMs) is possible. EEM is a composite of
emission scans from single sample recorded at
incrementing excitation wavelengths and arranged in a
grid (excitation x emission x intensity) which
providing a large amount of data that statically
analyzed (Handerson et al., 2009) and give better
understanding on NOM characteristics.
3. FORMATION OF DISINFECTANT BY
PRODUCTS (DBPs)
Chlorination process is the main disinfection process
use in water treatment because of its efficiency in
killing pathogenic organisms and cost effective.
However NOM in water react with chlorine to form
disinfectant by products (DBPs) that have reported as
hazardous materials to animals and humans (Bond et
al., 2012; Payankapo et al., 2008).
In water, NOM functional groups and structure
play an important role in DBPs formation. As an
example, hydrophobic fraction is more reactive with
chlorine while hydrophilic fraction is reactive to
bromine and iodine in water to form DBPs.
Nevertheless, Lu et al., (2009) reported that aromatic
carbon content in NOM was the main surrogate to
DBPs formation in chlorination process regardless of
its hydrophobicity nature. Therefore hydrophobic acid
recorded the highest DBPs formation during the
treatment (Matilainen et al., 2010). There are two
main DBPs species detected during the interaction of
NOM and chlorine which are THMs and HAAs
(Richardson et al., 2007).
Generally the formation of DBPs is dependent on
several factors during the treatment such as
disinfectant concentration, contact time, pH,
temperature and NOM properties and concentration
(Lu et al., 2009; Yee et al., 2009; Hong et al., 2007;
Nikolaou, and Lekkas, 2001). Increasing in these
factors will increase the formation of DBPs during the
treatment. In contrast, effect of pH is more
complicated as certain DBPs formation increases at
higher pH (e.g. THMs) while other species may
increase at lower pH (e.g. 3-oxopentanedionic) (Bond
et al., 2012).
The use of alternative disinfectant such as ozone,
chlorine dioxide and chloramine disinfectants was
able to reduce major DBPs formed by chlorine.
Unfortunately these disinfectants also formed its
specific DBPs and occurred at higher level (Lu et al.,
2009; Krasner et al., 2006). According to Krasner et
al. (2006) about 600 new DBPs form from a reaction
of NOM with disinfectants such as chlorine,
chloramine, ozone, and chloride which found in
drinking water by the year 2006 and 70% of
halogenated DBPs reported are unidentified.
Meanwhile Bond et al. (2012) and Richardson et al.
(2007) reported that the new products produce from
mono-chloramination such as N-
Nitrosodimethylamine (NDMA), haloacetonitriles and
halonitromethanes known to have high cytotoxicity
and genotoxicity. Table 3 shows the possible DBPs
formed during disinfection process and permissible
limit in drinking water.
4. TREATMENTS
To date, there are several treatment methods that have
been proposed or applied for NOM removal such as
enhanced coagulation, membrane filtration, adsorption
and ion exchange process and advanced oxidation
process. These methods of treatment have been
developed and enhanced in order to reduce NOM
concentration in drinking water sources and minimize
DBPs formation. The merits and demerits as well as
limitation of each treatments will be discuss here.
Ibrahim and Aziz
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
99
Table 3: Possible DBPs formation during disinfection process
DBPs Species
DBPs
Drinking Water Standards
(mg/L)
cCarcinogenicity
aUSEPA
bMalaysia
THMs
(human carcinogen)
Chloroform (CHCl3)
0.08
0.2
B2
Bromodichloromethanes (CHCl2Br)
0.08
0.06
B2
Dibromochloromethanes (CHClBr2)
0.08
0.1
C
Bromoform (CHBr3)
0.08
0.1
B2
HAAs
Dichloroacetic acid (DCAA)
0.06
0.05
B2
Trichloroacetic acid (TCAA)
0.06
0.1
B2
Nitrosamines
N-Nitrosodimethylamine (NDMA)
-
-
NA
N-nitrosodiethylamine (NDEA)
-
-
NA
Haloacetonitriles (HANs)
Dichloroacetonitriles (DCAN)
-
0.09
C
Trichloroacetonitrile (TCAN)
-
-
C
Haloacetamides
Dichloroacetamide (DCAcAm)
-
-
NA
Haloaldehydes
Dichloroacetaldehyde (DCA)
-
-
NA
Trichloroacetaldehyde (chloral
hydrate) (TCA)
-
-
NA
Haloketones
1,1,1-trichloropropanone (TCP)
-
-
NA
Halonitromethanes (HNM)
Trichloronitromethanes
(chloropicrin) (TCNM)
-
-
NA
Note: aUSEPA. (2012); bMOH. (2000); cNikolaou and Lekkas (2001). Group A: Human carcinogen; Group B: Probable human carcinogen (B1: Limited
evidence from epidemiological studies, B2: Sufficient evidence from animal studies); Group C: Possible human carcinogen;
4.1. Enhanced Coagulation
Enhanced coagulation can be defined as methods that
uses effective coagulant dosage to remove TOC or
minimized DOC residual after coagulation in drinking
water sources (Xie et al., 2012; Singer and Bilk, 2002;
Volk et al., 2002). In the beginning of water treatment
process, coagulation was employed with focus to
reduce turbidity. However the reduction of turbidity is
not reducing the amount of NOM in water. Hence, a
suitable condition needs to be created to obtain
optimum removal of NOM through coagulation
process. Thus conventional coagulation process was
enhanced by optimizing pH and coagulant dosage.
Optimizing coagulant dosage is very important to
avoid coagulant overdosing that lead to an increase in
the amount of sludge and pH reduction. Meanwhile
under-dosing usually leaves residual metal remained
in treated water. During treatment process, TOC
content plays an important role in determine
coagulation dosage required. For water sources with
SUVA value equal to 2 or less, TOC is not the factor
that control coagulant dose. But, if SUVA value
obtains is greater than 2, then coagulant dosage
required is increase with TOC concentration.
However, the efficiency of coagulation process is
not only dependent to pH, coagulant type and dosage
but other factors as well such as NOM characteristics
and presence of divalent cations. According to
Matilainen et al. (2005) and Yee et al. (2009),
coagulation process usually more effective in
removing larger molecular (1000 – 4000 g/mol) and
more hydrophobic NOM which primarily consist of
humic substances. Based on the study conducted by
Matilainen et al. (2005), ferric chloride is more
effective for removing NOM compared to aluminium
sulphate especially for high molecular mass materials
(> 3000 g/mol) during coagulation process.
Study conducted by Wang et al. (2013a) exhibit
that coagulation process was able to significantly
reduce the hydrophobic organic matter by destabilized
the particles during coagulation. Meanwhile, Duan
and Gregory, (2003), suggested that co-precipitation
and charge neutralization are the two main
mechanisms in coagulation process that remove humic
acid. Removing of humic substances through
enhanced coagulation may allowed the use of
disinfectant to treat pathogenic bacteria in drinking
water sources while reducing DBPs formation (Uyak
and Toroz, 2006). Still, coagulation process is not
effective in removing low molecular mass (< 500
g/mol) compounds with post coagulation residual
reach up to 90% for low molecular mass and about
50% for intermediate molecular mass (Matilainen et
al., 2005).
4.2. Advanced Oxidation Process (AOPs)
Generally, AOPs is defined as aqueous phase
oxidation methods based on the intermediacy of
highly reactive species such as hydroxyl (-OH) radical
in the mechanism to remove the target pollutants
(Comninellis et al., 2008). In NOM and DBPs cases, -
OH radicals is utilize to oxidize NOM as DBPs
precursor by eliminating hydrogen atoms or adding
electrophiles to their double bonds (Toor and
Mohseni, 2007). The reaction mechanism started with
–OH radicals received an electron from organic
materials. Then the process proceeded as carbon
centered radicals react rapidly with O2 to form peroxyl
radicals. This radical will react among themselves
which produced ketones, aldehydes and/ or CO2
(Lamsal et al., 2011).
International Journal of Scientific Research in Environmental Sciences, 2(3), pp. 94-106, 2014
100
The efficiency of this treatment is depending on
the specific type and concentration of pollutant itself
where more intensive treatment is needed when higher
concentration of pollutant is present and combination
of treatment may require to achieve optimal removal
(Matilainen and Sillanpaa, 2010). In order to obtain
greater efficacy, AOPs can be enhanced through
various combination of AOPs to increase the rate of
reactive species formation (e.g. UV/H2O2, UV/ozone,
UV/ TiO2/H2O2 and UV/ Fenton’s reagent)
(Comninellis et al., 2008). AOPs has great potential
in reducing DBPs formation by: 1) reducing TOC in
drinking water sources through complete oxidation or
mineralization of NOM to CO2 and 2) altering
physical or chemical characteristics of NOM by
partially oxidizes and reducing its molecular weight to
reduce its reactivity with disinfectant (Matilainen and
Sillanpaa, 2010; Toor and Mohseni, 2007).
Instead of the whole NOM structure, AOPs
treatment mainly mineralized aromatic structure of
NOM which is part of hydrophobic fraction (Sarathy
et al., 2011). This indicated that AOPs reduce more of
high molecular mass structure. Meanwhile, during
oxidation/ mineralization process, hydrophobic
structure was altered and molar mass of the fraction
was decrease. Consequently, hydrophilic fraction was
increased compared to its concentration in raw water.
Nevertheless, the efficiency of this treatment was
affected by the presence of carbon and bicarbonate ion
in raw water. Besides NOM components, hydroxyl
radical is also reacts with this ions and decrease the
number of radicals for NOM oxidation which lead to
low NOM removal (Lamsal et al., 2011). Hence
oxidation process is not suitable for treating high
alkalinity water. There are more researches (Rizzo et
al., 2013; Sarathy et al., 2011; Grebel et al., 2010)
conducted and discussed on the effectiveness of AOPs
in removing NOM and DBPs in drinking water.
Figure 2 shows the example in the application of
UV/H2O2 and BAC study conducted at Trojan
Technologies pilot facilities
4.3. Magnetic Ion Exchange Resin Treatment
(MIEX®)
Ion exchange is another alternative method in
removing NOM in drinking water. Resin
characteristic that has high water content and open
structure make it able to adsorb any charge materials
more efficiently (Matilainen, 2007). In recent years,
magnetic ion exchange resin (MIEX®) was developed
for reversible removal of negatively charge organic
ion which mainly focuses on DOC removal with the
aim to reduce DBPs formation in drinking water.
MIEX® is a strong base anion with ammonia
functional group (Mergen et al., 2008) and a
macroporous polyacrylic matrix in chloride form
(Boyer and Singer, 2006). This treatment utilized a
strong base-anion exchange resin by incorporating
magnetic iron oxide particles into the resin matrix and
applied to raw water in continuous-flow reactors
(Drikas et al., 2011).
David et al. (2004) show that the use of MIEX®
was able to increase the removal of DOC level in raw
water whilst reducing coagulant dosage during
coagulation process. Similar result was observed by
Drikas et al. (2011) where large amount of DOC was
removed during MIEX pre-treatment prior to
coagulation process. Thus, the amount of coagulant
required during coagulation process also decrease.
Drikas et al. (2011) also mentioned that MIEX
treatment is not dependent on the DOC concentration
in raw water since a consistent removal was obtained
during 2 year of study regardless of DOC
concentration.
Besides that, Boyer and Singer (2006) were
suggesting that MIEX resin has greater preference for
hydrophobic fraction. However the performance of
MIEX resin was decreased with elevation of sulfate
concentration in raw water. Meanwhile, Mergen et al.
(2008) and Bond et al., (2010) have mention that the
efficiency of resin in removing high molecular mass
fraction (hydrophobic) is declining after rapidly used.
These is happening because of humic and fulvic acid
in water cause the resin to clog by blocking adsorption
sites and prevent continuous adsorption of organic
fraction onto resin. Instead, removal of hydrophilic
fraction was more consistent with consecutive use of
the resin. This data confirm that ion exchange method
is more prominent for removing low molecular mass
fractions compare to hydrophobic fraction. Another
drawback for MIEX® treatment is carry-over of resin
fines (Boyer and Singer, 2006). Therefore another
treatment for solid liquid separation is required
following this treatment (Boyer and Singer, 2006).
Ibrahim and Aziz
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
101
Fig. 2: Schematic set-up for combination of AOPs and BAC treatment (Adopted from: Sarathy et al., 2011)
Fig. 3: River bank filtration system (Adopted from: Hiscock and Grischek, 2002)
4.4. River Bank/ Bed Filtration (RBF) system
Riverbank filtration (RBF) is a water treatment
technology that consists of extracting water from
rivers by pumping wells in the adjacent alluvial
aquifers (Jaramillo, 2012). Basic scheme of riverbank
filtration is shown in Figure 3 Typically aquifers
consist of deposits of sand, sand and gravel, large
cobbles and boulders. However, ideal condition
usually includes of coarse-grained, permeable water
bearing deposits that are hydraulically connected with
riverbed materials (Ray et al., 2003).
A reduction in the concentration of pollutants is
achieved by physical, chemical, and biological
processes that take place, between the surface water
and groundwater, and with the substrate (Jaramillo,
2012). The main processes in riverbank filtration that
involve in pollution level reduction consist of
dispersion, physical filtration, biodegradation, ion
exchange, adsorption, and dilution (Worch et al.,
2002). Other factors that also contribute for the
successful of this treatment are river water and
groundwater quality, the porosity of the medium,
water residence time in the aquifer, temperature and
pH conditions of water, and oxygen concentrations
(Kuehn and Mueller, 2000).
A study conducted by Singh et al. (2010) at river
bank of Yamuna River, India show that RBF was able
to reduce approximately 50 % of NOM component.
This study was suggesting that organic compounds are
diluted, sorbed and degrade during RBF process. Even
though RBF is capable of removing DOC, the
concentration of this component is still high and
exceed the upper limit (< 2 mg/L) recommended by
British Columbia Environmental Protection
Department.
Another related study was conducted by Lee et al.
(2009) in Republic of Korea. This study has reported
International Journal of Scientific Research in Environmental Sciences, 2(3), pp. 94-106, 2014
102
that RBF demonstrate stable chemical constituents for
safely producing drinking water. In spite of that, the
water produced from RBF is still possible to be
directly polluted from anthropogenic sources such as
manures and fertilizer because of their shallowness.
This specifies that RBF system cannot stand alone to
produce good drinking water quality without
optimization of RBF scheme protection. However,
some improvement, adjustment and/ or combination
with suitable treatment may increase RBF
performance.
4.5. Summary of treatment
Table 4 summarize the advantages and disadvantages
of each treatment available for NOM removal in
drinking water sources
Table 4: Methods of treatment used for NOM removal with positive and negative sides
Treatment Method
Positive
Negative
References
Enhanced Coagulation
Good in removing
Hydrophobic fraction
Required high coagulant
dosage and left
transphilic(50 %) and
hydrophilic(90 %) residual
in water
Xie et al., 2012,
Bond et al., 2010 and
Matilainen et al., 2005
Advanced Oxidation
Process (AOPs)
Materialize/ Oxidize HMM
components of NOM to
LMM
Increase LMM components,
Not suitable for high
alkalinity water,
Incomplete oxidation may
increase DBPs formation,
and
High cost
Matilainen and Sillanpaa.
2010
Lamsal et al., 2011
Anion Exchange Resin
At neutral pH both anion
exchange and adsorption is
taking place accordingly
Lower DOC removal for
high molecular mass
(HMM) fraction
Crouè et al., 1999
Magnetic ion Exchange
Resin Treatment (MIEX®)
Significantly remove all
NOM fraction. Hydrophilic
fraction removal is more
consistent with consecutive
use of resin
Clogging and reduce resin
efficiency to remove
hydrophobic fraction after
rapidly used.
Mergen et al., 2008
Bond et al., 2010
Nanofiltration
Effective for treating
neutral hydrophilic
compounds
Fouling
Bond et al., 2010
River Bank Filtration
(RBF)
Remove most of
biodegradable materials
Left NOM residual in water
especially hydrophilic
fraction
De Vet et al., 2010
AOPs and BAC filter
BAC filter increase the
biodegradability of
pollutant to be remove
No significant reduction of
NOM
Sarathy et al., 2011
5. CONCLUSION
To date, water quality monitoring in Malaysia is still
focusing on general parameters such as BOD5, pH,
COD, turbidity, TDS and colour but less attention was
given to NOM concentration in drinking water
sources. NOM is complex mixture of organic
compounds that can cause many problems in drinking
water quality and the most concern is the formation of
DBPs such as THMs and HAA from NOM fraction
(humic and non-humic substances). Continuous
exposure to DBPs in drinking water posing a serious
threat to human health thereby, the authorities set the
permissible limit of these materials to ensure the water
is safe for drinking purposes. Hence, it is important to
remove NOM from raw water more efficiently.
According to the pass studies (Table 1), NOM
characteristics are vary significantly from one sources
to another sources of water. Thus, its characteristic
plays an important role in deciding the treatment
option for raw water. Despite of all treatment
available for NOM removal, none of the discussed
treatments method is successful in removing all NOM
fractions present in water sources. Hence, more study
should be conducted to improve the efficiency of
existing methods whilst exploring another possible
alternative technology such as composite adsorbent
media (e.g. zeolite-carbon) which consist of both
hydrophilic and hydrophobic surface to exchange with
an opposite ion charge of organic carbon in NOM.
Acknowledgments
The authors are grateful to Ministry of Higher
Education Malaysia for providing LRGS Grant No.
203/PKT/6726001 – River bank/bed Filtration for
Ibrahim and Aziz
Trends on Natural Organic Matter in Drinking Water Sources and its Treatment
103
Drinking Water Source Abstraction and MyBrain15
Scholarship to fund this research.
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Nurazim Ibrahim is a PhD candidate in Civil Engineering (Environmental Engineering) at University
Sains Malaysia. She received her BSc (Hons) in Civil Engineering in 2008 from University Teknologi
Mara (UiTM) Pulau Pinang and MSc in Solid Waste Management in 2012 from the Universiti Sains
Malaysia. Currently her research is focusing on treatment of drinking water soures by adsorption using
composite media.
Dr Aziz is a Professor in environmental engineering at the School of Civil Engineering, Universiti Sains
Malaysia. Dr. Aziz received his Ph.D in civil engineering (environmental engineering) from University of
Strathclyde, Scotland in 1992. He has published over 200 refereed articles in professional
journals/proceedings and currently sits as the Editorial Board Member for 8 International journals. Dr
Aziz's research has focused on alleviating problems associated with water pollution issues from industrial
wastewater discharge and solid waste management via landfilling, especially on leachate pollution. He
also interests in biodegradation and bioremediation of oil spills.