trends on natural organic matter in drinking water sources and its treatment

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: [email protected]; Tel: 04-5996215; Fax: 04-5941009

Received 03 January 2013; Accepted 19 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

Themistokles, 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;

Croue et al., 1999).

According to the past studies (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

mailto:[email protected]

Ibrahim and Aziz


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;

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 Themistokles, 2001). Humic and

fulvic acids are examples of hydrophobic acid while

carboxylic and polyuronic acids are in hydrophilic

acids group (Bond et al., 2012; 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; Croue et

al., 1999; Marhaba et al., 2000)


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Typically, allochthonous NOM is the major

contributor to hydrophobic fraction while

authotochthonous is the main sources for hydrophilic

fraction (Croue 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;

Zularisan 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 Themistokles, 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. 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.

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 Croue

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

(Croue et al., 1999). Treatment option such as

coagulation, and oxidation process are not effective

for removing this type of fraction (Siva et al., 2011;

Bond et al., 2012; Matilainen et al., 2010). 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., 2012) 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

coagulant dosage may pose a risk to the consumer

such as Alzheimer’s disease as a consequence of Al

Ibrahim and Aziz


97

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 (EPA, 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 et al., (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.


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 (Duan

et al., 2009; 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 Themistokles, 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


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 Themistokles (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).


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 (Siva 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 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, Bond et al.

(2012) 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


101

Fig. 2: Schematic set-up for combination of AOPs and BAC treatment

Fig. 3: River bank filtration system

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.

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. 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.

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

that RBF demonstrate stable chemical constituents for


102

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., 2012 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

Croue 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.

Bond et al., 2010

Nanofiltration Effective for treating

neutral hydrophilic

compounds

Fouling Bond et al., 2012

Harisha et al., 2010

River Bank Filtration

(RBF)

Remove most of

biodegradable materials

Left NOM residual in water

especially hydrophilic

fraction

AOPs and BAC filter BAC filter increase the

biodegradability of

pollutant to be remove

No significant reduction of

NOM

Siva 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

Drinking Water Source Abstraction and MyBrain15

Scholarship to fund this research.

Ibrahim and Aziz


103

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106

Nurazim Ibrahim is a postgraduate student at School of Civil Engineering, Engineering Campus,

Universiti Sains Malaysia.

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.

trends on natural organic matter in drinking water sources and its treatment

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