Characteristics Of Natural Organic Matter Research Articles

Contributions of spatial, temporal, and treatment impacts on natural organic matter character using fluorescence-based measures

The potential application of fluorescence spectroscopy for monitoring of organic matter concentration and character at four water treatment facilities was investigated. Results are presented showing impacts on natural organic matter (NOM) due to intake location on the same water body and from individual unit processes including ozonation, granular-activated carbon filtration, and coagulation/flocculation. For validation and comparison of fluorescence methods, organic matter was quantified and characterized using liquid chromatography-organic carbon detection (LC-OCD). Principal component analysis (PCA) and parallel factors analysis were used for dimensionality reduction and to represent individual organic components observed through fluorescence excitation-emission matrices. Fluorescence results generally agreed with LC-OCD characterization, indicating that complete treatment reduced organic concentrations and preferential removal of humic-like material was associated with coagulation/flocculation. PCA results indicated higher concentrations of humic-like material at the Island water treatment plant intake that was not well reduced by inline polyaluminum chloride coagulation and direct filtration. Through fluorescence spectroscopy, ozonation increased Rayleigh scattering, which is correlated to small colloidal/particulate concentrations. Full-scale results from four water treatment plants presented demonstrate that fluorescence methods can characterize NOM, providing similar identification of trends to LC-OCD, with possible online application and use in real-time water treatment process control.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF–MS) coupled to XAD fractionation: Method to algal organic matter characterization

This work is focused on the development of an analytical procedure for the improvement of the Organic Matter structure characterization, particularly the algal matter. Two fractions of algal organic matter from laboratory cultures of algae (Euglena gracilis) and cyanobacteria (Microcystis aeruginosa) were extracted with XAD resins. The fractions were studied using laser desorption ionization (LDI) and Matrix-Assisted laser desorption ionization time-of-flight mass spectrometry (MALDI–TOF). A comparison with the natural organic matter characteristics from commercial humic acids and fulvic acids extracted from Suwannee River was performed.Results show that algal and natural organic matters have unique quasi-polymeric structures. Significant repeating patterns were identified. Different fractions extracted from organic matter with common origin had common structures. Thus, 44, 114 and 169Da peaks separation for fractions from E. gracilis organic matter and 28, 58 and 100Da for M. aeruginosa ones were clearly observed. Using the developed protocol, a structural scheme and organic matter composition were obtained. The range 600–2000Da contained more architectural composition differences than the range 100–600Da, suggesting that organic matter is composed of an assembly of common small molecules. Associated to specific monomers, particular patterns were common to all samples but assembly and resulting structure were unique for each organic matter. Thus, XAD fractionation coupled to mass spectroscopy allowed determining a specific fingerprint for each organic matter.

Investigating the feasibility and the optimal location of pulsed ultrasound in surface water treatment schemes

The deterioration of surface water quality due to extreme weather events and increasing human activities has exacerbated the common problems in drinking water production such as filtration fouling and DPBs formation. This in turn has urged for exploring alternative methods for the traditional treatment methods that are able to improve the removal of contaminants with minimal impact on environment and human health. In this study, the application of pulsed and continuous ultrasound for improving the quality of natural water with fresh natural organic matter (NOM) mainly driven from vegetation has been evaluated. The evaluation was performed using cost-effective and quick measurements such as specific UV–vis absorbance, CODMn, alkalinity and conductivity. The changes in the characteristics of NOM induced by ultrasound were used to develop a framework for evaluating ultrasound performance in improving conventional surface water treatment processes and to identify the best fit of ultrasound within the treatment scheme. Results of this study showed that pulsed ultrasound was as effective as or in some cases better than continuous ultrasound in improving water quality. According to the adapted assessment criteria supported by an extensive literature survey, the most effective location of ultrasound treatment within surface water treatment scheme was found to be prior to coagulation/flocculation.

The evolution of organic character in a drought- and flood-impacted water source and the relationship with drinking water treatment

A pilot-scale research investigation examining treatment technologies including coagulation, ion-exchange, activated carbon and membrane filtration and their impact on water quality coincided with a period of extensive variability in source water character. Distinct water quality periods as a result of extreme climatic conditions from drought to flood were observed and the natural organic matter (NOM) removal examined using a suite of organic characterisation techniques from simple ultraviolet (UV) absorbance to more advanced spectroscopic and chromatographic methods. The low specific UV absorbance (SUVA) and apparent molecular weight (AMW) distribution of the drought-impacted NOM was recalcitrant to coagulation with significant improvement in NOM removal resulting from the multi-step treatments. Among a number of discernible changes, floodwaters introduced high AMW, UV-absorbing NOM of terrestrial origin, which was shown to be more amenable to coagulation. Nevertheless the application of multi-step treatments resulted in further reduction in both the concentration and diversity of organic components. Filtration through granular activated carbon was observed to be the most variable treatment technology across the investigated period due to diminishing adsorption capacity. Conversely, the dual stage membrane filtration was shown to remove a broad range of organic matter, regardless of source water NOM concentration and character.

Formation and speciation of haloacetic acids in seawater desalination using chlorine dioxide as disinfectant

To evaluate the formation potential of disinfection byproducts (DBPs) in a SWRO system when chlorine dioxide (ClO2) is used as a chemical disinfectant, the impact of principle precursors such as natural organic matter (NOM) and bromide ion on haloacetic acids (HAAs) formation and its speciation was investigated. In the presence of high bromide levels found in seawater, the active oxidizing agents formed by the action of ClO2 can react with NOM, resulting in halogenation reactions, and the production of brominated DBPs as the predominant byproducts. Elevating the initial levels of organic substances and bromide ions not only enhanced the total content of HAA5 formed, but also shifted the speciation of HAAs from the chlorinated to fully brominated forms at higher disinfectant doses and longer contact times of ClO2 disinfection. In addition, HAA5 formation potential increased in the order of transphilic>hydrophobic>hydrophilic NOM, suggesting HAA5 yield formed during ClO2 disinfection significantly depends on the characteristics of NOM that can lead to different speciation distribution of DBPs. However, at high doses of ClO2, it was observed that the disinfectant dose plays a more important role in speciation distribution of HAA5 than the characteristics of organic precursors.

The effects of ultraviolet/H2O2 advanced oxidation on the content and characteristics of groundwater natural organic matter

This work investigates the effects of ultraviolet (UV)/H2O2 advanced oxidation on the content and characteristics of natural organic matter (NOM) originating from two different groundwaters (3.03–9.69 mg/L total organic carbon (TOC), 2.71–4.31 Lmg−1m−1 specific ultraviolet absorbance (SUVA)). Application of UV irradiation resulted in a minor reduction in the total content of NOM. Using UV/H2O2 advanced oxidation led to a significant reduction of the aromatic character of NOM (SUVA was reduced by up to 80%) and an increase in the hydrophilic character of the residual NOM, with the optimal UV/H2O2 treatment conditions depending on the water type. In addition, fluctuations in trihalomethane formation potential (THMFP) were observed depending on the UV/H2O2 process conditions, with a maximal reduction of about 40% achieved for both waters.

Natural Organic Matter Removal and Fouling Control in Low-Pressure Membrane Filtration for Water Treatment

Natural organic matter (NOM) is a primary component of fouling in low-pressure membrane filtration, either solely, or in concert with colloidal particles. Various preventive measures to interfere with NOM fouling have been developed and extensively tested, such as coagulation, oxidation, ion exchange, carbon adsorption, and mineral oxide adsorption. Therefore, this article aims to conduct a literature review covering the topics of low-pressure membrane processes, NOM characteristics and fouling behaviors, and diverse fouling control strategies. In-depth explanations and discussion are made regarding why some treatment options are able to remove NOM from source water, but do not reduce fouling. This review provides insight for hybridized membrane processes with respect to NOM removal and fouling mitigation in water treatment.

Trends on Natural Organic Matter in Drinking Water Sources and its Treatment

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.

Hydrophilic fraction of natural organic matter causing irreversible fouling of microfiltration and ultrafiltration membranes

Although membrane filtration is a promising technology in the field of drinking water treatment, persistent membrane fouling remains a major disadvantage. For more efficient operation, causative agents of membrane fouling need to be identified. Membrane fouling can be classified into physically reversible and irreversible fouling on basis of the removability of the foulants by physical cleaning. Four types of natural organic matter (NOM) in river water used as a source of drinking water were fractionated into hydrophobic and hydrophilic fractions, and their potential to develop irreversible membrane fouling was evaluated by a bench-scale filtration experiment together with spectroscopic and chromatographic analyses. In this study, only dissolved NOM was investigated without consideration of interactions of NOM fractions with particulate matter. Results demonstrated that despite identical total organic carbon (TOC), fouling development trends were significantly different between hydrophilic and hydrophobic fractions. The hydrophobic fractions did not increase membrane resistance, while the hydrophilic fractions caused severe loss of membrane permeability. These results were identical with the case when the calcium was added to hydrophobic and hydrophilic fractions. The largest difference in NOM characteristics between hydrophobic and hydrophilic fractions was the presence or absence of macromolecules; the primary constituent causing irreversible fouling was inferred to be “biopolymers”, including carbohydrates and proteins. In addition, the results demonstrated that the extent of irreversible fouling was considerably different depending on the combination of membrane materials and NOM characteristics. Despite identical nominal pore size (0.1 μm), a polyvinylidene fluoride (PVDF) membrane was found to be more rapidly fouled than a PE membrane. This is probably explained by the generation of strong hydrogen bonding between hydroxyl groups of biopolymers and fluorine of the PVDF membrane. On the basis of these findings, it was suggested that the higher fouling potential of the hydrophilic fraction of the dissolved NOMs from various natural water sources are mainly attributed to macromolecules, or biopolymers.

Removal of natural organic matter by titanium tetrachloride: The effect of total hardness and ionic strength

This study is the first attempt to investigate the effect of total hardness and ionic strength on coagulation performance and the floc characteristics of titanium tetrachloride (TiCl4). Membrane fouling under different total hardness and ionic strength conditions was also evaluated during a coagulation–ultrafiltration (C–UF) hybrid process. Coagulation experiments were performed with two simulated waters, using humic acid (HA, high molecular weight) and fulvic acid (FA, relatively low molecular weight), respectively, as model natural organic matter (NOM). Results show that both particle and organic matter removal can be enhanced by increasing total hardness and ionic strength. Floc characteristics were significantly influenced by total hardness and ionic strength and were improved in terms of floc size, growth rate, strength, recoverability and compactness. The results of the UF tests show that the pre-coagulation with TiCl4 significantly improves the membrane permeate fluxes. Under different total hardness and ionic strength conditions, the membrane permeate flux varied according to both NOM and floc characteristics. The increase in total hardness and ionic strength improved the membrane permeate flux in the case of HA simulated water treatment.

Minimizing raw water NOM concentration through optimized source water selection

Natural organic matter (NOM) is present in all raw water supplies and is the major precursor to chlorinated disinfection by‐products (DBPs). Reducing the amount of NOM entering treatment plants and better understanding the character of NOM in raw water supplies are essential for optimizing treatment and meeting more‐stringent regulations. A study of the unfiltered New York City (NYC) water supply system evaluated the extent to which alternative raw water selection strategies could reduce finished water DBP concentrations. A two‐year monitoring program was conducted to establish spatial and temporal patterns of DBP precursors in NYC's upstate reservoirs. System operations modeling was driven with a statistically generated, long‐term time series of dissolved organic carbon concentrations for each reservoir as a proof‐of‐concept evaluation of alternative operating rules to minimize precursor transport to terminal reservoirs. Results found that DBP precursors varied widely among reservoirs and over time but that modified reservoir operations could substantially reduce finished water DBP concentrations.

Fluorescence characteristics of natural organic matter in water under sequential exposure to UV irradiation/chlor(am)ination

The organic matter in International Humic Substances Society Natural Organic Matter (IHSS NOM) water exposed to ultraviolet (UV) irradiation and chlor(am)ine sequentially under practically relevant conditions was characterized based on fluorescence spectra. IHSS NOM water exposed to UV irradiation or chlor(am)ine alone was also evaluated. Both chlor(am)ine alone and UV/chlor(am)ine exposure showed similar chlor(am)ine demand and fluorescence spectra. UV irradiation and UV/chlorine exposure diminished the fluorescence intensity of IHSS NOM water, while UV/chloramine exposure resulted in increased fluorescence intensity. When compared with the results obtained following chlor(am)ination alone, IHSS NOM water showed decreased chlorine decay and increased chloramine decay after UV irradiation/chlor(am)ination. Additionally, IHSS NOM water exposed to UV/chloramine and chloramine showed less disinfection by-product (DBP) formation than water subjected to UV/chlorine and chlorine. Overall, these findings indicate that UV irradiation degrades NOM molecules to low-molecular-weight fractions, facilitating the subsequent reaction with chlor-(am)ine. However, chlorine and chloramine play different roles in the reaction. Chlorine degradation and substitution dominates the process of UV/chlorine exposure, while chloramine substitution is the major reaction during UV/chloramine exposure.

Characterization of natural organic matters using flow field-flow fractionation and its implication to membrane fouling

ABSTRACT Transport and deposition characteristics of natural organic matter (NOM) are systematically investigated using flow field-flow fractionation (Fl-FFF) at various chemical and physical conditions. Humic acid (HA) was chosen as model organic foulants. Prior to Fl-FFF analysis, HA was fractionated by membranes with different molecular weight cut-offs. To elucidate physicochemical factors affecting the deposition and transport characteristics of organic foulants, various concentrations of NaCl (i.e. up to seawater level) and CaCl2 were employed as carrier solutions in Fl-FFF. Each fractionated NOM showed different transport and deposition characteristics with respect to the chemical and physical conditions employed during Fl-FFF analysis. When the total dissolved solids (TDS) concentration increased, there was more significant variation in the retention time for large NOM fractions compared with small NOM fractions. This means that the transport and deposition tendency of the larger NOM fractions vari...

Modeling bromide effects on yields and speciation of dihaloacetonitriles formed in chlorinated drinking water

This study examined effects of bromide on yields and speciation of dihaloacetonitrile (DHAN) species that included dichloro-, bromochloro- and dibromoacetonitriles generated in chlorinated water. Experimental data obtained using two water sources, varying concentrations and characters of Natural Organic Matter (NOM), bromide concentrations, reaction times, chlorine doses, temperatures and pHs were interpreted using a semi-phenomenological model that assumed the presence of three kinetically distinct sites in NOM (denoted as sites S1, S2 and S3) and the occurrence of sequential incorporation of bromine and chlorine into them. One site was found to react very fast with the chlorine and bromine but its contribution in the DHAN generation was very low. The site with the highest contribution to the yield of DHAN (>70%) has the lowest reaction rates. The model introduced dimensionless coefficients (denoted as φ1DHAN, φ2DHAN and φ3DHAN) applicable to the initial DHAN generation sites and their monochlorinated and monobrominated products, respectively. These parameters were used to quantify the kinetic preference to bromine incorporation over that of chlorine. Values of these coefficients optimized for DHAN formation were indicative of the strongly preferential incorporation of bromine into the engaged NOM sites. The same set of φiDHAN coefficients could be used to model the speciation of DHAN released from their kinetically different precursors. The dimensionless speciation coefficients φiDHAN were determined to be site specific and dependent on the NOM content and character as well as pH. The presented model of DHAN formation and speciation can help quantify in more detail the generation of DHAN and provide more insight necessary for further assessment of their potential health effects.

The effects of matrices and ozone dose on changes in the characteristics of natural organic matter

This study investigates the effects of water matrices with different natural organic matter (NOM) contents (3.00–6.50mg DOC/L) and different ozone doses (0.2 and 0.8mg O3/mg DOC) on changes in NOM structure and reactivity towards the formation of disinfection by-products. Water matrices differ in the NOM structure and other matrix characteristics (i.e. alkalinity, bromide content) which affect the NOM oxidation mechanism. Ozone treatment results in partial oxidation of the fulvic acid fraction, and increases the hydrophilic fraction (by up to 70%) with increasing ozone dose. A slightly lower degree of oxidability was found in the NOM dominated by the hydrophilic fraction and in water with the highest alkalinity. The residual hydrophilic fraction after ozonation was the most reactive towards trihalomethanes (THMs) and chloropicrin formation, with a higher proportion of brominated THMs in the hydrophilic non-acidic fraction. Bromate formation increases with increasing bromide content in the raw water and with increasing ozone dose, and achieves a significant level for drinking water quality at a dose of 0.8mg O3/mg DOC.

Formation of disinfection byproducts upon chlorine dioxide preoxidation followed by chlorination or chloramination of natural organic matter

Chlorine dioxide (ClO2) is often used as an oxidant to remove taste, odor and color during water treatment. Due to the concerns of the chlorite formation, chlorination or chloramination is often applied after ClO2 preoxidation. We investigated the formation of regulated and emerging disinfection byproducts (DBPs) in sequential ClO2-chlorination and ClO2-chloramination processes. To clarify the relationship between the formation of DBPs and the characteristics of natural organic matter (NOM), changes in the properties of NOM before and after ClO2 oxidation were characterized by fluorescence, Fourier transform infrared spectroscopy (FTIR), and size and resin fractionation techniques. ClO2 preoxidation destroyed the aromatic and conjugated structures of NOM and transformed large aromatic and long aliphatic chain organics to small and hydrophilic organics. Treatment with ClO2 alone did not produce significant amount of trihalomethanes (THMs) and haloacetic acids (HAAs), but produced chlorite. ClO2 preoxidation reduced THMs, HAAs, haloacetonitriles (HANs) and chloral hydrate (CH) during subsequent chlorination, but no reduction of THMs was observed during chloramination. Increasing ClO2 doses enhanced the reduction of most DBPs except halonitromethanes (HNMs) and haloketones (HKs). The presence of bromide increased the formation of total amount of DBPs and also shifted DBPs to more brominated ones. Bromine incorporation was higher in ClO2 treated samples. The results indicated that ClO2 preoxidation prior to chlorination is applicable for control of THM, HAA and HAN in both pristine and polluted waters, but chlorite formation is a concern and HNMs and HKs are not effectively controlled by ClO2 preoxidation.

Membrane fouling due to alginate, SMP, EfOM, humic acid, and NOM

Several commercially available organic materials have frequently been used as surrogates for surface water natural organic matter (NOM) and for wastewater effluent organic matter (EfOM), e.g., for identifying the extent and mechanism of membrane fouling. However there is a lack of experimental evidence that the surrogate organic materials are representative of EfOM and surface water NOM. Therefore the main objectives were to compare the organic composition (by empirical fractionation methods), the molecular size distributions, and fouling and the mechanisms of fouling of ultrafiltration (UF) membranes for the surrogate materials sodium alginate, soluble microbial products (SMP), and commercial humic acid (HA) with the characteristics of EfOM and Suwannee River NOM (SRNOM). The fouling mechanisms were probed by measuring resistance to filtration as a function of permeate flux using several filtration modes, by determining the effects of Ca2+ on fouling, and by investigating the effectiveness of hydraulic and chemical cleaning on restoration of membrane permeability. Results showed that SMP was most similar to EfOM, Aldrich HA (AHA) was most similar to SRNOM, and alginate was a poor surrogate for either EfOM or SRNOM. Alginate was also unique among the five organic materials in that fouling was decreased when 0.8mM Ca2+ was added, consistent with the formation of a gel that formed a porous cake on top of the membrane. Fouling increased with addition of Ca2+ for the other materials. Addition of Ca2+ increased the colloidal fraction and the concentration of molecules >100kDa for all of the materials but the increases were particularly dramatic for alginate and were also large for AHA. Differences in fouling mechanisms and cake compressibility as a function of the applied trans-membrane pressure (TMP) between surrogate and natural organic materials were also observed.

Sorption Selectivity in Natural Organic Matter Studied with Nitroxyl Paramagnetic Relaxation Probes

Sorption site selectivity and mechanism in natural organic matter (NOM) were addressed spectroscopically by the sorption of paramagnetic nitroxyl compounds (spin probes) of different polarity, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl). The sorbents were Pahokee peat, Beulah-Zap lignite, and a polystyrene-poly(vinyl methyl ether) (PS-PVME) polymer blend representing the mixed aliphatic-aromatic, polar-nonpolar character of NOM. Nuclear-electron spin interaction serves as an efficient relaxation pathway, resulting in attenuation of the (13)C-CP/TOSS NMR signal for (13)C nuclei in proximity to the N-O· group (r(-6) dependence). In the natural solids the spin probes sorbed more specifically (greater isotherm nonlinearity) and had lower rotational mobility (broader electron paramagnetic resonance signals) than in PS-PVME. Titration with spin probe indicated almost no selectivity for the different carbon functional groups of PS-PVME, and little to no selectivity for the different carbon moieties of Pahokee and Beulah, including aromatic, alkyl, O-alkyl, di-O-alkyl, and O-methyl. In any case, sorption site selectivity of spin probes to NOM was always weaker than partition selectivity found in model solvent-water (toluene, hexadecane, anisole, octanol) and cellulose-water systems. The results indicate little or no preferential sorption in NOM based on functional group chemistry or putative microdomain character, but rather are consistent with the filling of pores whose walls have an average chemical environment reflecting the bulk chemical composition of the solid. This work demonstrates for the first time the use of paramagnetic probes to study sorption specificity.

Natural organic matter (NOM) in South African waters: NOM characterisation using combined assessment techniques

In order to remove natural organic matter (NOM) from water in a water treatment train, the composition of the NOM in the source water must be taken into account, especially as it may not necessarily be uniform since the composition is dependent on the local environment. The main thrust of this study was to ascertain whether a cocktail of characterisation protocols could help to determine the nature, composition and character of NOM in South African waters. The characterisation of South African water sources was done by sampling 8 different water treatment plants located within the 5 major source water types in South Africa. The NOM composition of all of the samples was first studied by applying conventional techniques (UV, DOC, SUVA and bulk water parameters). NOM characterisation was then further conducted using advanced techniques (BDOC, PRAM and FEEM), which were aimed at developing rapid assessment protocols. The FEEM and UV results revealed that the samples consisted mainly of humic substances with a high UV-254 absorbance, while some samples had marine humic substances and non-humic substances. The samplefs DOC results were within the range of 3.5 to 22.6 mgE..1 C, which was indicative of the extent of variation of NOM quantities in the regions where samples were obtained. The BDOC fraction of the NOM ranged between 12 and 66%, depending on the geographical location of the sampling site. A modified PRAM was utilised to characterise the changes in NOM polarity in the water treatment process. PRAM results also indicated that the NOM samples were mostly hydrophobic. The composition and character of the NOM was found to vary from one water treatment plant to another. Combining conventional and advanced techniques could be a powerful tool for NOM characterisation and for extracting detailed information on NOM character, which should inform its treatability.

Formation of N-nitrosamines from chlorination and chloramination of molecular weight fractions of natural organic matter

N-Nitrosamines are a class of disinfection by-products (DBPs) that have been reported to be more toxic than the most commonly detected and regulated DBPs. Only a few studies investigating the formation of N-nitrosamines from disinfection of natural waters have been reported, and little is known about the role of natural organic matter (NOM) and the effects of its nature and reactivity on the formation of N-nitrosamines. This study investigated the influence of the molecular weight (MW) characteristics of NOM on the formation of eight species of N-nitrosamines from chlorination and chloramination, and is the first to report on the formation of eight N-nitrosamines from chlorination and chloramination of MW fractions of NOM. Isolated NOM from three different source waters in Western Australia was fractionated into several apparent MW (AMW) fractions using preparative-scale high performance size exclusion chromatography. These AMW fractions of NOM were then treated with chlorine or chloramine, and analysed for eight species of N-nitrosamines. Among these N-nitrosamines, N-nitrosodimethylamine (NDMA) was the most frequently detected. All AMW fractions of NOM produced N-nitrosamines upon chlorination and chloramination. Regardless of AMW characteristics, chloramination demonstrated a higher potential to form N-nitrosamines than chlorination, and a higher frequency of detection of the N-nitrosamines species was also observed in chloramination. The results showed that inorganic nitrogen may play an important role in the formation of N-nitrosamines, while organic nitrogen is not necessarily a good indicator for their formation. Since chlorination has less potential to form N-nitrosamines, chloramination in pre-chlorination mode was recommended to minimise the formation of N-nitrosamines. There was no clear trend in the formation of N-nitrosamines from chlorination of AMW fractions of NOM. However, during chloramination, NOM fractions with AMW <2.5 kDa were found to produce higher concentrations of NDMA and total N-nitrosamines. The precursor materials of N-nitrosamines appeared to be more abundant in the low to medium MW fractions of NOM, which correspond to the fractions that are most difficult to remove using conventional drinking water treatment processes. Alternative or advanced treatment processes that target the removal of low to medium MW NOM including activated carbon adsorption, biofiltration, reverse osmosis, and nanofiltration, can be employed to minimise the formation of N-nitrosamines.