Characterization Of Natural Organic Matter Research Articles

Characterization of natural organic matter in low-carbon sediments: Extraction and analytical approaches

Organic carbon (OC) concentrations in subsurface sediments are typically 10 to 200 times lower than in surface soils, posing a distinct challenge for characterization. In this study, a range of chemical extractions were evaluated for extraction of natural organic matter (NOM) from two low-carbon (< 0.2%) alluvial sediments. The OC extraction efficiency followed the order pyrophosphate (PP)>NaOH>HCl, hydroxylamine hydrochloride>dithionite, water. A NOM extraction and purification scheme was developed using sequential extraction with water (MQ) and sodium pyrophosphate at pH 10 (PP), combined with purification by dialysis and solid phase extraction in order to isolate different fractions of sediment-associated NOM. Characterization of these pools of NOM for metal content and by Fourier transform infrared spectroscopy (FITR) showed that the water soluble fraction (MQ-SPE) had a higher fraction of aliphatic and carboxylic groups, while the PP-extractable NOM (PP-SPE and PP>1kD) had higher fractions of CC groups and higher residual metals. This trend from aliphatic to more aromatic is also supported by the specific UV absorbance at 254nm (SUVA254) (3.5vs 5.4 for MQ-SPE and PP-SPE, respectively) and electrospray ionization Fourier transform ion cyclotron resonance spectrometry (ESI-FTICR-MS) data which showed a greater abundance of peaks in the low O/C and high H/C region (0–0.4 O/C, 0.8–2.0H/C) for the MQ-SPE fraction of NOM. Radiocarbon measurements yielded standard radiocarbon ages of 1020, 3095, and 9360yearsBP for PP-SPE, PP>1kD, and residual (non-extractable) OC fractions, indicating an increase in NOM stability correlated with greater metal complexation, apparent molecular weight, and aromaticity.

Application of 3-D Fluorescence: Characterization of Natural Organic Matter in Natural Water and Water Purification Systems.

Natural organic matter (NOM) found in water sources is broadly defined as a mixture of polyfunctional organic molecules, characterized by its complex structure and paramount influence on water quality. Because the inevitable release of pollutants into aquatic environments due to an ineffective control of industrial and agricultural pollution, the evaluation of the interaction of NOM with heavy metals, nanoparticles, organic pollutants and other pollutants in the aquatic environment, has greatly increased. Three-dimensional (3-D) fluorescence has the potential to reveal the interaction mechanisms between NOM and pollutants as well as the source of NOM pollution. In water purification engineering system, the 3-D fluorescence can indicate the variations of NOM composition and gives an effective prediction of water quality as well as the underline water purification mechanisms. Inadequately treated NOM is a cause of precursors of disinfection byproducts (DBPs), posing a potential threat to human health. Effective control and measurement/evaluation of NOM have long been an important factors in the prevention of water pollution. Overall, 3-D fluorescence allows for a rapid identification of organic components thus indicating possible sources of water pollution, mechanisms of pollutant interactions, and possible DBPs formed during conventional treatment of this water. This article reviews the 3-D fluorescence characteristics of NOM in natural water and typical water purification systems. The 3-D fluorescence was effective for indicating the variabilities in NOM composition and chemistry thus providing a better understanding of NOM in natural water system and water engineering system.

Natural organic matter characterization by HPSEC and its contribution to trihalomethane formation in Athens water supply network

ABSTRACTSamples from the two main watersheds that provide Athens Water Supply and Sewerage Company (AWSSC) with raw water were examined for Dissolved Organic Carbon (DOC) and for their molecular weight distribution (MWD). In addition, water samples from water treatment plants (WTPs) and from the water supply network were examined for trihalomethane (THMs) levels. The main purpose of this study was to reveal the molecular composition of natural organic matter (NOM) and identify the individual differences between NOM from the two main Athens watersheds. High-performance size exclusion chromatography (HPSEC), a relatively simple technique, was applied to determine different NOM fractions' composition according to molecular weight. Various THM levels in the supply network of Athens are illustrated as a result of the different reservoirs' water qualities, and a suggestion for a limited application of chlorine dioxide is made in order to minimize THM formation.

Investigation of natural organic matter (NOM) character and its removal in a chlorinated and chloraminated system at Rand Water, South Africa

In its natural environment, natural organic matter (NOM) is not problematic. However, during water treatment NOM does affect water quality specifically during the disinfection step, where if NOM is present it reacts with disinfectants resulting in the formation of disinfection by-products. To emphasize the importance of NOM monitoring during potable water treatment this study aimed to characterize NOM and evaluate NOM removal by a conventional water treatment plant considering seasonal trends. NOM was characterized by making use of NOM polarity and specific ultraviolet absorbance. NOM removal was monitored with high-performance size exclusion chromatography, dissolved organic carbon (DOC) and UV254 analyses. The polarity rapid assessment method indicated that the hydrophobic and hydrophilic NOM fractions within the surface water increased during a period of heavy rain when floods occurred, but conversely decreased during an average rain season. Although NOM character showed variability during the 5-year study period, seasonal relationship during high and low flow seasons between aromatic NOM and total trihalomethane (TTHM) formation was not evident. Aromatic NOM was not the only precursor to TTHM formation, which stresses the need to implement advanced NOM characterization techniques during NOM monitoring to study reactivity of the individual NOM fraction with the disinfectant used at the water treatment plant.

Ion Accumulation Time Dependent Molecular Characterization of Natural Organic Matter Using Electrospray Ionization-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Natural organic matter (NOM) is a complex organic mixture and plays a crucial role in environmental processes. By using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), detailed molecular information on NOM could be achieved. In this paper, ion accumulation time (IAT), a key parameter of FTICR-MS for complex mixture detection, was the focus, and its effect on the molecular characterization of NOM by FTICR-MS was systematically investigated. A notable feature of selective detection of NOM molecules by FTICR-MS with different IAT was observed. Most of the polar molecules with high O/C ratio (O/C ratio >0.5) could be easily detected by FTICR-MS with a short IAT, but extending IAT led to the ion intensities of these molecules decreasing or even disappearing. Meanwhile, a large number of unsaturated and aromatic molecules with low O/C ratio (O/C ratio <0.6) and low polarity, all of which could not be observed with a short IAT, were remarkably detected by extending IAT. Results also revealed that the unsaturated and aromatic molecules, which could only be observed by extending the IAT, were not generated by the fragmentation of molecules in NOM or from the dissociation of NOM aggregations but originally existed in NOM samples. The selective detection of NOM molecules caused by IAT extension was possibly attributed to their different polarity and different stability in the collision cell. On the basis of these results, a novel strategy of combining mass spectrometric data of NOM obtained with different IAT by FTICR-MS was proposed. With this strategy, more than 4715 CHO-molecular formulas were assigned, where about 2000 more formulas were obtained in comparison with using a short IAT (2733 CHO-molecular formulas identified) solely. The strategy is simple and robust and can be used as an alternative method to obtain more molecular information on NOM in the environment.

Modeling and characterization of natural organic matter and its relationship with the THMs formation

&lt;p&gt;Natural organic matter (NOM) has been identified as the prominent precursor for disinfection by-products (DBPs) formation during chlorination. Various studies have shown that the characteristics of NOM influence the Trihalomethanes (THMs) formation mechanism. The present study represents NOM categorization in terms of total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm wavelengths (UV&lt;sub&gt;254&lt;/sub&gt;) and specific ultraviolet absorbance (SUVA) to investigate the effects of NOM on THMs formation mechanism. The high rate of dependency was found for each representative of NOM with respect to water quality characteristics and operational condition of disinfection process. Values of SUVA and UV&lt;sub&gt;254&lt;/sub&gt; is drastically reduced with respect from higher to a moderate chlorine dose which represent the chlorine contact is more predominant with hydrophobic fractions of NOM. The value of SUVA is decreasing with respect to temperature and reaction time, which reveled higher rate of utilization for hydrophobic fractions of NOM. Predictive modeling approach was carried out using multiple regression analysis with the combination of two surrogates at each stage of modeling with help of operational condition of disinfection process and water quality characteristics. The R&lt;sup&gt;2&lt;/sup&gt; value of the model was found in the range of 0.927 to 0.937 from the developed model and a model could be recommended for prediction of THMs in drinking water.&lt;/p&gt;

Benefits of multidimensional fractionation for the study and characterization of natural organic matter

The belief that chromatographic separation of complex environmental mixtures or natural organic matter (NOM) produces featureless humps from which little, if anything, can be learned is still pervasive. Meanwhile improvements in chromatography and the use of information-rich detection methods have led to meaningful fractionation and revealed consistent data. Here, we build on this work and developed a robust, facile two-dimensional separation with high orthogonality between dimensions. We illustrate that re-injections of fractions (both in the first and in the second dimension) leads to individual peaks at the expected retention times and use information-rich detection to investigate the basis on which NOM is fractionated. We demonstrate unprecedentedly feature-rich chromatograms are observed even with standard UV detection for polar NOM fractions. The second stage of fractionation is demonstrated to separate isomers, providing a direct look at isomeric complexity in NOM as well as a tool to reduce it. Consistent with expectation, but confirmed for the first time through mass spectral data, radicals were detected for NOM components that were generally nonpolar and grouped in the condensed aromatic structure – like region of van Krevelen plots. High-resolution tandem mass spectral data, furthermore, suggests that many higher-MW components of fulvic acids (especially the highly oxidized ones) have formulas that do not match any known compounds in the literature, supporting the hypothesis that fulvic acids are a unique compound-class. Combined, the data illustrate that meaningful reduction in complexity reveals new compositional and structural detail and avails new avenues of investigation.

Kinetics of natural organic matter (NOM) removal during drinking water biofiltration using different NOM characterization approaches

To better understand biofiltration, concentration profiles of various natural organic matter (NOM) components throughout a pilot-scale drinking water biofilter were investigated using liquid chromatography – organic carbon detection (LC-OCD) and fluorescence excitation and emission matrices (FEEM). Over a 2 month period, water samples were collected from six ports at different biofilter media depths. Results showed substantial removal of biopolymers (i.e. high molecular weight (MW) NOM components as characterized by LC-OCD) and FEEM protein-like materials, but low removal of humic substances, building blocks and low MW neutrals and low MW acids. For the first time, relative biodegradability of different NOM components characterized by LC-OCD and FEEM approaches were investigated across the entire MW range and for different fluorophore compositions, in addition to establishing the biodegradation kinetics. The removal kinetics for FEEM protein-like materials were different than for the LC-OCD-based biopolymers, illustrating the complementary nature of the LC-OCD and FEEM approaches. LC-OCD biopolymers (both organic carbon and organic nitrogen) and FEEM protein-like materials were shown to follow either first or second order biodegradation kinetics. Due to the low percent removal and small number of data points, the performance of three kinetic models was not distinguishable for humic substances. Pre-filtration of samples for FEEM analyses affected the removal behaviours and/or kinetics especially of protein-like materials which was attributed to the removal of the colloidal/particulate materials.

Insights into natural organic matter and pesticide characterisation and distribution in the Rhone River

Environmental contextNatural organic matter in surface waters is a transport vector for environmental pollutants with both its concentration and composition influencing pollutant fate. Characterisation of organic matter in surface waters, crucial to understanding pollutant transport, should also account for spatial variation along the water source. The present work characterises the natural organic matter in the Rhone River and describes the distributions of various pesticides and metabolites along the river. AbstractThorough characterisation of natural organic matter (NOM) in natural surface waters remains vital for evaluating pollutant dynamics and interactions with NOM under realistic environmental conditions. Here, we present the characterisation of NOM and pesticide compositions for nine sampling sites over the length of the Rhone River, also evaluating the advantages and limitations of different analytical techniques to determine how they complement one another. Together with dissolved and particulate organic carbon analyses, the dissolved organic matter (DOM, &lt;0.8μm) or NOM (unfiltered organic matter) was characterised with gel permeation chromatography, the polarity rapid-assessment method, excitation–emission matrix fluorescence, and pyrolysis–gas chromatography–mass spectrometry to evaluate both composition and distribution. An additional objective was the determination of the NOM degradation state (i.e. constantly produced autochthonous or weakly degraded allochthonous species), an important factor in assessing potential NOM–pollutant interactions. The NOM compositions (i.e. proteins, polyhydroxy aromatics, polysaccharides, amino sugars) and proportions were similar between sites, but variations were observed in the relative proportions of autochthonous and allochthonous material from north to south. Anionic proteins and polyhydroxy aromatics in a molecular weight range of ~1000–1200 Da comprised the majority of the DOM. As a pollutant case study, five pesticides (glyphosate, metalochlor, chlortoluron, isoproturon, propyzamide) and some of their metabolites (aminomethylphosphonic acid, metolachlor ethanesulfonic acid and metolachlor oxanilic acid) were measured. Several exhibited trends with the NOM, particulate organic carbon and suspended particulate matter distributions in the Rhone waters, suggesting a significant influence on pesticide fate and transport in the river.

Characterization of natural organic matter in water for optimizing water treatment and minimizing disinfection by-product formation

Introduction Natural organic matter(NOM)present in source water has significant impact on water treatment processes and on the quality of drinking water.NOM is a complex mixture of diverse groups of organic compounds,humic and fulvic acids,proteins,peptides,carbohydrates,and heterogeneous materials

A critical evaluation of an asymmetrical flow field-flow fractionation system for colloidal size characterization of natural organic matter

Colloidal retention characteristics, recovery and size distribution of model macromolecules and natural dissolved organic matter (DOM) were systematically examined using an asymmetrical flow field-flow fractionation (AFlFFF) system under various membrane size cutoffs and carrier solutions. Polystyrene sulfonate (PSS) standards with known molecular weights (MW) were used to determine their permeation and recovery rates by membranes with different nominal MW cutoffs (NMWCO) within the AFlFFF system. Based on a ≥90% recovery rate for PSS standards by the AFlFFF system, the actual NMWCOs were determined to be 1.9kDa for the 0.3kDa membrane, 2.7kDa for the 1kDa membrane, and 33kDa for the 10kDa membrane, respectively. After membrane calibration, natural DOM samples were analyzed with the AFlFFF system to determine their colloidal size distribution and the influence from membrane NMWCOs and carrier solutions. Size partitioning of DOM samples showed a predominant colloidal size fraction in the <5nm or <10kDa size range, consistent with the size characteristics of humic substances as the main terrestrial DOM component. Recovery of DOM by the AFlFFF system, as determined by UV-absorbance at 254nm, decreased significantly with increasing membrane NMWCO, from 45% by the 0.3kDa membrane to 2–3% by the 10kDa membrane. Since natural DOM is mostly composed of lower MW substances (<10kDa) and the actual membrane cutoffs are normally larger than their manufacturer ratings, a 0.3kDa membrane (with an actual NMWCO of 1.9kDa) is highly recommended for colloidal size characterization of natural DOM. Among the three carrier solutions, borate buffer seemed to provide the highest recovery and optimal separation of DOM. Rigorous calibration with macromolecular standards and optimization of system conditions are a prerequisite for quantifying colloidal size distribution using the flow field-flow fractionation technique. In addition, the coupling of AFlFFF with fluorescence EEMs could provide new insights into DOM heterogeneity in different colloidal size fractions.

Characterization of organic matter in natural waters by EEM fluorescence properties

Natural organic matter (NOM) as the main component of natural colloidal matter is a major concern in drinking water treatment due to well-documented disadvantages. The understanding of NOM properties is a crucial factor to determine the dissolved organic matter treatability. The main purpose of this study is to provide information for realization of physicochemical and compositional properties of NOM in relation to the impact factors related to the surface water quality. To achieve this goal, water samples were collected from major watersources of Istanbul as well as from lakes located in various parts of Turkey. A consistent data-set of basic parameters specifically related to the quantification of organic matter contents, namely dissolved organic carbon and spectroscopic parameters (UV–vis and fluorescence) of selected surface waters were evaluated. Besides UV–vis spectral parameters, fluorescence intensity as represented by the ratio of the emission intensity at λemis450nm to that at λemis500 nm, following excitation at λexc370nm was also successfully employed. Moreover, fluorescence fingerprinting of surface waters by using emission excitation matrix (EEM) features as a tool was explored. These analytical techniques could contribute to the knowledge and understanding of the characterization and composition of NOM in surface waters. Based on the attained results, it could be indicated that EEM contour plots could be successfully utilized as a tool in understanding of the organic matter present in natural waters.

Comprehensive characterization of natural organic matter by MALDI- and ESI-Fourier transform ion cyclotron resonance mass spectrometry

Natural organic matter (NOM) is a complex and non-uniform mixture of organic compounds which plays an important role in environmental processes. Due to the complexity, it is challenging to obtain fully detailed structural information about NOM. Although Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has been demonstrated to be a powerful tool for providing molecular information about NOM, multiple ionization methods are needed for comprehensive characterization of NOM at the molecular level considering the ionizing selectivity of different ionization methods. This paper reports the first use of matrix assisted laser desorption/ionization (MALDI) method coupled with FT-ICR-MS for molecular characterization of NOM within a mass range of 200–800Da. The mass spectral data obtained by MALDI were systematically compared with data generated by electrospray ionization (ESI). It showed that complementary molecular information about NOM which could not be detected by ESI, were provided by MALDI. More unsaturated and aromatic constituents of NOM with lower O/C ratio (O/C ratio<0.5) were preferentially ionized in MALDI negative mode, whereas more polar constituents of NOM with higher O/C ratio were preferentially ionized in ESI negative mode. Molecular anions of NOM appearing at even m/z in MALDI negative ion mode were detected. The results show that NOM molecules with aromatic structures, moderate O/C ratio (0.7>O/C ratio>0.25) and lower H/C ratio were liable to form molecular anions at even m/z, whereas those with higher H/C ratio are more likely to form deprotonated ions at odd m/z. It is speculated that almost half of the NOM molecules identified by MALDI may be aromatic or condensed aromatic compounds with special groups which are liable to absorb electron from other molecules to generate free radical anions during MALDI ionization.

Characterization of natural organic matter in bentonite clays for potential use in deep geological repositories for used nuclear fuel

The Nuclear Waste Management Organization (NWMO) is developing a Deep Geological Repository (DGR) to contain and isolate used nuclear fuel in a suitable rock formation at a depth of approximately 500m. The design concept employs a multibarrier system, including the use of copper-coated used fuel containers, surrounded by a low-permeability, swelling clay buffer material within a low permeability, stable host rock environment. The natural organic matter (NOM) composition of the bentonite clays being considered for the buffer material is largely uncharacterized at the molecular-level. To gain a better understanding of the NOM in target clays from Wyoming and Saskatchewan, molecular-level methods (biomarker analysis, solid-state 13C NMR and solution-state 1H nuclear magnetic resonance (NMR)) were used to elucidate the structure and sources of NOM. Organic carbon content in three commercially available bentonites analyzed was low (0.11–0.41%). The aliphatic lipid distribution of the clay samples analyzed showed a predominance of higher concentration of lipids from vascular plants and low concentrations of lipids consistent with microbial origin. The lignin phenol vanillyl acid to aldehyde ratio (Ad/Al) for the National sample indicated an advanced state of lignin oxidation and NOM diagenesis. The 13C NMR spectra were dominated by signals in the aromatic and aliphatic regions. The ratio of alkyl/O-alkyl carbon ranged from 7.6 to 9.7, indicating that the NOM has undergone advanced diagenetic alteration. The absence lignin-derived phenols commonly observed in CuO oxidation extracts from contemporary soils and sediments as well as the lack of amino acids suggests that the material corresponding to the aromatic signal is not composed of lignin or proteins but may be derived from another source such as black carbon or some other non-extractable aromatic-rich NOM. The aliphatic signal appears to correspond to long-chain compounds with little side branching based on the results of the one-dimensional (1D) and two-dimensional (2D) solution-state 1H NMR analyses. Overall, the organic geochemical analyses suggest that the NOM is composed mainly of plant-derived waxes and highly aromatic carbon with low contributions from small molecules. The compounds identified by the molecular-level analysis of NOM in the clay samples are hypothesized to be recalcitrant but future studies should examine if these compounds may serve as a microbial substrate to further test the observations of this study. Furthermore, our study suggests that the NOM has undergone diagenesis and that marine NOM signatures are no longer recognizable or detectable. As such, future work may also examine the diagenesis of these deposits to further understand the NOM geochemistry and paleoenvironmental conditions in bentonite deposits.

Combined use of resin fractionation and high performance size exclusion chromatography for characterization of natural organic matter

The number and complexity of natural organic matter (NOM) species limits identification of individual NOM compounds. The objective of this study was to employ several characterization techniques (resin fractionation, high performance size exclusion chromatography (HPSEC), and strategic UV254 absorbance) to samples from seven surface water sites in North America, and overcome the shortfalls of each tool. Resin fractionation indicated the samples were all high in hydrophobic acids (HOA), hydrophilic neutrals (HIN) and hydrophilic acids (HIA). Site B was the only site where HIAs were the highest NOM contributors. In the HPSEC analysis, each fraction exhibited a particular molecular weight (MW) range: 100–300 Da (HIN), 1-2 kDa (HOA), and the HIA fractions exhibited MWs between these two ranges. Strategic UV254 measurements were taken at two sites to supplement the HPSEC results, and determine the difference in UV absorbance per unit dissolved organic carbon (SUVA value). Most fractions showed SUVA values of approximately 5 L/mg-m; however, the hydrophilic bases and hydrophobic neutral fractions could not be accurately evaluated due to the very low DOC concentrations for these two fractions (< 0.2 mg/L). These methods are complimentary NOM characterization techniques, and the combined methodology addresses the analytical limits of each tool.

Fluorescence Characterization of Natural Organic Matter at a Northern Ontario Wastewater Treatment Plant

The fate of colored natural organic matter (CNOM) was investigated for a period of 16 months at a municipal wastewater treatment plant of a mid-sized city in Northern Ontario, Canada, using fluorescence spectroscopy. Our objectives were to assess the changes of CNOM at the inlet and outlet of the plant and to determine if these changes were correlated with parameters routinely measured at the plant. The fluorescence signals were spectrally resolved into humic-like, fulvic-like, and protein-like components using a parallel factor analysis (PARAFAC) routine. We found that the signals of the CNOM components in the raw sewage had protein-like characteristics, followed by fulvic-like and humic-like characteristics. Conversely, after treatment, the CNOM signals were dominated by fulvic-like components, followed by approximately equal signals of humic-like and protein-like components. The fluorescence signals were, on average, ∼60 % lower in the effluent for the protein-like components and ∼28 % lower for the humic-like components, suggesting a decomposition of these CNOM materials. The fluorescence signals showed a small apparent increase of fulvic-like components, by ∼4 %, suggesting that the material showing this signal is recalcitrant to decomposition, or it could be potentially produced in the process. We found weak but statistically significant correlations (R 2 > 0.3) between the total fluorescence signals and total carbon (TC), the flow rate through the plant, and rainfall in the raw sewage. Similarly, correlations were found between protein-like fluorescence of the protein-like components and total Kjeldahl nitrogen (TKN) and ammonium at the effluent (R 2 > 0.3).

Characterization of Natural Organic Matter in Conventional Water Treatment Processes and Evaluation of THM Formation with Chlorine

This study investigates the fractions of natural organic matter (NOM) and trihalomethane (THM) formation after chlorination in samples of raw water and the outputs from ozonation, coagulation-flocculation, and conventional filtration treatment units. All the water samples are passed through various ultrafiltration (UF) membranes. UF membranes with different molecular size ranges based on apparent molecular weight (AMW), such as 1000, 3000, 10,000, and 30,000 Daltons (Da), are commonly used. The NOM fraction with AMW < 1000 Da (1 K) is the dominant fraction within all the fractionated water samples. Its maximum percentage is 85.86% after the filtration process and the minimum percentage is 65.01% in raw water samples. The total THM (TTHM) yield coefficients range from 22.5 to 42 μg-TTHM/mg-DOC in all fractionated samples, which is related to their specific ultraviolet Absorbance (SUVA) levels. As the molecular weight of the fractions decreased, the TTHM yield coefficients increased. The NOM fractions with AMW values less than 1 K had lower SUVA values (<3 L/mg·m) for all treatment stages and also they had higher yield of TTHM per unit of DOC. The NOM fraction with AMW < 1 K for chlorinated raw water samples has the highest yield coefficient (42 μg-TTHM/mg-DOC).

Pilot-scale investigation of drinking water ultrafiltration membrane fouling rates using advanced data analysis techniques

A pilot-scale investigation of the performance of biofiltration as a pre-treatment to ultrafiltration for drinking water treatment was conducted between 2008 and 2010. The objective of this study was to further understand the fouling behaviour of ultrafiltration at pilot scale and assess the utility of different foulant monitoring tools. Various fractions of natural organic matter (NOM) and colloidal/particulate matter of raw water, biofilter effluents, and membrane permeate were characterized by employing two advanced NOM characterization techniques: liquid chromatography – organic carbon detection (LC-OCD) and fluorescence excitation-emission matrices (FEEM) combined with principal component analysis (PCA). A framework of fouling rate quantification and classification was also developed and utilized in this study. In cases such as the present one where raw water quality and therefore fouling potential vary substantially, such classification can be considered essential for proper data interpretation. The individual and combined contributions of various NOM fractions and colloidal/particulate matter to hydraulically reversible and irreversible fouling were investigated using various multivariate statistical analysis techniques. Protein-like substances and biopolymers were identified as major contributors to both reversible and irreversible fouling, whereas colloidal/particulate matter can alleviate the extent of irreversible fouling. Humic-like substances contributed little to either reversible or irreversible fouling at low level fouling rates. The complementary nature of FEEM-PCA and LC-OCD for assessing the fouling potential of complex water matrices was also illustrated by this pilot-scale study.

Treatability of South African surface waters by activated carbon

Natural organic matter (NOM) in water resources for drinking purposes can be removed by different methods, including activated carbon adsorption. Due to the variability of NOM in natural waters, both in terms of its nature and its concentration, a study was undertaken to investigate NOM removal for a wide range of South African surface waters, sampled at different periods, by the use of granular activated carbon (GAC). NOM removal was assessed by measuring the ultraviolet (UV) absorbance at 3 wavelengths, namely, 254 nm (UV254), 272 nm (UV272) and 300 nm (UV300). A comparison of data between the three wavelengths showed that any of the three wavelengths can be used to assess NOM removal by GAC, which is well described by the Freundlich equilibrium equation. A treatment target of 40% removal of initial UV254 absorbance was considered. It was observed that, although the GAC dosage was generally a function of the initial UV254 absorbance, differences existed between waters. This suggests that GAC usage rate is not only a function of the initial UV absorbance but also of the NOM composition, indicating a need for improved NOM characterisation. Comparison between the UV absorbance and dissolved organic carbon (DOC) data suggested that for some waters UV254 absorbance can be used as a rapid substitute for DOC. Finally, the high GAC dosage rates required for the target criterion revealed that the process is inadequate for use at the initial stage of raw water treatment; GAC adsorption should be used at later stages of drinking water treatment.Keywords: activated carbon, adsorption, Freundlich isotherm, natural organic matter, surface water,ultraviolet absorbance

Structural characterization of natural organic matter and its impact on methomyl removal efficiency in Fenton process

This study aimed to characterize the NOM structural variation during Fenton process, in which the methomyl and humic acid were selected as the investigated compounds. The preliminary degradation experiments were conducted at various H2O2 and Fe2+ concentrations without the presence of NOM to determine the applied Fenton reagent dosages for subsequent NOM impact on Fenton degradation. The methomyl removal at 80% was observed at the Fenton reagent ratio ([H2O2]/[Fe2+]) of 1 while Fe2+ concentration was no less than 2mM. In the presence of NOM, the methomyl removal by Fenton process was further enhanced apparently. The NOM used in this study was found to be a macromolecule with tryptophan-like and tyrosine-like functional groups through fluorescence spectrometry analysis. The addition of ferrous ions in the NOM solution initiated the reactions between Fe2+/Fe3+ redox couples and NOM molecules, breaking the NOM into smaller organic fractions. These organic fractions were further oxidized into even smaller molecules by hydroxyl radicals after H2O2 addition. The NOM might compete with methomyl for hydroxyl radicals, and enhance the catalytical generation of hydroxyl radicals by reducing Fe3+ to Fe2+ at the same time. Apparently, the increase in OH generation was more than the OH consumption by NOM presence, resulting in the observed enhancement of methomyl removal.