Characterization Of Natural Organic Matter Research Articles

Characterization of natural organic matter from Mediterranean coastal seawater

Natural organic matter (NOM) from seawater is a complex mixture of compounds that has only been roughly characterized. In this study, advanced techniques such as fractionation based on adsorption–desorption dynamics (on XAD ® resins), liquid chromatography–organic carbon detection (LC-OCD), excitation–emission matrix (EEM) fluorescence and membrane separation techniques were applied to the characterization of seawater NOM. Conventional analyses have shown that Mediterranean coastal seawater has a low NOM content, slightly aromatic and poorly biodegradability. Advanced analysis permitted better characterization by separating the NOM into different fractions. The NOM was found to be mainly hydrophilic (HPI) (70%) and slightly transphilic (TPI) (24%) from XAD fractionation. LC-OCD showed the seawater to be composed mainly of humic substances (HSs) and low molecular weight (LMW) neutrals that accounted for 37 and 40% of the dissolved organic carbon, respectively. The HSs contained hydrophobic, TPI and HPI compounds, revealing advanced hydrolysis, whereas the LMW neutrals were HPI compounds. Membrane separation revealed that most of the seawater NOM had a MW of 1 kDa contains mainly aromatic proteins, which are more biodegradable than whole seawater NOM.

NOM characterization by LC-OCD in a SWRO desalination line

Abstract The quantification and characterization of natural organic matter (NOM) in seawater reverse osmosis desalination (SWRO) is of great importance to improve our understanding of NOM role and to evaluate the performance of the different units involved in desalination facilities. In this study, we compared the effectiveness of two pre-treatment methods, operated in a pilot facility fed with Mediterranean seawater, in terms of determining NOM composition and NOM removal using liquid chromatography coupled with organic carbon detection (LC-OCD). LC-OCD was also used to assess the SWRO operation. Conventional pre-treatment using a flotation unit followed by dual-media filtration achieved 12% of dissolved organic carbon (DOC) removal. The same level of DOC removal was achieved by coupling flotation and ultrafiltration. In both pre-treatment methods, low-molecular-weight (LMW) neutrals and biopolymers were reduced by 33–40% and 18–19%, respectively. Reverse osmosis (RO) membranes acted as almost a complete barrier for humics, building blocks, and LMW neutrals, which had a rejection rate of over 97%. Despite this, 31 μgC L−1 of LMW acids and 48 μgC L−1 of biopolymers were found in the RO permeate. LMW acids could also be found in the RO permeate due to the affinity these compounds have with the membrane material. However, biopolymers should be more effectively rejected due to their structure and molecular weight (>20 kDa). The hypothesis proposed to explain the presence of biopolymers in permeate is a possible biofilm growth in the permeate side of the membrane module.

An enhanced capillary electrophoresis method for characterizing natural organic matter

Natural organic matter (NOM) is ubiquitous and is one of the most complex naturally occurring mixtures. NOM plays an essential role in the global carbon cycle; atmospheric and natural water photochemistry; and the long-range transport of trace compounds and contaminants. There is a dearth of separation techniques capable of resolving this highly complex mixture. To our knowledge, this is the first reported use of ultrahigh resolution counterbalance capillary electrophoresis to resolve natural organic matter. The new separation strategy uses a low pH, high concentration phosphate buffer to reduce the capillary electroosmotic flow (EOF). Changing the polarity of the electrodes reverses the EOF to counterbalance the electrophoretic mobility. Sample stacking further improves the counterbalance separation. The combination of these conditions results in an electropherogram comprised up to three hundred peaks superimposed on the characteristic "humic hump" of NOM. Fraction collection, followed by three-dimensional emission excitation spectroscopy (EEMs) and UV spectroscopy generated a distinct profile of fluorescent and UV absorbing components. This enhanced counterbalance capillary electrophoresis method is a potentially powerful technique for the characterization and separation of NOM and complex environmental mixtures in general.

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.

Recent advances in structure and reactivity of dissolved organic matter: radiation chemistry of non-isolated natural organic matter and selected model compounds

The importance of natural organic matter (NOM) as a source of carbon in natural waters, as the source of reactive oxygen species, or for the complications its presence causes in treatment of natural waters, is undeniable. Recent studies have also pointed to the major photochemical role of triplet excited state of natural organic matter in the environmental fate of pharmaceutical and personal care products (PPCPs) in waters. However, the characterization of NOM is problematic due to its complex molecular structure. One approach to better understand NOM chemistry is the use of model compounds. As the condensation of a plant's phenolic compounds leads to humification and the formation of NOM, a structurally broad group of nine phenolic compounds were selected as model compounds for this study. With methods used in the discipline of radiation chemistry, the oxidative chemistry and transient spectra of these phenols were studied. In addition, the oxidative chemistry and transient spectra of a sample of NOM from the Black River, North Carolina, USA, was characterized. This natural water sample was used as received and represents the first studies of non-isolated NOM by pulsed radiolysis. The results of the transient spectra of the NOM revealed that the radical intermediates were very long lived. This phenomenon was not captured using the nine model compounds suggesting that more complex compounds are needed to further our understanding of the oxidation chemistry of NOM.

Establishing a Measure of Reproducibility of Ultrahigh-Resolution Mass Spectra for Complex Mixtures of Natural Organic Matter

This study describes a method for evaluating the reproducibility of replicate mass spectra acquired for complex natural organic matter (NOM) samples analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, with regard to both peak detection and peak magnitude. Because studies of NOM characterization utilize not only the emergence and disappearance of peaks but also changes in relative peak magnitude, it is important to establish that the differences between samples are significantly larger than those between sample replicates. Here, a method is developed for correcting strict signal-to-noise thresholds, along with a new scheme for assessing the reproducibility of peak magnitudes. Furthermore, a systematic approach for discerning when the comparison of samples by the presence or absence of peaks is appropriate and when it is necessary to compare based on the relative magnitude of the peaks is presented. A variety of 10 different types of NOM samples are analyzed in duplicate or triplicate instrumental injections or experimental extractions. A framework for these procedures is provided, and acceptable reproducibility levels are recommended.

Assessment of a new combined fractionation technique for characterization of the natural organic matter in the coagulation process

Abstract The application of a new combined fractionation technique (CFT) using high performance size exclusion chromatography (HPSEC) and rapid resin fractionation (RRF) for characterization of natural organic matter (NOM) in raw and post-coagulated water samples was assessed. Two natural water samples from Myponga and Hope Valley reservoirs, South Australia, respectively, were selected for this NOM removal by coagulation study. With the use of HPSEC and RRF individually, removal in the low molecular weight (LMW) organic region was observed by comparison of the HPSEC profiles of raw and treated waters and the removal of the hydrophobic organics was observed by comparing the RRF results. A new organic fractionation and characterization technique involving the sequential application of the two techniques, called RRF–HPSEC, was developed to provide additional analytical information particularly to determine the key control factor for the removal of LMW organics. The RRF–HPSEC results showed that good removal...

Characterization of natural organic matter treated by iron oxide nanoparticle incorporated ceramic membrane-ozonation process

In this study, changes in the physical and structural properties of natural organic matter (NOM) were observed during hybrid ceramic membrane processes that combined ozonation with ultrafiltration ceramic membrane (CM) or with a reactive ceramic membrane (RM), namely, an iron oxide nanoparticles (IONs) incorporated-CM. NOM from feed water and NOM from permeate treated with hybrid ceramic membrane processes were analyzed by employing several NOM characterization techniques. Specific ultraviolet absorbance (SUVA), high-performance size exclusion chromatography (HPSEC) and fractionation analyses showed that the hybrid ceramic membrane process effectively removed and transformed relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions. Fourier transform infrared spectroscopy (FTIR) and 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy revealed that this process caused a significant decrease of the aromaticity of humic-like structures and an increase in electron withdrawing groups. The highest removal efficiency (46%) of hydroxyl radical probe compound (i.e., para-Chlorobenzoic acid (pCBA)) in RM-ozonation process compared with that in CM without ozonation process (8%) revealed the hydroxyl radical formation by the surface-catalyzed reaction between ozone and IONs on the surface of RM. In addition, experimental results on flux decline showed that fouling of RM-ozonation process (15%) was reduced compared with that of CM without ozonation process (30%). These results indicated that the RM-ozonation process enhanced the destruction of NOM and reduced the fouling by generating hydroxyl radicals from the catalytic ozonation in the RM-ozonation process.

The characterisation of natural organic matter (NOM) in South African waters

The removal of natural organic matter (NOM) from water is becoming increasingly important in order to prevent the formation of carcinogenic disinfection by-products (DBPs). The inadequate removal of NOM has a bearing on the capacity of other treatment processes to remove organic micro-pollutants or inorganic species that may be present in water. In order to effectively study the nature of South African water sources in terms of their NOM composition, water samples were collected from drinking water treatment plants in the five geographic water regions of South Africa. A raw water sample, an intermediate sample taken before sand filtration and a final sample after sand filtration were collected three times from these water treatment plants at two-month intervals and over three different seasons. Fluorescence excitation-emission matrices (FEEM), biodegradable dissolved organic carbon (BDOC), ultraviolet (UV) characterisation (200–900 nm) and dissolved organic carbon (DOC) analyses were used to characterise the NOM in the water samples. The FEEM and UV results revealed that the samples were composed mainly of non-humic substances with low UV-254 absorbance, while some samples had high humic substances with high UV-254 values. The samples' DOC results were within the range of 3.25–21.44 mg/L carbon, which was indicative of the varying nature of the NOM composition in the regions where samples were collected. The BDOC fraction of the NOM, on the other hand, ranged from 20 to 65%, depending on the geographical location of the sampling site.

Preface "Sources and rapid biogeochemical transformation of dissolved organic matter in the Atlantic surface ocean"

One of the most important issues needed to be studied to better understand global fluxes of marine organic matter is to resolve its molecular characteristics and mechanisms which convert fresh, labile biomolecules into semi-labile and refractory dissolved organic compounds (Jiao et al., 2010) which resist degradation for an average time of 5000 years (Bauer et al., 1992; Williams and Druffel, 1987). From a chemical point of view, the persistence of marine dissolved organic matter (DOM) is very unusual. The mostly oxygenand nutrient-rich oceanic water column should be conducive to a rapid microbial degradation of organic matter and subsequent release of CO2. Contrary to this expectation, however, a significant portion of the atmospheric carbon remains in the DOM of the oceans and circulates in global currents on long time scales. Despite the importance of gaining better insights into the molecular mechanisms affecting organic carbon dynamics, very little is known about these processes. Thus, recent reports from the intergovernmental panel on climate change (Denman et al., 2007) barely considered potential changes in quality, quantity and fluxes of marine organic matter. In the oceans, dissolved organic substances constitute an important source of organic carbon and organic nitrogen (Hansell et al., 2009). The pool of dissolved organic carbon (DOC) exceeds the amount of carbon stored in marine animals, plants and bacteria by a factor of about 200. The majority of DOM in the oceans is originally formed from CO2 by plankton and land plants during photosynthesis. The DOM, resulting from this organic material, is directly released into the water by marine plankton and during the degradation of these organisms. Also, DOM can be transported into the oceans via rivers and atmospheric deposits via aerosols. A small fraction of marine DOM, such as persistent organic pollutants or black carbon derivatives, can be derived from anthropogenic activities. DOM can bind to trace metals such as iron and is therefore also responsible for their distribution in the sea. The complex composition of DOM is an enormous analytical challenge, resulting in sparse information on chemical structures. The DOM complexity prevents resolution of single molecules by chromatographic separation or conventional mass spectrometry. However, within the last 10 years analytical instruments, which can deliver molecular signals, improved tremendously. Namely, improvements of nuclear magnetic resonance spectroscopy (NMR) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) opened a new analytical window for the molecular characterization of natural organic matter (e.g. Stenson et al., 2003; Kujawinski et al., 2004; Koch et al., 2005; Hertkorn et al., 2008; Witt et al., 2009). Meridional transits of polar research vessels offer a great opportunity to perform long-distance surface water transects with continuous water and air sampling, since frequent stops for long station work are usually not possible during such transit cruises. Trace metal (Pohl et al., 2011; Helmers, 1996) and plankton studies (Robinson et al., 2009) and a recent GEOTRACES pilot study in the Atlantic Ocean (Rutgers van der Loeff, 2007) are great examples for the importance of such projects. Previous work along the north–south transect also provided a high resolution comparison of bacterial and primary production (Hoppe et al., 2002). The authors suggested that the observed net heterotrophy required

Characterisation of natural organic matter (NOM) and its removal using cyclodextrin polyurethanes

Natural organic matter (NOM) occurs in all natural water sources when animal and plant material breaks down. NOM in water may react with chlorine and other disinfectants to produce disinfection by-products (DBPs), many of which are either carcinogenic or mutagenic. In this study the NOM content of the raw water from the Vaalkop Water Treatment Plant (which uses both chlorination and ozonation as treatment protocols) was characterised after fractionation on ion-exchange resins. Fractionation at different pH values resulted in the isolation of a neutral, a basic and an acidic component of either predominantly hydrophobic or hydrophilic NOM. In addition, NOM results from 3 open water bodies in Johannesburg were evaluated in the same manner. As expected, NOM from all water sources was predominantly hydrophobic (~60%). Each of the 6 isolated NOM fractions was percolated through synthetic cyclodextrin (CD) polyurethanes to determine the extent to which the CD polymers can remove NOM from water. The hydrophobic basic fraction and the hydrophilic acid fraction were most efficiently removed (24% and 10%, respectively). The remaining fractions were not much affected by the polymer treatment.

Characterization of Pyrogenic Black Carbon by Desorption Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

We present a new method for molecular characterization of intact biochar directly, without sample preparation or pretreatment, on the basis of desorption atmospheric pressure photoionization (DAPPI) coupled to Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Conventional ionization methods (e.g., electrospray or atmospheric pressure photoionization) for characterization of natural organic matter have limited utility for the characterization of chars due to incomplete solubility in common solvents. Therefore, direct ionization techniques that do not require sample dissolution prior to analysis are ideal. Here, we apply DAPPI FTICR mass spectrometry to enable the first molecular characterization of uncharred parent oak biomass and after combustion (250 °C) or pyrolysis (400 °C). Parent oak is primarily composed of cellulose-, lignin-, and resin-like compounds. Oak combusted at 250 °C contains condensed aromatic compounds with low H/C and O/C ratios while retaining compounds with high H/C and O/C ratios. The bimodal distribution of aromatic and aliphatic compounds observed in the combusted oak sample is attributed to incomplete thermal degradation of lignin and hemicellulose. Pyrolyzed oak constituents exhibit lower H/C and O/C ratios: approximately three-quarters of the identified species are aromatic. DAPPI FTICR MS results agree with bulk elemental composition as well as functional group distributions determined by elemental analysis and solid state (13)C NMR spectroscopy. Complete molecular characterization of biomass upon thermal transformation may provide insight into the biogeochemical cycles of biochar and future renewable energy sources, particularly for samples currently limited by solubility, separation, and sample preparation.

A three step approach for removing organic matter from South African water sources and treatment plants

The high variability in the levels and composition of natural organic matter (NOM) in South-African water sources in different regions means that no single treatment process can be prescribed for each water treatment plant operating in the country. In order to remove 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 local environmental situation. The primary objective of this study was to characterise the NOM present in South African source waters through an extensive sampling of representative water types across the country and then develop a rapid NOM characterisation protocol. Water samples were thus collected from eight different water treatment plants located throughout the country at different sites of their water treatment trains. Raw water samples, the intermediate samples before filtration and water samples before disinfection were collected at these drinking water treatment plants. The fluorescence excitation–emission matrices (FEEMs), biodegradable dissolved organic carbon (BDOC), ultraviolet (UV) characterisation (200–900nm) and dissolved organic carbon (DOC) analysis were used to characterise the NOM in the water samples. The FEEM and UV results revealed that the samples were composed mainly of humic substances with a high UV-254 absorbance, while some samples had marine humic substances and non-humic substances. The sample’s DOC results were within the range of 3.25–21.44mgC/L, which was indicative of the varying nature of the NOM composition in the regions where samples were obtained. The BDOC fraction of the NOM, on the other hand, ranged from 20% to 65%, depending on the geographical location of the sampling site. It is evident from the results obtained that the NOM composition varied per sampling site which would eventually have a bearing on its treatability. The various water treatment processes employed at the different treatment plants were able to effectively reduce NOM, as evidenced by a percentage DOC removal of between 11% and 85%. The highest DOC removal was achieved at the treatment plants that had highly humic and coloured raw water sources.

Inorganics in Organics: Quantification of Organic Phosphorus and Sulfur and Trace Element Speciation in Natural Organic Matter Using HPLC-ICPMS

A method is presented for the chemical characterization of natural organic matter (NOM). We combined reversed-phase chromatographic separation of NOM with high resolution inductively coupled plasma mass spectrometry. A desolvation technique was used to remove organic solvent derived from the preceding chromatographic separation. We applied our method to solid-phase extracted marine dissolved organic matter samples from South Atlantic and Antarctic surface waters. The method provided a direct and quantitative determination of dissolved organic phosphorus and sulfur in fractions of differing polarity and also allowed simultaneous speciation studies of trace elements. Dissolved organic carbon/phosphorus and carbon/sulfur ratios for the different chromatographic fractions of our two samples ranged between 341-3025 for C/P and 11-1225 for C/S. Differences in elemental distribution between the fractions were attributed to different biochemical environments of the samples. Sulfur was exclusively found in one hydrophilic fraction, while uranium showed a strong affinity to the hydrophobic fractions. Our method was designed to be easily adapted to other separation techniques. The elemental information will deliver valuable information for ultrahigh resolution molecular analyses.

Removal of NOM-constituents as characterized by LC-OCD and F-EEM during drinking water treatment

Natural organic matter (NOM) is of concern in drinking water because it causes adverse aesthetic qualities such as taste, odour, and colour; impedes the performance of treatment processes; and decreases the effectiveness of oxidants and disinfectants while contributing to undesirable disinfection by-products. The effective removal of NOM during drinking water treatment requires a good understanding of its character. Because of its heterogeneity, NOM characterization necessitates the use of multiple analytical techniques. In this study, NOM in water samples from two drinking water treatment trains was characterized using liquid chromatography with organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (F-EEMs) with parallel factor analysis (PARAFAC). These characterization methods indicate that the raw and treated waters are dominated by humic substances. The results show that whereas the coagulation process for both plants may be optimized for the removal of bulk DOC, it is not likewise optimized for the removal of specific NOM fractions. A five component PARAFAC model was developed for the F-EEMs, three of which are humic-like, while two are protein-like. These PARAFAC components and the LC-OCD fractions represented effective tools for the performance evaluation of the two water treatment plants in terms of the removal of NOM fractions.

Combining advanced NMR techniques with ultrahigh resolution mass spectrometry: A new strategy for molecular scale characterization of macromolecular components of soil and sedimentary organic matter

Molecular level characterization of complex biopolymers in nature is a key element to understanding the composition of natural organic matter (NOM) and fossil organic matter formation, such as kerogen and coal. Characterization of such geopolymers is difficult due to their heterogeneity and insolubility in common aqueous or organic solvents. Here, a strategy for extracting a representative sample is presented using the combined techniques of nuclear magnetic resonance (NMR) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) for chemical analysis and characterization of NOM. A variety of NOM samples (wood, kerogen, bitumen, whole sediments) are shown as examples for implementing the strategy, which include solvent extractions using pyridine. For most samples, the extracts are confirmed to be chemically representative of the insoluble solid, by comparing the liquids NMR spectrum of the extract to that of the whole, unfractionated NOM utilizing high resolution magic angle spinning (HRMAS) NMR. To assist in unambiguous peak assignment, a technique for post acquisition spectral denoising, using wavelet transformation (WT), is also employed on the 1D and 2D NMR spectra. The findings from the NMR data lay a foundation for the subsequent electrospray ionization FTICR-MS analysis of the pyridine extracts, since this instrument has the limitation of only analyzing liquid samples. The FTICR-MS analyses can, therefore, be used to molecularly represent the structural components of the NOM. Various compositional insights have been obtained on these samples, indicating the efficacy of the analytical techniques used.

Effect of ramp size and sample spinning speed on CPMAS 13C NMR spectra of soil organic matter

Cross polarization (CP) magic angle spinning (MAS) 13C NMR spectroscopy is a solid state NMR technique widely applied to study the chemical composition of natural organic matter. In high magnetic fields (>7 T), fast sample spinning is required in order to reduce the influence of spinning sidebands underlying other chemical shift regions. As the spinning speed increases, the Hartmann–Hahn matching profiles break down into a series of narrow matching bands. In order to account for this instability variable amplitude cross polarization techniques (e.g. VACP, ramp-CP) have been developed. In the present study, we experimentally verified the stability of the Hartmann–Hahn condition under two MAS speeds for different samples with known structure and two different humic acids. For a complete restoration of flat matching profiles, large ramp sizes were needed. The matching profiles of the humic acids showed that both samples needed different ramp sizes to restore flat profiles. A set up based on the matching profiles of the commonly used glycine would have led to an insufficient ramp size for one of the humic acids. For the characterization of natural organic matter, we hence recommend to roughly set the matching conditions with a standard and subsequently optimize the matching conditions on a more complex, preferably representative, sample such as a humic acid. We would suggest to either run an array of different ramp sizes until maximum signal intensity is reached for all chemical shift regions or, in the case of unavailable measurement time, to use a ramp size twice the spinning speed.

Treatability and characterization of Natural Organic Matter (NOM) in South African waters using newly developed methods

Managing the removal of Natural Organic Matter (NOM) or problematic components from water has become increasingly important. NOM is a heterogeneous mixture of organic compounds of human origin and derived from plant and microbial residues. The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. In addition the action of certain disinfection processes has been shown to lead to the formation of harmful disinfection by-products (DBPs). Owing to the complexity, in composition and structure, of NOM, the techniques currently employed for its characterization have a number of limitations, both in terms of quantification and removal of the NOM within short periods of time. The dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC) and Fluorescence Emission Excitation Matrices (FEEM) were used to characterize NOM from various water samples collected around South Africa. Characterization results gave an indication of the character of NOM present in all the water samples. FEEM and UV–Vis results indicated that most of the water samples were aromatic in nature, since they had high hydrophobic and humic acid-like materials content. Generally, the characterization data indicated a varying composition of NOM amongst the various sampling points. The polarity rapid assessment method (PRAM) was then employed as a rapid NOM characterization tool. The characterization under PRAM is based on preferential adsorption of dissolved organic matter (DOM) fractions onto solid phase extraction (SPE) sorbents. The PRAM also allows the separation of DOM into fractions by polarity, hence reducing the molecular heterogeneity of NOM and thus aiding the removal of specific NOM fractions from water. The PRAM provided a quick characterization of the NOM character. However, DOC quantification by the PRAM analysis was hindered by excessive carbon leaching from the SPE cartridges. The BDOC method of analysis is based on the bacteria fixed on the biologically active sand and gives a ratio of the biodegradable NOM versus the non-biodegradable NOM. For the BDOC analysis, the percentage DOC removal for the samples ranged from 12% to 61%.

Characterization of natural organic matter and disinfection byproducts formation potential in pilot-scale coagulation-ultrafiltration membrane combined process in winter

A pilot-scale ultrafiltration membrane plant was set up for treating Luanhe River water with flocculating and precipitation process of waterworks. The aim is to investigate the variation and characteristics of natural organic matter and disinfection byproducts formation potential in the whole process in winter. The results show that dissolved organic matter (DOM), UV254, trihalomethanes formation potential (THMsFP) and haloacetic acids formation potential (HAAsFP) of Luanhe River water were mainly distributed in the range of molecular weight (MW) 30 kDa and MW<1 kDa. It is the DOM in water backwashing in up way that made significant contribution to the higher dissolved organic carbon content in membrane backwash water. However, UV254, THMsFP and HAAsFP were mainly distributed in the range of MW<1 kDa. The highest concentrations of specific THMsFP and specific HAAsFP appeared in the MW fraction of 3–10 kDa. CHCl3 was the major THMs species during MBW chlorination and occupied more than 60% of the total THMsFP. Dichloroacetic acid and trichloroacetic acid were the main components in HAAsFP. The concentration of THMsFP and HAAsFP in MBW was influenced by operation period.

DBPS CONTROL IN EUROPEAN DRINKING WATER TREATMENT PLANTS USING CHLORINE DIOXIDE: TWO CASE STUDIES

The paper reports results of the experiments carried out at Fortore (Foggia, South Italy) and Mosina (Poznan, Poland) drinking water treatment plants aimed at DBPs control. Pilot scale GAC filters were installed in both plants in order to assess the efficacy of different kind of GAC for chlorites, NOM and THMs removal. Both pilot plants operated with and without chlorine dioxide pre-disinfection. In Fortore plant, because of free chlorine was added in ClO2 pre‐disinfection solution, THMs formation was evaluated. Results showed an high efficacy of chlorites removal on GAC filters up to 5500 and 10000 bed volumes for mineral and vegetal GAC in Fortore and up to 11000 bed volumes in Mosina. A preliminary characterization of natural organic matter (NOM) dissolved in Fortore raw water was performed as well, in order to confirm its reactivity towards chlorine dioxide. The presence of small molecules (&lt; 500 Da) in Fortore pre‐disinfected water, has resulted in THMs and carboxylic acids formation due a fast reaction with Cl2‐ClO2. GAC columns have shown percentages of removal ranging from 60 to 72% for THMs and ranging from 14.6 to 43% for TOC, so that adsorption represents an essential step for DBPs control. Santrauka Straipsnyje pateikiami eksperimentu, darytu atliekant DBPs kontrole Fortore (Foggia, Pietu Italija) ir Mosina (Poznan, Lenkija) geriamojo vandens ruošimo irenginiuose, rezultatai. Eksperimentiniai skirtingos rūšies GAC filtrai, skirti chlorido, natūraliu organiniu medžiagu (NOM) ir THMs šalinimo efektyvumui nustatyti, buvo irengti abiejuose vandens ruošimo irenginiuose. Abu eksperimentiniai vandens ruošimo irenginiai veike atlikus pirmini dezinfekavima chloro dioksidu ir dezinfekavimo neatlikus. Fortore vandens ruošimo irenginiuose laisvaji chlora pridedant i ClO2 pirmines dezinfekcijos tirpala, vertinta THMs susidarymas. Iš rezultatu buvo akivaizdu didelis chlorito sulaikymo GAC filtrais efektyvumas Fortore ir Mosina gyvenvietese. Taip pat nustatytos preliminarios NOM, ištirpusiu neapdorotame Fortore vandenyje, charak‐teristikos, taigi patvirtintas reaktyvumas su chloro dioksidu. Mažu molekuliu (&lt;500 Da) buvimas Fortore nedezinfekuotame vandenyje leme THMs ir karboksilines rūgšties susidaryma del greitos reakcijos su Cl2‐ClO2. Tyrimu duomenimis, THMs pašalinta nuo 60 iki 72 %, TOC ‐ nuo 14,6 iki 43 %, taigi ši adsorbcija yra svarbus etapas kontroliuojant DBPs. Резюме В статье представлены результаты экспериментов по осуществлению контроля побочных продуктов дезинфекции на очистных сооружениях питьевой воды в Форторе (Фоджия, Южная Италия) и Мосине (Познань, Польша). Экспериментальные фильтры GAC были установлены на обеих водоочистных установках с целью выявить эффективность разных фильтров GAC, предназначенных для очищения воды от хлорида и других вредных веществ. Обе экспериментальные водоочистные установки действовали с первичной дезинфекцией с применением диоксида хлора и без него. В Форторе, где в водоочистных установках в раствор ClO2 для первичной дезинфекции добавляли свободный хлор, оценивалось образование тригалометана. Результаты показали высокую эффективность очищения от хлоридов фильтрами GAC в Форторе и Мосине. Также установлены предварительные характеристики естественных органических веществ, растворенных в необработанной воде в Форторе. Небольшое количество молекул (&lt; 500 Da) в недезинфицированной воде в Форторе обусловило образование тригалометана и карбоксилановой кислоты в зависимости от скорости реакции с Cl2–ClO2. Фильтры GAC обеспечили 60–72-процентную очистку от тригалометана, а TOC – 14,6–43- процентную очистку. Таким образом, эта адсорбция является важным этапом контроля за побочными продуктами дезинфекции.