Hydrophobic Neutral Fractions Research Articles

MBR处理电镀废水出水中DOM的特征分析

利用XAD-8/XAD-4树脂对膜生物反应器(MBR)处理电镀废水出水中的溶解性有机物(DOM)进行了组分分离，将DOM分为过渡亲水性有机酸(TPI-A)、过渡亲水性中性有机物(TPI-N)、疏水性有机酸(HPO-A)、疏水性中性有机物(HPO-N)和亲水性有机物(HPI)五个组分，并对重金属冲击前后各组分的溶解性有机碳(DOC)、紫外–可见光谱和多糖的变化情况进行对比分析.结果表明，HPI、HPO-A和HPO-N是电镀废水中主要的有机成分，共占总DOC的87.5%，MBR的生物降解作用更适合去除疏水性物质含量较高的有机废水.电镀废水中的芳香性有机物主要来自HPO-N，多糖主要分布在HPO-A、HPO-N和TPI-N中。MBR对中性有机物的去除效果较好，重金属冲击前TPI-N和HPO-N中多糖的去除率分别达到73.3%和99.1%。 Using XAD-8/XAD-4 resins, dissolved organic matter (DOM) in the effluent of membrane bioreactor (MBR) used for electroplating wastewater treatment was fractionated into five fractions: transphilic acid (TPI-A), transphilic neutral (TPI-N), hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), and hydrophilic fraction (HPI). Thereafter, the changes of dissolved organic carbon (DOC), ultraviolet visible spectroscopy and polysaccharide of each fraction before and after metal impact were analyzed. HPI, HPO-A and HPO-N are the major organic constituents in electroplating wastewater, accounted for 87.5% of total DOC, biodegradation of MBR is more suitable for the removal of organic wastewater with high content of hydrophobic substances. Aromatic compounds in electroplating wastewater mainly from HPO-N, polysaccharide mainly distributed in HPO-A, HPO-N and TPI-N, TPI-N and HPO-N. The effect of MBR on the removal of neutral compounds is better. Before the impact of heavy metals, the removal rates of TPI-N and HPO-N were 73.3% and 99.1%, respectively.

Fouling characteristics of reverse osmosis membranes at different positions of a full-scale plant for municipal wastewater reclamation

Membrane fouling is an important shortcoming limiting the efficiency and wide application of reverse osmosis (RO) technology. In this paper, RO membranes in a full-scale municipal wastewater reclamation plant were autopsied. From the lead to tail position RO membranes in RO system, both of organic and inorganic matters on membranes reduced gradually. The higher ion products in RO concentrate didn't result in more serious inorganic scaling on the last position RO membranes, which was contrast with some other researches. Fe, Ca and Mg were major inorganic elements. Fe had a relatively low concentration in RO influent but the highest content on membranes. However, there was no specific pretreatment in terms of Fe removal. Ca and Mg scaling was controlled by the antiscalants injected. Organic fouling (75.0–84.5% of dry weights) was major problem on RO membranes due to the large amount of dissolved organic matters in secondary effluent as raw water. Hydrophilic acid (HIA, 48.0% of total DOC), hydrophobic acid (HOA, 23.6%) and hydrophobic neutral (HON, 19.0%) fraction was largest among the six fractions in RO influent, while HON (38.2–51.1%) and HOA (22.1–26.1%) tended to accumulate on membranes in higher quantities. Monitoring HON and HOA might help to forecast organic fouling.

A study on the reactivity characteristics of dissolved effluent organic matter (EfOM) from municipal wastewater treatment plant during ozonation

The reactivity of dissolved effluent organic matter (EfOM) in the process of ozonation was examined. Under different ozone dosages (0.42 ± 0.09, 0.98 ± 0.11 and 2.24 ± 0.17 mgO3/mg DOC), the EfOM before and after ozonation could be classified into four fractions according to their hydrophobicities. By ozonation, the hydrophobic fractions, especially hydrophobic acid (HOA) and hydrophobic neutral (HON), were found to undergo a process of transformation into hydrophilic fractions (HI), of which the HOA were first transformed into HON, and then the majority of the HON fraction was later converted to HI by further ozonation. It was noticeable that after ozonation, the fluorescence intensity in the humic-like and protein-like regions decreased as indicated by the excitation and emission matrix (EEM) spectra for the hydrophobic fractions. By coupling the EEM spectra with the molecular size analysis using high performance size exclusion chromatography (HPSEC), the difference between the characteristic distributions of the humic-like and protein-like fluorophores were further revealed. It could thus be extrapolated that ozone might have preferentially reacted with the protein-like hydrophobic fraction with molecular weight (MW) less than 100 kDa. Moreover, by X-ray photoelectron spectroscopy (XPS) analysis, it was identified that with increasing ozone dosage (from 0 to 2.24 ± 0.17 mgO3/mg DOC), the aromaticity of HON decreased dramatically, while aliphatics and ketones increased especially at the low ozone dose (0.42 ± 0.09 mgO3/mg DOC). Of the EfOM fractions, the HON fraction would have a higher content of electron enriched aromatics which could preferentially react with ozone rather than the HOA fraction.

Effect of freezing–thawing on dissolved organic matter in water

The aim of this study was to investigate the effect of freezing–thawing on the content, spectroscopic characteristics, and chlorine reactivity of dissolved organic matter (DOM) and its fractions in water. DOM was fractionated using XAD resins into five fractions: hydrophobic acid, hydrophobic neutral, transphilic acid, transphilic neutral, and hydrophilic fraction. The bulk DOM showed DOC variation rates ranging from −2.65 to 26.94%, and the five DOM fractions exhibited DOC variation rates ranging from −22.48 to 78.16%, after freeze–thaw treatments. DOC of water samples were significantly affected by freezing and thawing temperatures, times of freeze–thaw cycles, and freezing time. The aromaticity of DOM and its fractions decreased as a result of freezing–thawing. Both freezing and thawing temperatures had a significant impact on aromatic substances contained in DOM, while the times of freeze–thaw cycles and freezing time made a relative slight influence on them. The freeze–thaw treatments reduced the chlorine reactivity of DOM and its fractions. The freezing temperature and freezing time were significant factors influencing the reactivity of DOM. The freeze–thaw treatments led to an increase in the contents of four types of fluorescent materials contained in DOM. The effect of freezing–thawing was most significant on aromatic protein- and SMP-like fluorescent materials, secondary significant on humic acid-like fluorescent materials, and slightly on fulvic acid-like fluorescent materials.

Evaluating the removal of organic fraction of commingled chemical industrial wastewater by activated sludge process augmented with powdered activated carbon

Three different technologies, namely, individual activated sludge (AS) biodegradation, powdered activated carbon (PAC) absorption, and a combination of absorption and biodegradation (PAC–AS), were applied to treat commingled chemical industrial wastewater from a chemical industrial park in Tianjin, China. Experimental results showed that chemical oxygen demand and total organic carbon of organic matters in the PAC–AS system were reduced by 64.4% and 68.1% respectively. These results suggested the considerable additive effects of both AS degradation and PAC adsorption. Organic matter fractionation was employed to reveal the removal characteristics of organic compounds during treatment. AS degradation preferred to remove the compounds in hydrophilic and transphilic neutral fractions, whereas PAC absorption removed the compounds in hydrophobic fractions. Further chemical identification analysis showed that hydrophobic fraction mainly contained carboxylic acids, esters, and aromatic structures. Hydrophilic and transphilic neutral fractions contained phenol compounds. Most aromatic acids-like compounds were identified in transphilic acid (TPI-A) fraction. Esters in hydrophobic neutral fraction and phenols in hydrophobic acid fraction were easily removed by biodegradation and adsorption during treatment. However, aromatic acids-like compounds, which were dominant compounds in TPI-A fraction, were difficult to biodegradation and adsorption.

Insight into the composition and degradation potential of dissolved organic matter with different hydrophobicity in landfill leachates.

Dissolved organic matter (DOM) isolated from the leachates with different landfill ages was fractionated into hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophobic base (HOB) fractions and hydrophilic matter (HIM) based on hydrophobicity, and the composition and degradation potential of the bulk DOM and its fractions were investigated by excitation-emission matrix fluorescence spectra coupled with parallel factor analysis. Results showed that the bulk DOM comprised fulvic-, humic-, tryptophan- and tyrosine-like substances, as well as component C1, whose composition and origin was unidentified. Landfill process increased the content of component C1, fulvic- and humic-like matter. The HON fractions comprised primarily component C1 and tyrosine-like matter. The HOA, HOB and HIM fractions isolated from the young leachates consisted mainly of tryptophan- and tyrosine-like substances. As to the intermediate and old leachates, the HOA and HOB fractions comprised mainly component C1, while the HIM comprised mainly fulvic-like matter. The HIM showed the most resistant against biodegradation among the four fractions, and was the main component of leachate treatment. Advanced oxidation and/or membrane treatment are recommended to remove the HIM fraction due to its hydrophilic and stable characteristics.

Selenium speciation and extractability in Dutch agricultural soils

The study aimed to understand selenium (Se) speciation and extractability in Dutch agricultural soils. Top soil samples were taken from 42 grassland fields and 41 arable land fields in the Netherlands. Total Se contents measured in aqua regia were between 0.12 and 1.97mgkg–1(on average 0.58mgkg–1). Organic Se after NaOCl oxidation-extraction accounted for on average 82% of total Se, whereas inorganic selenite (selenate was not measurable) measured in ammonium oxalate extraction using HPLC–ICP-MS accounted for on average 5% of total Se. The predominance of organic Se in the soils is supported by the positive correlations between total Se (aqua regia) and total soil organic matter content, and Se and organic C content in all the other extractions performed in this study. The amount of Se extracted followed the order of aqua regia>1M NaOCl (pH8)>0.1M NaOH>ammonium oxalate (pH3)>hot water>0.43M HNO3>0.01M CaCl2. None of these extractions selectively extracts only inorganic Se, and relative to other extractions 0.43M HNO3 extraction contains the lowest fraction of organic Se, followed by ammonium oxalate extraction. In the 0.1M NaOH extraction, the hydrophobic neutral (HON) fraction of soil organic matter is richer in Se than in the hydrophilic (Hy) and humic acid (HA) fractions. The organic matter extracted in 0.01M CaCl2 and hot water is in general richer in Se compared to the organic matter extracted in 0.1M NaOH, and other extractions (HNO3, ammonium oxalate, NaOCl, and aqua regia). Although the extractability of Se follows to a large extent the extractability of soil organic carbon, there is several time variations in the Se to organic C ratios, reflecting the changes in composition of organic matter extracted.

Molecular Characterization of Dissolved Organic Matter and Its Subfractions in Refinery Process Water by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Dissolved organic matter (DOM) in oil refinery process water was fractionated by XAD-8 resin techniques into four subfractions: hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON), and hydrophilic substance (HIS) fractions. Negative and positive electrospray ion (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the composition of DOM and its subfractions. Compounds with multi-oxygen atoms were found to be predominant in DOM by either negative or positive ESI analysis, which are similar in composition to most other treated water samples. The DOM in the HOA fraction had a similar molecular composition to that of raw process water by negative ESI analysis. The DOM in the HOB fraction had a low molecular weight (MW) when analyzed by positive ESI, and basic nitrogen compounds, such as N1 class species, were found to be predominant. The DOM in the HON fraction was predominantly O2 class species. The DOM in the HIS fraction had a relative...

UV fluorescence, FTIR, and GC–MS analyses and resin fractionation procedures as indicators of the chemical treatability of olive mill wastewater

The organic matter content in original, untreated (COD = 150,000 mg/L; TOC = 36,000 mg/L; oil–grease = 8,200 mg/L; total phenols = 3,800 mg/L), and chemically treated olive mill wastewater was examined in detail by instrumental and analytical (resin fractionation) methods. For this purpose, two approaches were followed: (i) UV-fluorescence, FTIR, and GC–MS analyses as well as (ii) structural fractionation assessment employing XAD-8, XAD-4, AG-MP-50, and Duolite A-7 exchange resins to obtain hydrophobic-acidic, basic, neutral, and hydrophilic-acidic, basic, neutral fractions, respectively. Acid cracking (pH 2.0; T = 70°C), FeCl3 coagulation (pH 3.0; FeCl3 = 2,500 mg/L) electrocoagulation with stainless steel electrodes (pH 2.0; T = 65°C; A = 50 mA/cm2; t = 120 min), and the Fenton’s reagent (pH 2.0; T = 65°C; 20mM Fe2+: 200mM H2O2; t = 120 min) were selected for convenient chemical treatment of the effluent. Resin fractionation analyses of the original wastewater sample indicated that the major organic content composed of hydrophobic moieties (75–95%). The percent relative inhibition of the original wastewater was concentrated in the hydrophobic neutral fraction (100%). By employing instrumental analyses, several organic compounds could be identified. Relatively low molecular weight chemicals were qualified via GC–MS analysis, whereas FTIR results revealed an appreciable loss of aliphatic moieties together with an increase in aromatic structures.

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.

Composition and spectroscopic characteristics of dissolved organic matter extracted from the sediment of Erhai Lake in China

Purpose The content and composition of dissolved organic matter (DOM) in sediment directly affect nutrient cycling and material exchange in lake ecosystems. This study investigated the content and composition of DOM and its fractions in sediments, as well as the relationship between the different parameters and nitrogen (N) forms in DOM. The main aim of this study was to evaluate the compositional characteristics of DOM, hydrophobic bases (HOB), hydrophobic acids (HOA), hydrophobic neutral fractions (HON), and hydrophilic matter (HIM) in sediments from Erhai Lake, China.

Adsorption of carbamazepine by carbon nanotubes: Effects of DOM introduction and competition with phenanthrene and bisphenol A

Carbon nanotubes, organic contaminants and dissolved organic matter (DOM) are co-introduced into the environment. Thus, the interactions between these components have to be evaluated to better understand their environmental behavior. In this study, single-walled carbon nanotubes (SWCNTs) were used as sorbent, carbamazepine was the primary adsorbate, and bisphenol A and phenanthrene were used as competitors. Strong competition with bisphenol A and no effect of phenanthrene on adsorption of carbamazepine was obtained. The hydrophobic neutral fraction of the DOM exhibited the strongest reductive effect on carbamazepine adsorption, most probably due to interactions in solution. In contrast, the hydrophobic acid fraction decreased carbamazepine adsorption mainly via direct competition. When DOM and bisphenol A were co-introduced, the adsorption of carbamazepine was significantly reduced. This study suggests that the chemical nature of DOM can significantly affect the sorptive behavior of polar organic pollutants with carbon nanotubes when all are introduced to the aquatic system.

Effective removal of effluent organic matter (EfOM) from bio-treated coking wastewater by a recyclable aminated hyper-cross-linked polymer

Effluent organic matter (EfOM) is a complex matrix of organic substance mainly from bio-treated sewage effluent and is considered as the main constraint to further advanced treatment. Here a recyclable aminated hyper-cross-linked polymeric adsorbent (NDA-802) featured with aminated functional groups, large specific surface area, and sufficient micropore region was synthesized for effective removal of EfOM from the bio-treated coking wastewater (BTCW), and its removal characteristics was investigated. It was found that hydrophobic fraction was the main constituent (64.8% of DOC) in EfOM of BTCW, and the hydrophobic-neutral fraction had the highest SUVA level (7.06 L mg−1 m−1), which were significantly different from that in the domestic wastewater. Column adsorption experiments showed that NDA-802 exhibited much higher removal efficiency of EfOM than other polymeric adsorbents D-301, XAD-4, and XAD-7, and the efficiency could be readily sustained according to continuous 28-cycle batch adsorption–regeneration experiments. Moreover, dissolved organic matter (DOM) fractionation and excitation-emission matrix (EEM) fluorescence spectroscopy study indicated that NDA-802 showed attractive adsorption preference as well as high removal efficiency of hydrophobic and aromatic compounds. Possibly ascribed to the presence of functional aminated groups, relatively large specific surface area and micropore region of the unique polymer, NDA-802 possesses high and sustained efficiency for the removal of EfOM, and provides a potential alternative for the advanced treatment.

Fluorescence spectroscopic characterization of dissolved organic matter fractions in soils in soil aquifer treatment

This work investigated the effect of soil aquifer treatment (SAT) operation on the fluorescence characteristics of dissolved organic matter (DOM) fractions in soils through laboratory-scale soil columns with a 2-year operation. The resin adsorption technique (with XAD-8 and XAD-4 resins) was employed to characterize the dissolved organic matter in soils into five fractions, i.e., hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N), and hydrophilic fraction (HPI). The synchronous fluorescence spectra revealed the presence of soluble microbial byproduct- and humic acid-like components and polycyclic aromatic compounds in DOM in soils, and SAT operation resulted in the enrichment of these fluorescent materials in all DOM fractions in the surface soil (0-12.5 cm). More importantly, the quantitative method of fluorescence regional integration was used in the analysis of excitation-emission matrix (EEM) spectra of DOM fractions in soils. The cumulative EEM volume (Φ T, n ) results showed that SAT operation led to the enrichment of more fluorescent components in HPO-A and TPI-A, as well as the dominance of less fluorescent components in HPO-N, TPI-N, and HPI in the bottom soil (75-150 cm). Total Φ T, n values, which were calculated as [Formula: see text], suggested an accumulation of fluorescent organic matter in the upper 75 cm of soil as a consequence of SAT operation. The distribution of volumetric fluorescence among five regions (i.e., P i, n ) results revealed that SAT caused the increased content of humic-like fluorophores as well as the decreased content of protein-like fluorophores in both HPO-A and TPI-A in soils.

Fluorescence spectroscopic studies of the effect of granular activated carbon adsorption on structural properties of dissolved organic matter fractions

This work investigated the effect of granular activated carbon adsorption (GACA) on fluorescence characteristics of dissolved organic matter (DOM) in secondary effluent, by means of excitation-emission matrix (EEM) spectra, the fluorescence regional integration (FRI) method, synchronous spectra, the fluorescence index defined as the ratio of fluorescence emission intensity at wavelength 450 nm to that at 500 nm at excitation (λex)= 370 nm, and the wavelength that corresponds to the position of the normalized emission band at its half intensity (λ0.5). DOM in the secondary effluent from the North Wastewater Treatment Plant (Shenyang, China) was fractionated using XAD resins into 5 fractions: hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N) and hydrophilic fraction (HPI). Results showed that fluorescent materials in HPO-N and TPI-N were less readily removed than those in the other fractions by GACA. The relative content of fluorescent materials in HPO-A, TPI-A and HPI decreased whereas that in HPO-N and TPI-N increased as a consequence of GACA. Polycyclic aromatics in all DOM fractions were preferentially absorbed by GACA, in comparison with bulk DOM expressed as DOC. On the other hand, the adsorption of aromatic amino acids and humic acid-like fluorophores exhibiting fluorescence peaks in synchronous spectra by GACA seemed to be dependent on the acid/neutral properties of DOM fractions. All five fractions had decreased fluorescence indices as a result of GACA. GACA led to a decreased λ0.5 value for HPO-A, increased λ0.5 values for HPO-N, TPI-A and HPI, and a consistent λ0.5 value for TPI-N.

A comparison of organic matters responsible for immersed ultrafiltration membranes fouling in drinking water treatment

ABSTRACTMembrane fouling caused by natural organic matter is an important problem in drinking water treatment. In this study, bench‐scale experiments using three different types of ultrafiltration (UF) membranes were carried out with the surface water of the Songhua River in China in order to investigate the effect of natural organic matter on membrane fouling. Organic matter that caused reversible and irreversible fouling in the filtration operation was desorbed from the fouled membranes and subjected to chemical fractionation and Fourier transform infrared analyses. These analyses revealed that hydrophilic organic matter accounted for the majority of both reversible and irreversible fouling, regardless of the type of membrane. Results also demonstrated that the type of organic matter responsible for fouling differed significantly and depended on the type of membrane. The main types of organic matter that caused reversible fouling were hydrophilic organic matter and hydrophobic acids, for the polyvinyl chloride (PVC) and polysulfone (PS) membranes and hydrophilic matter and weakly hydrophobic acids, for the polyvinylidene fluoride (PVDF) membrane. Hydrophobic acids were largely responsible for the irreversible fouling of PVDF membranes. The PVC membrane was more vulnerable to fouling because of the hydrophilic fraction, and the PS membrane was most easily fouled by the hydrophobic neutral fraction. © 2012 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Interaction of phenanthrene with dissolved organic matter and its fractions from leachate of different landfill ages

Dissolved organic matter (DOM) in leachate from landfills of three different ages (0, 5, and 10 year) was partitioned into hydrophobic acid, hydrophobic neutral, and hydrophilic matter fractions using the fractionation method employing XAD-8 resin. The spectroscopic characteristics of these fractions were determined through constant-wavelength synchronous fluorescence spectrometry (CWSFS). The interaction characteristic of phenanthrene with these fractions was determined through the fluorescence quenching method and CWSFS. The results revealed that the composition of DOM became complex with the increase in landfill age. The partition coefficients (K doc) for the three DOM samples of different landfill ages are in the order 10 a DOM > 5 a DOM > 0 a DOM. The hydrophobic fraction showed the highest K doc value among the DOM fractions. Lower linearity Stern–Volmer plots were observed in 10 a DOM and its hydrophobic fractions. CWSFS spectra showed that a special site was fully occupied with the addition of the quencher. Desorption was found in some fractions. Therefore, CWSFS is a sensitive tool for the detection of DOM-polycyclic aromatic hydrocarbon interaction.

Microbial degradation of dissolved organic matter (DOM) and its influence on phenanthrene–DOM interactions

Microbial degradation-induced changes in the characteristics of dissolved organic matter (DOM), and the subsequent effects on phenanthrene–DOM interactions were investigated based on the microbial incubation of DOM collected from four different sources for 28 d. Partially biodegraded DOM presented higher specific UV absorbance (SUVA), lower protein-like fluorescence, higher humic-like fluorescence, lower aliphatic carbon fraction, and higher hydrophobic neutral fractions compared to the original DOM. Microbial changes in DOM led to an increase in the isotherm nonlinearity as well as the extent of phenanthrene binding. A negative relationship between SUVA and the Freundlich n values was established for the original and the biodegraded DOM, suggesting that aromatic condensed structures may play important roles in providing nonlinear strong binding sites irrespective of microbial degradation. In contrast, there were two separate slopes of the correlations between the percentage of hydrophobic acid (HoA) fraction and the n values for the original and the biodegraded DOM with a higher slope exhibited for the latter, implying that the microbial utilization of oxygen-containing structures in the HoA fractions may contribute to enhancing the associated isotherm nonlinearity.

Fluorescence excitation–emission matrix spectroscopy with regional integration analysis for characterizing composition and transformation of dissolved organic matter in landfill leachates

Dissolved organic matter (DOM) obtained from landfill leachates was separated into hydrophobic base, hydrophilic matter (HIM), hydrophobic acid (HOA), and hydrophobic neutral fractions. The composition and transformation of the DOM and its fractions were investigated. The results show that the DOM isolated from young, intermediate, and old landfill leachates were mainly composed of tyrosine-, tryptophan-, and humic- and fulvic-like substances, respectively. The primary fractions of the DOM in leachates were HOA and HIM. The HOA and HIM fractions from young leachates predominantly contained tryptophan- and tyrosine-like materials, respectively. The HOA fractions in intermediate and old leachates were mainly composed of humic- and fulvic-like materials, whereas the HIM fractions were dominated by tryptophan-like materials and humic- and fulvic-like substances. The hydrophobic organic fractions and humic- and fulvic-like substances increased with time, whereas the HIM and the tyrosine-like materials decreased during the landfill process, rendering biological processing of leachates ineffective.

Comparison of dissolved organic matter fractions in a secondary effluent and a natural water

This research compared the structural and chemical characteristics among dissolved organic matter (DOM) fractions within the same source and among different origins. Samples taken from the Taiping Wastewater Treatment Plant (TWTP) (Harbin, China) and from the Songhuajing River (SR), Heilongjiang Province, China were chosen to represent waters containing DOM of wastewater origin and of natural-water origin, respectively. DOM was fractionated using XAD resins into five fractions: hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N) and hydrophilic fraction (HPI). The SR fractions were more UV-sensitive and more reactive with chlorine in formation of trihalomethanes (THMs) than the TWTP secondary effluent (TSE) fractions. The aromatic character peaks in the Fourier-transform infrared (FT-IR) spectra of SR fractions were clearer than those of TSE fractions. On the other hand, the peaks of carbohydrates in TSE fractions were more prominent in comparison with SR fractions. In addition, the amide-2 peak was present in the spectra of all the five TSE fractions but not visible in the spectra of SR fractions. The fluorescence results showed that SR DOM fractions contained more fulvic acid-like fluorescent compounds while TSE DOM fractions had higher amounts of protein-like fluorescent components.