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.     

Recovery of iron oxide and calcium chloride from an iron-rich chloride waste using calcium carbonate

Journal of Material Cycles and Waste Management - The ilmenite-chloride process has used for the production of TiCl4 from the ilmenite (FeTiO3) ore, which produces cyclone dust containing mostly...     

Formation of CoAl layered double hydroxide on the boehmite surface and its role in tungstate sorption

Sorption of tungstate on boehmite(γ-Al OOH)is increased by co-sorption with Co~(2+)over the near-neutral p H range.Batch uptake experiments show up to a 3-fold increase in tungstate uptake over the range WO_4~(2-)=50–1000μmol/L compared to boehmite not treated with Co~(2+).Desorption experiments reveal a corresponding decrease in sorption reversibility for tungstate co-sorbed with Co~(2+).Reaction of boehmite with Co~(2+)results in the formation of Co Al layered double hydroxide(LDH),as confirmed by X-ray diffraction and X-ray absorption spectroscopy.Tungsten L_3-edge X-ray absorption near edge structure(XANES)reveals that W(VI)is octahedrally coordinated in all sorption samples,with polymeric tungstate species forming at higher tungstate concentrations.X-ray diffraction and X-ray absorption spectroscopy indicate that the mechanism for enhancement of tungstate uptake is the formation of surface complexes on boehmite at low tungstate concentrations,while exchange into the Co Al LDH becomes important at higher tungstate concentrations.The results provide a basis for developing strategies to enhance tungstate sorption and to limit its environmental mobility at near-neutral pH conditions.     

Longevity of organic layers of vertical flow ponds for sulfate reduction in treating mine drainages in South Korea

This study was carried out to evaluate longevity of available organic materials used for sulfate-reducing bacteria (SRB) activity in vertical flow ponds (VFPs) to treat mine drainage in South Korea. Spent mushroom compost samples (SMC) were tested as substrates in VFPs and analyzed for total organic carbon in VFPs, and were collected to analyze total organic carbon (TOC), T-N, T-P, K, metals and residual cellulose to check the longevity assessment. Chemical analysis revealed that the average contents of Fe, Al and Mn in SMC of VFPs were 19,907, 32,137 and 434 mg/kg, respectively. The contents of Fe and Al in SMC of VFPs were much higher than those of the unused SMC (control), but to the contrary, those of Mn showed a reversed tendency. Average TOC content of the controls was 64.19% but in one of the VFP substrates was as low as 15.92%. This might be resulted from SRB consumed the available organic carbon in SMC as VFPs system aged. Contents of T-N in VFPs tended to decrease as VFPs aged. The residual cellulose ranged from 3.88 to 6.72% (g/g). There existed a negative relationship between residual cellulose contents and ages of VFPs. Assuming that SMC in all VFPs had similar compositions when the VFPs were initially established, trend analysis predicted that the amount of carbon source for SRB might be available for 12-15 years further, depending on VFPs.     

Using fluorescence surrogates to track algogenic dissolved organic matter (AOM) during growth and coagulation/flocculation processes of green algae

Tracking the variation of the algogenic organic matter (AOM) released during the proliferation of green algae and subsequent treatment processes is crucial for constructing and optimizing control strategies. In this study, the potential of the spectroscopic tool was fully explored as a surrogate of AOM upon the cultivation of green algae and subsequent coagulation/flocculation (C/F) treatment processes using ZrCl₄ and Al₂(SO₄)₃. Fluorescence excitation emission matrix coupled with parallel factor analysis (EEM-PARAFAC) identified the presence of three independent fluorescent components in AOM, including protein-like (C1), fulvic-like (C2) and humic-like components (C3). Size exclusion chromatography (SEC) revealed that C1 in AOM was composed of large-sized proteins and aromatic amino acids. The individual components exhibited their unique characteristics with respect to the dynamic changes. C1 showed the highest correlation with AOM concentrations (R²?=?0.843) upon the C/F processes. C1 could also be suggested as an optical predictor for the formation of trihalomethanes upon the C/F processes. This study sheds a light for the potential application of the protein-like component (C1) as a practical surrogate to track the evolution of AOM in water treatment or wastewater reclamation systems involving Chlorella vulgaris green algae.     

Evaluating spectroscopic and chromatographic techniques to resolve dissolved organic matter via end member mixing analysis

Real-time or near real-time in-situ monitoring of dissolved organic matter (DOM) composition in natural waters and engineered treatment systems provides critical information to water quality scientists and engineers, particularly when the monitoring techniques can provide some information about the chemical nature of DOM. The efficacy of various indices derived from rapid, low-cost spectroscopic and chromatographic techniques to discriminate DOM composition was tested for samples prepared from well-defined mixtures of purified Aldrich humic acid (PAHA) and Suwannee River fulvic acid (SRFA). Sensitivities of the discrimination indices were examined by comparing (1) the differences between measured values and those predicted based from mass balance and the end member characteristics, and (2) the linear correlations between index values and mass ratios of the DOM mixtures. Size exclusion chromatography (SEC) results revealed that the weight-average molecular weight (MW(w)) may be a useful approach for tracking DOM mixing processes, although the number-average molecular weight (MW(n)) may be better for distinguishing different DOM compositions. Specific ultraviolet absorbance measured at 254 nm (SUVA(254)) performed better as a discrimination index than did two previously recommended absorbance ratios, both in terms of making better predictions of intermediate compositions and in exhibiting a more linear correlation with PAHA mass ratio. Several well-defined peaks in the derivative absorption spectra (301 and 314 nm for the first derivative, 217 nm for the third derivative, and 211 and 224 nm for the fourth derivative) also were found to be promising potential DOM discrimination indices. Finally, a fluorescence ratio based on humic- versus fulvic-like fluorescence proved to be a superior DOM discrimination index for the two DOM end members studied here. In general, this study illustrates the evaluation process that should be followed to develop rapid, low-cost discrimination indices to monitor DOM compositions based on end member mixing analyses.     

Tracking the spectroscopic and chromatographic changes of algal derived organic matter in a microbial fuel cell

Changes in the characteristics of algae-derived organic matter (AOM) were examined upon the operation of a microbial fuel cell (MFC) using multiple analytical methods. Temporal variations in the UV absorption and fluorescence excitation–emission matrix of the AOM revealed that less condensed humic-like components and large-sized protein-like fluorescent compounds were preferentially decomposed over the period of electricity generation. They also showed that low UV-absorbing extracellular organic matters (EOM) were produced at the end of the operation. SEC chromatograms demonstrated that smaller-sized UV-absorbing components were initially decomposed, followed by the net production of EOM with an intermediate molecular weight. Fourier transform infrared (FT-IR) spectra showed that proteins and polysaccharides were the two most dominant structures of the AOM in the MFC. Two-dimensional correlation spectroscopy combined with FT-IR provided additional valuable information on the sequential changes of the AOM, which occurred in the order of proteins → acidic functional groups → polysaccharides → amino acids/proteins.     

Anaerobic biotransformation of dinitrotoluene isomers by Lactococcus lactis subsp. lactis strain 27 isolated from earthworm intestine

Dinitrotoluenes are widely used as solvents and are intermediates in the synthesis of dyes, explosives, and pesticides. Environmental concerns regarding DNTs have increased due to their widespread use and their discharge into the environment. In this study, the anaerobic biodegradation of four dinitrotoluene isomers, 2,3-, 2,4-, 2,6- and 3,4-DNT, was investigated using Lactococcus lactis subsp. lactis strain 27, which was isolated from the intestines of earthworms. Liquid chromatography/mass spectrometry and NMR spectroscopy showed that L. lactis strain 27 non-specifically reduced the nitro groups on the tested dinitrotoluenes to their corresponding aminonitrotoluenes. L. lactis strain 27, however, did not reduce either sequentially or simultaneously two nitro groups of the dinitrotoluenes, resulting in the formation of the corresponding diaminotoluenes. In vitro formation of dinitroazoxytoluenes suggested the presence of oxygen-sensitive hydroxylaminonitrotoluenes. L. lactis strain 27 was capable of reducing 2,4-, 2,6-, 2,3-, and 3,4-dinitrotoluenes up to 173.6, 66.6, 287.1, and 355 microM, respectively in 12 h incubation. A relatively rapid reduction was observed in the case of the 2,3-, and 3,4-dinitrotoluenes, which have vicinal nitro groups on their arene structure. Non-specific anaerobic reduction of dinitrotoluenes by the intestinal bacterium L. lactis strain 27 differentiated the extent of reduction of DNTs according to the substitutional position of the nitro groups and produced in vitro more toxic dinitroazoxytoluenes, suggesting that anaerobic biotransformation of dinitrotoluenes could increase environmental risk.     

Microbial transformation of dissolved organic matter from different sources and its influence on disinfection byproduct formation potentials

Biodegradation-induced changes in the characteristics of dissolved organic matter (DOM) and the subsequent effects on disinfection byproduct formation potentials (DBPFPs) were investigated using six different sources of DOM (algae, leaf litter, reed, compost, paddy water, and treated municipal sewage effluent). Microbial incubation of the DOM samples increased the specific ultraviolet absorbance and humic-like fluorescence but decreased the protein/tannin-like fluorescence and relative distribution of smaller-sized DOM components. Comparison of the original versus biodegraded DOM samples using resin fractionation and pyrolysis–gas chromatography/mass spectrometry revealed that the biodegradation-induced changes were highly dependent on DOM sources and exhibited no consistent trends among the different sources. Changes in DBPFPs also differed with DOM source. Vascular plant-derived DOM (leaf litter and reed) demonstrated an enhancement in specific DBPFP after biodegradation, whereas little change or even a slight decrease was observed for the other DOM sources. Correlations that were significant between specific DBPFPs and the aromatic content or humic-like fluorescence for the original DOM samples were no longer significant after microbial degradation. The relative abundance of hydrophobic to hydrophilic structures in DOM is suggested to be a general indicator for the formation potential of trihalomethanes irrespective of DOM source and the state of biodegradation.