Hydrophobic Neutral Fractions Research Articles

Rainwater extracting characteristics and its potential impact on DBPs generation: A case study

Frequent extreme precipitation events due to global warming can lead to large amounts of pollutants entering source water bodies via surface runoff and wet deposition, thus posing a threat to water supply security. In order to better understand the source characteristics and leaching mechanisms of rainwater dissolved organic matter (DOM), as well as its disinfection by-products formation potential (DBPsFP) during disinfection processes, rainwater samples were collected and extracting experiments were conducted. Three components were identified in rainwater through Parallel factor (PARAFAC) analysis, which were microbial humic-like component C1 (63.1 %), protein (tryptophan-like) component C2 (28.9 %), marine or terrestrial humic-like component C3 (8.1 %). The average molecular weight of rainwater fractions was ordered: hydrophobic neutral (HON) < hydrophobic bases (HOB) < hydrophobic acidic (HOA) < hydrophilic (HIS). The HOA and HON fractions of rainwater were the dominant precursors of trihalomethanes (THMs), while the rainwater HON fraction and hydrophilic fraction were the main precursor of haloacetic acids (HAAs) and trihloroacetonitrile (TCAN), respectively. Subsoil extracts had a higher concentration of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) than topsoil extracts. Partial least squares path modeling (PLS-PM) demonstrated that the extraction temperature was the dominant factor affecting the abundance of DOM in the topsoil extracts (R2 = 0.28), while the extraction time accounted more for the abundance of fluorescence substance and physicochemical indices in the subsoil extracts (R2 = 0.23 and 0.32, respectively). These results provide key information for controlling the impacts of global warming, in particular the risk of water sources being heavily contaminated by request rainfalls.

Changes in the structural characteristics of EfOM during coagulation by aluminum chloride and the effect on the formation of disinfection byproducts

The effects of coagulation on the removal efficiency of different fractions of effluent organic matter (EfOM) from wastewater treatment plants were investigated to identify changes in their structural characteristics and the influences on trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP). The results indicated that coagulation performed better for the removal of hydrophobic base (HOB) and hydrophobic neutral (HON) fractions than hydrophilic (HI) and hydrophobic acid (HOA) fractions. The removal efficiency was higher under neutral than under acidic conditions for all fractions. As a result, lower levels of THMFP and HAAFP were detected at pH7. The excitation-emission matrix spectra indicated that the HI fraction contained humic acid-like substances that reacted with chlorine to form THMs. The HON fraction contained soluble microbial byproduct-like substances with a higher potential to create HAAs. The results of Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-pressure size exclusion chromatography (HP-SEC) of the raw and coagulated water indicated that a higher molecular weight, α-carbon, COOH, aromatic structures, and polysaccharides were associated with a higher production of disinfection byproducts (DBP). These results elucidate the coagulation efficiencies of EfOM fractions associated with different mechanisms and facilitate the prediction of DBP formation by each fraction based on specific structural characteristics.

Removal of dissolved organic matter in road runoff by granules prepared using sludge from waterworks

Abstract This work assessed the elimination of dissolved organic matter (DOM) in road runoff by a granular sludge-clay (GSC) adsorbent. The rates of adsorption were found to be consistent with the pseudo-second-order kinetic model. The data at equilibrium resulted in a maximum adsorption capacity of 4.466 mg/g at 298 K, which was in good agreement with the Langmuir isotherm model. The adsorption of DOM relies on pH. The higher removal efficiency of DOM was observed at pH 4.0 and 7.0. To clarify the related adsorption mechanism, isolated DOM fractions and their removal potentials were identified. The results showed hydrophobic acid (HoA) and hydrophobic neutral (HoN) fractions which contained abundant fulvic-like substances were more preferentially removed by the GSC. The adsorption mechanism of DOM in road runoff by GSC involves both electrostatic attraction and ligand exchange reactions. GSC synthesized using the sludge from waterworks is a very promising filler to replace soils or gravels that can be applied in some green infrastructures for removing DOM from road runoff.

Characteristics of dissolved ozone flotation for the enhanced treatment of bio-treated drilling wastewater from a gas field

Working fluid preparation using treated drilling wastewater is of great potential for drilling wastewater reuse, especially in water-deficient and ecologically fragile areas, which require low levels of organic matter and suspended solids (SS). This study established the dissolved ozone flotation (DOF) process as the advanced treatment process to replace the original electrocatalytic system (ECS) which exhibited low organic and suspended solids removal efficiency. Higher and more stable organic matter, suspended solids and turbidity removal efficiency were obtained for the DOF process. Consequently, the lower fouling potential and higher water production rate of treated water from DOF process was observed for the following reverse osmosis (RO) system. In addition, brine drilling fluids can be successfully prepared using DOF effluent directly, which exhibited promising practical implications in the advanced drilling wastewater treatment. Based on organic matter fractionation and redundancy analysis (RDA), the hydrophobic acid (HOA), hydrophobic neutral (HON) and hydrophilic fraction (HI) contents significantly impacted brine drilling fluid preparation. Based on X-ray photoelectron spectroscopy (XPS) analysis, the aromatic carbon species in the HOA, HON and HI fractions were found to be the critical factors deteriorating the brine drilling fluid preparation. However, oxygen-containing groups played a positive role. The favorable brine drilling fluid preparation performance using DOF effluent directly can be ascribed to the removal of HOA, HON and HI fractions and enhanced generation of oxygen-containing groups in ozone flotation zone.

Changes in dissolved organic matter during water treatment by sequential solid-phase extraction and unknown screening analysis

Isolation of complex dissolved organic matter (DOM) from environmental water is a major challenge for unknown screening analysis by high-resolution mass spectrometry. In this study, DOM in process water during advanced drinking water treatment was fractionated sequentially by three solid-phase extraction (SPE) cartridges based on the polarity and charge of DOM molecules. By sequential SPE with unknown screening analysis, over 3000 DOM features were found in raw water, whereas around 2000 were obtained by a single SPE. The hydrophobic neutral (HPON) fraction contained CHO features with highest averaged molecular weight followed by hydrophobic acid (HPOA) and then hydrophilic acid (HPIA). The average degree of carbon double bond equivalents and carbon oxidation states indicated that the HPON fraction contained molecules that were more unsaturated and less oxidized than those of the HPOA and HPIA fractions. Ozone selectively decomposed (1) more unsaturated and less oxidized HPON features, (2) more unsaturated HPOA compounds, and (3) less oxidized HPIA molecules. Oxidation by-products were mostly HPON and HPIA compounds that were more oxidized than the decomposed molecules. During biological activated carbon (BAC) filtration, less oxidized HPON were preferentially removed, whereas HPOA were removed without selectivity. HPON and HPIA molecules with more oxidized character were found to be refractory to BAC treatment. HPON with more unsaturated and HPIA with more oxidized characters were decomposed by chlorine. Many types of HPIA decomposed during chlorination were the oxidation by-products of ozonation that were refractory to BAC treatment. Sequential SPE with unknown screening analysis provided previously unknown details of the molecular characteristics of DOM and its changes during advanced water treatment.

Characteristic of dissolved organic matter polar fractions with variable sources by spectrum technologies: Chemical properties and interaction with phenoxy herbicide

Dissolved organic matter (DOM) is ubiquitous with high biological and chemical activity. The large intake of DOM from compost, plant residues or soil can modify the behaviors of agrochemicals. Phenoxy herbicide is the third widely used herbicide around the world with both aromaticity and polarity. However, how the diverse fractions of DOM interacting with phenoxy herbicide and the underlying mechanisms remain unknown. Thus, it is crucial to investigate the heterogeneous chemical properties of DOM fractions from variable sources and explore the interactive mechanisms. In this study, polar DOM derived from compost, rice straw and soil were fractionated, and the chemical properties of fractions were analyzed by spectrum technology and the complex interaction with phenoxy herbicide was assessed by infrared spectroscopy. Results showed that hydrophobic acid (HOA) was the largest component (49.6%) in compost DOM, while hydrophilic matter (HIM) was the main component in the polar DOM from rice straw and soil. The 4-chloro-2-methylphenoxyac etic acid (MCPA) as one representative of phenoxy herbicides was used in our study, and the results showed the interaction between different DOM fractions and MCPA was heterogeneous. HOA containing abundant fulvic-like component and polar groups resulted a greatly complex interaction with MCPA mainly via hydrophobic force, ligand exchange and hydrogen bonding. Hydrophobic neutral fraction and acid-insoluble matter showed a medium interaction with MCPA as a result of enrichment with the high aromatic humic-like molecules. Inversely, no significant interaction between HIM and MCPA was observed. Our research revealed that the aromatic framework associated with polar groups in DOM dominated the interaction with phenoxy herbicide, which might affect the bioavailability, toxicity, and mobility of phenoxy herbicide.

Dissolved Organic Matter Singlet Oxygen Quantum Yields: Evaluation Using Time-Resolved Singlet Oxygen Phosphorescence

Singlet oxygen (1O2) generation quantum yields from chromophoric dissolved organic matter (CDOM) have been reported for many samples over the past 4 decades. Yet even for standardized isolates such as those from the International Humic Substance Society (IHSS), wide-ranging values exist in the literature. In this manuscript, time-resolved 1O2 phosphorescence was used to determine the 1O2 quantum yields (ΦΔ) of a variety of dissolved organic matter (DOM) isolates and natural waters. In general, the 1O2 quantum yield values in this study are in the middle, although below the median of the range of past reported values (e.g., for Suwannee River Natural Organic Matter IHSS isolate: 1.8% vs 0.23-2.89%). Notably, hydrophobic neutral fractions of DOM isolates were found to possess the highest 1O2 quantum yields, an interesting result given that these fractions are not retained in typical humic and fulvic acid isolation procedures that use XAD resins. The excitation wavelength dependence of 1O2 generation from CDOM was also examined, and an approximate linear decrease with longer excitation wavelength was observed. This work advances the understanding of CDOM photoprocesses, especially in relation to wavelength-dependent 1O2 production, which is valuable for assessing real-world environmental behavior.

Characterizing the roles of organic and inorganic foulants in RO membrane fouling development: The case of coal chemical wastewater treatment

• RO fouling behavior of real coal industrial wastewater was analyzed in detail. • Roles of hydrophobic/philic organics and inorganics (Ca/Mg/Si) were identified. • HON and HIN had the highest fouling potential per unit concentration. • Polysaccharide was responsible for rapid initial fouling and low steady-state flux. • Si further limited the steady-state flux by altering foulant layer structure. In this study, various fouling characteristics on the surface of a commercial reverse osmosis (RO) membrane were identified, in terms of different organic and inorganic components. Specifically, a practical secondary wastewater of coal chemical industry was used as the feed solution, and was fractionated into six hydrophobic/hydrophilic acid/base/neutral portions. RO membrane fouling behaviors at different stages were critically described using two characteristic parameters, i.e., initial flux decline rate and final steady-state flux. These parameters were quantified using Michaelis-Menten relation as a model fitting method. In general, the hydrophilic neutral (HIN) and hydrophobic neutral (HON) fractions had the fastest initial fouling rate and the lowest steady-state flux, mainly due to their high contents of polysaccharide. Among the organic constituents (polysaccharide/protein/humic acid), polysaccharide was the most responsible for rapid initial flux decline and low final steady-state flux, as proved by Kendall’s correlation. Among the inorganic constituents (Ca/Mg/Si), Si was found to exert the greatest influence on the final steady-state flux. This indicates that polysaccharide and Si played a combined role in determining the foulant layer permeability at the prolonged fouling stage, and a possible mechanism is that Si might alter the structure of polysaccharide gel layer. Further information on the fouling layers was systematically provided by means of Fourier transform infrared spectroscopy, confocal laser scanning microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy with fractal dimension analysis.

Effect of dissolved organic matter fractions on photodegradation of phenanthrene in ice.

The effect of dissolved organic matter (DOM) fractions on photodegradation of phenanthrene (PHE) in ice was investigated. DOM in surface water and wastewater samples was fractionated using XAD-8/XAD-4 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 photodegradation rate of PHE in ice was about 40% greater than that in water. The screening effect and quenching effect contributed 3-12% and 88-97% toward the inhibition of DOM fractions on PHE photodegradation in ice, respectively. The contribution ratios of singlet oxygen (1O2) and hydroxyl radical (OH) produced from DOM fractions to PHE photodegradation rates in ice were 9-31% and 2-13%, respectively. Among five DOM fractions, HPO-A was most efficient in advancing PHE photodegradation in ice through 1O2 mechanism. When excluding the photosensitized effect of 1O2 and OH produced from DOM fractions, the quencing effect of DOM fractions on PHE photodegradation in ice was closely related to their PHE binding ability.

Characterization of dissolved organic matter and membrane fouling in coagulation-ultrafiltration process treating micro-polluted surface water

Coagulation–ultrafiltration (C–UF) is widely used for surface water treatment. With the removal of pollutants, the characteristics of organic matter change and affect the final treatment efficiency and the development of membrane fouling. In this study, we built a dynamic C–UF set-up to carry out the treatment of micro-polluted surface water, to investigate the characteristics of dissolved organic matter from different units. The influences of poly aluminum chloride and poly dimethyldiallylammonium chloride (PDMDAAC) on removal efficiency and membrane fouling were also investigated. Results showed that the dosage of PDMDAAC evidently increased the UV254 and dissolved organic carbon removal efficiencies, and thereby alleviated membrane fouling in the C–UF process. Most hydrophobic bases (HoB) and hydrophobic neutral fractions could be removed by coagulation. Similarly, UF was good at removing HoB compared to hydrophilic substances (HiS) and hydrophobic acid (HoA) fractions. HiS and HoA fractions with low molecule weight accumulated on the surface of the membrane, causing the increase of transmembrane pressure (TMP). Membrane fouling was mainly caused by a removable cake layer, and mechanical cleaning was an efficient way to decrease the TMP.

Enhanced electricity generation and organic matter degradation during three-chamber bioelectrochemically assisted anaerobic composting of dewatered sludge

Composting microbial fuel cells can generate electricity from recycled organic waste at accelerated degradation rates. However, the problem of high internal resistance (Rint), which results in low power density, is a technical obstacle related to this process, and the preferential conversion of the organic fraction by bioelectrogenesis remains unclear. This study involved designing a novel three-chamber bioelectrochemically assisted anaerobic composting process (AnCBE,III) to dispose of dewatered sludge (DS), which was operated at reduced internal resistance. The maximum power density of the AnCBE,III was higher (7.0–8.6 W/m3) than that of the two-chambered AnCBE,II (4.7–5.7 W/m3), with lower Rint (63.8–88.5 Ω) than that of the AnCBE,II (78.8–98.5 Ω). At the end of composting, the AnCBE,III had higher total chemical oxygen demand (TCOD) removal (42.3 ± 0.5%) than the AnCBE,II (32.1 ± 0.5%). During electrogenesis, the dissolved organic carbon (DOC) [hydrophilic fraction and hydrophobic acid fraction of EBOM] (extracellular biological organic matter) was substantially removed, the hydrophobic neutral fraction of aromatic macromolecules was increasingly solubilized (by 13.2%), and the aromatic protein-like and humic acid-like substances were substantially removed. The results demonstrate that the increases in both the proton exchange area and cathode surface area in the AnCBE,III can enhance electricity generation and organic matter degradation.

Is ozonation environmentally benign for reverse osmosis concentrate treatment? Four-level analysis on toxicity reduction based on organic matter fractionation

Ozonation is a promising option to treat reverse osmosis concentrate (ROC). However, a systematic understanding and assessment of ozonation on toxicity reduction is insufficient. In this study, ROC sampled from a typical industrial park wastewater treatment plant of China was fractionated into hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON), and hydrophilic fraction (HI). Systematic bioassays covering bacteria, algae, fish, and human cell lines were conducted to reveal the role of ozonation in toxicity variation of the four ROC fractions. HOA in the raw ROC exhibited the highest toxicity, followed by HON and HI. Ozonation significantly reduced total organic carbon (TOC) and UV254 values in HOA, HON, and HI and their toxicity except in HOB. Correlation analysis indicated that chemical data (TOC and UV254) of HOA and HON correlated well with their toxicities; however, poor correlations were observed for HOB and HI, suggesting that a battery of toxicity assays is necessary. This study indicates that TOC reduction during ozonation could not fully reflect the toxicity issue, and toxicity assessment is required in conjunction with the chemical data to evaluate the effectiveness of ozonation.

Fouling characteristics and fouling control of reverse osmosis membranes for desalination of dyeing wastewater with high chemical oxygen demand

Fouling of reverse osmosis (RO) membranes is a severe problem for desalination of dyeing wastewater with high chemical oxygen demand (COD). In this paper, fouled RO membranes in a pilot-scale desalination system of biologically treated dyeing wastewater containing high COD (143–228mg/L) with or without injection of non-oxidizing biocides were analyzed. The two non-oxidizing biocides used are K5030 (a kind of isothiazoline biocide) and FR110 (an inorganic base type of combined chlorine agent), respectively. For the RO membrane from the system without non-oxidizing biocide injection to the influent, a typical biofilm occurred on the RO membrane in a short operation time of 19days. The injection of non-oxidizing biocides caused a decline of nearly 99.0% in active biomass on the RO membrane. Burkholderiales ruled mature biofilm on the RO membrane without injection of non-oxidizing biocide. Pseudoxanthomonas exhibited a certain resistance to non-oxidizing biocides and ruled the bacterial community on the RO membrane with injection of non-oxidizing biocides. Fe, P and Al were major inorganic elements on RO membranes, decreasing with injection of non-oxidizing biocides. Hydrophobic neutral (HON) fraction was the most major organic component of dissolved organic matter (DOM) on RO membranes, decreasing notably with injection of non-oxidizing biocides.

Reductions of dissolved organic matter and disinfection by-product precursors in full-scale wastewater treatment plants in winter

The reductions of dissolved organic matter (DOM) and disinfection byproduct precursors in four full-scale wastewater treatment plants (WWTPs) (Liaoning Province, China) where different biological treatment processes were employed in winter were investigated. The total removal efficiencies of dissolved organic carbon (DOC), ultraviolet light at 254 nm (UV-254), trihalomethane formation potential (THMFP), and haloacetic acid formation potential (HAAFP) were in the range of 70.3–76.0%, 49.6–57.3%, 54.4–65.0%, and 53.7–63.8% in the four WWTPs, respectively. The biological treatment was the predominant process responsible for the removal of DOC, THMFP, and HAAFP in WWTPs. Differences in the reduction of UV-254 were not significant (p > 0.05) among biochemical reaction pool, secondary sedimentation tank, and disinfection tank. Biological aerated filter and suspended carrier activated sludge processes achieved higher DOM removal than the conventional active sludge and anaerobic–anoxic–oxic processes. Hydrophobic neutral and hydrophilic fraction were removed to a higher degree through biological treatment than the other three DOM fractions. HAAFP removal was more efficient than THMFP reduction during biological treatment. During primary treatment, fluorescent materials in secondary sedimentation tanks were preferentially removed, as compared to the bulk DOM. Humic-like fluorescent compounds were not readily eliminated during biological treatment. The fluorescent materials were more susceptible to chlorine than nonfluorescent compounds.

Fractionation and characterization of dissolved organic matter (DOM) in refinery wastewater by revised phase retention and ion-exchange adsorption solid phase extraction followed by ESI FT-ICR MS

Although the progress of high resolution mass spectrometry in the past decade has enabled the molecular characterization of dissolved organic matter (DOM) in water as a whole, fractionation of DOM is necessary for a comprehensive characterization due to its super-complex nature. Here we proposed a method for the fractionation of DOM in a wastewater based on solubility and acidic-basic properties. Solid phase extraction (SPE) cartridges with reversed phase retention and ion-exchange adsorption capacities, namely MAX and MCX, were used in succession to fractionate a petroleum refinery wastewater into four fractions: hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophobic base (HOB), and hydrophilic substance (HIS) fractions. According to the total organic carbon (TOC) analysis, 72.6% (in term of TOC) of DOM was extracted in hydrophobic fractions, in which HON was the most abundant. Hydrophobic extracts were characterized by negative and positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. Compounds with multiple oxygen atoms were predominant in the HOA, which were responded strongly in the negative ESI MS. Nitrogen containing compounds were the major detected species by positive ion ESI in all hydrophobic fractions. The molecular composition of the DOM were discussed based on the FT-ICR MS results. The fractionation provided salt free samples which enables the direct analysis of the fractions by ESI and a deep insight into the molecular composition of DOM in the wastewater. The method is potential for routine evaluation of DOM in industry wastewaters, as well as environmental water samples.

Composition and Evolution Characteristics of Dissolved Organic Matter During Composting Process

According to the fraction method presented by Leenheer, dissolved organic matter (DOM) extracted from chicken manure with different composting time was fractionated into five groups [i. e., hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON) fractions, acid-insoluble (AIM) and hydrophilic matter (HIM)] using the XAD-8 resin based on its polarity and electric charge characteristics. The composition and structures of these fractions were investigated by elemental analysis, FTIR and 1H-NMR spectra. The results showed that the HIM and HOA fractions accounted for 32%-44% and 35%-47% of DOM, respectively, during the composting process, while the sum of the fractions HOB, AIM and HON was responsible for less than 25% of DOM. The HIM content decreased while the hydrophobic component increased after composting. The elemental analysis indicated that, during the composting process, the N, C, S content of all five fractions increased, the H/C ratio decreased, but the humification degree increased; The result from 1H-NMR analysis showed that the HIM had low alkyl chain, short branched chain, high branches and carbohydrate structure, which was opposed to the HON fraction. The composition of AIM was similar to that of humic acids, while the HOB was rich in nitrogen-containing compounds. The result from the FTIR analysis showed that the HOA and HOB fractions were rich in abundant carboxyl, ester group and hydroxyl functional group. Besides the above functional groups, the AIM and HIM were rich in benzene groups. The HON fraction was rich in aliphatic functional group except for the abovementioned functional groups. The aliphatic functional group was degraded and the benzene functional group after composting.

Treatment of domestic sewage with anoxic/oxic membrane-less microbial fuel cell with intermittent aeration

An anoxic/oxic microbial fuel cell (MFC) reactor was applied to treat domestic sewage with intermittent aeration at cathodic chamber. The MFC yielded maximum power density of 2.05W/m3 at current density 6.05A/m3, 91.7±0.3% chemical oxygen demand (COD) and 98.2±0.3% ammonia-nitrogen (NH3-N) removals could be reached with most of the hydrophilic (HPI), hydrophobic acid (HPO-A), transphilic acid (TPI-A) of the former being consumed with minimal residual aromatics and the most of NH3-N being converted to N2. When the circuit was opened, the COD removal was dropped to 81.1±0.6% and NH3-N to 80.4±0.9% with most of the HPI, TPI-A and hydrophobic neutral (HPO-N) fractions of the former being consumed with excess aromatic residue and 60% of the latter being converted to NO2−-N or NO3−-N in effluent. Bioelectrochemical reactions in the tested MFC enhance COD and NH3-N removals from domestic sewage.

Release of dissolved organic matter from melting ice

The elution behavior of dissolved organic matter (DOM) from melting ice, as well as the effect of freezing and thawing temperatures on the elution behavior of DOM from melting ice, was evaluated. 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 bulk DOM and its five fractions, as well as ultraviolet (UV)‐absorbing substances, trihalomethane (THM) and haloacetronitrile (HAA) precursors, and fluorescent materials in DOM exhibited a first flush behavior during ice melting, i.e., preferential elution with the early melt water fractions; the first flush behavior of DOM was stronger at higher freezing temperatures and/or at lower thawing temperatures, whereas DOM was eluted from the ice more uniformly at lower freezing temperatures and/or at higher thawing temperatures. The higher dissolved organic carbon (DOC) concentration in ice was, the higher degree of enrichments of DOM within the first melt water fraction was. HAA precursors were more strongly enriched in the early melt water samples than THM precursors during ice melting. The fluorescent materials were released more uniformly over the entire melt period, as compared with the bulk DOM. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1458–1467, 2016

Effect of pH on binding of pyrene to hydrophobic fractions of dissolved organic matter (DOM) isolated from lake water

In order to better understand the compositional and structural complexity of dissolved organic matter (DOM) macromolecules and provide mechanistic information on the binding of hydrophobic organic contaminants (HOCs) to DOM, we fractionated large amounts of lake water into three hydrophobic DOM-fractions. The variation of the partitioning coefficients (K DOC) of pyrene at different pH levels was examined by florescence quenching titration. Results show that, relative to the more polar acidic DOM-fractions, the hydrophobic neutral fraction exhibits a higher sorption ability to pyrene. Generally, the sorption of pyrene to the three hydrophobic fractions is strongly pH-dependent. The K DOC values of pyrene generally increase with decreasing pH levels, which is especially obvious in the sorption of pyrene to the fulvic acid fractions, suggesting that the binding is controlled by hydrophobic interactions. The mechanisms underlying the binding of pyrene to the hydrophobic fractions were also discussed. Our data are beneficial to further understanding the binding of HOCs to DOM and how it has been affected, which may result in more accurate predictions of K DOC.

Electricity generation from food wastes and characteristics of organic matters in microbial fuel cell

The microbial fuel cell (MFC) was evaluated as an alternative way to recover electricity from canteen based food waste. Characteristics of the organics in food waste before and after the MFC treatment were analyzed to investigate how the organic matters were biodegraded and transformed during the MFC treatment. A maximum power density of 5.6W/m3 and an average output voltage of 0.51V were obtained. During the MFC operation, the hydrophilic and acidic fractions were more readily degraded, compared to the neutral fractions. Additionally, aromatic compounds in the hydrophilic fraction were more preferentially removed than non-aromatic compounds. The MFC could easily remove the tryptophan protein-like substances in all fractions and aromatic proteins in hydrophilic and hydrophobic neutral fractions. Additionally, the hydrophobic amide-1 proteins and aliphatic components were readily hydrolyzed and biodegraded in the MFC. These findings may facilitate the pretreatment and posttreatment choices for MFC system fed with food waste.