Modeling Formation of Natural Organic Matter Fouling Layers on Ultrafiltration Membranes

Three simple mathematical models to describe fouling of an ultrafiltration membrane by natural organic matter (NOM) are developed and compared. These models attribute the fouling to: (1) an increase of the effective pore length by an amount equal to the thickness of the NOM gel layer that forms on the membrane surface; (2) formation of a uniform, microporous NOM gel layer on the membrane surface, made of primary particles comprising tens to hundreds of NOM molecules; or (3) narrowing of the membrane pores by sorption of a monolayer of NOM molecules along the full length of each pore. The key parameters characterizing each model are identified and estimated based on data for flux and film growth gathered in the same system. In each case, the estimated parameter values are plausible in light of the known physical properties of the membrane and NOM molecules.     

Cost Optimization of Nanofiltration with Fouling by Natural Organic Matter

An artificial neural network and genetic algorithm routine has been developed for predicting and optimizing membrane system performance. The model predicted system behavior in response to operating conditions of applied pressure and crossflow velocity. Artificial neural networks accurately modeled mechanisms involved in fouling of membranes by natural organic matter. The model correctly predicted the effects of calcium within the solution in exacerbating fouling, binding of the divalent calcium ions to the natural organic matter macromolecules, and the formation of complexes. The model also correctly predicted the role of increased pressure in inducing fouling and the reverse scenario of mitigating fouling with increased crossflow velocity. The model was applied to membrane plant design for determining cost-effective operations. The genetic algorithm routine searched the predictions of the system model to determine the optimal operating conditions. Fouling conditions induced by the presence of calcium resulted in escalating costs with increases in calcium concentration. Membrane-related cost components were shown to be a significant cost factor that is sensitive to operating conditions and represents a prime target for optimization.     

Use of Dubinin–Astakhov Equation to Describe Preloading Effect of Natural Organic Matter

This note presents a simple model to quantify the preloading effect of naturally occurring organic matter (NOM) in water on the adsorption capacity of activated carbon for a trace synthetic organic chemical (SOC). The model was developed from the Dubinin–Astakhov (DA) equation based on the assumption that the NOM preloading irreversibly reduced the limiting adsorption pore volume for the target SOC. Given that the DA-n value equal to one, the model reduces to a form similar to the one obtained by modifying the Freundlich equation directly. By assuming that the reduction of the limiting adsorption pore volume was proportional to the volume of NOM adsorbed, the NOM preloading effect was correlated directly to the amount of total organic carbon preloaded on the carbon. The resulting model was then compared with the experimental data in the literature. This simple model may be useful for certain practical applications that require only the estimation of the NOM preloading effect on the adsorption capacity of a target SOC from natural water.     

Natural Organic Matter Removal by Adsorption onto Carbonaceous Nanoparticles and Coagulation

Nanoparticles have emerged as promising adsorbents for water purification. In this study, nanoscale carbon black was employed to remove natural organic matter (NOM) from water in the presence and absence of coagulation. Standard Suwannee River NOM was employed as the targeted pollutant. In the absence of coagulation, more than 60% NOM removal was achieved by carbon black adsorption. A higher hydrogen ion concentration (pH) (3–5) was favorable for NOM removal. More than 35% NOM was removed by carbon black adsorption in the first 20 min, and the adsorption of NOM onto carbon black occurred within about 2 h. Proper stirring was essential for the mixture of NOM and carbon black, while insufficient stirring or overstirring decreased NOM removal efficiency. When low dosages of coagulants were used in combination with carbon black at pH 6–7, the removal efficiency of NOM increased significantly. Depending on the coagulant, the sequencing of adsorption and coagulation can be important. Almost 90% NOM was removed in 15 min by carbon black adsorption and alum coagulation, which is a higher removal than for conventional treatment. This study indicated that carbon black might be an important adsorbent for NOM removal in water treatment in combination with low doses of alum.     

Effect of Bromide Ion on Haloacetic Acid Formation during Chlorination of Biscayne Aquifer Water

Water drawn from the Biscayne Aquifer, an extensively used potable water supply source in Florida, was used to study the effect of the bromide ion on haloacetic acid (HAA) formation during chlorination. The source water contained an ambient bromide ion concentration (160 μg∕L) and a substantial concentration of natural organic matter (nonpurgeable organic carbon = 10.9 mg∕L). A systematic evaluation, encompassing a range of bromide ion concentration spikes, and reaction times at fixed pH, chlorine dose, and temperature conditions, was conducted. Two chlorinated HAAs (dichloroacetic acid and trichloroacetic acid), two brominated HAAs (dibromoacetic acid and tribromoacetic acid), and three mixed HAAs (bromochloroacetic acid, bromodichloroacetic acid, and dibromochloroacetic acid) were found. Monobromoacetic acid and monochloroacetic acid were below detection limits in all of the chlorinated samples. In contrast to the findings of previous studies, the molar yield of HAAs increased as the initial bromide ion concentration increased. Concentrations of total HAAs, brominated, and mixed HAAs increased substantially, while chlorinated HAAs decreased slightly, with the addition of the bromide ion.     

Character of Organic Matter in Soil-Aquifer Treatment Systems

The objective of this study was to investigate the character and fate of bulk organics in reclaimed water used for groundwater recharge via soil-aquifer treatment (SAT). The study design followed a watershed guided approach considering hydraulically corresponding samples of drinking water sources, SAT-applied wastewater effluents, and subsequent post-SAT samples representing a series of different travel times in the subsurface. Water samples were fractionated into hydrophobic acids, transphilic acids, and hydrophilic carbon using a XAD resin-based protocol. Extensive characterization of organic carbon in the different samples was performed using state-of-the-art analytical techniques including excitation–emission matrix fluorescence spectroscopy, size exclusion chromatography, carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR), Fourier transform infrared spectroscopy (FTIR), and elemental analysis. During SAT, transphilic and hydrophilic organic matter were preferentially removed. The results generally demonstrated that naturally derived (NOM) and effluent-derived organic matter after SAT overlap extensively in molecular weight distribution, amount and distribution of hydrophobic and hydrophilic carbon fractions, and chemical characteristics based on elemental analysis and 13C-NMR and FTIR spectroscopy. However, the residual portion of the dissolved organic carbon contained both effluent-derived organic matter and NOM.     

Characteristics and Reactivity of Algae-Produced Dissolved Organic Carbon

Algae (green, blue–green, and diatom) grown in inorganic media produced particulate and dissolved organic carbon (DOC). DOC produced by a green-alga contains 25% hydrophobic acids. DOC from all algae had specific ultraviolet absorbance values less than 2.0?m?1?(mg/L)?1. Algae-produced DOC was biologically labile; greater than 60% degraded in bioreactors within 5 days. The biodegradable material likely included carbohydrates, amino acids, and amino sugars, which were present in hydrophobic acid isolates. Chlorination of algal DOC formed disinfection by-products; DOC from the green alga, Scenedesmus quadricauda, produced chloroform [0.53?micromole?per?mg?carbon?(μmol/mg?C)], dichloroacetic acid (0.27?μmol/mg?C), and trichloroacetic acid (0.14?μmol/mg?C). This work complements other studies, which focused on algal total organic carbon (DOC and cellular material), and clearly demonstrates the importance of identifying algae-derived sources of DOC in water supplies and removing such DOC in water treatment plants prior to chlorination.     

Effects of Organic Matter on Physical, Strength, and Volume Change Properties of Compost Amended Expansive Clay

In recent years, the recycling and composting of municipal solid wastes has gained acceptance as an alternative to landfilling and incineration. Compost materials have been used as soil amendments in landscaping, erosion control, expansive soil treatment, and turf management. Compost amended soils are enriched with decomposed organic matter and hence usually exhibit different strength and compressibility in soil behaviors. An experimental investigation was carried out on compost amended soils to understand the effects of decomposed organic matter on strength and volume change properties. Two types of composts, a biosolids compost and a dairy manure compost, and a control cohesive soil were chosen as test materials. Tests conducted on these materials showed that the presence of organic matter enhanced shrinkage resistance and shear strength at low compost proportions (20–30%). At high proportions (beyond 30%), the shear strength reached plateau conditions. One-dimensional vertical swell and secondary consolidation properties increased with an increase in compost proportions. As low proportions of composts yielded better enhancements to most expansive soil properties, it was concluded that compost materials can provide engineering benefits to control soils when used in moderate proportions.     

Modeling the Transformation of Chromophoric Natural Organic Matter during UV/H2O2 Advanced Oxidation

This research developed a differential kinetic model to predict the partial degradation of natural organic matter (NOM) during ultraviolet plus hydrogen peroxide (UV/H2O2) advanced oxidation treatment. The absorbance of 254?nm UV, representing chromophoric NOM (CNOM) was used as a surrogate to track the degradation of NOM. To obtain reaction rate constants not available in the literature, i.e., reactions between the hydroxyl radical (?OH) and NOM, experiments were conducted with “synthetic” water, using isolated Suwannee River NOM, and parameter estimation was applied to obtain the unknown model parameters. The reaction rate constant for the reaction between ?OH and total organic carbon (TOC), k?OH,TOC, was estimated at 1.14(±0.10)×104??L?mg-1?s-1, and the reaction rate constant between ?OH and CNOM, k?OH,CNOM, was estimated at 3.04(±0.33)×104??L?mol-1?s-1. The model was evaluated on two natural waters to predict the degradation of CNOM and H2O2 during UV/H2O2 treatment. Model predictions of CNOM degradation agreed well with the experimental results for UV/H2O2 treatment of the natural waters, with errors up to 6%. For the natural water with additional alkalinity, the model also predicted well the slower degradation of CNOM during UV/H2O2 treatment, owing to scavenging of ?OH by carbonate species. The model, however, underpredicted the degradation of H2O2, suggesting that, when NOM is present, mechanisms besides the photolysis of H2O2 contribute appreciably to H2O2 degradation.     

Comparative Study between a Hybrid System and a Biofilm System for the Treatment of Ammonia and Organic Matter in Wastewaters

The efficiency of two similar gas-lift bioreactors, a biofilm reactor and a hybrid circulating floating bed reactor (CFBR), were studied and compared. In the biofilm CFBR the biomass grew preferably adhered on a plastic granular support, whereas in the hybrid CFBR both suspended biomass and biofilms were allowed to grow in the reactor. COD/NH4+ ratio (COD=chemical oxygen demand) was manipulated between 0.0 and 8.0?g/g, maintaining the ammonia influent concentration around 50?mg N–NH4+/L, the ammonia loading rate at 0.9?kg N–NH4+/m3?day and the hydraulic retention time at 1.36?h. At low COD/NH4+ ratio (0 and 0.5?g/g) both systems behaved similarly, achieving ammonia removal percentages higher than 95%. In the biofilm CFBR a reduction of the nitrification percentage from 95 to 20% was observed when a COD/N–NH4+ ratio up to 8?g/g was applied in the influent. However, at the same operational conditions, the nitrification process in the hybrid CFBR was slightly affected. In the hybrid-CFBR reactor heterotrophs growing in suspension consumed the COD source faster than those growing in biofilms as was monitored. The growth of heterotrophic microorganism in suspension had a beneficial effect for the nitrifying population growing in the biofilm of the hybrid CFBR. Nitrifying activity of the biofilm was not limited by the presence of heterotrophs consuming dissolved oxygen, displacing the nitrifying bacteria or creating mass transfer resistance as was observed in the biofilm CFBR.     

Studies on the Kinetics of Carbon Tetrachloride Chlorination of Refractory Metal Oxides

Studies on the kinetics of chlorination of the oxides of titanium, zirconium, niobium and tantalum by carbon tetrachloride gas in dilution with nitrogen, at low and moderate temperatures, have been carried out. In each case, the effect of time, temperature, partial pressure of carbon tetrachloride and the particle size, on the chlorination of the oxide, has been studied. The influence of some physico-chemical properties of the oxides and their halides on the kinetics process, has been discussed. The chlorination results below and above the dissociation temperature of carbon tetrachloride (～ 773 K) have been examined to find out the difference in the kinetics by CCl₄ and those by elemental carbon and chlorine. From these kinetics results, the mechanism of the chlorination of each of the oxides, has been established and compared. The optimum experimental conditions for preparing the metal chlorides, keeping in view of the maximum utilisation of the carbon tetrachloride, have been established. The merits of carbon tetrachloride as a chlorinating agent, have been highlighted. From these kinetics results, the scope for chlorinating the refractory metal oxides, as well as their mixed oxides, at lower temperatures and lower partial pressures of carbon tetrachloride, with the scope for recycling the reagent, has been briefly discussed. Some preliminary results on the preferential chlorination of these oxides by carbon tetrachloride present in a typical tin slag, have been presented, to further substantiate the merits of carbon tetrachloride as a low temperature chlorinating agent.     

Studies on the Kinetics of Carbon Tetrachloride Chlorination of Refractory Metal Oxides

Abstract

Studies on the kinetics of chlorination of the oxides of titanium, zirconium, niobium and tantalum by carbon tetrachloride gas in dilution with nitrogen, at low and moderate temperatures, have been carried out. In each case, the effect of time, temperature, partial pressure of carbon tetrachloride and the particle size, on the chlorination of the oxide, has been studied. The influence of some physico-chemical properties of the oxides and their halides on the kinetics process, has been discussed. The chlorination results below and above the dissociation temperature of carbon tetrachloride ( ～ 773 K.) have been examined to find out the difference in the kinetics by CC1₄ and those by elemental carbon and chlorine. From these kinetics results, the mechanism of the chlorination of each of the oxides, has been established and compared. The optimum experimental conditions for preparing the metal chlorides, keeping in view of the maximum utilisation of the carbon tetrachloride, have been established. The merits of carbon tetrachloride as a chlorinating agent, have been highlighted. From these kinetics results, the scope for chlorinating the refractory metal oxides, as well as their mixed oxides, at lower temperatures and lower partial pressures of carbon tetrachloride, with the scope for recycling the reagent, has been briefly discussed. Some preliminary results on the preferential chlorination of these oxides by carbon tetrachloride present in a typical tin slag, have been presented, to further substantiate the merits of carbon tetrachloride as a low temperature chlorinating agent.     

NOM在去除MIB、GSM上的作用

文章介绍了引起饮用水臭味的痕量污染物土臭素（geosmin，GSM）和二甲基异冰片（2-methylisobomeol，MIB）的来源和危害。阐述了臭氧氧化、活性炭吸附去除MIB、GSM时的主要影响因素，分析了各因素对去除率的影响程度及原因。     

Crushed Glass-Dredged Material (CG-DM) Blends: Role of Organic Matter Content and DM Variability on Field Compaction

Trial embankments comprised of crushed glass-dredged material (CG-DM) blends and a 100% DM embankment were constructed to provide the necessary data sets to determine if a moisture content (MC) correction was required for the nuclear density (ND) gauge, as DM may contain a high organic matter content (OC). The MCs of thin-walled tube samples of CG-DM blends collected immediately below the ND gauge were compared to the corresponding ND gauge readings. A direct correlation between the MC data pairings from the tube samples and ND gauge readings showed that the ND gauge was greater than 97% accurate for MCs up to 55% and OCs up to 10% for the CG-DM blends evaluated in this study. However, the MC determined by the ND gauge was underpredicted (not overpredicted) by approximately 2.5%, contrary to theoretical expectations. A comparison of the average MC results per embankment indicated that the ND gauge was generally within 1% of the tube sample values, again on the low side. Interestingly, the rutting of the individual embankment lifts, often used as an informal metric for compaction compliance also was found to be contrary to expectations. The (re)constructed CG-DM embankments of this study were again shown to satisfy local Department of Transportation embankment construction criteria in most cases.     

Combined Effects of Aging and Cosolvents on Sequestration of Phenanthrene in Soils

The objective of this study is to investigate the effect of organic cosolvents on the extractability of hydrophobic organic compounds (HOCs) from soils after defined aging periods following HOC contamination. Phenanthrene was used as the representative HOC. Two soils with organic matter contents 2.9 and 6.5%, respectively, were investigated. The soils were spiked with phenanthrene, then saturated in water or mixtures of water and methanol, and aged for up to 422 days. After freeze drying, the extent of phenanthrene release was measured using a mild extraction process. The results show that as aging period increases, phenanthrene removal from the soils becomes more difficult. The amount of easily extractable phenanthrene tended to increase when more methanol existed in the pore fluid during aging, but the difference largely diminished after about 400 days. At the early stage of aging, extraction of phenanthrene from the soil with lower organic matter content tended to be less difficult compared with that from the soil containing more organic matter. The opposite appeared to be true when the aging time was longer than 200 days. From the results, we propose that a shift in the predominant sequestration mechanisms occurred after a certain period of time, in which hydrophobic interactions between HOCs and organic matter gradually yield to physical trapping of the sorbate molecule in the meso- and micropores of the soil particles.     

Simultaneous Removal of Organic Matter and Nitrogen Compounds in Autoaerated Biofilms

This paper describes the simultaneous removal of organic matter and nitrogen compounds carried out using an autoaerated multispecies biofilm growing on gas-permeable hollow-fiber membranes. In order to perform the aerobic heterotrophic oxidation and nitrification processes, the biofilm absorbs atmospheric oxygen through the inside walls of hollow fibers and consumes substrate from the bulk liquid. A mass balance calculated the consumed oxygen. Depending on the removed organic and nitrification rates, the oxygen flux through the hollow fibers can reach up to 90% of the total oxygen consumed, whereas the remaining 10% pertains to the dissolved oxygen from the influent wastewater. Without the biofilm the oxygen transfer rate through clean hollow fibers is 3.5?g?m?2?day?1, whereas the oxygen transfer rate through the biomembrane (hollow fiber+biofilm) achieves a maximum value of 25?g?m?2?day?1. The enhanced oxygen transfer using the biological pathway may be attributed, among many other factors, to the mobility of the microorganisms generating microturbulence, which produces more active bioturbulent diffusiveness than the molecular diffusion in the biofilm. It has also shown that the oxygen utilization efficiency was affected by the substrate utilization rate.     

Competitive Sorption of Pesticides onto Treated Wood Charcoal and the Effect of Organic and Inorganic Parameters on Adsorption Capacity

This paper presents competitive sorption of coexisting pesticides onto treated wood charcoal and describes the effect of various water quality parameters, viz., pH, ionic strength, chloride concentration, presence of calcium and magnesium, fertilizers, humic acid, polyacrylic acid, and also the effect of coexisting pesticides on the sorption of endosulfan onto treated wood charcoal. The coexisting pesticides were found to hinder the performance of wood charcoal in removing endosulfan. Competitive uptake study revealed that endosulfan occupies more sites followed by atrazine and monocrotophos. Solubility in water could be one of the major reasons for this preferential order. The presence of humic acid was found to show much more significant influence on the performance of wood charcoal than the presence of polyacrylic acid. Among fertilizers, single superphosphate was found more influential. Most of it, among the other reasons, could be due to the competition of the coexisting molecules for the available adsorption sites on wood charcoal. Other parameters have resulted in some fluctuations in performance, but the effects are not significant. Endosulfan removal efficiency faltered at higher pH values, and ionic species did not affect the sorption as endosulfan is nonionic under neutral conditions.     

Enhancing the Biodegradation of Polycyclic Aromatic Hydrocarbons: Effects of Nonionic Surfactant Addition on Biofilm Function and Structure

The application of surfactants for the bioremediation of sites contaminated with polycyclic aromatic hydrocarbons has been widely reported, because they are known to increase PAH solubility and desorption, thereby enhancing their bioavailability to biofilm microorganisms. The effects of a nonionic surfactant on the biodegradation of PAHs in porous media, as well as the fate of the surfactant, were investigated in this study. Column experiments in the presence of the surfactant showed that the degradation of the two-ring PAH alone was not significantly affected, but that there was a small enhancement of three- and four-ring PAH degradation when they were present as sole substrates and when using Triton X-100. This was due to the higher solubility of the PAHs in the presence of the surfactant. Biofilm seemed to respond well to binary mixtures of phenanthrene–naphthalene and pyrene–naphthalene, with removals of 45.5 and 24.1%, respectively, in the presence of the surfactant; however, higher biodegradations were always achieved by having just PAH mixtures without the surfactant, indicating the importance of cometabolic mechanisms over improved solubilization of PAHs. Optical sections taken using a confocal laser scanning microscope allowed observation of a heterogeneous web-like matrix of biofilm, with diverse biological aggregate structures.     

Impact of Booster Chlorination on Chlorine Decay and THM Production: Simulated Analysis

The effect of conventional and booster chlorination on chlorine residuals and trihalomethane (THM) formation in drinking water distribution systems was modeled using the EPANET hydraulic modeling software. The model results suggest that booster chlorination may allow utilities to meet disinfection goals better by carrying chlorine residuals to remote points in the distribution system while lowering the total mass of chlorine applied to the system. The model results suggest that booster chlorination may provide the greatest advantages to points in the distribution system located near storage tanks by providing a more consistent chlorine residual and possibly reducing THM formation. A new version of the EPANET model, the EPANET Multispecies model, was also used to compare chlorine decay due to reactions in the bulk fluid and reactions occurring at the pipe wall. The results suggest that chlorine decay due to wall reactions can be very significant at remote points in the distribution system. Additionally, if THMs are assumed to form primarily through reactions in the bulk fluid, use of the new EPANET Multispecies software allows for calculation of THM formation based solely on chlorine reactions in the bulk fluid rather than on overall chlorine decay.     

磷石膏水洗液中磷、氟、有机物的去除

研究了煤质炭、果壳炭和秸秆灰三种吸附材料对模拟溶液中磷、氟、有机物的去除效果,并进行了磷石膏水洗液中多种污染物同步去除研究。结果表明：三种吸附材料对磷和氟的去除效果为秸秆灰>煤质炭>果壳炭,对有机物的去除效果为煤质炭>秸秆灰>果壳炭,强酸条件有利于磷和氟的去除,但对有机物去除影响不大。秸秆灰对磷、氟和煤质炭对有机物的吸附过程均符合二级动力学模型和Langmuir模型,其理论最大吸附量分别为磷88.20 mg/g、氟63.98 mg/g、有机物131.32 mg/g。120 g/L秸秆灰与50 g/L煤质炭同时投加至磷石膏水洗液中反应120 min后,污染物剩余浓度为磷9.57 mg/L、氟12.88 mg/L、有机物31.86 mg/L,反应后pH为8.95,满足《磷肥工业水污染物排放标准》（GB 15580—2011）要求。秸秆灰对溶液中磷、氟等阴离子的去除机理为静电吸附和化学沉淀,煤质炭对溶液中有机物的去除机理为离子交换和物理吸附。