A new method for the evaluation of the reversible and irreversible fouling propensity of MBR mixed liquor

In this paper, a new fouling measurement method is presented as a pragmatic approach to determine a mixed liquor's fouling propensity. The MBR-VFM (VITO Fouling Measurement) uses a specific measurement protocol consisting of alternating filtration and physical cleaning steps, which enables the calculation of both the reversible and the irreversible fouling resistances. The MBR-VFM principle, set-up and measurement protocol are described as well as the evaluation of the fouling measurement method. Finally, the MBR-VFM was validated by comparing the fouling propensity measured on-line by the MBR-VFM in a lab-scale MBR with the fouling of the MBR membranes themselves. Our experiments indicated that the MBR-VFM can accurately measure fouling and that it can even be detected earlier than can be seen from the on-line filtration data of the lab-scale system itself. Furthermore, the differences measured in reversible and irreversible fouling seemed to be related to the observed impact of physical and chemical cleaning respectively. Therefore, the application of the MBR-VFM as an on-line sensor in an advanced control system, enabling the deployment of the measured fouling data for the control of membrane cleaning, seems feasible and will be tested in the near future.     

Effects of polyether–polyamide block copolymer coating on performance and fouling of reverse osmosis membranes

The effects of a water-permeable polymer coating on the performance and fouling of high-flux (ESPA1 and ESPA3) and low-flux (SWC4) polyamide reverse osmosis (RO) membranes were investigated. It was anticipated that the coating would create a smoother hydrophilic surface that would be less susceptible to fouling when challenged with a motor-oil/surfactant/water feed emulsion (used as a model foulant). AFM and FT-IR analyses confirm that a 1 wt.% polyether–polyamide (PEBAX^® 1657) solution applied to ESPA and SWC4 membranes produces a continuous polymer coating layer and, thereby, provides smoother membrane surfaces. However, pure-water permeation data combined with a series-resistance model analysis reveal that the coating does not only cover the surface of the polyamide membrane, but also penetrates into its porous ridge-and-valley structure. During a long-term (106-day) fouling test with an oil/surfactant/water emulsion, the rate of flux decline was slower for coated than for uncoated membranes. This improvement in fouling resistance compensated for the decrease in permeate flux for SWC4 over a period of approximately 40 days. However, the coating material is believed to penetrate more deeply into the polyamide surface layer of the high flux, high surface area ESPA membranes relative to the low-flux SWC4, resulting in significant water flux reduction.     

Effect of solution chemistry on the fouling potential of dissolved organic matter in membrane bioreactor systems

Dissolved organic matter (DOM) as a potent foulant in membrane bioreactor (MBR) systems has attracted great attention in recent years. This paper attempts to elucidate the effect of solution chemistry (i.e. solution pH, ionic strength, and calcium concentration) on the fouling potential of DOM with different characteristics. Results of microfiltration experiments showed that the fouling potential of DOM having higher hydrophobic content increased more markedly at low pH due to the reduced ionization of carboxylic and phenolic functional groups of aquatic humic substances. In contrast, the fouling potential of hydrophilic DOM components and the molecular size of DOM appeared to be less affected by solution pH. The more compact molecular configuration of DOM at high ionic strength contributed to form a denser fouling layer, and limited the amount of foulants retained by the membranes on the other hand. DOM fouling potential greatly increased with increasing calcium concentration. The magnitude of the increase, however, was independent of the hydrophobicity of DOM, suggesting strong interactions exist between calcium ions and hydrophilic DOM components. Moreover, it was observed that the main mechanism governing the effect of calcium ions on the molecular size of DOM transited from charge shielding to complex formation as calcium concentration increased.     

Reversed-phase ion-pair systems to predict partition coefficients of β-carbolines by HPLC and TLC

Summary A group of 17 β-carbolines was studied in HPLC and TLC systems in order to predict their partition coefficients (log P values). On account of the basic or acid character of some of these compounds, an ion pairing system gave the best results. Both HPLC and TLC data were comparable for log P prediction but severe pH conditions required the use of TLC plates. Retention data are quantitatively related to lipophilicity (expressed as the Hansch constant) and polarity (as the inductive constant) of the solute molecule.     

Novel ultrafiltration membranes with the least fouling properties for the treatment of veterinary antibiotics in the pharmaceutical wastewater

Dendrimers have received more attention in all fields of research these days. In the present study, polyamidoamine (PAMAM) dendrimers were synthesized on the acrylic ultrafiltration membranes to minimize fouling as an important deficiency in the separation process. The antifouling activity of these dendrimers with different generations (G0‐3) was tested to restrict three macrolides (tylvalosin, tylosin, and tulathromycin) and two pleuromutilins (tiamulin and valnemulin) as veterinary antibiotic drugs with amine groups and positive charges at pH = 7 of the membrane surface. These compounds are risky for human consumption. Due to having several amine functional groups and branches, PAMAM dendrimers can be a great coating agent for antifouling. G3 PAMAM dendrimer‐coated membranes had the best performance (water flux: 130.7 L/m²·h, rejection of tulathromycin: 91.4%, flux recovery ratio: 86.3%). The function of this ultrafiltration process depended on pore size and also charge surface. A significant reduction for irreversible and reversible fouling was observed for this new ultrafiltration membrane (F_ir: 14.5%, F_re: 21.9%). This observation was confirmed by the power law model. Three 5‐hour cycle ultrafiltration processes were carried out for veterinary antibiotic wastewater that showed 3.18% loss of initial water flux (for the third cycle), final cleaning efficiency of 96.82%, and tylvalosin rejection of 94.1%.     

Determination of inorganic nickel compounds in the particulate matter of emissions and workplace air by selective sequential dissolutions

A speciation method of inorganic nickel compounds in airborne particulate, based on selective sequential extractions, is described. It allows the separation and the determination of Ni(0), Ni(II) soluble salts such as sulphate and chloride, Ni insoluble compounds such as nickel oxide and sulphide, to which a different toxicity and therefore a different risk are related. The nickel concentration in each fraction was determined by Flame or Furnace Atomic Absorption Spectroscopy. The proposed procedure has been tested first, on synthetic samples prepared with the different nickel compounds, in the presence of atmospherical particulate matter not containing nickel, in order to take into account the possible matrix influence. The speciation was then repeated on four different samples (fly ash deriving from a solid waste incinerator and three RSMS from NIST: Coal Fly ash SRM 1633b, Urban Particulate 1648, Washington Dust 1649), followed by an evaluation of matrix spiking and recovery analyses. Performing multiple analyses of the spiked samples assessed the repeatability of the procedure.     

Chemical characterization of selected metals by X-ray fluorescence method in particulate matter collected in the area of Krakow, Poland

This study presents the results of year long (2007–2008) particulate matter collecting campaigns. The three particle size fractions of particulate matter were collected in Krakow, Poland. Fine fraction consists of particles of a diameter below 2.5 µm, medium is between 2.5 and 8 µm and coarse fraction contains particles above 8 µm. Elemental concentrations were evaluated for each sample. Following elements were measured by EDXRF method: K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, and Pb. During each sampling campaign meteorological parameters such as temperature, wind speed, wind direction, humidity were taken from the same place. The highest values of mass particulate matter showed results from January 2008 and April 2008. These were about 14 µg/m³ for fine fraction, 8 µg/m³ for medium and 16 µg/m³ for coarse fraction. The lowest values were observed in May 2007, they were 4, 6, 6 µg/m³, respectively. During the winter season the wind speed was low and particulate matter remained in the air in high concentrations. In May 2007 the speed of wind was higher, reaching 2–3 m/s. PM was blown away from the city from the direction of N–W. Measured concentrations of elements were low, they were below permissible values specified by EU. The coarse fraction concentrations of Ca, Mn, and Fe were higher and characterized by the same trend. These samples were collected when the wind speed was low and its direction was from south-east. As concentrations of Cr, Cu, and Zn were low, these elements did not come from the south-east direction of Krakow. Concentration of Br correlates to the concentration of Pb. It suggests that they came from the same source (vehicles fuels burning).     

A systematic insight into fouling propensity of soluble microbial products in membrane bioreactors based on hydrophobic interaction and size exclusion

Soluble microbial products (SMPs) contained in membrane bioreactor (MBR) supernatant have been proved to be main foulants. To obtain a comprehensive understanding of the fouling potential of SMPs on the basis of both hydrophilic/hydrophobic properties and molecular size, MBR supernatant of a pilot-scaled system treating municipal wastewater was partitioned into different hydrophilic/hydrophobic fractions by DAX-8 resins, with joint size partition of hydrophilic fraction also undertaken. A series of stirred dead-end filtration tests were conducted to investigate the flux decline. Hydrophilic fraction was found the dominant foulant responsible for flux deterioration, which was mainly attributed to the subclass of molecular weight above 100 kDa. The molecular weight distribution and atomic force microscopy images indicated that large molecules in hydrophilic fraction plugged the membrane pores. The backwash tests showed the flux decline caused by hydrophilic fraction was much less recoverable by hydraulic cleaning. It can be inferred that steric factor, i.e. size exclusion was the primary cause in the initial stage of fouling, while the role of hydrophobic interaction was of less significance. Additional modeling work indicates that the main fouling mechanism was complete blocking, further confirming the predominance of size exclusion contributing to membrane fouling by SMPs in MBR supernatant.     

Organic and inorganic fouling at quartz-liquid interface in ultraviolet photoreactors during on-line sterilization of cheese whey

This article reports on lamp fouling during on-line ultraviolet (UV) sterilization of cheese whey. The extent of fouling as well as the composition of fouling materials was studied after the operation of three tubular UV reactors of different flow thicknesses (18, 13, and 6 mm) for 48 h at a 2-h residence time. Lamp fouling, which significantly affected the sterilization efficiency, was realized after an extended period of operation. The extent of lamp fouling increased with a decrease in the thickness of the flowing cheese whey (14.42, 15.31, and 25.25 g for 18-, 13-, and 6-mm thickness, respectively). A strong relationship between the extent of fouling and the steady-state outlet temperature was observed. The rouling material contained 63.51 to 77.19% protein, 12.57 to 16.49% fat and 6.51 to 9.47% minerals on dry weight bases compared with 1% protein, 0.5% fat, and 0.4% minerals in raw cheese whey. The organic and inorganic material concentrations in the fouling material increased with a decrease in the flow thickness. The fouling mechanism was owing to adsorption and direction exchange, which were enhanced by the high temperature and low pH attained in the study. Improved designs of UV reactors in which the contact between the flowing material and the quartz surface should be developed.     

Optimization of a portable microanalytical system to reduce electrode fouling from proteins associated with biomonitoring of lead (Pb) in saliva

There is a need to develop reliable portable analytical systems for on-site and real-time biomonitoring of lead (Pb) from both occupational and environmental exposures. Saliva is an appealing matrix since it is easily obtainable, and therefore a potential substitute for blood due to existing reasonably good correlation between Pb levels in blood and saliva. The microanalytical system is based on flow-injection/stripping voltammetry with a wall-jet (flow-onto) microelectrochemical cell. Samples that contain as little as 1% saliva can cause electrode fouling, resulting in significantly reduced responsiveness and irreproducible quantitations. In addition, incomplete Pb release from salivary protein can also yield a lower Pb response than expected. This paper evaluates the extent of in vitro Pb-protein binding and the optimal pretreatment for releasing Pb from the saliva samples. Even in 50% by volume of rat saliva, the electrode fouling was not observed, due to the appropriate sample pretreatment and the constant flow of the sample and acidic carrier that prevented passivation by the protein. The system offered a linear response over a low Pb range of 1-10 ppb, low detection limit of 1 ppb, excellent reproducibility, and reliability. It also yielded the same Pb concentrations in unknown samples as did the ICP-MS. These encouraging results suggest that the microanalytical system represents an important analytical advancement for real-time non-invasive biomonitoring of Pb.     

Applications of isothermal titration calorimetry to measure enzyme kinetics and activity in complex solutions

The application of isothermal titration calorimetry (ITC) was tested towards measurements of enzyme kinetics in complex solutions containing high concentrations of proteins. Such investigations are important, due to the increasing interest in biochemical reactions in physiological relevant media as well as the application of enzymes in industrial processes. In contrast to spectral methods, measurements performed with ITC, are independent of the optical properties of solutions, making it possible to measure enzyme kinetics in concentrated solutions of macromolecules. In this study the kinetic properties of hexokinase was investigated in concentrated protein solutions (BSA). It was found, that the quality of the measured kinetic data was independent of protein concentration in the investigated range (0-250 mg BSA ml⁻¹). All results could be accounted for by Michaelis-Menten's approach and both k_cat and K_M decreased with increasing protein concentrations. The decrease in K_M with increasing protein concentration was ascribed to an increase in the ratio of activity coefficients between the native enzyme and the enzyme-substrate complex. The decrease in k_cat with increasing protein concentrations indicates that crowding by BSA effect the conformational changes/rehydration that accompanies catalysis and/or diffusion of product from the enzyme-product complex. The methodology is discussed together with an analysis of the experimental results.     

Decarbonation and preservation method for the analysis of organic C and N contents and stable isotope ratios of low-carbonated suspended particulate material

The aim of this study was to determine a simple routine procedure to preserve, decarbonate and analyse low-carbonated filters of suspended particulate organic matter (POM) for particulate organic carbon and nitrogen content, and . Our goal was to analyse these four parameters from a single and entire filter of POM without altering the organic material.First, freezing (−20 °C) versus oven-drying (60 °C) were compared as the initial preservation step. Afterwards, non-acidified samples were compared to acid-treated samples using 0.12N HCl (diluted HCl rinsing at the end of the filtration) or 12N HCl (filters exposed to HCl fumes for 4 h in a dessicator). Regarding the preservation methods, our results indicate that freezing increases the uncertainty of measurements and, in combination with concentrated HCl treatment, leads to a loss of particulate nitrogen and an alteration of the signature. Consequently, we recommend drying to preserve filter samples. Regarding acid treatments, we found that (i) diluted HCl would not be sufficient to fully remove the carbonate from our samples, (ii) in contrast, a 4 h exposure of the filters to the HCl fumes was enough to remove all the inorganic carbon, and (iii) the concentrated HCl treatment did not alter the nitrogen measurements (only when drying without freezing is used to preserve the filters). Consequently, we propose that low-carbonated POM filters are preserved by drying and carbonates are removed by exposing the filters to HCl fumes (4 h) for the analysis of particulate organic C and N content and isotope ratios.     

Speciation of antimony in airborne particulate matter using ultrasound probe fast extraction and analysis by HPLC-HG-AFS

A fast extraction procedure has been developed for Sb(III) and Sb(V) oxoanions speciation in airborne particulate matter samples. Different extraction media (diammonium tartrate, hidroxilammonium clorhidrate, citric acid + ascorbic acid, phosphoric acid and citrate solutions) were tried, with assistance of an ultrasonic probe. The operation power and time of extraction were also optimized. The higher extraction recoveries were obtained with a 100 mmol L⁻¹ hidroxilammonium clorhidrate aqueous solution assisted by the ultrasound probe operated at 50 W during 3 min. The extracts were analyzed by HPLC-HG-AFS. The chromatographic separation of Sb(III) and Sb(V) was also optimized using diammonium tartrate and phthalic acid as mobile phases. The separation of both Sb species was performed in less than 3 min under isocratic conditions, using a 200 mmol L⁻¹ diammonium tartrate solution. The proposed extraction procedure and the HPLC-HG-AFS instrumental coupling have been successfully applied to airborne particulate matter samples, with high Sb content, collected in heavy traffic streets from Buenos Aires (Argentina). The results showed the presence of both Sb species at similar concentrations in the ng m⁻³ level. The extraction yield was higher than 90% for all the analyzed samples.     

两种前处理方法应用于气相色谱-质谱联用测定水产品中三氯杀螨醇残留量

建立了两种样品前处理方法应用于气相色谱串联质谱法测定水产品中三氯杀螨醇残留量。样品经氯化钠配合乙腈/水均质研磨,超声辅助提取,提取液经净化后,供气相色谱-质谱联用(GC/MS)分析。采用选择离子扫描方式(SIM),外标法定量。在优化前处理和上机条件下测试,三氯杀螨醇检出限(S/N≥10)为0.006mg/kg,在加标水平0.01～0.10mg/kg范围内,方法Ⅰ的回收率为76.8%～110.3%,RSD为3.06%～9.43%;方法Ⅱ的回收率为76.6%～100.4%,RSD为3.21%～8.35%。该方法的准确度和精密度符合农残分析要求,可为我国水产品出口提供技术支持。     

Development of a systems analysis approach for resolving the structure of biodegrading soil systems

An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption, and biodegradation of napththalene.     

Application of the extended LJ potential-based equation of state to predict the density of five different classes of refrigerant systems (HCFCs,HFCs, HFEs,PFAs, and PFAAs)

The major goal of this work is to apply the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) to predict the density of five different classes of refrigerant systems including chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers, perfluoroalkanes, and perfluoroalkylalkane. This EoS is based on an effective near-neighbor pair potential of the Lennard-Jones (12,6,3) type. The temperature dependencies of the parameters of the equation of state can be calculated at any temperature for each refrigerant. The calculated parameters along with the ELJ-based EoS have been used to calculate the density and isothermal compressibility coefficient of different refrigerants. A comparison between the predicted results and experimental data shows that the agreement is good. The total absolute average deviation of density for 14,871 data was found to be 0.34 compared with experimental data. Comparisons with the other EoSs show that the ELJ-based EoS is more accurate than other EoSs for most of the studied refrigerants.     

Failure of the CNDO/2 method to predict the barriers and conformations in some conjugated systems

The potential functions for rotation about the CC single bonds in glyoxal, 1,3-butadiene, benzaldehyde, biphenyl, and 2,2′-difluorobiphenyl have been calculated by the CNDO/2 method.     

Experimental realization of sustained simple kinetic regimes of release of particulate solutes subject to slow dissolution in the containing matrix

We examine the short-time and long-time limiting cases of the general equation commonly used to describe the kinetics of release of a particulate solute embedded in a planar solid matrix, complicated by slow dissolution of the particles in the matrix. The conditions under which the said limiting cases may be expected to yield sustained simple kinetic regimes of solute release in practice are determined. Finally an experimental illustration of the (simultaneous) occurrence of both simple regimes in a single system (consisting of strongly soluble and sparingly soluble salts embedded in an emulsified asphalt matrix) is given.     

聚苯胺修饰碳纤维超微pH传感器研究及其在植物柱头活体测试中的应用

作为探测生命奥秘的重要手段,微电极技术已广泛应用于活体分析[1－3]．传统的pH玻璃电极难以实现活体微区或微环境分析,因此,研制微型和超微型pH传感器意义重大．本文采用电化学聚合法将聚苯胺修饰在碳纤维微柱电极上,制成对pH具有能斯特响应的超微型pH传感器,与pH玻璃电极比较,发现它具有响应快、稳定性高、重现性好及选择性高等特点．用该超微pH传感器首次实现了对答苔属植物活体柱头乳突细胞和花粉粒表面微环境的pH值测定．为生物学家深入研究花粉萌发的生理过程和机理提供了十分有用的信息．1实验部分1．1仪器和试剂M366双恒…     

Calix[4]resorcinarenetetrathiol Modified Gold Electrodes: Applications to the Adsorption and Electrochemical Determination of N‐Nitrosamines

Preliminary results reported in this paper relate to the capture, retention and subsequent analysis of cationic N‐nitrosamines, from aqueous solutions, at calix[4]resorcinarenetetrathiol modified gold electrodes. Adsorptive stripping voltammetric regimes at electrodes of this type have allowed quantifications of N‐nitroso‐N‐butyl‐N‐propylamine down to concentrations of 10^?10 M. Calix coatings have been shown, in certain cases, to allow an enhancement in the adsorptive uptake and subsequent analysis of N‐nitrosamines in solution in comparison to signals obtained at bare gold electrodes, although the coatings may become saturated when higher concentrations or when longer preaccumulative deposition times are employed.