Charge and separation characteristics of nanofiltration membrane embracing dissociated functional groups

The current work focused on the investigation of charge and separation characteristics of nanofiltration （NF） membrane embracing dissociated functional groups under different electrolyte solutions. The electro-kinetic method was carried out to assess the membrane volume charge density （X） with different salt concentrations ranging from 0.1 to 10 mol. m-3 and different electrolyte species, such as type 1-1, type 2-1 and type 3-1. The Donnan steric pore model-dielectric exclusion （DSPM- DE） model was employed to evaluate the separation characteristics of the NF membrane for wide range of electrolyte concentration （from 25.7 to 598.9mol·m^-3）. The results indicated that the dissociation of the hydro- philic functional groups and the specific adsorption contributed to charge formation on membrane surface. The former played a dominant role in type 1-1 and type 2-1 electrolytes at dilute aqueous solutions （0.1-0.5 mol · m^3）. However, for type 3-1 electrolyte, specific adsorp- tion should contribute to the charge effect to a large extent. Moreover, the correlation between the volume charge density and feed concentration was in accordance with Freundlich isotherm. Furthermore, it was found that the separation characteristic of NF membrane could be evaluated well by DSPM-DE model coupling with electro-kinetic method in a whole concentration range.     

A model of 90Sr distribution in the sea near Daya Bay Nuclear Power Plant in China

The impact on the environment ofradionuclide release from nuclear power plants has attracted increased attention, especially after the accident at Fukushima Daiichi Nuclear Power Plant in Japan. Based on the mechanisms of adsorption/desorption at solid/liquid interfaces and a surface micromorphology model of sediments, a theoretical expression of the distribution coefficient Kd is derived. This coefficient has significant effects on the distribution of radionuclide in seawater, suspended sediment and seabed sediment. Kd is then used to simulate ^90Sr transport in the sea near the Daya Bay Nuclear Power Plant. The simulation results are compared with field measurements of tidal level, current velocity, suspended sediment concentration and ^90Sr concentrations in the same period. Overall, the simulated results agree well with the field measured data. Thus, the derived expression for Ka is capable of interpreting realistic adsorption/desorption processes. What＇s more, conclusion is drawn that about 40% ^90Sr released by Daya Bay Nuclear Power Plant will be adsorbed by suspended sediment and 20% by seabed sediment, only about 40% ^90St will remain in the sea near Daya Bay Nuclear Power Plant in South China Sea.     

Effects of phosphorus concentration on Cr（VI） sorption onto phosphorus-rich sludge biochar

To investigate effects of phosphorus content on Cr（VI） sorption onto phosphorus-rich biochar, sewage sludge of different phosphorus concentrations from 4 to 60 mg.g-1 by dry weight were prepared and carbonized to make biochar for batch sorption experiments. Test results revealed that different phosphorous concentration of raw sludge had respective impacts on surface area, pore surface area, average pore diameter and pH value of derived biochar. The adsorption kinetics of phosphorus-rich biochar could be described by the pseudo-second-order model. The sorption isotherm data followed Langmiur model better than Freundlich model. Biochar produced from sludge with phosphorus concentration of 20 mg. gl gave the largest chromium sorption capacity, which could be attributed to its largest surface area and pores surface area comparing with those of＇biochars from sludge with other phosphorus concentrations. The chromium loaded biochar was analyzed using Fourier Transform Infrared Spectroscopy and X-ray Diffraction measurement. The results indicated that chemical functional groups hydroxyl and methyl on surface of biochar were involved in Cr（VI） binding and its reducing to Cr（III）. Then, a portion of Cr （III） in form of various phosphate precipitates was bound onto biochar surface and the rest was released into the solution. The experimental results suggested that phos- phorus played an important role in pore and surface area development of sludge biochar during pyrolytic process. It also could react with Cr（III） on the biochar surface that impacted on capacity of Cr（VI） removal from solution by sludge biochar. Therefore, phosphorus concentration in sludge should be considered when sludge pyrolytic residue would be reused for heavy metals sorbing.     

Genotoxic Effect of Phenol on the Cells of Onion (Allium cepa) Roots

The roots of onion (Allium cepa) stand out for having cells with large size and small number of chromosomes.These characteristics make them useful in bioassays for the measurement of a variety of cytogenetic and morphological parameters , in which they can be used as toxicity indicators of the induction and formation of micronuclei and chromosomal aberrations.Based on this background , the potential genotoxic effect of phenol concentration on cells of A.ceparoots was investigated either in terms of induced aberrations or micronuclei formation.The results demonstrated that the higher the concentration of phenol , the higher the incidence of abnormalities , thus confirming the genotoxicity of this pollutant.     

Controlling microbiological interfacial behaviors of hydrophobic organic compounds by surfactants in biodegradation process

Bioremediation of hydrophobic organic compounds （HOCs） contanlinated soils involves several physicochemical and microbiological interracial processes among the soil-water-microorganism interfaces. The participation of surfactants facilitates the mass transport of HOCs in both the physicochemical and microbiological interfaces by reducing the interfacial tension. The effects and underlying mechanisms of surfactants on the physi-cochemical desorption of soil-sorbed HOCs have been widely studied. This paper reviewed the progress made in understanding the effects of surfactant on microbiological interlhcial transport of HOCs and the underlying mechanisms, which is vital for a better understanding and control of the mass transfer of HOCs in the biodegradation process. In summary, surfactants affect the microbiological interfacial behaviors of HOCs during three consecutive processes： the soil solution-microorganism sorption, the transmembrane process, and the intracellular metabolism. Surfactant could promote cell sorption of HOCs depending on the compatibility of surfactant hydrophile hydrophilic balance （HLB） with cell surface properties; while the dose ratio between surfactant and biologic mass （membrane lipids） determined the transmembrane processes. Although surfactants cannot easily directly affect the intracellular enzymatic metabolism of HOCs due to the steric hindrace, the presence of surfactants can indirectly enhanced the metabolism by increasing the substrate concentrations.     

Effects of shear force on formation and properties of anoxic granular sludge in SBR

This paper reports the effects of shear force on anoxic granular sludge in sequencing batch reactors （SBR）. The study was carried out in two SBRs （SBR1 and SBR2） in which sodium acetate （200mg COD·L^-1） was used as the sole substrate and sodium nitrate （40 mgNO3-N·L^-1） was employed as the electron acceptor. The preliminary objective of this study was to cultivate anoxic granules in the SBR in order to investigate the effects of shear force on the formation of anoxic granular sludge and to compare the properties of anoxic sludge in the SBR. This study reports new results for the values of average velocity gradient, a measure of the applied shear force, which was varied in the two SBRs （3.79 s^-1 and 9.76 s^-1 for SBR1 and SBR2 respectively）. The important findings of this research highlight the dual effects of shear force on anoxic granules. A low shear force can produce large anoxic granules with high activity and poor settling ability, whereas higher shear forces produce smaller granules with better settling ability and lower activity. The results of this study show that the anoxic granulation is closely related to the strength of the shear force. For high shear force, this research demonstrated that： 1） granules with smaller diameters, high density and good settling ability were formed in the reactor, and 2） granular sludge formed faster than it did in the low shear force reactor （41days versus 76 days）. Once a steady-state has been achieved, the nitrate and COD removal rates were found to be 98% and 80%, respectively. For low shear force, such as was applied in SBR1, this research demonstrated that： 1） the activity of anoxic granular sludge in low shear force was higher than that in high shear force, 2） higher amount of soluble microbial products （SMPs） were produced, and 3） large pores were observed inside the larger granules,which are beneficial for nitrogen gas diffusion. Electron microscopic examination of the anoxic granules in both reactors showed that the morphology of the granules was ellipsoidal with a clear outline. Coccus and rod-shaped bacteria were wrapped by filamentous bacteria on the surface of granule.     

Quantitative characterization of Cu binding potential of dissolved organic matter （DOM） in sediment from Taihu Lake using multiple techniques

Dissolved organic matter （DOM） plays an important role in heavy metal speciation and distribution in the aquatic environment especially for eutrophic lakes which have higher DOM concentration. Taihu Lake is the third largest freshwater and a high eutrophic lake in the downstream of the Yangtze River, China. In the lake, frequent breakout of algae blooms greatly increased the concentration of different organic matters in the lake sediment. In this study, sediment samples were collected from various part of Taihu Lake to explore the spatial difference in the binding potential of DOM with Cu. The titration experiment was adopted to quantitatively characterize the interaction between Cu（II） and DOM extracted from Taihu Lake sediments using ion selective electrode （ISE） and fluorescence quenching technology. The ISE results showed that the exogenous DOM had higher binding ability than endogenous DOM, and DOM derived from aquatic macrophytes had a higher binding ability than that derived from algae. The fluorescence quenching results indicated that humic substances played a key role in the complexation between DOM and Cu（II） in the lake. However, because of the frequent breakout of algae blooms, protein-like matters are also main component like hnmic matters in Taihu Lake. Therefore, the metals bound by protein-like substances should be caused concern as protein-like substances in DOM were unstable and they will release bound metal when decomposed.     

Assessment of metals in dry-toilet collected matters from suburban areas of Ulaanbaatar,Mongolia, using biosolids quality guidelines and potential ecological risk index

Dry-toilet collected matter （DCM） from traditional dry-toilet pits are a potential health and ecological risk in suburban areas. In this study, the characteristics of metals in DCMs from suburban areas of Ulaanbaatar were surveyed. The results indicate that DCMs contain a high percentage of organic matter and nutrients, while heavy metals are at low levels, which shows good agricultural potential. The concentration ranges of Cr, Cu, Hg, Ni, Pb, and Zn were 11±5, 46±9, 0.08±0.05, 9±3, 17±9, and 338±86mg·kg^-1, respectively. The concentration of Cd was below 0.5 mg.kgl, and a high positive relation was shown between chromium and nickel concentrations. The heavy metals in DCMs were safe for land application but Zn in DCMs was close to the effects range median （ERM）, which is toxic in some cases, such as amphipod bioassays. Because it is mandatory to treat DCMs to reduce pathogens, in the case of heavy metal enrichment and agricultural reuse, composting or pyrolysis are better choices than incinera- tion. Compared with global soil background values, the heavy metals in DCMs showed a low level of ecological risk, but a medium level when compared with Mongolian soil background values. The ecological risk of six heavy metals was in the descending order Hg 〉 Cu 〉 Zn 〉 Pb 〉 Ni 〉 Cr and the contribution rate of Hg exceeded 60%.     

Isolation,identification, culture conditions,and laccase production of white rot fungus北大核心CSCD

The white rot fungi are members of Basidiomycota, which can degrade lignin and form white rot. They are high producers of extracellular laccases. In the present study, pure culture strain of high-temperature and high-laccase production types (numbered as BUA-01) was isolated from the fruiting bodies of a white rot fungus collected in the campus of Beijing University of Agriculture. The taxonomic characteristic was determined based on morphological and ITS sequence analysis. Furthermore, the optimal culture conditions for the mycelia were determined, including carbon source, nitrogen source, C/N ratio, growth factors, temperature, and pH. Extracellular laccase production was investigated in liquid fermentation with different concentrations of Cu (CuSO4) as inducer. Decolorizing activity of the fermentation broth was assayed using three azo dyes: Evans blue, methyl orange, and eriochrome black T. The results showed that the strain possessed the highest homology toward Trametes hirsuta, with the homology ratio of 100% and the genetic distance of 0, suggesting that the strain BUA-01 belonged to the genus Trametes. The culture condition investigated revealed that the optimal condition for mycelia growth included the following: carbon source, starch; nitrogen source, soybean powder and yeast extract; C/N ratio, 40/1 and 10/1; temperature, 37 °C; and pH, 6.0-7.0. The assayed growth factors had no significant effect on mycelial growth. It demonstrated high laccase activity in liquid fermentation. The highest extracellular laccase activity of 1 081.33 ± 6.3 U/mL was observed in the broth with a Cu adjunction concentration of 0.25 mmol/L after a 96-h culture period. It was about 26-fold higher than that of the control group. The isolated strain exhibited significant decolorizing activity toward the azo dyes Evans blue, methyl orange, and eriochrome black T, with the decolorization rate at 12 h of 93.31% ± 0.16%, 92.37% ± 0.42%, 79.25% ± 0.64%, respectively. This suggests that the strain possesses potential applications in laccase production and dye degradation. © 2018 Science Press. All rights reserved.     

Effect of environmental forcing on the fate of nutrients, dissolved organic matter and heavy metals released by a coastal wastewater pipeline

Discharges of nutrients, urea, dissolved organic matter and heavy metals by a sewage underwater pipeline are analysed in comparison to environmental conditions in a shallow coastal zone. Variable thermo-haline stratifications of the water column and currents in upper (2.62-34.97 cm s^-1) and deeper (0.83-10.91 cm s^-1) layers drive vertical diffusion and lateral transport of wastewaters. Loads of reactive phosphorus (0.13 tons d^-1) and ammonium (1.62 tons d^-1) by the pipeline are not negligible compared to the major river loads in the gulf. High concentrations of urea (≤11.51 μmol N dm^-3) were found in the area of wastewater release. Ammonium uptake (6.14-534 nmol N dm^-3 h^-1) strongly exceeded nitrate uptake (0.19-138 nmol N dm^-3 h^-1), indicating that discharges of ammonium by the pipeline are actively assimilated by plankton community even at low levels of light. Distribution of Zn (≤27.7 ppb), Cu (≤25.6 ppb), Cd (≤0.80 ppb) and Pb (≤13.5 ppb) in the water column and the measurement of their complex-forming capacity in seawater did not indicate a persistent perturbation of the pelagic environment due to heavy metals.     

Removal of Cr(VI) from aqueous solution using waste weed, Salvinia cucullata

Biosorption studies of Cr(VI) were carried out using waste weed, Salvinia cucullata. Various adsorption parameters were studied, such as agitation speed, contact time, pH, particle size, and concentrations of adsorbent and adsorbate. The equilibrium was achieved in 12 h. A lower pH favoured adsorption of Cr(VI). The kinetics followed pseudo-second-order rate equations. The adsorption isotherm obeyed both the Langmuir and Freundlich models. The calculated activation energy (1.1 kJ mol^-1) suggested that the adsorption followed a diffusion-controlled mechanism. Various thermodynamic parameters such as Δ G^°, Δ H^°, and Δ S^° were also calculated. The positive values of enthalpy indicated the endothermic nature of the reaction, and Δ S^° showed the increasing randomness at the solid liquid interface of Cr(VI) on the adsorbent, which revealed the ease of adsorption reaction. These thermo-dynamic parameters showed the spontaneity of the reaction. The maximum adsorption of uptake (232 mg g^-1) compared well with reported values of similar adsorbents. The rate-determining step was observed to follow an intra-particle diffusion model.     

Ozone kinetics of dimethyl sulfide in the presence of water vapor

The outdoor smog chamber was used to thorough investigate the rate constants of gas-phase reaction between dimethyl sulfide （DMS） and ozone （O3） under conditions of relative humidity 55.0%-67.8% at （296±2）K for the first time. The rate constants were measured, at a total pressure of 1 atm, to be （10.4±0.2） × 10^-19 cm^3·molecule^-1·s^-1 at relative humidity of 67.5%±0.3% at 298K, （10.1±0.1） × 10^-19cm^3·molecule^-1·s^-1 at relative humidity of 66.5%±0.5% at 296K, （7.75±0.39） × 10^-19cm^3·molecule^-1·s^-1 at relative humidity of 64.8%± 0.1% at 294K and （3.42±0.21） × 10^-19cm^3·molecu- le^-1·s^-1at relative humidity of 55.8%±0.8% at 295K. Base on these results, it is possible to see the reaction of O3/ DMS in the presence of water vapor as an important sink for DMS in the earth atmosphere.     

Responses of bacterial strains isolated from drinking water environments to N-acyl-L-homoserine lactones and their analogs during biofilm formation

Often as a result ofbiofilm formation, drinking water distribution systems （DWDS） are regularly faced with the problem of microbial contamination. Quorum sensing （QS） systems play a marked role in the regulation of microbial biofilm formation; thus, inhibition of QS systems may provide a promising approach to biofilm formation control in DWDS. In the present study, 22 bacterial strains were isolated from drinking water-related environments. The following properties of the strains were investigated： bacterial biofilm formation capacity, QS signal molecule N-acyl-L-homoserine lactones （AHLs） production ability, and responses to AHLs and AHL analogs, 3-chloro-4-（dichloromethyl）-5-hydroxy-2（5H）- furanone （MX） and 2（5H）-furanone. Four AHLs were added to developed biofilms at dosages ranging from 0.1 nmol.L J to 100nmol.L1. As a result, the biofilm growth of more than 1/4 of the isolates, which included AHL producers and non-producers, were significantly promoted. Further, the biofilm biomasses were closely associated with respective AHLs concentrations. These results provided evidence to support the idea that AHLs play a definitive role in biofilm formation in many of the studied bacteria. Meanwhile, two AHLs analogs demon- strated unexpectedly minimal negative effects on biofilm formation. This suggested that, in order to find an applicable QS inhibition approach for biofilm control in DWDS, the testing and analysis of more analogs is needed.     

Using crosslinked polyvinyl alcohol polymer membrane as a separator in the microbial fuel cell

Separator between anode and cathode is an essential part of the microbial fuel cell （MFC） and its property could significantly influence the system perfor- mance. In this study we used polyvinyl alcohol （PVA） polymer membrane crosslinked with sulfosuccinic acid （SSA） as a new separator for the MFC. The highest power density of 7594-4 mW-m-2 was obtained when MFC using the PVA membrane crosslinked with 15% of SSA due to its desirable proton conductivity （5.16 x 10-2 S.cml）. The power density significantly increased to 11064- 30 mW.m-2 with a separator-electrode-assembly config- uration, which was comparable with glass fiber （11704- 46 mW.m-2）. The coulombic efficiencies of the MFCs with crosslinked PVA membranes ranged from 36.3% to 45.7% at a fix external resistance of lO00f2. The crosslinked PVA membrane could be a promising alter- native to separator materials for constructing practical MFC system.     

水体中悬浮颗粒物对酞酸酯的吸附和解吸特性

选择水体中的悬浮颗粒物(SPM)--沉积颗粒物和浮游植物颗粒(铜绿微囊藻和普通小球藻),研究它们对邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二异辛酯(DEHP)的吸附和解吸行为.结果表明,SPM对DBP 和DEHP的吸附在很短的时间内即可达到平衡,沉积颗粒物约为2h,浮游植物颗粒约为0.5h;SPM对DEHP的吸附能力明显大于DBP;不同SPM对同一种化合物的吸附能力差异较大,这与颗粒物中有机质的类型和结构有关;在实验浓度范围内,SPM对DBP和DEHP的吸附和解吸等温线具有较好的线性关系,解吸过程存在明显的迟滞现象,且沉积颗粒物比浮游植物颗粒物具有明显的迟滞效应,DBP比DEHP具有较大程度的迟滞效应.     

Multistep conversion of cresols by phenol hydroxylase and 2,3-dihydroxy-biphenyl 1,2-dioxygenase

A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the first time. Docking studies displayed by PyMOL predicted that cresols and methylcatechols could be theoretically transformed by this multistep conversion system~ High performance liquid chromatography mass spectrometry （HPLC-MS） analysis also indicated that the products formed from multistep conversion were the corresponding 3-methylcatechol, 4-methylcatechol, 2- hydroxy-3-methyl-6-oxohexa-2,4-dienoic acid （2- hydroxy-3-methyl-ODA） and 2-hydroxy-5-methyl-6-oxo- hexa-2,4-dienoic acid （2-hydroxy-5-methyl-ODA）. The optimal cell concentrations of the recombinant E. coli strain BL21 （DE3） expressing phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） and pH for the multistep conversion of o- and m-cresol were 4.0 （g-L-1 cell dry weight） and pH 8.0, respectively. For the first step conversion, the formation rate of 3- methylcatechol （0.29μmol·L-1·min-1·mg-1cell dry weight） from o-cresol was similarly with that ofmethylca- techols （0.28 μmol·L-1·min-1·mg-1 cell dry weight） from m-cresol by strain PHrND. For the second step conversion, strain BphCLA_4 showed higher formation rate （0.83 μmol·L-1·min-1·mg-1 cell dry weight） for 2-hydroxy-3-methyl- ODA and 2-hydroxy-5-methyl-ODA from m-cresol, which was 1.1-fold higher than that for 2-hydroxy-3-methyl- ODA （0.77 μmol·L-1·min-1·mg-1. mglcell dry weight） from ocresol. The present study suggested the potential application of the multistep conversion system for the production of chemical synthons and high-value products.     

Denitrification potential in a Louisiana wetland receiving diverted Mississippi River water

Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO₃^- was determined in sediment-water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO₃^- removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m^-2 d^-1 over 16 d for a 1750-mg NO₃-N m^-2 addition, and 170 mg N m^-2 d^-1 over 16 d for a 3500-mg NO₃-N m^-2 addition. The total N₂O-N emissions from the 1750- and 3500-mg NO₃-N m^-2 additions were 19 and 54 mg N m^-2 accounting for 1.1% and 1.5% of the applied NO₃-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m^-2 d^-1 (21 and 32 g N m^-2 yr^-1) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO₃^--N m^-2 of added nitrate in floodwater, respectively. The total N evolved over 11 d as N₂O + N₂ was equivalent to 436 and 921 mg N m^-2 (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO₃^- applied to the overlying water increased the rate of NO₃^- loss and N₂O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO₃^- application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO₃^- in the river water, reducing the amount of NO₃^- reaching to offshore areas.     

乳状液膜法萃取氨基酸的研究

本文以ＴＯＭＡＣ为载体，ＥＣＡ４３６０Ｊ为表面活性剂，内外相Ｃｌ＾－浓度梯度为推动力，研究了Ｌ－苯丙氨酸在乳状液膜体系中的传输，并对影响液膜萃取的各种因素进行了系统的阐述，确定了此体系的最佳膜相组成的实验条件，实现了Ｌ－苯丙氨酸的提取和浓缩。