Screening and identification of cellulose degrading bacterium Bacillus siamensis BREC-11 with tolerance to furfural北大核心CSCD

Furfural is a toxic metabolic inhibitor that is created during the conversion of lignocellulose to produce fuel, which can retard fermentation and increase production costs. thus, it is important for lignocellulosic conversion that the ability of the strain to resist furfural stress be improved. A cellulose-degrading bacterium BREC-11 with tolerance to furfural was isolated from the intestinal tract of Omphisa fuscidentalis hampson larvae via the addition of furfural in the medium. Based on analyses of morphological observations, physiological and biochemical characterizations, and 16S rDNA sequences, strain BREC-11 was shown to represent a member of the genus Bacillus and was named B. siamensis BREC-11. to study the tolerance concentration of strain BREC-11, a wide range of furfural formaldehyde concentrations were tested and strain BREC-11 was shown to grow in the mineral medium containing furfural up to 3.5 g/L. Cellulase activity of strain BREC-11 was determined at the tolerable concentration of 3.5 g/L furfural after incubation at 30 ℃ and 150 r/min for 2 days. Results indicated that filter paper enzyme, CMC-Na enzyme, and β-glucosidase activity was 0.1 U/mL, 0.21 U/mL, and 0.07 U/mL, respectively. BREC-11 is a cellulose-degrading bacterium with resistance to furfural, which has potential application in future bio-refinery processes. © 2018 Science Press. All rights reserved.     

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.     

Microbial fuel cell with three-dimensional electrodes for domestic wastewater treatment and electricity generation北大核心CSCD

A single chamber microbial fuel cell (MFC) with three-dimensional electrodes packed bed carbon felts was developed to treat domestic wastewater while simultaneously generating electricity. The influence of batch and continuous operation mode on treatment effectiveness and electricity production of the MFC was investigated to provide a reference for the application of the MFC. The MFC with a total working volume of 1 440 mL was operated in the fed-batch mode for 5 d repeatedly three times, and then shifted to the continuous mode. During the testing of the continuous mode, wastewater was continuously pumped into the anode compartment at a flow rate of approximately 0.2 mL/min, resulting in a hydraulic retention time of 5 d. During the batch test, the MFC obtained 91.1% chemical oxygen demand (COD) and 98.2% NH4 +-N removal, which accorded with the first criteria specified in the discharge standard of pollutants for municipal wastewater treatment plants in China (GB18918-2002). A maximum power density of 27.88 mW/m3 was achieved at a 51 Ω external resistor. During the continuous test, the COD removal efficiencies ranged from 83.2% to 97.4%. The concentration of NH4 +-N gradually decreased within 5 d and was then maintained below 9.45 mg/L, thus an enhanced removal performance of NH4 +-N was acquired. However, a low removal efficiency of total nitrogen was observed owing to the accumulation of NO3 --N in the effluent since day 11. Additionally, the MFC continually generated electricity with a maximum power density of 582.5 mW/m3 and average output voltage of 0.087 7 V during the stable period in the continuous operation mode. Moreover, 16S rRNA gene high-throughput sequencing showed that Thauera sp., Saprospiraceae-UN sp., and OPB56-UN sp. were identified as dominant populations. The results suggested that the organic matter associated with power generation was constantly utilized by the microorganisms in the reactor, which caused an excellent electricity generation performance during the continuous test. Therefore, the continuous operation mode could improve the low output voltage phenomenon in the MFC. Thauera sp., as a type of nitrate-reducing bacteria, was enriched in the autotrophic denitrifying microbial communities; therefore, bio-enrichment with denitrifying bacteria such as Thauera sp. could decrease the concentration of NO3 --N in the effluent during the continuous operation mode, which is expected to be an innovation for improvement of wastewater treatment. © 2018 Science Press. All rights reserved.     

Screening and degradation characteristics of a tetracycline-degrading bacterial strain北大核心CSCD

Tetracycline is widely used in livestock and poultry breeding industry, which can cause serious problems to the environment. Antibiotic pollution has become an important environmental issue. This study aimed to isolate and identify a well-functioning tetracycline-degrading bacteria strain from activated sludge and to investigate its optimum degradation conditions. The strain was identified through morphological features, Gram staining, and the sequence analysis of 16S rRNA. Furthermore, the temperature, initial pH of the medium, inoculation amount, and type of metallic salt were analyzed to investigate the tetracycline degradation performance of the isolated strain. Based on the single factor test, the method of response surface analysis was adopted to optimize the degradation condition. The strain was named TTC-1 and identified as Klebsiella pneumoniae. The optimum condition for tetracycline degradation was determined as follows: temperature of 34.4 °C, pH of 7.22, and MnSO4 concentration of 0.32 g/L. Under this optimum condition, the predicted tetracycline degradation rate was 93.77%, whereas the observed value was 94.26%. The experimental results showed that the proposed model had high accuracy. TTC-1 showed a good performance in degrading tetracycline, which can provide reference for the bacteria during the biological treatment of tetracycline containing wastewater. © 2018 Science Press. All rights reserved.     

The oligopeptides production by the feather-degrading bacterium Bacillus methylotrophicus H0北大核心CSCD

Due to the high nutritive value of oligopeptides and the waste of feather resources, this study aimed at screening efficient strains of bacteria able to rapidly degrade feathers and produce large quantities of value-added oligopeptides. In order to assess the potential yield of oligopeptides, the promising strain H0 was selected from 16 feather-degrading microorganisms. To identify the strain, we analyzed the morphological and physiological characteristics of different strains, and carried out a gene sequence analysis of their 16S rRNAs. A single factor experiment was used to promote feather degradation and oligopeptide production, and the characteristics of the oligopeptides produced were also analyzed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). The strain was identified as Bacillus methylotrophicus. The optimal initial pH and temperature for oligopeptide production were 11 and 40 °C, respectively. After 72 h of fermentation under these optimal conditions, the feathers were almost completely degraded, with a 38.19% of oligopeptides (accounting for 67.53% of the total soluble peptides) and a 11.11% of free amino acids produced. LC-MS/MS analysis indicated that the oligopeptides were mainly short peptides containing 5-10 amino acids, with a molecular mass (Mr) of less than 1 300. Moreover, the peptides were abundant in branched-chain amino acids, that might be responsible for the antioxidant property of the feather hydrolysate. Our results demonstrate the great capability of B. methylotrophicus H0 in feather degradation and oligopeptide production. This research provides a high-quality microorganism resource, and the scientific basis for the development of feather-derived oligopeptide products. © 2018 Science Press. All rights reserved.     

Removal of pharmaceutical and personal care products by sequential ultraviolet and ozonation process in a full-scale wastewater treatment plant

The application of appropriate advanced treat- ment process in the municipal wastewater treatment plants （WWTPs） has become an important issue considering the elimination of emerging contaminants, such as pharma- ceutical and personal care products （PPCPs）. In the present study, the removal of 13 PPCPs belonging to different therapeutic classes by the sequential ultraviolet （UV） and ozonation process in a full-scale WWTP in Beijing was investigated over the course of ten months. Most of the target PPCPs were effectively removed, and the median removal efficiencies of individual PPCPs, ranging from -13% to 89%, were dependent on their reaction rate constants with molecular ozone. Noticeable fluctuation in the removal efficiencies of the same PPCPs was observed in different sampling campaigns. Nevertheless, the sequential UV and ozonation process still made a significant contribution to the total elimination of most PPCPs in the full-scale WWTP, by compensating for the poor or fluctuant removal performance of PPCPs by biologic treatment process.     

Isolation,identification, and the degradation characteristics of a BDE-47 degrading strain北大核心CSCD

In an effort to remove BDE-47 residues from the environment, a bacterial strain that is capable of utilizing BDE-47 as the sole carbon source was isolated and screened from soil collected from an e-waste recycling area in Tianjin to analyze the degradation properties. The strain was preliminarily identified as Enterobacter sp. according to a 16S rDNA gene sequence analysis. The strain degraded 35.8% of 525 μg/L of BDE-47 in 35 d when the initial concentration of bacteria was 7.1 × 105 cells/ mL. The product of the biodegradation of BDE-47 was BDE-28. The biodegradation of BDE-47 fit well with first-order kinetics, and its degradation kinetics was ln Ct = - 0.104t + 6.22. With the addition of an electron acceptor, such as Fe3+, SO4 2- and NO3 -, the BDE-47 degradation rate was significantly increased to 49.8%, 59.1%, and 67.3%, respectively. The above results revealed that the strain could degrade BDE-47, which is of importance in the application of environmental bioremediation of BDE-47. © 2018 Science Press. All rights reserved.     

Simultaneous removal of arsenate and fluoride from water by AI-Fe （hydr）oxides

A1-Fe （hydr）oxides with different A1/Fe molar ratios （4：1, 1：1, 1：4, 0：1） were prepared using a co- precipitation method and were then employed for simultaneous removal of arsenate and fluoride. The 4A1 ： Fe was superior to other adsorbents for removal of arsenate and fluoride in the pH range of 5.0-9.0. The adsorption capacity of the A1-Fe （hydr）oxides for arsenate and fluoride at pH 6.50.3 increased with increasing A1 content in the adsorbents. The linear relationship between the amount of OH released from the adsorbent and the amount of arsenate or fluoride adsorbent by 4A1 ： Fe indicated that the adsorption of arsenate and fluoride by A1- Fe （hydr）oxides was realized primarily through quantita- tive ligand exchange. Moreover, there was a very good correlation between the surface hydroxyl group densities of A1-Fe （hydr）oxides and their adsorption capacities for arsenate or fluoride. The highest adsorption capacity for arsenate and fluoride by 4A1 ： Fe is mainly ascribed to its highest surface hydroxyl group density besides its largest pHpzc. The dosage of adsorbent necessary to remove arsenate and fluoride to meet the drinking water standard was mainly determined by the presence of fluoride since fluoride was generally present in groundwater at much higher concentration than arsenate.     

Screening and characterization of extremophiles in spacecraft assembly environment北大核心CSCD

Spacecrafts need to strictly control microorganisms before entering space flight. The Spacecraft Assembly, Integration, and Test Center (AITC) is an important environmental source for spacecrafts to carry microorganisms. The assembly clean room has characteristics of ventilation, dryness, and lack of nutrients that are not conducive to the growth and reproduction of microorganisms, except for extremophiles. In this study, based on the internal air and surface environment of the AITC in China, 13 strains of bacteria were identified by plate culture and 16S sequence analysis, and their extreme environmental tolerance, antibiotic resistance, and film-forming ability were tested. All these bacteria belonged to the Firmicutes and Proteobacteria phyla, and nine strains belonged to the Bacillus genus. All 13 strains of bacteria were salt-tolerant, acid-tolerant, and alkali-tolerant, and 69.2% of the bacteria survived heat shock at 80 ℃. Among these, one strain of Sphingomonas sp. JCM7513 isolated from the surface environment was insensitive to all the tested antibiotics and had strong drug resistance, while the other 12 strains were sensitive to most β-lactam antibiotics but had strong resistance to tetracyclic antibiotics and erythromycin. Most of the isolated bacteria exhibited strong biofilm-forming abilities. The study showed that there are a certain number of extremophiles in the spacecraft assembly environment. To protect spacecrafts from biological corrosion and planetary protection forward pollution, more effective monitoring and elimination methods are needed. © 2022 Science Press. All rights reserved.     

N2O emission from a sequencing batch reactor for biological N and P removal from wastewater

Nitrous oxide （N2O） is a greenhouse gas that can be released during biological nitrogen removal from wastewater. N2O emission from a sequencing batch reactor （SBR） for biological nitrogen and phosphorus removal from wastewater was investigated, and the aims were to examine which process, nitrification or denitrification, would contribute more to N2Oemission and to study the effects of heterotrophic activities on N2O emission during nitrification. The results showed that N2O emission was mainly attributed to nitrification rather than to denitrification. N2O emission during denitrification mainly occurred with stored organic carbon as the electron donor. During nitrification, NaO emission was increased with increasing initial ammonium or nitrite concentrations. The ratio of N2O emission to the removed ammonium nitrogen （N2O- N/NH4-N） was 2.5% in the SBR system with high heterotrophic activities, while this ratio was in the range from 0.14% to 1.06% in batch nitrification experiments with limited heterotrophic activities.     

Isolation,identification, culture conditions,and laccase production of a wild mushroom 'Huaier'北大核心CSCD

In the present study, fruiting bodies of a wild medicinal mushroom, 'Huaier, ' were collected from Populus canadensis in the Beijing Xiangshan Park. The pure culture strain was obtained from fruiting bodies using the tissue isolation method. It was stored and numbered as XS-01. It was systematically classified using morphological and ITS identification. Further studies were focused on mycelia optimum culture conditions and laccase production by liquid fermentation. A 598-bp partial ITS region sequence (GenBank accession number KY93348) was obtained using PCR method. Phylogenetic tree and genetic distance analysis were performed using the MEGA 6.0 software. The present strain possessed the highest homology (100%) with Perenniporia robiniophila, and the genetic distances were 0.000. Based on the ITS sequencing and morphological characteristics of fruiting bodies and mycelia, XS-01 was identified as P. robiniophila. Based on mycelial growth rate and quality, mycelia optimum culture conditions were revealed to be as follows: the optimum carbon sources were starch and maltose, the optimum nitrogen source was yeast extracts, the optimum C/N ratio range was 30/1 - 60/1, the best growth temperature was 32 °C, the optimum pH was 7, and the optimum growth factor was VB1. Further study of Cu2+ on extracellular laccase production revealed that 1.0 mmol/L Cu2+ could significantly enhance the enzyme production, with the highest activity of 417.5 U/mL when cultured for 96 h and an increase ratio of 93.4% to the control. On the other hand, 2.0 mmol/L Cu2+ can markedly decrease the enzyme production laccase activity at 96 h to 79.0 U/mL, which was 36.6% of that of the control. In conclusion, a pure strain of T. robiniophila with high extracellular laccase activity was obtained, suggesting its potential application for artificial cultivation and laccase production. © 2018 Science Press. All rights reserved.     

A new efficient azo dye-decolorizing bacterium Paenibacillus dendritiformis GGJ7 and its decolorization process北大核心CSCD

This paper aimed to find an efficient bacterium for decolorizing azo dyes. A strain which could decolorize Congo Red efficiently was isolated from Congo Red. The strain was identified as Paenibacillus dendritiformis GGJ7 (GGJ7, in short) by 16S rRNA gene sequence (NCBI accession No. KY655213). Strain GGJ7 was applied to the decolorization of azo dyes in this research, and influencing factors of decolorization were investigated, including diverse nutritional conditions, culture conditions (pH, temperature, oxygen conditions), and various dyes. The results demonstrated that the decolorization rate of Congo Red by strain GGJ7 was much higher than that of the other eight strains (e.g., YRJ1, YRJ2 etc.) in our previous work. The optimal conditions for Congo Red decolorization were 25 g/L LB broth as nutrient source, 30 °C, pH 7, and an anaerobic environment. The mechanism of decolorization was mainly biodegradation, and the decolorization process of strain GGJ7 was conformed to the first-class kinetics model: -ln (At /A0) = 0.6058t - 0.1082. For different azo dyes, the decolorization rate was up to 95%. Strain GGJ7 only needed 1 h to decolorize 50 mg/L Methyl Orange, 25 mg/L Croceine Scarlet, and 25 mg/L Methyl Red, needed 3 h to decolorize 50 mg/L Orange G and 50 mg/L Orange G6, and needed 4 h to decolorize 50 mg/L Congo Red. In summary, strain GGJ7 is an efficient azo dye-decolorizing bacterium, and it has a potential application in treating printing and dyeing wastewater. © 2018 Science Press. All rights reserved.     

Enhancement of MK-7 synthesis by engineered strains of Bacillus subtilis natto that overexpress men genes and by increasing available dissolved oxygen北大核心CSCD

In recent years, researchers have discovered novel physiological functions of vitamin K2. In addition to promoting blood clotting, it can prevent osteoporosis and cardiovascular disease and is expected to treat some tumors and Parkinson’s disease. Bacillus subtilis natto is a probiotic that has been approved by the U.S. Food and Drug Administration for use as a bioproducer of vitamin K2. Its product’s main form is MK-7, which has a long half-life in the human body and high bioavailability. Bacillus subtilis natto displays great potential for large-scale biological preparation of vitamin K2. In this study, the Sipizizen method of Bacillus subtilis transformation was optimized to make it suitable for molecular transformation of Bacillus subtilis natto. Vectors for overexpression of all 8 genes involved in the menadione synthetic pathway were constructed, and changes in MK-7 fermentation yield after transformation of Bacillus subtilis natto were investigated. Three enzymes were found to exert significant effects on MK-7 synthesis, namely isopentenyltransferase (MenA), 1,4-dihydroxy-2-naphthoyl-CoA synthase (MenB), and nornaphthoquinone methyltransferase (MenG). A modified strain (BN-pABG) with higher MK-7 productivity was obtained by concerted overexpression of menA, menB, and menG. In a 5 L bioreactor, MK-7 synthesis was further enhanced by optimizing oxygen supply. The final yield of MK-7 from the modified strain was 62.21 mg/L, 1.26 times higher than that of the original strain. These results show that combined overexpression of menA, menB, and menG strongly promotes MK-7 synthesis by Bacillus subtilis natto, and optimizing the oxygen supply conditions also promotes more robust MK-7 synthesis. © 2022 Authors. All rights reserved.     

Isolation,identification, and biological characteristics of a wild Chaga mushroom北大核心CSCD

In this study, a pure culture strain (numbered as F1501) was obtained using tissue separation and purification methods from the sclerotia of Chaga mushroom from Russia. Further researches included studies on classification, optimum growth conditions of mycelia, extracellular polysaccharides from fermentation broth and their antioxidant activity, and artificial acclimation. According to the identification of the internal transcribed spacer (ITS) region, it was confirmed that F1501 was a species of the genus Inonotus and family Hymenochaetaceae, which had 99% similarity with Inonotus obliquus. F1501 was further classified as I. obliquus based on the morphological characteristics of its mycelia and sclerotia. The optimal carbon source, nitrogen source, C/N ratio, growth factor, temperature, and pH value for the growth of the F1501 strain mycelia were maltose, beef extracts, 10/1, B2, 28 °C, and 8.0, respectively. Liquid fermentation of F1501 was performed using PD media and a 10% inoculation amount at 28 °C and 150 r/min for 7 d. The content of polysaccharides in the fermentation broth was 476.32 mg/L, with a total antioxidant activity of 0.19 mmol/L (Trolox) and hydroxyl free radical-scavenging activity of 72.7%. Artificial acclimation study revealed that the fruiting body-like structure was obtained using cottonseed hulls as the main substrate. In the present study, a new strain of I. obliquus and its biological characteristics were explored, which could provide a theoretical basis for the artificial acclimation and development of wild mushrooms. © 2018 Science Press. All rights reserved.     

Occurrence and fate of antibiotics in advanced wastewater treatment facilities and receiving rivers in Beijing,China

The occurrence and removal of 13 antibiotics were investigated in five wastewater treatment plants （WWTPs） with advanced wastewater treatment processes in Beijing, China. Most of the target antibiotics were detected in the secondary and tertiary effluents, with the concentrations of 4.8-1106.0 and 0.3-505.0ng·L^-1. Fluoroquinolone antibiotics showed relatively high concentrations in all samples （782-1814ng·L^-1）. Different tertiary treatment processes showed discrepant antibiotics removal performances. Ozonation process was found more effective in removing target antibiotics compared to the coagulation-flocculation-sedimentation process and sand filtration process. Investigation of the target antibiotics in three typical urban rivers in Beijing was carried out to understand antibiotics occurrence in surface water environment. Eight antibiotics were detected in the studied rivers, with highest concentration of antibiotics in the fiver which was mainly replenished by reclaimed water. This study showed the necessity of employing more effective advanced treatment facilities to further reduce the discharge amount of antibiotics.     

Process control factors for continuous microbial perchlorate reduction in the presence of zero-valent iron

Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorate reducers were obtained from a wastewater treatment plant and inoculated into the reactor without further acclimation. Examined parameters included hydraulic residence time （HRT）, pH, nutrients requirement, and perchlorate reduction kinetics. The minimum HRT for the system was concluded to be 8 hr. The removal efficiency of 10 mg. L-1 influent perchlorate concentration was reduced by 20%-80% without control to the neutral pH （HRT = 8 hr）. Therefore pH was determined to be an important parameter for microbial perchlorate reduction. Furthermore, a viable alternative to pH buffer was discussed. The microbial perchlorate reduction followed the first order kinetics, with a rate constant （K） of 0.761 hr-1. The results from this study will contribute to the implementation of a safe, cost effective, and efficient system for perchlorate reduction to below regulated levels.     

Occurrence and removal of N-nitrosodimethylamine and its precursors in wastewater treatment plants in and around Shanghai

Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine （DMA）, trimethylamine （TMA）, dimethyl- formamide （DMFA） and dimethylaminobenzene （DMAB）. DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process （CEPP） had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA （19%-85%） and NDMA FP （16%-76%）, moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination.     

Production of N2O in two biologic nitrogen removal processes: a comparison between conventional and short-cut nitrogen removal processes

The N2O production in two nitrogen removal processes treating domestic wastewater was investigated in laboratory-scale aerobic-anoxic sequencing batch reactors （SBRs）. Results showed that N2O emission happened in the aerobic phase rather than in the anoxic phase. During the aerobic phase, the nitrogen conversion to N2O gas was 27.7% and 36.8% of NH＋-N loss for conventional biologic N-removal process and short-cut biologic N-removal process. The dissolved N2O was reduced to N2 in the anoxic denitrification phase. The N2O production rate increased with the increasing of nitrite concentration and ceased when NH＋-N oxidation was terminated. Higher nitrite accumulation resulted in higher NEO emission in the short-cut nitrogen removal process. Pulse-wise addition of 20 mg NO2 -N. L- 1 gave rise to 3-fold of N2O emission in the conventional N-removal process, while little change happened with 20 mg NOS-N L-1 was added to SBR1.     

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.     

Removal of 17β-estradiol in laccase catalyzed treatment processes

The removal of 17β-estradiol （E2） in laccase catalyzed oxidative coupling processes was systematically studied in this work. We focused on the influence of pH and natural organic matter （NOM） on the performance of the enzymatic treatment processes. It was found that the optimal pH for E2 removal was between 4 and 6. The removal of E2 was slightly inhibited in the presence of NOM. Enzymatic transformation of E2 was second-order in kinetics with first-order to both the concentrations of the enzyme and contaminant. Mass spectrum （MS） analysis suggested that coupling products were formed through radical-radical coupling mechanism. The results of this study demonstrated that laccase catalyzed oxidative coupling process could potentially serve as a treatment strategy to control steroid estrogens.