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Plasmon-mediated photocatalytic water splitting has attracted extensive attention due to its bright future in using visible light, but the enhancement mechanism is still unclear, and the efficiency...

Photocatalytic water splitting is an ideal way of generating hydrogen, a renewable energy source, from solar energy that would help solve environmental problems. However, current photocatalysts are...

Plasmonic metals under photoexcitation can generate energetic hot electrons to directly induce chemical reactions. However, the capability and fundamental insights of the transportation of these hot electrons at plasmonic metal-2D material interfaces remain unclear. Herein, hot-electron transfer at Au-graphene interfaces has been in situ studied using surface-enhanced Raman spectroscopy (SERS) with atomic layer accuracy. Combining in situ SERS studies with density functional theory calculations, it is proved that hot electrons can be injected from plasmonic Au nanoparticles to graphene and directly penetrate graphene to trigger photocatalytic reactions. With increasing graphene layers, the transportation of hot electrons decays rapidly and would be completely blocked after five layers of graphene. Moreover, the transfer of hot electrons can be modulated by applying an external electric field, and the hot-electron transfer efficiency under electrochemical conditions is improved by over three times in the presence of a monolayer of graphene. These fundamental understandings about hot-electron transfer provide insightful information to promote the design of more efficient plasmonic materials and devices.

模板法是可控合成复合纳米材料的一种重要手段. 然而, 纳米材料在模板, 尤其是复合模板上的选择性生长仍面临巨大挑战. 本文以自组装聚乙烯-金纳米颗粒一维复合纳米链为软-硬复合模板, 实现金属在该模板上可控地选择性沉积、生长. 通过选择恰当的表面活性剂来调节金属生长的热力学, 金属可以选择性地生长在金纳米颗粒的表面, 得到金属间歇包覆的复合纳米链; 也可以同时包覆在聚乙烯和金纳米颗粒的表面, 得到金属完全包覆的豌豆荚状复合纳米链. 不同的包覆方式和包覆材料选择都会导致材料光学性质的变化. 时间差分有限元模拟表明, 金包覆的豌豆荚状复合纳米链的表面金壳层和内部金纳米颗粒之间存在极强的表面等离子体耦合作用. 在表面增强拉曼实验中, 该复合纳米链表现出很强的增强信号.

A type of broadband (325−980 nm) self-powered photodetector based on graphene/GaAs van der Waals heterojunction is reported. By simply spinning a layer of Ag nano-particles (Ag NPs) onto graphene/GaAs heterostructure, the responsivity and detectivity of our devices for the whole spectrum range are enhanced significantly. The maximum photocurrent responsivity of 210 mA W−1 (increased by 38%) and detectivity of 2.98 × 1013 Jones (increased by 202%) are achieved at 405 nm, which is about two or three orders of magnitude larger than other graphene based self-powered photodetectors. The mechanism of the improvement originates from the overlap the depletion region of graphene/GaAs heterostructure, the surface plasmon enhanced light field region below the surface and the light absorption region of the GaAs layer. The external quantum efficiency (EQE) measurement, transient photoluminescence (PL) test and the comparative theoretical simulation show that the surface plasmon enhancement should only be applicable for graphene/direct band gap semiconductor heterostructure, where the semiconductor should have a high optical absorption coefficient. The obtained high performance broadband photodetector with excellent detectivity is a promising candidate for many important optoelectronic applications, such as ultrasensitive image sensor in charge coupled displayer field, which requires colour sensors not only with high photo responsivity but also in a wide spectral range.

Near-infrared photodetectors (NIRPDs) have attracted great attention because of their wide range of applications in many fields. Herein, a novel self-driven NIRPD at the wavelength of 980 nm is reported based on the graphene/GaAs heterostructure. Extraordinarily, its sensitivity to light illumination (980 nm) is far beyond the absorption limitation of GaAs (874 nm). This means that the photocurrent originates from the separation of photo-induced carriers in graphene, which is caused by the vertically built-in electric field formed through the high quality van der Waals contact between graphene and GaAs. Moreover, after introducing NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) onto the graphene/GaAs heterojunction, the responsivity increases to be as superior as 5.97 mA W-1 and the corresponding detectivity is 1.1 × 1011 cm Hz0.5 W-1 under self-driven conditions. This dramatic improvement is mainly ascribed to the radiative energy transfer from UCNPs to the graphene/GaAs heterostructure. The high-quality and self-driven UCNPs/graphene/GaAs heterostructure NIRPD holds significant potential for practical application in low-consumption and large-scale optoelectronic devices.

Surface plasmon resonance (SPR) has been utilized in many fields, such as surface-enhanced Raman spectroscopy (SERS) and solar energy conversion. Here we developed an Au@CdS core-shell nanostructure, a bifunctional nanoparticle, used as an efficient catalyst for SPR enhanced photocatalytic degradation, and as a substrate for in situ SERS detection of methylene blue (MB) and p-nitrophenol (pNTP). With integration of an Au nanoparticle into a CdS shell, the degradation process was significantly accelerated under 500 nm long-pass (λ > 500 nm) visible light irradiation, which was caused by the injection of hot electrons. Moreover, a highly uniform, monolayer film of Au@CdS nanoparticles (NPs) has been prepared and used as both a SERS substrate and catalyst. The decomposition of MB molecules and nitrogen coupling reaction of pNTP were observed during the 638 nm laser illumination. We demonstrate that a plasmonic core-semiconductor shell nanocomposite can be a promising material for photocatalysis and in situ SERS study.

Summary Light-excited energetic electrons, or so-called hot electrons (HEs), in plasmonic metal nanostructures have received much attention in the past few years. Plasmonic metal nanostructures, acting as light absorbers with higher efficiency and adjustability than dye molecules and inorganic semiconductors, can generate HEs under specific light conditions. However, the overall efficiency of the plasmonic systems remain unsatisfactory. Therefore, it is important to study the generation and transfer processes of plasmon-induced HEs, which are necessary for efficient plasmon-enhanced applications. In this review, we summarize the basic concepts and mechanisms of HE generation and transportation, then highlight the use of in situ surface-enhanced Raman spectroscopy (SERS) as a probe for HE-induced chemical reactions. We also discuss the opportunities and remaining challenges in promoting fundamental understanding of, and practical applications for, HEs.

A hydrophobic SPG (shirasu porous glass) membrane-aerated biofilm reactor (MABR) with genetically engineered microorganism (GEM) biofilm formed on the SPG membrane surface was applied to treat atrazine wastewater. The contaminant removal performance and its influencing factors were investigated during the stable operation of this MABR. The results indicated that the oxygen supply capacity could be increased in the SPG membrane aeration when the membrane pore size and the aeration pressure increased, which could improve the performance of COD and atrazine removals. The maximum oxygen supply capacity of hydrophobic SPG membrane with pore size of 1.5 μm was estimated to be about 22.4 g·(m

The surface properties and performance of activated carbon (AC) used for catalytic ozonation were investigated after nitric acid modification (N-AC) and Cu (II)-loaded (N-Cu-AC). The results showed that the nitric acid modification could increase the amount of surface functional groups of AC. As a result, the adsorption capacity and catalytic activity of AC could be improved. The surface functional groups and Cu (II)-loaded of N-Cu-AC showed a synergistic effect on catalytic ozonation, where the catalytic activity of Cu (II)-loaded was more stable. N-Cu-AC was an effective and reusable catalyst for catalytic ozonation. The highest TOC removal efficiency of 58.0% could be achieved when N-Cu-AC was used for 60 min-catalytic ozonation treatment of acid red 3R.

2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS

The structure and surface chemical properties of activated carbon after nitric acid modification and their influences on adsorption and catalytic ozonation of acid red 3R were investigated. The results showed that both specific surface area and micropore volume of activated carbon decreased, but mesopore volume increased after nitric acid modification. The adsorption capacity and catalytic ozonation performance of modified activated carbon were influenced due to the increased surface acidic functional groups. The adsorption capacity of modified activated carbon was enhanced under acidic condition due to dispersion interaction between increased surface acidic functional groups and acid red 3R. The increase in surface acidic functional groups of activated carbon was also considered to be responsible for improvement of the catalytic ozonation of acid red 3R under alkaline condition, because of their participation in the ozone decomposition and OH generation.

Using granular activated carbon (GAC) as electric particle electrode and heterogeneous catalyst loaded metal oxide to replace insulated particle in bipolar packing bed cell (BPBC), the electro-heterogeneous catalytic oxidation system was constructed. Adopting impregnation method to prepare γ-Al2O3 supported catalysts containing Cu and Ce, it was evenly mixed with GAC to construct packing materials. Using stainless steel as anode, porous graphite as cathode and packing materials between them, landfill leachate was treated by an electro-catalytic oxidation process and COD removal efficiency was studied. The activity of catalysts was explored, and using scanning electron microscope (SEM) and X-ray diffraction (XRD), the microstructure and morphology were characterized. The operating parameters such as cell voltage, initial pH, airflow and inter-electrode distance were also investigated. The results showed that when the metal ion concentration in soaking solution was 2% for Cu, 9% for Ce, the activity of prepared catalyst was the highest. Under the conditions of an applied voltage of 15.0 V, pH of 7.0, airflow of 0.08 m3/h, and an inter-electrode distance of 3.0 cm, the removal efficiencies of COD reached 92.9%. Qualitative analysis of the interim products was carried out, adopting ultraviolet-visible spectrum, and the mechanism of electro-heterogeneous catalytic oxidation reaction was discussed. The whole degradation involves two main processes: electro-oxidation and electro-coagulation.

Methanogens play an important role in the anaerobic digestion and production of methane, and show significant influence on the performance of anaerobic wastewater treatment process. Then the methanogens in anaerobic granular sludge samples from full-scale UASB bioreactors treating avermectin or starch wastewater were detected by FISH using 16S rRNA gene-based probe and functional gene-based probes. The results showed that the hybridization of methanogens in simultaneous FISH with mcrA gene-based and 16S rRNA gene-based probes was high coincident and the coincidence degree was about 60%-80%, implying the preferable hybridization consistency between functional gene-based probe and 16S rRNA gene-based probe. The relative abundance of methanogens obtained in FISH analysis using 16S rRNA gene-based probe seemed higher than that using functional gene-based probes, indicating that functional gene could provide more specific detection of methanogens than 16S rRNA gene probably. For functional gene-based probes, the methanogen-specificity was in the following order: mcrA＜F420＜mtr. During the development process of both granular sludge samples, the maximum relative abundance of methanogens was obtained at its mature phase using all probes. The relative abundance of methanogens in the sludge sample treating avermectin wastewater was lower than that treating starch wastewater, indicating smaller methanogenic population in the sludge sample treating avermectin wastewater due to inhibitory effect of antibiotic residue on methanogens probably.

In order to investigate ecotoxicity effect of 2,4-dinitrotoluene (2,4-DNT) to freshwater fish(Brocarded carp), the acute toxicity test and the sub-lethal expriment were conducted in lab. The acute toxicity test show that 96h LC50 value of 2,4-DNT to Brocarded carp is 19.67 mg/L. Its toxicity rating is moderately toxic to fish. Based on the result of the acute toxicity test, fish was exposed to different concentrations (1/2LC50, 1/4LC50, 1/16LC50, 1/256LC50, surface water standard concentration) and killed at 3, 7, 10 and 14 day after exposure. The activities of Superoxide Dismutase (SOD) and Catalase (CAT) in liver tissue were analyzed. The results indicated the activities of SOD and CAT were inhibited from the third day in all treatment groups at post-exposure, they were lower than those of the control group (p＜0.01). The SOD and CAT activities of the control group were stable during 14-days. The CAT and SOD activities had the same changing trend and they were unstable under the pollution stress. The CAT enzyme was more sensitive than SOD enzyme under pollution stress. The results demonstrate that the SOD and CAT activities of liver in Brocarded Carp might be the promising biomarker of 2,4-DNT exposure to freshwater fish. Therefore it is suggested that the couple index of SOD and CAT could be used as biomarker of nitroaromatics compounds, when their pollutions affected living beings in aquatic environment.

2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS2 can only absorb up to 10% of the incident light in the visible, which is not sufficient to achieve a high optical-to-electrical conversion efficiency. To overcome this shortcoming, a "gap-mode" plasmon-enhanced monolayer MoS2 fluorescent emitter and photodetector is designed by squeezing the light-field into Ag shell-isolated nanoparticles-Au film gap, where the confined electromagnetic field can interact with monolayer MoS2 . With this gap-mode plasmon-enhanced configuration, a 110-fold enhancement of photoluminescence intensity is achieved, exceeding values reached by other plasmon-enhanced MoS2 fluorescent emitters. In addition, a gap-mode plasmon-enhanced monolayer MoS2 photodetector with an 880% enhancement in photocurrent and a responsivity of 287.5 A W-1 is demonstrated, exceeding previously reported plasmon-enhanced monolayer MoS2 photodetectors.

Although the dominant members of microbial communities in wastewater bio-treatment systems were often paid attention due to their possible important roles in treatment performance, their population sizes, especially the unculturable species, were still little known. Then PCR-DGGE was used in an attempt to estimate the dominant microbial population sizes in the anaerobic granular sludge treating streptomycin wastewater, coupled with an inoculated strain (Esherichia coli) with known population sizes as an internal standard. The results indicated that the band intensities of the inoculated strain in DGGE profiles showed good correlation with population sizes. Then it was possible to estimate the dominant microbial population sizes by means of comparing their DGGE band intensities with the inoculated strain. The estimated results demonstrated that the sizes of major dominant microbial populations in the sludge sample were at the level of 107–108 CFU/g. The sizes of secondary dominant microbial populations were at the level of 105–106 CFU/g. The microbial populations with the size level lower than 103 CFU/g were undetectable by PCR-DGGE. These results provided a potential approach to evaluate dominant microbial population sizes in complex microbial communities.

Membrane-aerated biofilm reactor (MABR) represent a novel membrane-biological wastewater treatment technology. In addition, bioaugmented treatment using genetically engineered microorganism (GEM) biofilm in MABR is proposed to improve refractory pollutant removal. In the present study, a SPG membrane aerated-biofilm reactor (SPG-MABR) with GEM biofilm formed on the SPG membrane surface was applied to treat atrazine wastewater. The influences of air pressure, biofilm biomass and liquid velocity on the performance of the SPG-MABR were investigated. The variation of GEM biofilm during the SPG-MABR operation was observed. The results indicated that the increased air pressure could promote atrazine and COD removal as well as re-oxygenation by increasing oxygen permeability coefficient. A higher biofilm biomass could also enhance atrazine and COD removal, but simultaneously reduce the re-oxygenation rate because biofilm thickness and oxygen transfer resistance increased. When liquid velocity in the SPG-MABR was decreased under laminar flow condition, atrazine and COD removal was improved due to the facilitated contaminant diffusion from wastewater to biofilm. The atrazine removal efficiency reached to 98.6% in the SPG-MABR after 5d treatment at air pressure of 300 kPa, biofilm biomass of 25 g x m(-2) and liquid velocity of 0.05 m x s(-1). The microbial polymorphism of GEM biofilm was observed during the SPG-MABR operation. The surface of GEM biofilm was gradually covered by other microbial cells and the distribution of GEM cells reduced, but inside the GEM biofilm, the GEM cells were still dominant.

Electrochemical oxidation degradation of azo dyes has become a widely used method in recent years. Iron phosphomolybdate (FePMo12) was synthesized with molybdophosphoric acid and ferric salt. Morphology and microstructure of catalyst were chararerized by IR spectrometry and X-ray diffraction. The heteropolyanion showed a Keggin structure. Electrochemical oxidation of acid red 3R was investigated in the presence of FePMo12 supported on modified 4A molecular sieve (4A) as packing materials in the reactor. The results showed that the optimal technological conditions for decolorization of acid red 3R simulated wastewater were as follows: active component load 3% , electrolytic voltage 22 V, initial pH 4, air-flow 0.08 m3 h- ', electrode span 3.0 cm. Under the opñrrizd conditions, the decolorization efficiency, COD and TOC removal efficiencies reached 75.3% , 65.4% and 46.0% after 90 min, respectively. With the addition of NaCI to the dyes solution during electrolysis, the decolorization efficiency increased, while the effect of Na2SO4 on the degradation was negative. The efficiency of degradation and mineralization of the acid red 3R were estimated based on the absorbance measurements by UV-vis. It shows that the conjugated structure of dye was destroyed primarily.

Supported phosphotungstic acid catalysts on gamma-Al2O3 (HPW/gamma-Al2O3) were prepared by solution impregnation and characterized by FTIR, XRD, TG-DTA and SEM. The heteropolyanion shows a Keggin structure. Electro-chemical oxidation of Acid Red 3R was investigated in the presence of HPW supported on gamma-Al2O3 as packing materials in the reactor. The results show that HPW/gamma-Al2O3 has a good catalytic activity for decolorization of Acid Red 3R. When HPW loading was 4.6%, pH value of Acid Red 3R was 3, the voltage was 25.0 V, air-flow was 0.04 m3 x h(-1), and electrode span was 3.0 cm, the decolorization efficiency of Acid Red 3R can reach 97.6%. The removal rate of color had still about 80% in this electro-chemical oxidation system, after HPW/gamma-Al2O3 was used for 10 times, but active component loss existed. The interim product was analyzed by means of Vis-UV absorption spectrum. It shows that the conjugated structure of dye is destroyed primarily.

The quinone respiration process of Paracoccus versutus strain GW1 was characterized and the effects of the four redox mediators on the denitrification process were studied. The experiment results suggested that quinones were utilized by Paracoccus versutus strain GW1 as electron acceptors in the respiratory chain and reduced to hydroquinone. Batch experiments were carried out to investigate the biocatalyst effect of redox mediators as catalyst on the denitrification process at 35 degrees C. All four redox mediators tested were able to enhance the nitrate removal efficiency and the denitrification efficiency by 1.14-1.63 fold and 1.12-2.02 fold, respectively. The accelerating effect from high to low was AQDS1,5-AQDSAQSalpha-AQS. In the presence of redox mediators, the stabilized ORP values in the nitrate decomposition process were reduced by 33-75 mV. The pH variations in denitrification with redox mediators showed similar tendency to that of the conventional nitrate removal process. In the concentration range of 0-0.32 mmol x L(-1), AQDS had the best accelerating effect and a linear correlation was found for the denitrification rate K and the AQDS concentration cAQDS. This study indicated that the application of redox mediators significantly improved the denitrification process by enhancing the decomposition rate.

The methanogenic community in anaerobic granular sludge from a full-scale UASB treating avernectin wastewater was analyzed based on mcrA gene, compared to 16S rRNA gene. The results indicated that the diversity indices of methanogenic community, including Shannon diversity index, Margalef richness index and Berger-Parker dominance index, were no difference between mcrA gene-based and 16S rRNA gene-based PCR products analysis by DGGE, although their DGGE band patterns were different, implying that the diversity analysis of methanogenic community based on mcrA genes was consistent with 16S rRNA gene. The phylogenetic analysis of dominant methanogenic populations based on these two target genes also showed resemble and Methanobacteriales and Methanosarcinales were determined to be the main orders of methanogenic populations in anaerobic granular sludge. On the other hand, the difference in phylogenetic analysis suggested simultaneously some group-specific of the two target genes. The hybridization of methanogenic community in FISH analysis based on two target genes was almost identical except a little different hybridization areas. The average relative abundance of methanogenic community was 24.25% +/- 6. 47% detected by FISH based on mcrA gene, lower than that based on 16S rRNA gene (33.42% +/- 2.34%). Then it could be concluded that the analysis of methanogenic community based on mcrA gene and 16S rRNA gene exhibited high resemblance and mcrA gene could used to be target gene for methanogenic community, as an alternative of 16S rRNA gene.

Four selected quinone redox mediators with similar structure were conducted to accelerate reactive brilliant red K-2BP decolorization, and the accelerating structure-activity of redox mediators on the decolorization was also studied. Batch experiments were carried out to determine the catalyst effect on the decolorization of reactive brilliant red K-2BP with temperature of 35 degrees C and under anaerobic conditions. The experiment results suggested that (1) four similar chemical structure redox mediators [1, 4, 5, 8-Tetrachloroanthraquinone (1,4,5,8-AQ), Anthraquinone (AQ), 1,8-Dichloroanthraquinone (1,8-AQ), 1,5-Dichloroanthraquinone (1,5-AQ)], all accelerated the decolorization rate of reactive brilliant red K-2BP and the reaction rate was enhanced 1.4-3 times; (2) the accelerating order was 1,8-AQ1 ,5-AQAQ1,4,5,8-AQ at the quinone mediator concentration of 4 mmol x L(-1) and reactive brilliant red K-2BP concentration of 300 mg x L(-1); (3) under the reactive brilliant red K-2BP concentration of 300 mg x L(-1), 1,8-AQ had best accelerating effect, and the relationship between decoloring rate constants and 1,8-AQ concentration; (4) and the mediator acclerating effects also related to substituent positioning effects and conjugated effects. The structure-activity mathematical model of redox mediators was put forward, which could improve water-insoluble redox mediators catalytic strengthening theory system.

Atrazine removal in membrane bioreactor (MBR) and conventional activated sludge reactor (CAS) bioaugmented by genetically engineered microorganism (GEM) was investigated. PCR-DGGE was used to analyze microbial community variation of both bioreactors in different running stages. The results indicated that high removal efficiency of atrazine was obtained in both bioreactors bioaugmented by GEM. The average removal efficiencies of atrazine reached up to 88.6% in MBR and 85.3% in CAS. Atrazine removal bioaugmented by GEM would be helpful to maintain sludge bioactivity in both bioreactors. The performance of MBR was better than CAS. The GEM density decreased quickly in both bioreactors after GEM inoculation and then became stable. The stable GEM densities in MBR and CAS were 2.1×103 CFU/mL and 1.7×103 CFU/mL, respectively. PCR-DGGE analysis showed microbial community variation in different running stages of both bioreactors. The biodiversity and stability of microbial community decreased in the presence of atrazine exposure and recovered after efficient atrazine removal. MBR seemed better than CAS to maintain biodiversity and stability of microbial community.

Removal of atrazine was investigated when genetically engineered microorganism (GEM) was inoculated into membrane bioreactor (MBR) and hybrid bioreactor for bioaugmentation. The performances of atrazine removal in two bioreactors were explored. The variations of GEM density and atzA gene abundance in two bioreactors were also determined. The results indicated that removal activities of COD and ammonia nitrogen were inhibited a little by atrazine and recovered after bioaugmentation by inoculated GEM. The better removal performance of COD and ammonia nitrogen was obtained in MBR. The biological removal efficiency of atrazine was improved significantly when bioaugmented treatment by GEM was applied. The atrazine removal increased gradually and the average removal rates reached up to 38.94% in MBR and 29.36% in hybrid bioreactor in the later running period. After inoculated, GEM densities in two bioreactors decreased rapidly and then tended to be constant. The stable GEM densities in MBR, suspended sludge and adherent biofilm of hybrid bioreactor were 5 x 10(3) CFU/mL, 1.1 x 10(3) CFU/mL and 0.4 x 10(3) CFU/mL, respectively. Fluorescence in situ hybridization (FISH) was used to detect azA gene in two bioreactors and the result indicated that the average relative abundances of atzA gene decreased initially and increased subsequently. The largest average relative abundance of atzA gene was obtained in MBR. The average relative abundance of atzA gene in adherent biofilm is larger than that in suspended sludge in the hybrid bioreactor. The horizontal transfer of atzA gene was the possible important reason responsible for high gene abundance.

Methanogens is considered to be important functional microbial population in anaerobic granular sludge. Fluorescence in situ hybridization was used to analyze methanogens of anaerobic granular sludge in a full-scale UASB treating avermectin wastewater. The results indicated that the distribution forms of methanogens, Methanobacteriales and Methanosarcinales were identical on the surface and inner face of granular sludge samples in different formation stages (with different diameters) , although the relative abundances of these methanogens were different. The relative abundances of methanogens on the inner face were larger than these on the surface of granular sludge samples. The relative abundances of Methanobacteriales were larger than these of Methanosarcinales. The relative abundances of methanogens in all granular sludge samples ranged from (25.50 +/- 8.63)% to (48.67 +/- 8.87)%. The maximum relative abundances of methanogens were obtained in mature granular sludge with diameter of 1.0-2.0 mm, (47.08 +/- 8.26)% on the surface and (48.67 +/- 8.87)% on the inner face, respectively. The avermectin residue in wastewater showed possible inhibition effect on methanogens. The maximum specific methanogenic activities of granular sludge samples ranged from 1.311 to 1.562 g/(g x d), varying as same as COD removal ratios and relative abundances of methanogens, implying the strong correlation of methanogens with bioactivity of granular sludge.

Genetically engineered microorganism (GEM) leaking from bioreactors to natural environment will lead to potential ecological risk when applied for wastewater bioaugmentation treatment. An atrazine-degrading GEM was used in a conventional activated sludge bioreactor (CAS) and a membrane bioreactor (MBR) to investigate leaking density of GEM. in the effluent. Survival of GEM in the simulated natural environments after leakage was also explored. The results showed that the maximum leakage happened at the initial time of GEM inoculation. When inoculating density was 10(10) CFU/mL, the maximum leaking density from CAS was close to inoculating density as well as the maximum leaking density from MBR was only 10(2) CFU/mL. Leaking density was the key factor influencing GEM survival in the simulated environments. When leaking density from CAS reached to 10(10) CFU/mL, GEM with high density would survive in the simulated water and soil environments for a long time (more than 30 d), which would lead to high potential ecological risk. On the contrary, when leaking density from MBR was 10(2) CFU/mL, GEM would disappear quickly in the simulated environments, which meant low potential ecological risk. Environmental conditions also affected GEM survival. Increasing water content and organic compounds content of soil as well as creating environmental selective pressure (adding atrazine) were profitable for GEM survival.