进水盐度对膜生物反应器运行效能的影响研究

进水盐度对膜生物反应器(MBR)的运行效能影响显著,尤其是进水含盐量为5 g/L时,明显恶化了污泥可滤性,膜污染速率加快;MBR混合液中溶解性微生物产物(SMP)和胞外聚合物(EPS)含量随钠离子浓度变化而变化,其中SMP中蛋白质含量与钠离子浓度密切相关;与紧密结合态EPS(TB)相比,钠离子含量对松散结合态EPS(LB)浓度的影响更大;不同盐度对COD及NH4+-N影响不明显,系统对COD及NH4+-N的去除效果稳定,分别保持在92%及94%以上,高盐度对MBR总磷去除率降低明显。     

Characterization of adsorption properties of extracellular polymeric substances (EPS) extracted from sludge

Extracellular polymeric substances (EPS) of sludge play an important role in the adsorption of organic pollutants in wastewater biological treatments. Experiments were conducted to characterize the adsorption properties of EPS extracted from aerobic sludge (AE-EPS) and anaerobic sludge (AN-EPS) using a dye-probing method in this study. A model cationic dye, Toluidine blue (TB), was used as the dye probe. The adsorption of dye onto EPS to produce a dye-EPS complex would cause a change in the solution absorbance, attributed to the difference between the visible spectra of the dye and dye-EPS complex. From the change in the absorbance, the equilibrium absorption capability of EPS could be evaluated. Results indicate that Langmuir adsorption isotherm was able to adequately describe the adsorption equilibrium of TB onto both EPS at various pH values. From the Langmuir adsorption isotherm, the maximum binding capabilities were calculated to be 1.9 and 2.5 mmol/g EPS for AE-EPS at pH 7.0 and 11.0, and 1.6 and 1.9 mmol/g EPS for AN-EPS at pH 7.0 and 11.0, respectively. The first-order rate constants were calculated to be 0.033 and 0.35 min(-1) for AE-EPS at pH 7.0 and 11.0, and 0.069 and 0.18 min(-1) for AN-EPS at pH 7.0 and 11.0, respectively. The results of the present study demonstrated that the dye-probing method was appropriate for investigating the adsorption process of EPS in aqueous solution.     

Extraction and Characterization of Extracellular Polymeric Substances in Biofilm and Sludge via Completely Autotrophic Nitrogen Removal Over Nitrite System

Extracellular polymeric substances (EPS) were extracted from sludge and biofilm via the completely autotrophic nitrogen removal over nitrite (CANON) system. Tightly bound (TB)-EPS were extracted using four physical methods, namely, cationic exchange resin (CER), sonication, heating, and steaming. CER was the most effective and most suitable method for extraction among the four methods. Moreover, the ultraviolet–vis spectra of TB-EPS indicated that few cells were destroyed by the CER method. The major component contents of total EPS, proteins, carbohydrates, humic substances, and DNA in sludge were 60.77, 49.84, 21.63, and 9.01 mg/g volatile suspended solids (VSS) and 90.03, 29.01, 15.96, and 10.04 mg/g VSS in biofilm, respectively. The Fourier transform infrared (FT-IR) spectra results indicated differences in the EPS functional groups between biofilm and sludge. The results of the batch experiments showed that the biofilm activity was significantly higher than that of the sludge in the CANON system. Furthermore, biomass activity was probably influenced by the EPS composition and distribution in the sludge and biofilm.     

Visualisation and characterisation of biopolymer clusters in a submerged membrane bioreactor

A laboratory wastewater treatment membrane bioreactor (MBR) with a submerged hollow-fibre membrane was used to investigate the major foulants in sludge mixtures. Confocal laser scanning microscopy (CLSM) with a triple fluorescent staining protocol, i.e., SYTO9 for microbial cells, ConA-TRITC lectin for polysaccharides and NanoOrange for proteins, was utilised to visualise the fouling materials. A pool of biopolymer clusters (BPCs) ranging from 2.5 to 60 μm in size was identified in the liquid phase of the MBR sludge and in the cake sludge on the membrane surface. According to the CLSM examination, BPC are free and independent organic solutes that are different from biomass flocs and extracellular polymeric substances (EPS) and much larger than soluble microbial products (SMP). Compared to EPS, BPC contain more polysaccharides and proteins and less humic substances. It is believed that BPC are an important foulant that interacts with biomass flocs to form the sludge fouling layer on the membrane. A filtration test observed with the CLSM shows that BPC are apparently formed by the adsorption and affinity clustering of SMP within the sludge deposited on the membrane surface. The cake sludge on the fouled membrane has a much higher BPC content (16.8 mg TOC/g SS) than the MBR bulk sludge (0.4 mg TOC/g SS). It is argued that BPC behave as a glue to facilitate the growth of an impermeable sludge cake on the membrane surface, thus resulting in serious MBR fouling. These CLSM findings provide the first direct evidence of the presence of BPC in MBR and illustrate their essential role in membrane fouling.     

Unraveling pharmaceuticals removal in a sulfur-driven autotrophic denitrification process: Performance,kinetics and mechanisms

The removal of eight typical pharmaceuticals (PhACs) (i.e., ibuprofen (IBU), ketoprofen (KET), diclofenac (DIC), sulfadiazine (SD), sulfamethoxazole (SMX), trimethoprim (TMP), ciprofloxacin (CIP) and enoxacin (ENO)) in sulfur-driven autotrophic denitrification (SdAD) process were firstly investigated via long-term operation of bioreactor coupled with batch tests. The results indicated that IBU and KET can be effectively removed (removal efficiency > 50%) compared to other six PhACs in SdAD bioreactor. Biodegradation was the primary removal route for IBU and KET with the specific biodegradation rates of 5.3±0.7～18.1±1.8 µg g^?1-VSS d^?1 at initial concentrations of 25-200 µg/L. The biotransformation intermediates of IBU and KET were examined, and the results indicated that IBU was biotransformed to three intermediates via hydroxylation and carboxylation. KET biotransformation could be initiated from the reduction of the keto group following with a series of oxidation/reduction reactions, and five intermediates of KET were observed in this study. The microbial community composition in the system was markedly shifted when long-term exposure to PhACs. However, the functional microbes (e.g., genus Thiobacillus) showed high tolerance to PhACs, resulting in the high efficiency for PhACs, N and S removal during long-term SdAD reactor operation. The findings provide better insight into PhACs removal in SdAD process, especially IBU and KET, and open up an innovative opportunity for the treatment of PhACs-laden wastewater using sulfur-mediated biological process.     

原子吸收光谱法测定改性梨渣吸附Pb(Ⅱ)的研究

通过原子吸收光谱法研究了在不同pH、吸附剂量、Pb2+浓度和吸附时间条件下磷酸酯化改性梨渣吸附Pb2+的行为。结果表明:溶液初始pH 4.2时,Pb2+的吸附达到最大值;酯化梨渣≥10 g/L能除去Pb2+为30 mg/L溶液中的91%的Pb2+。酯化梨渣对Pb2+的吸附符合Langmuir等温模型,其最大吸附能力为43.99 mg/g。Pb2+达到吸附平衡的时间为40 min,准一级反应动力学方程可描述酯化梨渣对Pb2+的吸附过程。     

Biosorption of copper(II) and cadmium(II) by a novel exopolysaccharide secreted from deep-sea mesophilic bacterium

The biosorption behaviors and mechanisms of a novel exopolysaccharide (EPS), which is secreted by a mesophilic bacterium (namely Wangia profunda (SM-A87)) isolated from deep-sea sediment, for heavy metals Cu(II) and Cd(II) have been studied in this paper. The effects of SM-A87 EPS concentration, solution pH and ionic strength on the metal uptake were investigated by employing batch adsorption techniques, respectively. The optimum biosorption capacities were observed at pH 5.0 for Cu(II) with 48.0 mg/g and pH 6.0 for Cd(II) with 39.75 mg/g, respectively. Addition of salts decreased Cu(II) or Cd(II) uptake in the order of K⁺ < Na⁺ < Ca²⁺. Langmuir and Freundlich models were employed to describe the biosorption equilibrium data, indicating the favorable biosorption occurs and larger biosorption capacity and intensity for Cu(II) than for Cd(II). The biosorption kinetics for both metals can be well described by pseudo-second-order kinetic model, compared with pseudo-first-order and intraparticle diffusion kinetic models. The competitive biosorption was also studied, indicating that in two-component solution with different metal ratios, the selective biosorption of SM-A87 EPS for Cu(II) was much higher than for Cd(II). The Fourier transform infrared spectroscopy (FT-IR) analysis indicated possible functional groups (e.g., OH, COO and COC) of SM-A87 EPS involved in metal biosorption process, which indicated the potential of using SM-A87 EPS as an effective sorbent for Cu(II) or Cd(II) removal from water.     

表面活性剂对污泥脱水性能影响的机理研究:Gemini表面活性剂与聚电解质相互作用的分子动力学模拟

表面活性剂可以与污泥表面的胞外聚合物(EPS)吸附形成胶束,释放出自由水和结合水,从而达到改善污泥脱水性能的目的.本文采用粗粒化的分子动力学模拟方法,研究了Gemini表面活性剂与EPS形成复合物的过程和结构.聚电解质链的亲疏水性对吸附过程有显著影响,亲水聚电解质链与Gemini表面活性剂吸附的主要驱动力为静电吸引,Gemini表面活性剂头基吸附在链上,尾链朝向溶剂;疏水聚电解质链与Gemini表面活性剂吸附过程由静电作用与疏水作用共同促进,Gemini表面活性剂以平行于聚电解质链的构型存在.Gemini表面活性剂联结基团长度对吸附过程的影响甚微;聚电解质链的电荷密度对亲水聚电解质链的吸附产生协同作用,对疏水聚电解质链的吸附不产生作用.     

Towards chemical analysis of nanostructures in biofilms I: imaging of biological nanostructures

Due to their direct influence on the stability of bacterial biofilms, a better insight into the nanoscopic spatial arrangement of the different extracellular polymeric substances (EPS), e.g., polysaccharides and proteins, is important for the improvement of biocides and for process optimization in wastewater treatment and biofiltration. Here, the first application of a combination of confocal laser-scanning microscopy (CLSM) and atomic force microscopy (AFM) to the investigation of river-water biofilms and related biopolymers is presented. AFM images collected at selected areas of CLS micrographs dramatically demonstrate the heterogeneity of biofilms at the nanometer scale and the need for a chemical imaging method with nanoscale resolution. The nanostructures (e.g., pili, flagella, hydrocolloids, and EPS) found in the extracellular matrix are classified according to shape and size, which is typically 50–150 nm in width and 1–10 nm in thickness, and sets the demands regarding spatial resolution of a potential chemical imaging method. Additionally, thin layers of the polysaccharide alginate were investigated. We demonstrate that calcium alginate is a good model for the EPS architecture at the nanometer scale, because of its similar network-like structure. Figure CLSM-AFM allows imaging of nanometer-sized extracellular structures     

复合催化剂α-(Fe，Cu)OOH/RGO的制备、表征及其协同H2O2在可见光下去除环丙沙星性能

采用一步回流法制备了α-(Fe,Cu)OOH/RGO复合催化剂,通过粉末X射线衍射、扫描电子显微镜和X射线光电子能谱等对催化剂进行了表征,并以30 mg·L^-1的环丙沙星(CIP)为目标污染物,研究了不同制备条件下所得催化剂在可见光照射下协同H2O2对CIP的去除效果。结果表明,成功实现了α-(Fe,Cu)OOH纳米棒在石墨烯二维薄片上原位生长,α-(Fe,Cu)OOH/RGO复合材料的可见光吸收边发生红移,禁带宽度从2.02 eV变为1.76 eV。石墨烯复合不但增强了对污染物的吸附能力,而且加快了光生电子的分离、迁移速率,还提高了反应体系中电子的传导效率。当石墨烯复合比例(质量分数)为1%时,复合催化剂的催化性能最佳。当催化剂投加量为0.40 g·L^-1,H2O2浓度为0.10 mol·L^-1时,反应120 min,CIP被全部去除。α-(Fe,Cu)OOH/RGO循环使用5次,对CIP的去除率均在90%以上,表明催化剂具有较强的催化活性和较好的稳定性。     

Treatment of pulp and paper mill wastewaters with poly aluminium chloride and bagasse fly ash

The present study deals with the use of poly aluminium chloride (PAC) as a coagulant and bagasse fly ash (BFA), which is generated in sugar mills, as an adsorbent for the removal of chemical oxygen demand (COD) and colour of pulp and paper mill effluents. Under optimal conditions of pH 3 and initial PAC dosage of 3 g/l, about 80% COD removal and 90% colour removal were obtained. The optimal conditions for the adsorptive removal of COD and colour with BFA were pH 4 and BFA dosage of 2 g/l. Under these conditions, COD and colour removal were, respectively, 50 and 55%. Adsorptive removal of COD by BFA followed second-order kinetics. Intra-particle diffusion was found to be rate controlling. Freundlich and Langmuir adsorption isotherms were found to fit the equilibrium adsorption data with BFA. Two-stage treatment using PAC (3 g/l) as a coagulant in the first stage and BFA (2 g/l) as an adsorbent in the second stage gave the combined COD and colour removal of nearly 87 and 95%, respectively, for different effluents without any pH adjustment. Two-stage adsorptive treatment using BFA (2 g/l) in both the stages gave a combined COD and colour removal of about 70%. The sludge obtained can be dewatered by centri-clarifiers, dried, briquetted and incinerated to recover its energy content.     

Response of aerobic sludge to AHL-mediated QS: Granulation,simultaneous nitrogen and phosphorus removal performance

The effects of different species and concentrations’ signal molecules on aerobic activated sludge system were investigated through batch experiments. Results showed that the fastest NH₄⁺-N oxidization rate and the most extracellular polymeric substances (EPS) secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone (C₆-HSL) into the aerobic activated sludge. Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing (AHLs-mediated QS), nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C₆-HSL. It was found that C₆-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge (AGS) system. Microbial compositions considerably shifted with long-term C₆-HSL-manipulation. Exogenous C₆-HSL-manipulation inhibited quorum quenching-related (QQ-related) activities and enhanced QS-related activities during the stable period. The proposed C₆-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS, which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.     

The performance and degradation mechanism of sulfamethazine from wastewater using IFAS-MBR

Sulfamethazine(SMZ) is an important sulfonamide antibiotic.Although the concentration in the environment is small,it is harmful.The drug residues can be transferred,transformed or accumulated,affecting the growth of animals and plants.In this study,the integrated fixed-film activated sludge membrane bioreactor(IFAS-MB R) were constructed to investigate the performance and degradation mechanism of SMZ.The addition of SMZ had a significant impact on the removal of the chemical oxygen demand(COD) and ammonia nitrogen(NH_4^+-N).The optimal operating conditions were hydraulic retention time(HRT) at 10 h and solid retention time(SRT) at 80 d,respectively.On this basis,the effects of different SMZ concentrations on nutrient removal,degradation,and sludge characteristics were compared.The removal efficiency of SMZ increased with the increase of SMZ concentration.The maximum removal rate was as high as 87%.The SMZ dosage also had an obvious effect on sludge characteristics.As the SMZ concentration increased,the extracellular polymer substances(EPS) concentration and the membrane resistance both decreased,which were beneficial for the reduction of membrane fouling.Finally,seven kinds of SMZ biodegradation intermediates were identified,and the possible degradation pathways were speculated.The microbial community results showed that the microbial diversity and richness in the reactor decreased after adding SMZ to the influent.The relative abundance of Bacteroidetes,Actinobacteria,Saccharibacteria and Nitro spirae increased at the phylum level.Sphingobacteria and Betaproteobacteria became dominant species at the class level.The relative abundance of norankp-Saccharibacteria and Nitrospirae increased significantly,and norank-p-Saccharibacteria may be the dominant bacteria for SMZ degradation.     

柚子皮生物炭质用于河水中苯系物的固相微萃取

苯、甲苯、乙苯和二甲苯(邻二甲苯、间二甲苯、对二甲苯)组成的苯系物(BTEX)是炼油厂和石化厂等工业园区普遍制造和排放的碳氢化合物,具有一定的毒性和致癌作用,对生态环境和人类健康造成极大威胁。研究以低成本、绿色且富含木质素和含氧官能团的柚子皮作为植物原料,在有限氧条件下采用程序升温热解法制备了柚子皮生物炭质吸附剂,通过N₂吸附-脱附等温线和孔径分布图对不同热解温度下制备的柚子皮生物炭质吸附剂的孔隙结构进行了考察。结果表明:在1000 ℃热解温度下制得的柚子皮生物炭质具有更高的比表面积(749.9 m²/g)、更大的孔体积(0.42 cm³/g)、更集中的孔径分布(2~3 nm)。将吸附剂通过溶胶-凝胶法(sol-gel)涂覆在铁丝上制成固相微萃取纤维,与气相色谱-火焰离子化检测器(GC-FID)相结合,对影响萃取和分离BTEX的条件进行优化,建立了用于BTEX检测的高灵敏度分析方法。方法具有检出限低(0.004~0.032 μg/L)、线性范围宽(1~100 μg/L)、线性关系好、萃取效率高(约为商品化涂层聚二甲基硅氧烷(7 μm)的2.9~18.3倍)等优势。此外,应用该方法已成功在河水样本中检测出了乙基苯(4.80 μg/L),邻二甲苯(3.00 μg/L)和对二甲苯、间二甲苯(2.46 μg/L)。最后将该方法应用于河水样本的加标试验中,得到了满意的回收率(75.7%~117.6%)。实验结果表明所建立的分析方法可实现对环境水样(河水)中BTEX的低成本、高灵敏度检测。     

Biosorption and desorption of copper (II) ions by Bacillus sp.

Batch biosorption experiments were conducted to investigate the removal of Cu²⁺ ions from aqueous solutions by a series of bacterial strains isolated from a local activated sludge process. The characteristics of 12 isolates were identified and examined for their ability to bind Cu²⁺ ions from aqueous solution. Among the isolates, two species exhibited biosorption capacity >40 mg of Cu/g of dry cell. Isotherms for the biosorption of copper on bacterial cells were developed and compared, and the equilibrium data fitted well to the Langmuir and Freundlich isotherm models. The biosorption of copper increased significantly with increasing pH from 2.0 to 6.0 regardless of the species. More than 90% of copper sorbed on the cells of Bacillus sp. could be recovered by washing with 0.1 M HNO₃ for 5 min. The performance of two different desorption processes was also tested and compared. The results show that five biosorption and desorption cycles are a better operation process than five successive biosorptions followed by one desorption to remove and recover copper from aqueous solution. The biosorbent could be used for at least five biosorptions and desorption cycles without loss of copper removal capacity. It can be concluded that the activated sludge or sludge-isolated bacteria could be a potential biosorbent for copper removal.     

Copper(0)-mediated radical polymerization of styrene at room temperature

The “living’/controlled radical polymerization (LRP) of styrene (St) at room temperature is rarely reported. In this work, copper(0) (Cu(0))-mediated radical polymerization of St at room temperature was investigated in detail. Dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) as well as a binary solvent, tetrahydrofuran/1,1,1,3,3,3-hexafluoro-2-propanol were used as the solvents, respectively. Methyl-2-bromopropionate and ethyl 2-bromoisobutyrate were used as the initiators, respectively. The polymerization proceeded smoothly with moderate conversions at room temperature. It was found that DMF was a good solvent with the essential features of LRP, while DMSO was a poor solvent with uncontrollable molecular weights. Besides, the match among the initiator, solvent and molar ratios of reactants can modulate the livingness of the polymerization, and the proper selection of ligand was also crucial to a controlled process. This work provided a first example of Cu(0)-mediated radical polymerization of St at room temperature, which would enrich and strength the LRP technique.     

Acoustic sensing of the bacterium-substratum interface using QCM-D and the influence of extracellular polymeric substances

It is commonly assumed that bacterial presence on a QCM sensor-surface is associated with a negative frequency shift according to conventional mass-loading theory. Here, we demonstrate that bacteria adhering to QCM sensor-surface may yield positive frequency shifts up to 1.9×10(-6) Hz per bacterium according to a coupled-oscillator theory. Furthermore, it is demonstrated that the excretion of extracellular polymeric substances (EPS) by adhering bacteria can change the frequency shift in the negative direction by 1.7×10(-6) Hz per bacterium, according to conventional mass-loading theory. The difference in frequency shifts between an EPS-producing and a non-EPS producing staphylococcal strain correlated with the excretion of 3×10(-14) g EPS per bacterium, representing only a few percent of the weight of a bacterium. Thus an adsorbed molecular mass as low as a few percent of the mass of an adhering bacterium significantly alters the QCM-signal. Since adhesion of many different bacterial strains is accompanied by molecular adsorption of EPS, with potentially opposite effects on the QCM-signal, a combination of the coupled-oscillator and normal mass-loading theory has to be applied for proper interpretation of QCM-frequency shifts in bacterial detection.     

Adsorption kinetics,isotherms and mechanisms of three-component covalent organic polymer/sodium alginate beads for ciprofloxacin removal from aqueous solution

Ciprofloxacin (CIP), an important representative fluoroquinolone antibiotic, has been frequently detected in water sources, thus threatening aquatic organisms and human health. In this work, a porous three-component covalent organic polymer (SLEL-6) was synthesized through multi-component (MC) reaction systems for adsorptive removal of CIP from aqueous solution, followed by an encapsulation process to achieve SLEL-6/sodium alginate (SA) beads with boosted adsorption ability, reusability and recyclability. By virtue of the hierarchical porous natures, functional groups as well as π-rich skeletons, SLEL-6 and SLEL-6/SA beads could deal with CIP contamination effectively. Moreover, the adsorption isotherms of CIP by SLEL-6 and SLEL-6/SA beads follow the Langmuir model showing high theoretical maximum adsorption capacities of 57.47 and 163.93 mg g⁻¹, respectively. Furthermore, the plausible mechanisms are proposed according to experimental studies of influencing factors, coupled with characterizations before and after adsorption. This work therefore highlighting the immense potential of COP-based SA composite beads as new-type globular adsorbents for eliminating fluoroquinolones from aqueous solution.     

微孔羟基磷灰石/聚(甲基丙烯酸甲酯-苯乙烯)复合微球的制备及其吸附性能

以微孔纳米羟基磷灰石(HAP)为无机载体,甲基丙烯酸甲酯(MMA)和苯乙烯(St)为聚合单体,采用悬浮聚合法制备了HAP/P(MMA-St)复合微球。研究了影响球体粒度及其分布的主要因素和微球的吸附性能。结果表明,表面活性剂用量(质量分数,下同)为1‰,MMA用量为2%,HAP用量为30%,转速为300r/min时复合微球的合格球收率最高,为86.4%。当微球中HAP的质量分数为36.07%时,HAP/P(MMA-St)微球对牛血清蛋白的最大吸附量Qe=18.70mg/g,比未加HAP时,增加了4.65mg/g。