超声波-树脂法提取活性污泥胞外聚合物的研究

研究了超声波与树脂联合使用方法对活性污泥胞外聚合物(EPS)的提取效果。研究结果表明:超声波-树脂组合形式的提取效果最优,而超声波后置组合形式的细菌细胞破损程度较大;超声波-树脂法对不同来源的污泥都有较好的提取效果,提取得到的EPS量占污泥挥发分的8%～13%;与EDTA法、加热提取法相比较,超声波-树脂法具有提取效率高、化学污染小、细胞破损量小以及操作方便的优点。     

Inorganic fractions in extracellular polymeric substance extracted from activated sludge and biofilm samples by different methods

This study highlighted the inorganic fractions in the extracellular polymeric substance (EPS) extract from two activated sludges and one biofilm. Nine EPS extraction methods (centrifugation, sonication, cation exchange resin (CER) + sonication, CER, heating, formaldehyde + heating, formaldehyde + NaOH, ethanol and EDTA) were used in the study. The EPS extracts had large inorganic fractions, which ranged from 28% to 94% of the EPS dry weight. The EPS inorganic fraction was dependent on the source of the sludge and wastewater, the kinds of bacteria and the extraction method. The EPS extracts obtained by heating and sonication had smaller inorganic fractions than those obtained by centrifugation. The compositions of the inorganic fraction of EPS extracts obtained with CER and sonication + CER showed similar trends. The chemical extraction methods could contaminate the inorganic composition of EPS extracts by impurities, carrying over of the extractant itself or by changing the pH of the solution. Ethanol was the most effective extractant for obtaining inorganic ions.     

Comparison of extracellular polymeric substances (EPS) extraction from two different activated sludges

The characteristics of extracellular polymeric substances (EPS) extracted with five different extraction protocols from two different activated sludges were studied. The results showed that the major EPS constituent extracted by centrifugation was protein for the sludge in sequencing batch reactor treating chemical wastewater, and nucleic acid for the sludge in moving bed biofilm reactor treating synthetic urban wastewater. The order of EPS extraction amounting from the two sludges was formaldehyde + NaOH > formaldehyde + heating > EDTA > heating > centrifugation. The different extraction methods, the wastewater type, and activated sludge source greatly affected the amount and composition of EPS. The chemical extracted methods were more effective than the physical methods in extracting EPS for the two sludges. Moreover, formaldehyde combined NaOH was most effective in extracting EPS for the two sludges. However, chemical extraction could contaminate the EPS solution, which was pointed out by infra-red analysis and was also proved by cell lyses during EPS extraction and carrying over of the chemical extractant. Therefore, this study highlights that the choice of EPS extraction method should consider both the extraction yield and content and the contamination of extracting reagents to the EPS solution. The extraction procedures should be optimized and most effective.     

Application of metaproteomic analysis for studying extracellular polymeric substances (EPS) in activated sludge flocs and their fate in sludge digestion

Metaproteomic analysis, comprising protein separation and identification, was applied to study extracellular proteins in activated sludges and to track their fate in sludge digestion under both anaerobic and aerobic conditions. The complex sludge proteins were first separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and further analysed by liquid chromatography tandem mass spectrometry (LC-MS/MS) to search their identification. Base extraction and cation exchange resin (CER) method were used to extract EPS from sludges at 0, 12 and 30 days of batch digestion. Several important observations were made during this study. Firstly, protein bands were well separated by extraction/SDS-PAGE protocol used in this study. Secondly, numerous protein bands remained after digestion, indicating that these proteins are not easily degradable in sludge digestion. Thirdly, protein bands detected following anaerobic and aerobic digestion differed, suggesting that proteins degraded in two different digestion environments are not the same. Finally, protein bands that emerged distinctively following anaerobic digestion was found to be subunits of methyl-coenzyme M reductase, the enzyme involved in methane generation, in Methanosarcina barkeri. These results demonstrated that metaproteomic investigation on activated sludge EPS is useful for studying floc formation in activated sludges and their degradation in various digestion environments.     

Adsorption of Zn(II) and Cd(II) ions in batch system by using the Eichhornia crassipes

In this work, the displacement effects on the sorption capacities of zinc and cadmium ions of the Eichornia crassipes-type biosorbent in batch binary system has been studied. Preliminary single metal sorption experiments were carried out. An improvement on the Zn(II) and Cd(II) ions removal was achieved by working at 30 °C temperature and with non-uniform biosorbent grain sizes. A 60 min equilibrium time was achieved for both Zn(II) and Cd(II) ions. Furthermore, it was found that the overall kinetic data were best described by the pseudo second-order kinetic model. Classical multi-component adsorption isotherms have been tested as well as a modified extended Langmuir isotherm model, showing good agreement with the equilibrium binary data. Around 0.65 mequiv./g maximum metal uptake associated with the E. crassipes biosorbent was attained and the E. crassipes biosorbent has shown higher adsorption affinity for the zinc ions than for the cadmium ones in the binary system.     

Microbial Fe(II)-oxidation by nitrate in activated sludge

The oxidation of Fe(II) to Fe(III) by addition of nitrate and nitrite to activated sludge was studied to determine whether the process was biological or chemical (chemodenitrification). It was shown that the process was mainly biological, although the microorganisms involved have not yet been described. Investigations in a full scale treatment plant suggested that the process most likely took place m the anoxic (denitrification) tank. Details of the kinetics and stoichiometry have not yet been determined, but the process may he of significance for keeping Fe(III) oxidized, which is important for P-removal and for floc structure. Furthermore, in some treatment plants, the oxidation may also be of significance for nitrate removal (denitrification).     

膨润土对水泥固化体中Pb(II), Zn(II), Cd(II) 及Cr(VI)浸出的影响

为了确保含重金属废弃物在水泥基材料中的安全资源化利用,研究了在不同p H条件下纯水泥对Pb(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ)及Cr(Ⅵ)等重金属的固化效果及加入膨润土后的影响。结果表明:除Cr(Ⅵ)之外,纯水泥对Pb(Ⅱ)、Zn(Ⅱ)及Cd(Ⅱ)的固化效果较好,当重金属的掺量达到5‰时,即便在p H=3的强酸条件下,其浸出毒性仍然低于国家标准。加入膨润土后,可进一步降低水泥基材料中各重金属的浸出率,当膨润土掺量为30%、酸性条件下,28d龄期固化体中Zn(Ⅱ)、Cd(Ⅱ)、Cr(Ⅵ)的浸出浓度分别降低了60.9%、51.3%及53.3%,CH峰值下降、AFt峰值明显增高,但膨润土对Pb(Ⅱ)有负效应,酸性溶液中的浸出量高于中性溶液。     

Mechanism of adsorption of ferric iron by extracellular polymeric substances (EPS) from a bacterium Acidiphilium sp

The aim of this study was to assess the sorption of Fe(III) by extracellular polymeric substances (EPS) of the Acidiphilium 3.2Sup(5) bacterium, which has promising properties for use in microbial fuel cells (MFC). The EPS of A. 3.2Sup(5) was extracted using EDTA. The sorption isotherms were determined using aliquots of purified EPS. The exosubstances loaded with metal were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction spectroscopy (XRD) and Fourier transform infrared spectroscopy (FTIR). The sorption uptake approaches to 536.1 +/- 26.6 mg Fe(III) (g EPS)(-1) at an initial ferric concentration of 2.0 g l(-1). The sorption of Fe(III) by EPS can be fitted to the Freundlich model. The sorption process produces hydrated iron (III) oxalate [Fe(OH)(C2O4) x 2H2O] by a reversible reaction (log K = 1.06 +/- 0.16), indicating that a shift in the sorption of the cation can be easily achieved. Know the magnitude and form of iron sorption by EPS in MFC can foresee the potential impact on the metabolism of iron-reducing and iron-oxidazing bacteria and, therefore, on the feasibility of the system.     

Effects of extracellular polymeric substances on granulation of anoxic sludge in sequencing batch reactor

Variations of extracellular polymeric substances (EPS) and its components with sludge granulation were examined in a lab-scale sequencing batch reactor (SBR) which was fed with sodium nitrate and sodium acetate. Ultrasonication plus cation exchange resin (CER) were used as the EPS extraction method. Results showed that after approximately 90 d cultivation, the sludge in the reactor was almost granulated. The content of extracellular polysaccharides increased from 10.36 mg/g-VSS (volatile suspended solids) at start-up with flocculent sludge to 23.18 mg/g-VSS at 91 d with matured granular sludge, while the content of extracellular proteins were almost unchanged. Polysaccharides were the major components of EPS in anoxic granular sludge, accounting for about 70.6-79.0%, while proteins and DNA accounted for about 16.5-18.9% and 4.6-9.9%, respectively. It is proposed that EPS play a positive role in anoxic sludge granulation and polysaccharides might be strongly involved in aggregation of flocs into granules.     

Adsorption of Zn(II) on dialdehyde m-phenylenediamine starch

A new chelating material dialdehyde m-phenylenediamine starch (DASMPA) was synthesized by reacting m-phenylenediamine with dialdehyde starch. The obtained material was characterized by element analysis and Fourier transform infrared (FT-IR) spectra. The FT-IR of DASMPA showed an absorption peak at 1605.95 cm(-1) indicating the formation of a Schiff base (C=N). Adsorption activity of DASMPA for Zn(2+) was also investigated in terms of contact time, pH, the initial Zn(II) concentration and temperature, the results revealed that pH = 5, t = 1 h were the optimal conditions. With the degree of substitution (DS) of the DASMPA increased, the adsorption capacity increased gradually. The adsorption equilibrium data correlated well with Freundlich isotherm. Moreover, lower temperature was preferable for the process as it was exothermic.     

Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant.

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 degrees C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36-37 degrees C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36-37 degrees C. The results showed a truly thermophilic stage (60 degrees C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 degrees C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.     

Removal of dissolved copper(II) and zinc(II) by aerobic granular sludge.

This study investigated the adsorption kinetics of dissolved copper(II) and zinc(II) by aerobic granular sludge. Two series of batch experiments were conducted at different initial copper(II), zinc(II) concentrations (Co) and initial granule concentrations (Xo). Results showed that the biosorption kinetics of individual copper(II) and zinc(II) by aerobic granules were closely related to Co and Xo. The maximum biosorption capacity of individual copper(II) and zinc(II) by aerobic granules was 246.1 mg g(-1) and 180 mg g(-1), respectively. In order to theoretically interpret the results obtained, two kinetic models previously developed for biosorption were employed and compared in this study. It was found that the model proposed by Liu et al. (2003) could fit the experimental data very well, but the second-order model failed to fit the data in some cases. It appears that aerobic granules would be potential biosorbent with high efficiency for the removal of dissolved copper(II) and zinc(II) from wastewater.     

活性污泥法的工艺参数控制(上)

活性污泥法的工艺控制是通过各工艺参数的控制来实现的,有些运行参数的控制要求还因污水处理要求和运行模式而异.只有正确理解各运行参数的涵义,了解不同工艺及相同工艺下不同运行模式的控制要求,才能通过科学管理控制好工艺运行状态,使处理系统高效低耗地运行.主要介绍了活性污泥法的工艺运行参数在实际应用中的理解和控制方法,阐述了一些书面定义和观点与实际应用时情况不相符的原因,提出了各控制参数与其他因素的关系及相关方面的一些综合分析思路,以期对运行管理有一定的参考作用.     

活性污泥法的工艺参数控制(下)

2 污泥沉降比(SV30) 2.1 理论定义及实际应用上的理解 SV30是指曝气池混合液在量筒静止沉降30 min后污泥所占的百分体积.     

沉淀池排泥水中二氯乙酰胺前体物研究

为了得出给水厂沉淀池排泥水中二氯乙酰胺(dichoro-acetamide,DCAc Am)主要前体物特性,研究排泥水中二氯乙酰胺生成势(DCAc Am FP)与不同组分特征ρ(DON)、ρ(DON)/ρ(DOC)值之间的关系。结果表明:沉淀池排泥水的ρ(DON)值为0.3~0.6 mg/L高于原水中的值(0.2~0.4 mg/L),且亲水性小分子量占大部分;DCAc Am FP达到5~8μg/L。DCAc Am FP与不同组分DON之间存在一定的相关关系(R2=0.623),DCAc Am FP与ρ(DON)/ρ(DOC)值之间存在很强的线性相关性(R2=0.868),表明DCAc Am的主要前体物为氨基酸、蛋白质类亲水性小分量含氮有机物。     

Adsorption and Desorption of Zn,Cu, and Cr by Sediments from the Raisin River (Michigan)

Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000–9,000 μg/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficients computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid (24–48 hr) in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model (DiToro et al. 1986) could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes: rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility or bioavailability than would otherwise be assumed.     

低浓度剩余活性污泥涡凹气浮浓缩工艺研究

采用CAF5型涡凹气浮对低浓度剩余活性污泥浓缩进行了试验研究,结果表明:絮凝剂采用FO4440SH,最佳投加量为1kg/tDS,表面活性剂采用1227,最佳投加量0.2kg/tDS,最佳固体负荷为230kgMLSS/(m3·d),最佳水力负荷为90m3/(m2·d),出水SS为200~250mg/L,在浓缩过程中污泥中的磷不会释放。     

Adsorption of allura red dye by cross-linked chitosan from shrimp waste

The present study was designed to evaluate the chitosan, which has been obtained by deacetylation of chitin, as a biosorbent. The chitin was isolated from fermented shrimp waste by an important local industrial food biopolymer. The aim of this work was the characterization of chitosan and preparation of cross-linked chitosan- tripolyphosphate (chitosan-TPP) beads for the removal of allura red food dye from aqueous solutions. Conditions of batch adsorption such as pH, time and adsorbent dose were examined. The effectiveness of cross-linked chitosan beads for dye removal was found to be higher for pH 2 (98%, percentage of dye removal) and tends to decrease at pHs of 3 to 11 (up to 49%). The values of percentage removal show that the adsorption capacity increases with time of contact and dosage of chitosan-TPP, but red dye adsorption is mainly influenced by pH level. The cross-linked chitosan-TPP beads can significantly adsorb allura red monoazo dye from aqueous solutions even at acidic pHs unlike raw chitosan beads that tend to dissolve in acidic solutions. Consequently, this modified chitosan has characteristics that allow minimization of environmental pollution and widening the valorization of shrimp waste.     

Use of sesame stalk biomass for the removal of Ni(II) and Zn(II) from aqueous solutions

In this study an agricultural residue, sesame stalk, was evaluated for the removal of Ni(II) and Zn(II) metal ions from aqueous solutions. Biosorption studies were carried out at different pH, biosorbent dosage, initial metal ion concentrations, contact time, and solution temperature to determine the optimum conditions. The experimental data were modeled by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Langmuir model resulted in the best fit of the biosorption data. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and to evaluate rate constants. The best correlation was provided by the second-order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The experimental results showed that sesame stalk can be used as an effective and low-cost biosorbent precursor for the removal of heavy metal ions from aqueous solutions.