非饱和黄土的结构强度与抗剪强度

本文分析了非饱和黄土强度的组成和结构强度的来源，给出了结构强度的确定方法，研究了结构强度的变化规律，结果表明：非饱和黄土的结构强度可用其天然结构破坏后所丧失的强度衡量，结构强度与初始含水量间具有幂函数关系；结构强度与不稳定凝聚力具有良好的线性关系；提出了非饱和黄土结构强度终止含水量的概念；给出了非饱和黄土抗剪强度的计算公式。     

Microbiological and structural aspects of granular sludge from autotrophic denitrifying reactors.

Denitrification is applied in the tertiary treatment of wastewater to reduce N-pollutants. Fluorescence in situ hybridisation (FISH), CARD (catalyzed reporter deposition)-FISH, cloning, and scanning electron microscopy (SEM) were applied to follow the evolution of the microbial composition and structure of granular sludge in autotrophic denitrifying bioreactors fed with nitrate and thiosulfate. With this goal, FISH oligonucleotide probes for the autotrophic denitrifiers, Thiobacillus denitrificans and Thiomicrospira denitrificans, were designed and their utility tested. CARD-FISH and cloning data showed that bacterial diversity changed with bioreactor operation time. After 110 days of operation, the abundance of Thiobacillus denitrificans cells increased considerably: from 1 to 35% of total DAPI-stained cells and from no isolated clones to 30% of the total positives clones. This fact strongly suggests that this microorganism played a dominant role in the autotrophic denitrification. The Archaeal diversity remained almost unchanged and it was mainly represented by Methanosaeta soehngenii. Scanning electron microscopy results indicated a considerable loss in the integrity of the sludge granules during the operation, with risk of sludge buoyancy.     

石灰改性淤泥的抗压和抗剪强度试验研究

对未改性淤泥和石灰改性淤泥进行无侧限抗压强度试验,得到了长期养护90 d和360 d试样的应力应变关系、抗压强度、变形模量和破坏应变。通过固结排水直接剪切试验,得到淤泥固化前后的剪切应力位移关系、凝聚力和内摩擦角。结果表明:石灰的掺入使试样破坏应变明显减小,无侧限抗压强度和变形模量显著增加;石灰掺量达到某种程度后,继续添加石灰并不能改善土体力学性质,反而会引起劣化效果;抗压强度与变形模量之间服从线性关系,抗压强度与破坏应变之间服从幂函数关系;石灰掺量和法向压力变化会诱发试样剪切应力位移曲线发生变化;石灰可有效提高淤泥试样的凝聚力,但对内摩擦角并无显著影响。     

污泥-生活垃圾混合填埋体抗剪强度特性研究

污泥送入生活垃圾填埋场进行混合填埋是国内外常用的处置途径之一。混合填埋体强度参数对填埋场稳定性有重要影响,为此在实验室开展了不同击实功、不同污泥添加量以及不同生化降解时间条件下污泥-生活垃圾混合试样的强度试验,对其强度特性进行研究。结果表明：① 随着击实功的增加,混合试样的抗剪强度整体上逐渐增大,当其密度超过1 050 kg/m3时,混合试样的内摩擦角和凝聚力增加不明显甚至有减小现象,其抗剪强度增加幅度很小甚至减小。② 随着污泥添加量的增加,混合试样的内摩擦角逐渐减小,凝聚力逐渐增加,但是当污泥添加量超过40%时,其凝聚力反而减小。③ 随着生化降解的进行,混合试样抗剪强度整体趋势在增加,凝聚力和内摩擦角的整体趋势也在增加。     

非饱和黄土抗剪强度与结构强度的关系特性

分析了非饱和黄土强度的组成和结构强度的来源,通过常规三轴试验对非饱和黄土的抗剪强度和结构强度规律进行了研究.结果表明:非饱和黄土的凝聚力随初始含水率的增大逐渐减小,呈较好的指数函数关系;同一含水率下结构强度随围压的增大而增大,在同一围压下结构强度随含水率的增加而逐渐减小,呈较好的幂函数关系;结构强度与其粘聚力之间有显著的线性相关关系.     

The importance of night‐time observations for determining habitat preferences of stream biota

Observations of the presence or density of individuals in specific habitats are often used to develop predictive models of preferential habitat use and habitat suitability curves. However, most studies only use day‐time observations to model habitat associations. In this paper, we present day and night observations of habitat use by two abundant species of freshwater shrimp, Atya lanipes and Xiphocaris elongata, in a tropical montane stream. At night, the number of shrimp observed was an order of magnitude greater than during the day. Habitat preferences of Atya changed, with more individuals using low velocity edge sites at night. Xiphocaris were not readily visible during the day, but were very abundant at night. Our results suggest that habitat models cannot be based only on day‐time observations. Because the level of nocturnal activity is not known for most species of fish and invertebrates, studies of habitat preferences should include both day and night observations. Copyright © 2000 John Wiley & Sons, Ltd.     

砒砂岩抗剪强度与其结构特征关系

通过直剪试验、X射线衍射、电镜分析的方法,分析了红色砒砂岩和白色砒砂岩力学性能随含水率的变化规律,观测了砒砂岩的颗粒粒径分布、矿物组成及微观形貌,探讨了砒砂岩结构特征对抗剪强度的影响。结果表明,含水率对红色和白色砒砂岩抗剪强度的影响不同,红色砒砂岩抗剪强度随含水率增大先增大后减小,黏聚力起主导主用,白色砒砂岩抗剪强度随含水率增大而减小,摩擦力和咬合力起主导作用;红色和白色砒砂岩的主要矿物是石英、长石、蒙脱石和方解石,长石的易于风化,蒙脱石的遇水膨胀及方解石的易分解,导致砒砂岩力学性能较差;白色砒砂岩以粗砂为主,含少量细砂,颗粒有明显棱角,孔隙较大,导致颗粒间具有较强的摩擦力和咬合力,而红色砒砂岩细砂含量较多,结构连接较致密,导致滑动过程中以黏聚力为主导,咬合摩擦作用较弱。     

Parameter sensitivity analysis for activated sludge models No. 1 and 3 combined with one-dimensional settling model.

The aim of this study was to suggest a sensitivity analysis technique that can reliably predict effluent quality and minimize calibration efforts without being seriously affected by influent composition and parameter uncertainty in the activated sludge models No. 1 (ASM1) and No. 3 (ASM3) with a settling model. The parameter sensitivities for ASM1 and ASM3 were analyzed by three techniques such as SVM-Slope, RVM-SlopeMA, and RVM-AreaCRF. The settling model parameters were also considered. The selected highly sensitive parameters were estimated with a genetic algorithm, and the simulation results were compared as deltaEQ. For ASM1, the SVM-Slope technique proved to be an acceptable approach because it identified consistent sensitive parameter sets and presented smaller deltaEQ under every tested condition. For ASM3, no technique identified consistently sensitive parameters under different conditions. This phenomenon was regarded as the reflection of the high sensitivity of the ASM3 parameters. But it should be noted that the SVM-Slope technique presented reliable deltaEQ under every influent condition. Moreover, it was the simplest and easiest methodology for coding and quantification among those tested. Therefore, it was concluded that the SVM-Slope technique could be a reasonable approach for both ASM1 and ASM3.     

The fundamentals of wastewater sludge characterization and filtration.

The move to greater emphasis on the disposal of wastewater sludges through routes such as incineration and the added cost of landfill emplacement puts high demands on dewatering technology for these sludges. A clear problem in this area is that wastewater sludges are slow and difficult to dewater and traditional methods of laboratory measurement for prediction of filtration performance are inadequate. This is highly problematic for the design and operational optimisation of centrifuges, filters and settling devices in the wastewater industry. The behaviour is assessed as being due to non-linear behaviour of these sludges which negates the use of classical approaches. These approaches utilise the linear portion of a t versus V2 plot (where t is the time to filtration and V is the specific filtrate volume) to extract a simple Darcian permeability. Without this parameter, a predictive capacity for dewatering using current theory is negated.     

The importance of measuring the sludge filterability at an MBR - introduction of a new method

Sludge properties have a strong impact on the operational aspects of membrane bioreactors (MBRs). Poor sludge properties cause stronger membrane fouling and reduce the filtration performance of MBRs. Up to now there is no general method used to measure the fouling or filtration relevant sludge properties in MBRs. The aim of this work was to develop a simple but reliable method to supply operators a tool to monitor the important sludge properties for their application and to compare this method with existing techniques. Through extensive research a new method called the sludge filtration index (SFI) has been developed to indicate the appropriate sludge parameters for MBR systems in a cheap and easy manner. The SFI can be measured with simple laboratory equipment and offers operators a powerful tool to monitor the conditions of their sludge, independent of the membrane conditions.     

灵敏度分析法确定水文地质参数的基本模型及其应用

本文基于泰斯方程论述了灵敏度分析法确定水文地质参数的基本原理,即把水位降深看做是以导水系数和弹性释水系数为变量的函数,利用最小二乘法原理,计算求得理论降深与观测降深最佳拟合时的导水系数和弹性释水系数。针对目前只能在泰斯假设条件下利用非稳定流试验数据确定水文地质参数的问题,根据数值积分理论,推求了多种特征类型的降深计算模型和对应的灵敏度系数计算模型,列出了三种类型的推求结果。引用了两个抽水试验实例,根据编制的计算机程序,采用灵敏度分析法求解了水文地质参数,计算结果与实测资料一致。     

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.     

The effect of flow equalisation and prefermentation on the sludge production and sludge characteristics in a BNR plant.

A full-scale study investigated the influence of diurnal flow equalisation and prefermentation on the characteristics of sludge. The diurnal variations in the sludge concentration and the level of sludge blanket in the secondary clarifiers were evened out significantly with the use of an equalization basin. Stable conditions in the aeration basin and in the secondary clarifiers contributed to the improvements in the performance of the BNR plant. A decrease in the waste activated sludge production and an improvement in the settleability were also observed. The low WAS yield was attributed to the low yield COD compounds produced by the prefermentation, longer sludge age and constant conditions obtained by the flow equalisation. Some evidence was found that good settling properties would be related to the amount of suspended solids fed to the biological process as well as to the good performance of the biological process.     

Co-conditioning and dewatering of alum sludge and waste activated sludge.

Co-conditioning and dewatering behaviors of alum sludge and waste activated sludge were investigated. Two different sludges were mixed at various ratios (2:1; 1:1; 1:2; 1:4) for study. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. Relatively speaking, waste activated sludge, though of higher solid content, was more difficult to be dewatered than alum sludge. It was found that sludge dewaterability and settlability became better with increasing fraction of alum sludge in the mixed sludge. Dosage required of the cationic polyelectrolyte (KP-201C) for dewatering was reduced as well. It is proposed that alum sludge acts as skeleton builder in the mixed sludge, and renders the mixed sludge more incompressible which is beneficial for sludge dewatering. Implications of the results of the study to the sludge management plan for Taipei City that generates both alum sludge and waste activated sludge at significant amount are also discussed. The current sludge treatment and disposal plan in Metropolitan Taipei could be made more cost-effective.     

不均匀及不连续结构面抗剪强度模拟试验研究

在不同类型结构面与岩桥组合的大型剪切试验和不同比例岩桥与夹泥层组合的中型剪切试验基础上,对比分析了试验结果与常用的面积加权法计算值之间的关系,探讨了试验过程中应力、应变的变化规律和特征。结果表明,大型剪切试验值一般小于峰值面积加权计算值,而中型剪切试验的摩擦系数接近或小于计算值,粘聚力的试验值大于计算值,且岩桥位置不同对试验结果有一定影响。就剪切变形破坏特征而言,常常是前块首先变形,当变形达到一定量值后中块开始变形,然后是后块变形,直至破坏。当岩桥所占面积比例较小且剪应力较低时,夹泥层变形多大于岩桥变形;剪应力高或岩桥所占面积比例较大,则二者变形相近。岩桥剪切破坏面的特征与岩桥所占比例有关,岩桥所占面积比例较小的试件,岩桥在夹泥附近被直接剪断;岩桥所占面积比例较大的试件,岩桥破坏面为锯齿状,与剪应力方向形成约45°夹角。     

大坝结构可靠性影响因子的全局重要性分析

传统方法一般采用灵敏度系数分析各项不确定因子对大坝结构可靠性的影响,但灵敏度系数只在因子设计验算点处取值,针对该局部性取值的缺点,研究了大坝结构可靠性影响因子的全局重要性分析方法。首先,在建立大坝结构可靠性分析模型的基础上,考虑不确定因子在整个失效域内的变化,构建了影响因子的全局重要性测度指标。然后,采用基于截断重要抽样的蒙特卡洛法,实现了因子全局重要性的量化分析。最后,建立了某坝的结构可靠性分析模型,计算对比了各不确定因子的全局重要性测度和灵敏度系数,结果表明全局重要性测度能更全面地反映不确定因子对大坝结构可靠性的影响。     

Mineralisation of hazardous organic compounds in a sludge reed bed and sludge storage.

Linear alkylbenzene sulphonates (LAS) and nonylphenolethoxylates (NPE) may be detrimental to the environment if spread in inappropriately large concentrations. Mineralisation of LAS and NPE in mesophilic digested sludge was observed during a 9-month monitoring programme where three separate treatment methods were investigated. Sludge was treated in a sludge reed bed under aerobic conditions, by storage in a container under anaerobic conditions, and by storage in a sludge pile turned over mechanically at intervals to improve the oxygen influx. Treatment in a sludge reed bed was shown to be effective. Mineralisation of 98% of LAS and 93% of NPE was observed. Only limited mineralisation occurred on the surface of the sludge stored in a container. A reduction of LAS and NPE of 90% and 43%, respectively, was observed in the sludge which was stored in a pile and frequently turned.     

The effect of anoxic selectors on sludge bulking.

The effect of the substrate feeding pattern on sludge settleability in denitrifying systems was investigated. The feeding pattern was simulated in two sequencing batch reactors (SBR). SBR1 simulates a system with a limiting substrate (acetate) and a non-limiting electron acceptor (nitrate), while SBR2 simulates the opposite condition. Sludge volume index (SVI) was the main observed parameter. The stoichiometry, substrate uptake rate, storage capacity as well as sludge morphology and mixed culture population dynamics were also determined. Results show that independent of the feeding pattern, the settleability of the sludge remained good (SVI approximately 50 mL/g) and stable. Neither the concentration of the acetate nor of the nitrate offered any limitations on sludge settleability, assuring that a good bio-P activity is present in nitrate limiting systems. Filamentous bacteria belonging to the TM group were usually present, although in low numbers. Despite the diffused, irregularly shaped and open floc structure, good settleability was observed. The results obtained were in line with the hypothesis on diffusion based selection.     

The discharged excess sludge treated by Oligochaeta.

To overcome unstable worm growth, a new worm-reactor was developed for oligochaete growth. The bench scale of this worm-reactor was used to treat the discharged excess sludge from a pilot activated sludge system, and experiments were carried out to investigate the sludge reduction induced by Oligochaeta. Due to difficult getting free-swimming worms such as Aeolosoma hemprichicii and Nais elinguis, Tubifex tubifex was thus selected and inoculated in Reactor 1 at the start-up phase except the control reactor (Reactor 2). Tubifex occurred in Reactor 1 throughout the operation period after its inoculation, and mainly attached on the carriers and aggregated on the bottom of the worm-reactor. Free-swimming worms such as Aeolosoma hemprichicii, Nais elinguis, and Aulophorus furcatus were found in both reactors since the 35th day. Microscopic investigation showed that these free-swimming worms naturally produced in the pilot activated sludge system, and entered into both reactors along the discharged sludge. Results clearly showed that the average sludge reduction in Reactor 1 was 59%, much higher than that in the control. The characteristics of sludge settling was improved by worm growth, but was not too much. High ammonia nitrogen concentration in influent sludge was toxic to worms, and then inhibited worm growth. Both the total inorganic nitrogen and phosphorus releases into effluent sludge were observed in Reactor 1, but such increases were not heavy.     

The preparation of synthetic sludge for lab testing.

For carrying out sludge lab-scale tests, and interlaboratory trials for standards validation, the availability of samples with "certified and constant" characteristics is required. When "dried sludge" samples cannot be used, problems arise because (i) most fresh sludge characteristics change with storage time, also because some preservation practices are not applicable or their effects unknown, (ii) some fresh sludge characteristics are strongly affected by handling, and (iii) fresh sludge requires particular precautions and authorization for transportation. This means that using "fresh sludge" samples cannot guarantee reliability and reproducibility of results, so a valid alternative consists in testing "synthetic suspensions" samples to be on-site prepared. This should also give the possibility to compare results obtained in different places and times. Within this framework, Task Group 3 (TG3) of Working Group 1 (WG1) of Technical Committee 308 (TC308) of European Standardization Committee (CEN) undertook the preparation of a Technical Report dealing with the preparation of synthetic suspensions, both inorganic and organic, in repeatable conditions, able to describe the behaviour of a real sludge. This paper discusses a proposal for ingredients and modalities to prepare such synthetic suspensions that will be systematically tested in already planned lab experiments to define an optimal recipe.