高压静电场促进活性污泥絮体沉淀的试验研究

将带有绝缘层的金属电极接通高压静电后置入沉淀筒中，通过对比试验考察了施加高压静电场对活性污泥絮体沉淀的影响。结果表明，施加高压静电场能够明显促进活性污泥絮体的沉淀，但促沉效果受污泥浓度（SS）、电极入水长度（L）、电压（U）等因素影响。促沉效果随SS的增大而变差；SS不同则最佳的L也不同，L值过大或过小时促沉效果都不好；当电压≤20kV时，促沉效果随电压的增加而提高，20kV时的总体促沉效果较好。当SS〈2．5g／L（SVI为300～400mL／g）和SS〈4．5g／L（SVI为100mL／g左右）时，施加高压静电场可使SV减小20％～30％。此外，经高压静电场处理后对COD、浊度的去除速度加快，而DO值下降，电导率和pH值则变化不大。     

Physical and chemical properties of activated sludge floc

Physical and chemical characteristics of activated sludge such as floc size, density, specific surface, carbohydrate content, dehydrogenase activity and settleability were investigated by seven parallel bench scale activated sludge units operated under different sludge ages (1.1–17.4 days). The analytical methods used included a dye adsorption technique for specific surface area determinations, the Coulter Counter method for floc size measurements and interference microscopy for floc density determinations. The typical floc sizes were found to be in the range 10–70 μm with floc densities in the range 1.015–1.034 g cm⁻³. A strong correlation between floc density and size was obtained. The specific surface areas measured (typically 100–200 m² g⁻¹ dry sludge) were found to be one to two orders of magnitude higher than the corresponding geometric floc surface areas, indicating a porous floc structure. Sludge settleability, for non-filamentous sludges, was well correlated to both floc size, density and specific surface area, but not to the sludge carbohydrate content, which was found to vary between 6 and 18%.     

阳离子表面活性剂改善污泥脱水性能的机理研究

研究了两种含有不同长度疏水链的阳离子表面活性剂CSG—1和CSG-2对活性污泥脱水性能的影响，探讨了两种活性剂在活性污泥体系中的作用机理。结果表明，投加约为干污泥质量10％的CSG-1可使滤饼的含水率降至78％左右，此时污泥的沉降效果较好，污泥毛细吸水时间（CST）也较短（约为62s）；与CSG-1相比，CSG-2虽可使滤饼含水率降至约74％，但其对污泥过滤性能和沉降效果的改善均较差。对CSG—1和CSG-2改善污泥脱水性能的机理研究表明，阳离子表面活性剂通过静电引力和范德华力而被吸附于污泥表面，改变了活性污泥絮体的特性，并引起胞外聚合物（EPS）的分布发生变化，从而改善了污泥的脱水性能，同时也导致了絮体颗粒粒径发生了显著变化。     

Control of activated sludge settleability using preaeration and preprecipitation

This paper deals with the addition of a preaeration and a preprecipitation stage to a conventional activated sludge process. The experiments were carried out in a pilot plant using wastewater from the city of Valencia (Spain) as feed. The effect of the F/M ratio and sludge age on sludge settleability was established. In both cases, process stability was observed to increase with respect to the conventional process. Good sludge settleability was thus assured in a greater F/M ratio range. A comparative economic study was also carried out.     

Automatic Monitoring of Activated Sludge Settling Characteristics and Plant Control Applications

A fully automatic instrument has been developed to allow the on-line measurement of activated sludge settling characteristics. The monitor uses the derived data to calculate final sedimentation tank solids loadings and the required rates of returned activated sludge pumping. The instrument has been developed by Thames Water Utilities Limited and is now manufactured under licence by Phox Systems Ltd. It samples mixed liquor and returned sludge alternately and measures solids concentration, the initial settling rate (or rate of hindered settlement) and the stirred specific volume index. The stirred specific volume index at a standard solids concentration of 3.5 g/l is derived from the data. Actual and maximum final sedimentation tank loadings (kg/m²h) are calculated, and the required returned sludge pumping rate is predicted and may be controlled by the monitor. Tests have been carried out on a number of sewage-treatment works during several years of development, and some of the results are presented and discussed.     

絮凝体沉速在线测量方法及其应用研究

提出了在絮凝池在线测量絮凝体沉速的方法,通过连续采集絮凝体图像和计算机数据处理,跟踪絮凝体运动轨迹,从而计算每一个絮凝体的沉速,同时介绍了数据处理的过程和基本算法。将基于该方法的絮凝体沉速测量设备(FVD)应用于临江水厂,对试验结果进行的分析表明,絮凝体沉速既可作为评价絮凝效果的指标,又可作为控制混凝剂加注量的依据。     

海水盐度对二沉池污泥沉降性能的影响

采用传统活性污泥法工艺研究了冲厕海水进入城市污水系统后,其盐度对污泥沉降性能的影响。结果表明,盐度对污泥沉降性能的影响比较明显,盐度有利于污泥沉降。随着盐度的提高,污泥的沉降性能越来越好,污泥容积指数逐渐降低,污泥出现膨胀的ＳＶＩ临界点显著降低。     

自来水厂排泥水处理技术

针对黄浦江水系闵行水厂排泥水的处理,通过污泥沉降特性研究,采用收集、浓缩、平衡、投加聚丙烯酰胺（ＰＡＭ）、离心机固液分离的工艺流程和ＰＬＣ中央控制,提高了自动化程度。浓缩池上清液能达标排放,离心机分离水的泥饼含固率≥４２％,ＰＡＭ加注率１．０￣１．５ｋｇ／ｔ干泥。研究表明,该工艺可作为黄浦江水系水厂排泥水处理的工艺设计依据。     

溶解氧和污泥粒径分布对城市污水SND影响

为了进一步探讨同步硝化反硝化的反应机理,采用SBR工艺,考察溶解氧和污泥粒径分布对城市污水同步硝化反硝化的影响。结果表明:低溶解氧(平均DO=0.5~0.8 mg/L)条件下,氮平衡计算证实SBR工艺发生了明显的SND现象,总氮中大约23.11%的氮是通过SND现象去除的。当DO浓度为0.5 mg/L时,硝态氮生成量与氨氮的减少量之比为0.454,硝化速率与反硝化速率基本相当。当DO浓度为4.296 mg/L时,硝化反应产生的氨氮的减少量与硝态氮的生成量相等,此时基本不发生SND现象。当SND发生时,污泥菌胶团颗粒的平均颗粒粒径仅为5.02μm~6μm,说明SND不是单纯的\"微环境作用\"的结果。     

运行温度对活性污泥特性的影响

对比研究了低温[(5±2)℃]和常温[(20±1)℃]运行的活性污泥系统处理生活污水的污泥特性,低温和常温时的污泥沉降指数(SVI)分别为250mL g和65mL g,污泥比阻分别为2.19×1012cm g和1.42×1012cm g,体积粒度分别为161μm和112μm。低温运行时颗粒密度是影响污泥比阻的主要因素,而常温运行时颗粒大小是影响污泥比阻的主要因素;与常温运行时相比,低温运行时活性污泥所携带的负电荷少而具有更高的亲水性,胞外分泌物含有更多的粘性物质,污泥难于压缩、沉降。     

A method for characterizing the complete settling process of activated sludge

Based on batch settling tests, a model describing the compression settling process of activated sludge was developed and validated by experiments. Furthermore, a theoretical equation for determining the critical point when the compression settling stage commences, and a new velocity function for the compression settling were deduced from the model. By combining the new model and the conservation of mass, it was proved that the Vesilind function was also capable of describing the compression settling velocity on condition that the appropriate parameters were estimated. Dividing the complete settling process of activated sludge into the zone settling and compression settling stages, and describing them by the Vesilind function with different parameter sets was more reasonable for characterizing the complete settling process of activated sludge. The method was applied to predict the sludge blanket height during batch settling tests, and the results showed that the settling processes could be simulated well.     

全尾砂沉降性能及其影响因素

全尾砂固结排放工艺是一种处理尾矿的高效安全新型排放工艺,尾砂沉降性能综合反映了尾砂物理特性、离析等特点,是影响过滤机对尾矿浓缩脱水效率的重要因素,对全尾砂固结干排工艺的应用研究具有指导意义。采用全尾砂料浆进行单因素试验,考察不同浓度下料浆沉降性能,建立了不同浓度全尾砂料浆沉降速度的数学模型。根据沉降速度数学模型可知较低浓度料浆沉降速度快,沉降周期长且极限下沉量大,而较高浓度料浆则相反;全尾砂料浆沉降速度曲线大致符合单峰右拖尾类型:初期沉降速度不断增大直至最大下沉速度,以最大沉速下沉一定时间后速度减缓,最后停止沉降。采用均匀设计法,建立不同浓度及不同粒级组成的5因素6水平均匀试验,对配级尾砂沉降性能进行研究。试验结果表明,极限下沉量与浓度、-210~+120 μm尾砂含量、-120~+75 μm尾砂含量呈负相关,与+210 μm尾砂含量、-75 μm尾砂含量呈正相关;浓度对尾砂料浆的极限下沉量影响最大,粗颗粒(+210 μm)次之,细颗粒(-75 μm)对极限下沉量影响排在粗颗粒和浓度之后,中粒径(-210~+75 μm)的影响最小。在浓度较低时,配级尾砂沉降速度比全尾砂缓慢,尾砂级配占主导因素;在浓度较高时,配级尾砂和全尾砂沉降速度相差不大,此时主导因素为料浆浓度。     

An experimental study of low concentration sludge settling velocity under turbulent condition

Particle Image Velocimetry (PIV) was used to study the settling of activated sludge flocs under turbulent flow conditions. Experimental results showed that a larger particle diameter led to a higher settling velocity while the higher turbulence intensity led to lower settling velocity. Based on the measurements a mathematical relation has been derived which correlates the settling velocity for individual sludge flocs under turbulent conditions through a modified Vesilind equation. Settling velocity shows a power-type relation to sludge particle diameter and an exponential-type relation with turbulence intensity and sludge concentration.     

An examination of the surface characteristics of activated sludge in relation to bulking during the treatment of paper mill wastewater

The addition of mineral talc, Aquatal^®(Toulouse, France), to activated sludge treating paper mill effluents and its effect on settlement characteristics has been investigated. One laboratory study and a full‐scale investigation on a large waste water treatment plant (WWTP) with a capacity of 500.000 population equivalent (p.e.) have been carried out using this mineral. The sludge in the full‐scale plant was filamentous and had specific sludge volume index (SSVI) values in excess of 250. The talc dosing which was adapted to sludge settleability reduced SSVI values by 38%, improved the total suspended solids' concentrations by 86% and reduced the specific sludge load by 34%. In the laboratory‐scale plant, the sludge had SSVI values of 200–260 before treatment and was hydrophilic. The use of Aquatal^® at a dose of 0.7 g/g mixed liquor suspended solids (MLSS) took 2 weeks to reduce the SSVI to 78. It also increased the hydrophobicity to a balanced 50%. The use of mineral converted the somewhat diffuse flocs into a compact structure.     

Comparison and evaluation of empirical zone settling velocity parameters based on sludge volume index using a unified settling characteristics database

Over the past few decades classic and contemporary research on the process of secondary clarification in activated sludge plants has illuminated several aspects of the solids-flux theory which actually require a closer examination. Inter alia the most challenging and controversial part in the field has been the development of reliable models for the settling properties of the activated sludge in the settler. Numerous studies have been performed aiming at the evolvement of reliable mathematical formulas that would satisfactorily describe this behaviour, but no universally accepted solution seems to exist to date. That is mostly because different experimental conditions, sludge types and instrumentation have been employed, thus complicating the process of reaching a conclusive result. In order to bring theoretical and practical developments of secondary settling tank design and simulation closer together, a number of related tasks are addressed in this study by the use of an integrated and unified settling characteristics database. Several drawbacks and advantages of the methodologies published hitherto are examined on a universal basis and under the same assumptions in order to reveal artifacts that complicate the procedure of settling velocity estimation. It is suggested that universally accepted solutions may be feasible especially for design purposes. For simulation analysis real-time data of settling velocity should be tested rather than values derived from laboratory experiments which are shown to produce different results depending on the applied approach. In conclusion, an integrated database is proposed as a means for a more robust and universally accepted design procedure.     

Density effects on activated sludge zone settling velocities

A recently developed method to manipulate biomass density based on the addition of synthetic microspheres was used to isolate density effects on zone (hindered) settling velocities in samples from full-scale activated sludge plants over a range biomass densities and concentrations. Settling velocities increased by as much as a factor of five as density was increased by microsphere addition. The effects of density on the Vesilind sedimentation model parameters (V=V(o)e(-kX) , where V is the settling velocity, X is the biomass concentration, and V(o) and k are constants) were evaluated. The parameter V(o) was positively correlated with density for values greater than approximately 1.02 g/mL, while k values were approximately constant in this range. New models were developed for settling velocity as a function of both density and biomass concentration, and these may be useful for future incorporation with clarifier models to improve predictions of system performance, particularly when biomass characteristics known to affect density are variable, such as polyphosphate and nonvolatile suspended solids content.     

Evaluation of alternative sludge settleability indices

Proposed modifications of the standard sludge volume index (SVI) to eliminate its unpredictable variation with suspended solids (SS) concentration include stirring, conduct of the test at constant SS concentration, and dilution. We have tested these modifications by making correlations between the respective indices and the content of filamentous organisms in activated sludge expressed in terms of total extended filament length. The results indicate that diluted SVI is the best index of sludge settleability among those tested. Correlation of diluted SVI with specific functional relationships between settling velocity and SS concentration would enable the application of this parameter to prediction of thickening capacity in secondary clarifiers.     

An improved method using respirography for the design of activated sludge aeration systems

For the computation of the oxygen uptake for the aeration tank of the biological treatment plant several methods are available such as the OC/L method, Emde's method with fixed coefficients, Eckenfelder's method, and the method of levels of dissolved oxygen. The method for the determination of oxygen uptake for the treatment of industrial wastewaters was developed. The advantage of this method is a simple calculation of oxygen uptake for industrial biological treatment plant due to independent measurement of oxygen uptake for individual phases. The method is rapid and allows easy determination of individual phases of oxygen uptake.     

Compaction of flocculated material

The device used in the experiment consists of a flat-bottomed graduated cylinder and a coaxial plunger. A suspension flocculated with chemicals is sedimented after being mechanically worked within the graduate, and the supernatant water is removed with a pipette. The plunger is thrust into the sludge at a constant speed. The sludge is not only compressed but also flows into the annular gap between the plunger and the graduate, resulting in liberation of water. The liberated water is accumulated on the sludge in the annular gap. The “sludge bulkiness” β is used to describe the volumetric proportion of sludge and solids in it. The sludge bulkiness values before and after the “plunger test” are denoted as β_i and β_f, respectively. The values of β_i and β_j have been explored as a function of the time of the mechanical working. As a result, there is a definite time lag between the maximum value of β_i and the minimum value of β_f. The minimum value of β_j is obtained when the sludge consists of “pelleted flocs”.     

吸附架桥机理主导下APAM的多级絮凝效能

对吸附架桥机理主导下阴离子聚丙烯酰胺(APAM)的絮凝过程进行了研究,通过改变絮凝剂投加工况,对比分析常规絮凝与多级絮凝在污染物去除效果、絮体性能、絮体生长动力学与污泥调理能耗等方面的差异。结果表明,相同投药量下,两级絮凝的出水浊度低于三级絮凝和常规絮凝,两级絮凝在最少的APAM投加量(2 mg/L)下达到最低的出水浊度(19.53 NTU);与常规絮凝相比,两级絮凝的絮体成长速率、平均粒径和沉降速率分别增加12.67%、30μm、36.74%。两级絮凝在投加间隔为240 s、投配比为1∶1条件下絮凝效能最优,出水浊度为15.34 NTU,絮体沉降速率为1.1 NTU/s,絮体密度达到1.123 4 g/cm³。絮体破碎再絮凝过程中,两级絮凝与常规絮凝破碎后均能恢复至破碎前水平,但破碎后均出现不可逆的絮体结构破损,粒径在0~100μm的絮体颗粒增多,粒径>400μm的絮体减少,破碎后两级絮凝的絮体强度因子(68.15%)高于常规絮凝(41.63%),两级絮凝的絮体强度和抗破碎剪切能力更高。在剩余污泥调理方面,两级絮凝产生的污泥只需要投加40mg/L的APAM就可以达到最低的滤饼含水率(75.5%)。因此,两级絮凝可以显著提升除浊效能与絮体性能,是强化絮凝的发展方向。