活性污泥胞外聚合物EPS的影响因素研究

胞外聚合物EPS对活性污泥的表面特性、生物絮凝、沉降及脱水性能等具有重要的影响,主要对污泥负荷Ns,DO,温度,Ca2+,pH及废水水质等因素对EPS的影响进行了研究。试验结果表明:Ns,pH及废水水质对EPS的含量、成分有显著的影响;DO,温度对EPS的影响较小;同时随着进水Ca2+浓度的增加,污泥的EPS,脱氢酶及OUR增加。     

胞外生物高聚物絮凝剂的研究进展(上)

就微生物分泌的胞外生物高聚物絮凝剂 (EBF)的研究和应用做了一个全面的综述 ,对化学絮凝剂与生物絮凝剂的比较 ,胞外生物高聚物絮凝剂产生菌的分离、培养条件、EBF的分类、化学组成和结构、絮凝机理和在絮凝过程中物理化学因素的影响以及生物絮凝的遗传学研究等进行了详细的分析讨论。     

氯化钠对无机聚合物浆体流变性能的影响

研究了氯化钠对无机聚合物浆体标准稠度需水量、凝结时间和流变性能的影响,采用Herschel-Bulkey(H-B)流变模型对浆体流变曲线进行拟合获得流变参数。研究结果表明:无机聚合物流体模型属于H-B流体模型,相关系数达0.999以上,无机聚合物浆体剪切增稠程度随氯化钠掺量的增加而降低。氯化钠对无机聚合物浆体有缓凝效果;随着氯化钠掺量的增加,浆体的标准稠度需水量略有增加。随着剪切速率的增加,无机聚合物剪切应力逐渐增大,塑性黏度先降低后增大即浆体呈现出先剪切稀化再剪切增稠的规律;随着氯化钠掺量的增加,无机聚合物的剪切屈服应力逐渐降低,塑性黏度系数基本不受影响,触变环面积呈现出先增加后减少的规律。     

白洋淀养鸭废水对生物膜生物量和胞外酶活性的影响

为了对应用生物膜进行湖泊的生态监测与评价提供理论依据,通过微宇宙试验研究了不同浓度梯度养鸭废水对生物膜生物量和胞外酶活性的影响。结果表明:养鸭废水会显著增加生物膜的生物量;在短期暴露中,生物膜的生物量与养鸭废水浓度线性相关;而在长期暴露中则符合Logistic方程,养鸭废水对生物膜生物量的促进具有饱和效应。养鸭废水对生物膜胞外酶活性的效应受暴露时间的影响:短期暴露(24 h)时养鸭废水会促进碱性磷酸酶、β-葡萄糖苷酶和亮氨酸肽酶活性的增加,3种酶活性均随养鸭废水浓度的升高而呈对数增加;长期暴露(60 d)时,养鸭废水对3种酶活性均产生抑制作用,酶活性随养鸭废水浓度升高而呈对数降低。     

粗骨料表面构造及其对混凝土性能的影响

长期以来,混凝土骨料表面构造的研究一直停留在定性描述的水平,难以定量表征和研究。本文提出了表征骨料表面构造的5个指标:凹凸度、凹凸比、全周凹凸度、全周凹凸比和凹周比。测试了灰岩碎石、破碎卵石和卵石的表面构造,研究了具有等腰三角形断面凹槽的圆柱体骨料-浆体的界面应力,发现骨料凹周比和全周凹凸比越大,骨料对混凝土强度的贡献越大,对提高混凝土强度越有利,这一结论得到了混凝土性能试验的验证。     

往复隔板絮凝池边壁形状对絮凝反应的影响研究

通过往复隔板絮凝池混凝反应的模型试验 ,对不同边壁条件下的絮凝效果进行了分析比较 ,可知边壁的形状对改善水流结构起着显著的作用。将絮凝池拐角及隔板端面设计为圆弧形 ,可保持所要求的紊流能耗和最佳水力条件 ,为老水厂改造提供了一条有效途径。     

絮凝对三峡水库泥沙沉降的影响

现场与室内实测的泥沙级配差异证实了三峡水库中存在泥沙絮凝现象,絮凝会加速水库泥沙淤积速率。为了确定絮凝对泥沙沉降速率的影响,现场采集了三峡水库原样泥沙,基于三峡水库水体环境,采用室内静水沉降试验对三峡水库中泥沙絮凝沉降规律进行了研究。研究结果表明,当试验采用的初始含沙量大于0.3 kg/m3时,部分单颗粒泥沙会聚集形成絮团,且泥沙絮凝程度以及沉速增加的幅度与水体中含沙量呈正比。参与絮团形成的单颗粒泥沙粒径均位于0.022 mm以下,小于临界粒径的泥沙占全沙的83%;采用絮凝因数和物质沉降通量因数分别表征絮凝对泥沙沉降的影响程度,这两种因数都随含沙量增加而增加,含沙量在1.5 kg/m3以下时其最大值分别为5.03和1.66,表明絮凝对三峡库区汛期的泥沙淤积有可能造成较大影响。     

聚合物水泥砂浆的耐腐蚀性能

选用盐酸、硫酸、饱和硫酸钠3种腐蚀溶液对聚合物水泥砂浆的耐腐蚀性能进行系统研究。研究结果表明:聚合物水泥砂浆在5%的盐酸溶液中浸泡30 d,90 d,180 d后其强度保持率均高于普通水泥砂浆;在饱和硫酸钠溶液中浸泡180 d后其抗折强度保持率超过100%;而在5%的硫酸溶液中随时间的增长,其抗压强度保持率的下降趋势平缓,浸泡180 d其抗压强度保持率基本维持在29%以上。掺入聚合物后水泥砂浆的密实性明显提高,而且形成柔性的网状胶膜结构,有效地提高了聚合物水泥砂浆的耐盐酸侵蚀性能。     

新型复合絮凝剂PFAZS的絮凝性能研究

在活化硅酸中加入铁、铝和锌离子,制成聚硅酸铁铝锌(PFAZS)复合絮凝剂,并通过单因素试验得出最佳的反应条件,实际水样试验得到对浊度和COD的去除效率.结果表明:聚硅酸铁铝锌(PFAZS)的处理效果及稳定性要优于常用絮凝剂聚硅酸铝(PASS),最适反应条件为 PFAZS用量1.25 mL/L、原水pH值6～9、原水浊度10～30 NTU、温度0～30 ℃.对于饮用水源水, PFAZS对浊度去除率可达90.6%;对于生活污水,浊度的去除率达到91.3%,COD的去除率达到72.7%.     

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。     

Extracellular polymers in partly ozonated return activated sludge: impact on flocculation and dewaterability.

The purpose of this study was to evaluate the influence of partial ozonation of return activated sludge on settling properties and dewaterability of sludge. Sequencing batch reactors with two sets of aerobic and alternating anoxic/aerobic conditions were used. In each set, one reactor served as a control and the other was subject to the ozone treatment (doses in the range of 0.016-0.080 mg O3/mg TSS of initial excess sludge). The level of total suspended solids (TSS) in each reactor was controlled at 1,800 mg/l. To evaluate settleability and dewaterability, settling kinetic studies, sludge volume index (SVI) and capillary suction time test (CST) were used. For extraction and quantifying sludge biopolymers, thermal-ethanolic extraction was employed. The ratio of bound-to-total extracellular polymer substances (EPS) was higher for the strictly aerobic reactor than for the alternating anoxic/aerobic one, indicating the stronger structure of the aerobic flocs. After ozone treatment, the fraction of bound EPS was released and solubilized, increasing soluble EPS. Increased apparent food-to-microorganism (F/M) ratio favoured production of EPS in ozonated reactors, enhancing flocculation, which had potential to improve settling. Dewaterability, measured by CST test, was better in alternating anoxic/aerobic reactors than in aerobic ones, indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation.     

Influence of flocculation and settling properties of activated sludge in relation to secondary settler performance.

Floc characteristics were studied at a full scale activated sludge treatment plant with a unique process solution incorporating pre-denitrification with post-nitrification in nitrifying trickling filters. Since greater nitrogen removal is achieved when more secondary settled wastewater is recirculated to the trickling filters, the secondary settlers are always operated close to their maximal capacity. The flocculation and settling properties are therefore crucial and have an effect on the overall plant performance. Since the plant is operated at a short sludge age, these properties change quickly, resulting in variable maximal secondary settler capacity. The dynamics in floc structure and microbial community composition were studied and correlated to the secondary settler performance. Fluorescence in situ hybridisation was used to investigate the microbial community structure and their spatial distribution. The floc structure could to some extent be related to the flocculation and settling properties of the sludge. Even small differences had an influence suggesting that colloidal properties also play a significant role in determining the floc properties. No correlation between microbial community composition and settling properties could be established with the group-specific probes investigated.     

Towards mechanistic models for activated sludge flocculation under different conditions based on inverse problems

Experimental data of Ca-induced activated sludge flocculation under different conditions of temperature and dissolved oxygen are investigated in order to model the influence of changing physical and chemical factors. However, current kernel structures for collision frequency and efficiency are unable to describe activated sludge flocculation data. Therefore, an earlier developed methodology based on an inverse problem is applied, yielding empirical models, to find out how flocculation is affected by these different environmental conditions. This contribution shows the useful application of inverse problems to improve the understanding of complex aggregation mechanisms.     

Solving the inverse problem for aggregation in activated sludge flocculation using a population balance framework.

Many systems contain populations of individuals. Often, they are regarded as a lumped phase, which might, for some applications, lead to inadequate model predictive power. An alternative framework, Population Balance Models, has been used here to describe such a system, activated sludge flocculation in which particle size is the property one wants to model. An important problem to solve in population balance modelling is to determine the model structure that adequately describes experimentally obtained data on for instance, the time evolution of the floc size distribution. In this contribution, an alternative method based on solving the inverse problem is used to recover the model structure from the data. In this respect, the presence of similarity in the data simplifies the problem significantly. Similarity was found and the inverse problem could be solved. A forward simulation then confirmed the quality of the model structure to describe the experimental data.     

淤泥絮凝脱水的室内试验研究

自然状态下淤泥中细颗粒泥沙难以形成大的絮团,对其进行自然或者机械脱水都是极度困难的。因此,在运输河湖疏浚淤泥过程中,极易造成二次污染。通过在淤泥中添加阴离子型絮凝剂（PAM）,对淤泥的絮凝脱水效果进行了分析,探讨了淤泥絮凝脱水的影响因素和颗粒粒径变化规律。结果表明,絮凝剂加入比例和淤泥含水率对淤泥絮凝脱水均有影响;随着絮凝剂加入量的增加,絮团颗粒的当量粒径呈增大趋势;当投加量超过一定值后,淤泥颗粒级配基本保持稳定;当絮凝剂比例在0.3%,淤泥含水率在200%时,淤泥脱水效果最佳。     

Aerobic granular sludge technology: an alternative to activated sludge?

Laboratory experiments have shown that it is possible to cultivate aerobic granular sludge in sequencing batch reactors. In order to direct future research needs and the critical points for successful implementation at large scale, a full detailed design of a potential application was made. The design was based on the laboratory results, and two variants of a full-scale sewage treatment plant based on Granular sludge Sequencing Batch Reactors (GSBRs) were evaluated. As a reference a conventional treatment plant based on activated sludge technology was designed for the same case. Based on total annual costs both GSBR variants proved to be more attractive than the reference alternative (7-17% lower costs). From a sensitivity analysis it appeared that the GSBR technology was less sensitive to the land price and more sensitive to a rain weather flow (RWF). This means that the GSBR technology becomes more attractive at lower permissible RWF/DWF ratios and higher land prices. The footprint of the GSBR variants was only 25% compared to the reference. However, the GSBR with primary treatment only cannot meet the present effluent standards for municipal wastewater in The Netherlands, mainly because of a too high suspended solids concentration in the effluent. A growing number of sewage treatment plants in the Netherlands are going to be faced with more stringent effluent standards. In general, activated sludge plants will have to be extended with a post treatment step (e.g. sand filtration) or be transformed into Membrane Bioreactors. In this case a GSBR variant with primary treatment as well as post treatment can be an attractive alternative.     

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.