絮凝条件对絮体分形结构的影响

在85kg/m³的含沙高浊水中投加阳离子高分子聚合物,借助图像分析技术与沉降技术分析探讨了不同絮凝条件下泥沙絮凝形态学参数:絮体粒径、絮体有效质量密度、絮体自由沉速、浑液面沉速与上清液余浊等的变化规律.利用表征参数“分维”定量控制不同絮凝条件(如搅拌速率、搅拌时间、高分子浓度等)对含沙高浊水絮体结构分形特性的影响.实验证明,不合适的絮凝条件将导致絮体分形构造疏松脆弱,分维值低.絮凝条件合适时(快速絮凝强度为:r₁=300r/min,t₁=10s;慢速絮凝强度:r₂=120r/min,t₂=180s;CP浓度:0.1%),絮体分形结构处于最佳状态.该状态下的絮体具有粒径较大、沉速快、有效质量密度高、粒度分布均匀,分维值最高(D₃=2.16)的特点.而且,由静沉实验测得浑液面沉速高,上清液余浊也低.泥沙絮体分形结构达最佳时的混凝性能、沉降性能与结构密实性均较理想.     

Are flocculants required in a flocculant process?

The effectiveness of solids abatement by pH increase was investigated using the jar test procedure with a bentonite tap water suspension and an urban wastewater and an oxidation pond effluent. The results indicated that, depending on the suspended particles and on the dissolved ions, pH values between 9.5 and 12 induced extensive solids elimination without adding any other chemical than a base, i.e. sodium hydroxide or lime. The major effective reactions are then the calcium carbonate precipitation and the magnesium hydroxide precipitation. Moreover, this process does not require a flocculation step but only a precipitation step where the particles are entrapped by sweep coagulation and adsorption-coagulation. A continuous reactor was operated with an oxidation pond effluent. A suspended solids concentration less than 30 mg/l was obtained by adjusting pH between 11 and 11.5 while the reactor was operated up to 20 m/h superficial upflow velocity corresponding to a residence time through the whole unit of only 5 minutes. The sludge settling velocity depends on pH and on the primary particles but a maximum settling velocity larger than 1 m/h is easily reached. The concentration factor is then about 100. Environmental policy implications of this technique are that it allows to significantly upgrade a stabilization pond effluent and can be used when a high pH situation is acceptable.     

有机质、CaCl_2和MgCl_2对细颗粒泥沙絮凝沉降的影响

在CaCl2和MgCl2浓度为0~1.0mmol/L,泥沙浓度为10g/L时,用吸管法研究了有机质、CaCl2和MgCl2对细颗粒泥沙静水絮凝沉降的影响,结果表明,去除有机质后,细颗粒泥沙絮凝沉降加快,其絮凝所需的最佳电解质浓度降低;CaCl2和MgCl2的絮凝能力无明显差异,有机质含量对其几乎没有影响;在相同盐度下,细颗粒泥沙的絮凝沉降速度随电解质摩尔浓度的增大而增大.     

Performance of a novel vertical-flow settler: a comparative study

By increasing particle concentration and G value （root-mean-square velocity gradient） to enhance flocculation, a novel vertical-flow settler was designed to increase sedimentation effectiveness, and to simultaneously improve operational stabilization. Due to the gradual decrease in upward flow-rate of raw water, a floes blanket would form and suspend in the middle section of the settler, not at the bottom as in a conventional clarifier. Enough large floes, resulted from flocculation or fltration, would continuously settle out of the floes blanket, and simultaneously, the floes in raw water or those forming above the blanket would ceaselessly enter the floes blanket. As a result, the floes concentration in the blanket could keep a dynamic balance. The hydrodynamic shear in the blanket was improved by flow separation, which was induced by the abrupt change in flow channel. Due to the floes blanket and improved hydrodynamic shear, flocculation would be enhanced, which was helpful for removing fine particles in raw water. A comparative study showed that the novel vertical-flow settler had a much better performance in the removal of the particles in raw water than a conventional one, when they treated kaolin suspensions of different concentrations （500, 100 and 50 mg/L, respectively） coagulated by polyaluminum chloride（PAC1） at the up-flow rates of 1 and 2 mm/s, respectively.     

持续水动力作用下湖泊底泥胶体态氮、磷的释放

为揭示水动力扰动及其后续沉淀效应对湖泊内源氮、磷营养盐释放的作用,通过室内试验模拟了水体在受到持续扰动后又长时间静置沉淀的整个过程. 结果表明,水动力扰动初期可引起底泥颗粒态和胶体态氮、磷向水体大量释放. 在连续扰动0.5 d时,水体总氮(TN)和总磷(TP)浓度分别达最高值2.106 mg/L和0.272 mg/L; 连续扰动1 d时,水体中胶体氮(CN)和胶体磷(CP)含量分别达最高值0.452 mg/L和0.052 mg/L; 之后虽继续扰动,因颗粒物和胶体物质的凝聚沉淀作用超过了其悬浮量,TN、TP、CN、CP的含量却转而降低.在停止扰动后的静置过程中,大颗粒悬浮物迅速沉淀,而胶体物质沉降缓慢,静置时间超过1 d后,CN和CP含量才开始因絮凝沉淀而降低.真溶解态氮(UDN) 和真溶解态磷(UDP)含量在扰动阶段升高较少而在静置1　d之后有持续大幅度升高,说明胶体的吸附作用在扰动阶段限制了水体溶解态氮磷含量的升高,且延长了其悬浮后在水柱中的停留时间,在扰动后的静置阶段,胶体又会将吸附的氮磷解吸释放到水体中,从而延缓了营养盐去除和水质的改善.     

混凝过程中流场结构的PIV测量与表征

采用粒子成像速度场仪(PIV)在不投加专用示踪粒子的条件下,以混凝絮体为示踪粒子,对Taylor-Couette反应器内的絮凝反应流场进行测量与表征.结果表明,内筒旋转雷诺数Re在900~2900时,流场中产生的涡具有相似的特殊波状涡结构,相邻涡旋形态大小发生周期性变化,涡间存在主流液体的移动,这种涡结构有利于絮体结合生长成较大的絮体颗粒,便于沉降而导致较高的絮凝沉淀去除率.这也证实PIV技术能够在进行混凝反应的同时,用混凝过程中的微絮体为示踪粒子对混凝过程进行流场测量,不必再额外添加示踪粒子,就能较好地反映混凝过程中涡旋的形态变化特征,从而实现对絮凝过程的同步测量与表征.     

鄱阳湖悬浮颗粒物絮凝沉降典型藻类的动力学研究

为了探讨鄱阳湖水动力条件改变引起的悬浮颗粒物浓度变化可能导致的鄱阳湖浮游植物群落结构的变化,本文研究了鄱阳湖悬浮颗粒物絮凝沉降3种典型藻类的动力学过程.以铜绿微囊藻(蓝藻)、四尾栅藻(绿藻)和菱形藻(硅藻)为研究对象、鄱阳湖采集沉积物为悬浮颗粒物,使用混凝试验搅拌仪模拟动力学条件,在颗粒物投加量为20 mg·L-1时分别研究了静置沉降时间、扰动强度和扰动时间对颗粒物絮凝沉降藻细胞的影响.结果表明,絮凝沉降效率:蓝藻绿藻硅藻.在扰动强度为20 s-1、扰动时间为30 min时,0.5~4 h静置沉降时间均促进3种藻类的絮凝沉降.绿藻和硅藻的絮凝沉降效率随着静置沉降时间的延长而降低,前0.5 h的絮凝沉降效率最大;而蓝藻的絮凝沉降效率变化无明显规律.扰动时间和静置沉降时间均为30 min时,随着扰动强度在2~40 s-1增加时,3种藻的絮凝沉降效率逐渐增大.扰动强度为20 s-1、静置沉降时间为30 min时,5~60 min扰动时间均促进藻细胞的絮凝沉降,并且随着扰动时间的增加,絮凝沉降效率呈先增大后降低的趋势.30 min为蓝藻絮凝沉降的最佳扰动时间,絮凝沉降效率为12.56%;45 min为绿藻和硅藻絮凝沉降的最佳扰动时间,絮凝沉降效率分别为11.93%和7.54%.因此,水动力条件的改变可以引起悬浮颗粒物与藻类的絮凝沉降效率发生变化,从而对藻类的群落结构以及水华发生规律产生影响.     

Cationic content effects of biodegradable amphoteric chitosan-based flocculants on the flocculation properties

A series of biodegradable amphoteric chitosan-based flocculants (3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) modified carboxymethyl chitosan, denoted as CMC-CTA) with different substitution degrees of CTA were prepared successfully. The content of carboxymethyl groups in each CMC-CTA sample was kept almost constant. The solubility of the various flocculants showed that, higher cationic content of flocculants caused a better solubility. The flocculation experiments using kaolin suspension as synthetic water at the laboratory scale indicated that the substitution degree of CTA was one of the key factors for the flocculation properties. With the increase of cationic content, the flocculants were demonstrated better flocculation performance and lower dosage requirement. Flocculation kinetics model of particles collisions combining zeta potential and turbidity measurements was employed to investigate the effects of the cationic content of the flocculants on the flocculation properties from the viewpoint of flocculation mechanism in detail. Furthermore, flocculation performance using raw water from Zhenjiang part of Yangtze River at the pilot scale showed the similar effects to those at the laboratory scale.     

Effect of water chemistry on the aggregation and photoluminescence behavior of carbon dots

Carbon dots are rapidly emerging carbon-based nanomaterials that, due to their growing applications, will inevitable find their way to natural waters; however, their environmental fate is mostly unknown. Carbon dots with different surface functionality were fabricated and characterized by TEM and FT-IR. Their surface charge, given by the zeta potential, and their hydrodynamic diameter in suspension were investigated under a variety of environmentally relevant conditions. The effect of ionic strength was studied in the presence of monovalent (NaCl) and divalent (CaCl₂) cations, for pH levels from 3 to 11; humic acid was used as a model for dissolved natural organic matter. Total potential energies of interactions were modeled by classical DLVO theory. The experimental results showed that water chemistry altered the surface charge of the nanomaterials, but their hydrodynamic size could not be correlated to those changes. Evidence of specific interactions was found for the amino functionalized particles in most cases, as well as the plain carbon dots in the presence of Ca^2 + and humic acid. Nanoparticles remained largely stable in suspension, with some exception at the highest ionic strength considered. DLVO theory did not adequately capture the aggregation behavior of the system. Moreover, cation and/or humic acid adsorption negatively affected the emission intensity of the particles, suggesting limitations to their use in natural water sensing applications. The particular stability shown by the carbon dots results in exposure to organisms in the water column and the possibility of contamination transported to significant distances from their source.     

壳聚糖接枝三元共聚阳离子絮凝剂对高岭土悬浊液的絮凝特性

采用烧杯混凝实验研究了壳聚糖(CTS)、CTS与丙烯酰胺和丙烯酸乙酯季铵盐三元接枝共聚阳离子絮凝剂(CAS)对高岭土悬浊液的絮凝特性.结果表明,CAS具有比CTS絮凝效果好、用量少、pH值适用范围广等优点.CAS絮凝效能受胶体颗粒性质的影响小,对自来水和蒸馏水配置的高岭土悬浊液均具有较好的絮凝效能.中性条件下,CAS的最佳投加量仅为CTS的1/10.在pH值2.0-11.0范围内,CAA对浊度的去除率在95%左右.CAS投加量与原水浊度的关系为:投加量低于0.5nag·L-1时,絮凝效果随原水浊度的升高降低;投加量大于0.5 mg·L-1,浊度去除率随原水浊度的增大而提高;投加量超过1.0 mg·L-1后,对浊度(10～160 NTU)的悬浊;液浊度去除率均在85%以上.悬浮颗粒聚集状态的变化分析、颗粒ξ电位测定、絮体粒径分布测定及其形态结构的观察结果表明,电性中和、吸附架桥是CAS的主要絮凝作用机理,絮凝过程是多种机制共同起作用的动态变化过程.     

高浓度悬浊液絮体分形结构的发展变化研究

以黄河泥沙为代表的高浓度悬浊液架桥絮凝实验研究表明,絮体结构具有分形特性.絮体的分形构造在从疏松多孔、开放的分枝状DLCA构造逐步演变到密实的最佳RLCA构造后,又开始呈现疏松脆弱结构的特征.絮体的最佳分形结构只能保持一段时间.絮体分形结构的发展变化规律可用参数"分维"来表征.利用"分维"作为定量控制工具以获取沉降性能与脱水性能良好的理想絮体构造.絮体分形结构还受含沙量、搅拌强度、搅拌时间等因素的影响.      

磷酸废水封闭循环处理的实验研究

本法由４个化工单元操作组成：旋流离心分离、絮凝、重力沉降和混合稠浆过滤。实验结果表明：第１级旋流离心分离效率在８０％以上。第２级含固相细粒的旋流溢流采用絮凝预处理后,沉降速度提高近３０倍,清液含固量在２００×１０－６以下。１、２级稠浆在混合比为１．５可达良好的过滤性能。本实验结果为磷酸废水封闭循环处理工艺设计、设备设计,以及操作控制提供了理论依据。     

混凝过程中絮体形貌的PIV成像观测与表征

采用粒子成像速度场仪(PIV)对Taylor-Couette反应器内的混凝过程中絮体的微观形貌进行了观测与表征.结果表明,内筒转速在20～60r/min范围内,生成的絮体颗粒较大,粒径分布均匀,絮凝沉淀效果最好.由于内筒旋转速度的变化直接导致混凝流场形态的变化,所以混凝过程中流场形态的变化对絮体生长过程有重要影响,进而直接影响到混凝效果.混凝过程中流场的周期性变化、涡间存在液体传递的波状涡结构有利于絮体颗粒的结合生长,并导致较高的絮凝沉淀去除率.这也说明PIV技术能够在测量流场的同时较好地反映混凝过程中微絮体的形貌变化特征,从而实现对絮凝过程的原位观测与表征.     

聚合氯化铝（PACl）混凝絮体的破碎与恢复

通过烧杯实验以及在线粒度监测考察了聚合氯化铝（PACl）混凝所生成絮体的破碎以及随后絮体的恢复情况.结果发现,絮体的破碎以及恢复情况因混凝区域的不同而呈现不同的规律.在稳定区,絮体的强度较大,不易破碎,且破碎后的絮体可进一步增长,其恢复因子高达259%;在电中和混凝区,絮体的强度最小,易于破碎,但破碎后可完全恢复;在再稳区和卷扫混凝区,絮体的强度较大,不易破碎,但破碎后不能完全恢复,其中后者的恢复因子仅为18.6％.再搅拌强度越大,对絮体的破碎及恢复程度的影响越大.对于卷扫混凝,经再搅拌破碎后而得到部分恢复的絮体,相对于未经再搅拌的絮体而言,其絮体层与水体间界面的沉降高度及平均沉降速率均较低,且在絮凝沉降区和区域沉降区,该絮体界面的瞬时沉降速率在同一絮体浓度下均较低,但在压缩沉降区,二者的瞬时沉降速率相同.     

A new polystyrene-latex-based and EPS-containing synthetic sludge

Since the living microorganisms in activated sludge continuously change, it is difficult to conduct controlled experiments and achieve reproducible results for evaluating sludge characteristics. Synthetic sludge, as a chemical surrogate to activated sludge, could be used to investigate the sludge physicochemical properties, and it is desirable to prepare synthetic sludge with similar structure and properties to real activated sludge to explore the flocculation and settlement processes in activated sludge systems. In this work, a high-strength synthetic sludge was prepared with functional polystyrene latex particles as the framework and extracellular polymeric substances (EPS) to modify its surface. The flocculation and settling characteristics of the microspheres and the prepared synthetic sludge were tested. Compared with other three functional polystyrene latex microspheres, the synthetic sludge prepared with EPS-modified polystyrene latex microspheres showed good settling characteristics and a significantly higher strength. They could be used for studying the physicochemical properties of activated sludge.     

铝盐去除浓缩脱水污泥水中悬浮物和磷的效果研究

采用混凝沉淀法处理污泥水中的悬浮固体和磷,考察了聚合氯化铝(PAC)、聚硫氯化铝(PACS)以及PAC和阴离子聚丙烯酰胺(aPAM)复配不同投加量对污泥水沉降性能和磷去除的影响。实验结果表明,PAC和PACS混凝处理污泥水效果基本一致,会恶化污泥水沉降,且随PAC投药量的增加,污泥水SV30越大。PAC与aPAM复配混凝处理污泥水,也难以改善污泥水的沉降性能。结果表明,铝盐混凝剂不适合同步去除污泥水悬浮固体和磷,建议先寻求其它混凝剂改善污泥水沉降再用铝盐除磷。     

Particle size distribution and removal in the chemical-biological flocculation process

The particle characterization from the influent and effluent of a chemical-biological flocculation (CBF) process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatment (CEPT) process and a primary sediment tank process were also analyzed for comparison. The results showed that CBF process was not only effective for both the big size particles and small size particles removal, but also the best particle removal process in the three processes. The results also indicated that CBF process was superior to CEPT process in the heavy metals removal. The high and non-selective removal for heavy metals might be closely related to its strong ability to eliminate small particles. Samples from different locations in CBF reactors showed that small particles were easier to aggregate into big ones and those disrupted flocs could properly flocculate again along CBF reactor because of the biological flocculation.     

混凝机理物理模型中混合剪切阶段的研究

在总结絮凝剪切理论和实验研究的基础上,从亚微观的角度上,提出了混凝过程的物理模型,该模型从理论上强调了絮凝剪切碰撞的有效性和结合了分形维数评价混凝效果及过程。该模型指出:只有胶体颗粒与充分分散的药剂充分接触,才有可能充分地形成微絮体,也才有可能充分地或高效地(短时间内)形成大絮体。也就是说充分地混合剪切,才有高质量的凝聚,才可能有高效地絮凝。我们强调这种混合剪切是指在一定的流体力作用下颗粒与药剂的充分分散和接触。无机絮凝剂从添加到分散,到与颗粒发生接触作用,到脱稳颗粒形成微絮体乃至以后的大絮体,它在一定的弱搅拌强度下需要一定的时间;添加有机絮凝剂时则需要较强的搅拌强度。试验也证明:在上述条件下,其混凝沉降效果大大优于传统的混凝沉降效果。     

太行山油松人工林土壤水稳性团聚体稳定性及其演变机制

土壤水稳性团聚体是反映土壤质量好坏与土壤抗侵蚀能力的重要指标.通过野外调查与室内分析,研究太行山南麓不同恢复年限（33、45和49 a）油松人工林土壤水稳性团聚体的稳定性状况及其影响因素.结果表明:不同恢复年限油松人工林土壤水稳性团聚体均以大团聚体（>0.25 mm）为主,大团聚体含量在80%以上,但恢复49 a油松人工林土壤水稳性大团聚体含量在0~50 cm各土层中均低于恢复33 a油松人工林,且在10~40 cm土层差异显著.随着油松人工林的逐步恢复,>2 mm粒级的土壤水稳性团聚体含量下降,土壤水稳性团聚体分形维数（D）、破坏率（PAD）波动增加,平均质量直径（MWD）和几何平均直径（GMD）在0~40 cm深度范围内明显减小,2 mm粒级的土壤水稳性团聚体可以作为油松人工林土壤水稳性团聚体稳定性的重要度量阈值.土壤黏粒会促使小粒级土壤水稳性团聚体的形成,而有机质、速效磷、速效钾、砂粒等能够促进小粒级土壤水稳性团聚体向大粒级转化,从而提高土壤水稳性团聚体稳定性.研究显示,油松人工林恢复过程中土壤团聚状态良好、稳定性强、分散性弱,但恢复到一定阶段会引起土壤水稳性团聚体稳定性降低,这与土壤有机质、速效磷、速效钾以及机械组成变化等有直接关系.      

悬浮颗粒物浓度对溢油沉潜过程影响的试验研究

溢油事故发生后,漂浮油会与水中的悬浮颗粒物发生相互作用形成油-悬浮颗粒物聚合体（oil-suspended particulate matter aggregates,OSAs）,进而分散在水中或沉降到水底。实验室通过批量振荡实验,利用紫外分光光度法,研究了天然沙土对阿曼原油沉潜过程的影响。结果表明,当振荡频率一定时,沙土能够显著促进阿曼原油在水中的沉潜,其中大部分以半潜油的形式悬浮在水中,少部分与沙土相互作用形成了油-悬浮颗粒物聚合体。随着振荡时间的增加,阿曼原油的沉潜率迅速增大,达到最大值后趋于稳定。当沙土的浓度在100~400 mg/L范围内增加时,阿曼原油的最大沉潜率和沉潜速率提高,沉潜过程达到平衡所需要的时间缩短。