絮凝方式对净水厂排泥特性的影响

在不同的聚合氯化铝(PAC)投量下,考察了网格、折板和机械搅拌三种絮凝方式对沉淀池排泥周期和污泥静沉性能的影响。结果表明,当PAC投量20 mg/L时,网格絮凝池中矾花的沉降性能最好,相应的沉淀池排泥周期也最长,为10 h;当PAC投量为25 mg/L时,三者的排泥周期均为8 h左右,排泥水初始含固率也基本相同,此时,与网格池和搅拌池相比,折板池的污泥静沉性能最好、上清液浊度最低、浓缩后的污泥体积最小,表明该池型更适于对排泥水进行再絮凝沉淀。     

机械搅拌絮凝工艺在哈尔滨磨盘山净水厂的应用

以哈尔滨磨盘山净水厂目前所采用的机械搅拌絮凝工艺作为研究对象进行生产性试验,分析并比较了不同原水水温及浊度下该工艺的絮凝性能,并对水中矾花进行了分析,验证了该工艺在应用中的可行性,并提出将原水浊度为0.7 NTU作为临界值适时调整,以进一步保证该工艺的絮凝效果。     

壳聚糖接枝聚丙烯酰胺的絮凝性能中试研究

以长江镇江段原水为处理对象,在中试规模下通过正交试验方法研究了壳聚糖接枝聚丙烯酰胺的絮凝性能,并考察了不同因素对其絮凝效果的影响。结果表明,不同因素对该絮凝剂絮凝效果的影响程度为:絮凝剂投量絮凝时间絮凝搅拌速度;当絮凝剂投量为0.5 mg/L,絮凝时间为20 min,三联机械搅拌絮凝池的搅拌速度依次为150、100和50 r/min时,絮凝效果最佳,此时砂滤出水浊度1 NTU,满足《生活饮用水卫生标准》(GB 5749—2006)的要求;与现行使用的聚合硫酸铁相比,使用该絮凝剂时砂滤出水浊度略高,但其用量远低于聚合硫酸铁的(平均约为25mg/L)。另外,壳聚糖接枝聚丙烯酰胺的絮凝效果随接枝率的增大而先升后降,当接枝率为286%时,絮凝效果最好。     

膜生物反应器发生污泥膨胀后的控制措施研究

以膜生物反应器处理学校洗浴污水,考察了污泥发生膨胀时反应器对污染物的去除效果,并探讨了控制污泥膨胀的方法。结果表明,污泥膨胀对膜生物反应器去除COD和BOD5的效果影响不大,但会使系统对氨氮的去除率有所下降。采用化学絮凝法控制污泥膨胀,静态试验结果表明三氯化铁和聚丙烯酰胺的絮凝效果较为理想,但现场投加时发现,反应器内较强的水力搅拌作用使得聚丙烯酰胺的絮凝效果变差,而三氯化铁可作为控制污泥膨胀的应急措施,采用营养平衡法可从根本上解决污泥膨胀问题。     

吴江水厂竖流式折板絮凝池的设计优化

介绍了多道并联、单通道3级串联竖流式折板絮凝池在吴江净水厂工程中的设计应用,并对该厂一、二期的运行成果进行了分析比较.二期工程中在反应池至沉淀池之间设置了过渡区,实现了絮凝G值的平稳过渡,从而有效提高了絮凝效果.     

机械破碎强度对絮体破碎再絮凝过程的影响

采用连续流混凝沉淀反应器,研究了絮凝过程中机械搅拌强度对絮体破碎再絮凝过程以及出水水质的影响。结果发现,絮体破碎再絮凝的平均粒径无法恢复至破碎前的水平,同时絮体内部结构发生了变化。当破碎阶段的搅拌转速为250 r/min时,破碎后的絮体再絮凝程度较高,絮凝结束阶段絮体平均粒径为72.9μm,接近破碎前的水平(76.1μm),同时几何分形维数由未破碎时的1.80降至1.75,说明絮体的内部结构变得更加紧实;近球态絮体的比例升至58.7%,长链态絮体比例则降至41.3%,说明机械破碎可以改变絮体形态;对于浊度为100 NTU的原水,沉淀出水浊度由未破碎时的6.69 NTU降至破碎再絮凝后的5.85 NTU,说明适当地进行机械破碎可以提高絮凝处理效果。     

微涡旋絮凝在宁夏某水厂改造中的应用评价

采用传统折板絮凝池处理低浊水时面临絮体沉降性差、“跑矾”等现象.为解决上述问题,宁夏某水厂采用微涡旋絮凝工艺对折板絮凝池进行升级改造,但改造完成后的运行效果仍不理想.通过分析对比微涡旋絮凝池和折板絮凝池中的颗粒数、浊度、絮体沉降体积、分形维数、分子荧光光谱等,讨论现有微涡旋改造的不足,并建立一套评价体系,以指导水厂的升级改造.试验结果表明:经过微涡旋改造后除第二絮凝段外,其他各段对浊度的去除率分别提高了8.7％、6.7％、6.5％、56.1％,絮体颗粒数分别降低了20.8％、14.7％、25.2％、48.4％;第二絮凝段由于布水方式和填加微涡旋球过多(水力扰动过大、短流)等问题,使得絮体的形成受到影响,对浊度和颗粒数的去除率相比折板絮凝池无明显提高.所采用的评价指标能够评价水厂微涡旋改造,具有广泛的应用性,为今后水厂的升级改造提供了良好的评价体系.     

折板絮凝池设计方案的探讨

本文分析介绍了折板絮凝池的设计原理,并从絮凝时间、单池设计流量与折板间距、GT值和流速的选取等方面对具体设计要点进行了详细阐述。     

异波折板絮凝池絮凝控制指标研究

由于Camp和Stein的速度梯度公式G值存在理论及应用上的缺陷 ,首次针对异波折板絮凝池 ,提出单位造涡强度———FS 这一宏观控制指标。由于折板单元的水力特征决定了其本身的造涡强度 ,将FS 与絮凝效果有机地结合起来 ,在宏观上就便于通过控制折板单元的水力特征来达到对絮凝效果进行控制的目的     

磁絮凝强化污水处理的试验研究

以对COD、浊度、TP、氨氮的去除效果为考察指标,对城市生活污水进行磁絮凝试验研究.通过试验确定了最佳混凝剂的种类,同时还研究了混凝剂用量、磁粉用量、搅拌条件、药剂投加顺序等因素对处理效果的影响.试验结果表明:磁絮凝处理城市生活污水的效果要好于传统混凝的,并且磁粉的加入提高了对污水中磷的去除效果,对COD、浊度、TP和氨氮的去除率分别提高到61.30％、98.90％、98.13％和18.58％.采用该技术不仅能缩短絮凝与沉降时间,减少絮体体积,而且更易于实现固液磁分离.     

菱形翼片隔板絮凝反应器的研发及应用

基于后台阶流理论,设计了菱形翼片隔板絮凝反应器,实现了同时对流体微观涡旋强化及宏观涡旋均布进行有效控制。同时结合数值模拟计算结果和中试处理效果,优化了菱形翼片隔板絮凝反应器的特征尺寸参数,并将其用于钢厂废水回用项目。工程运行结果表明,单套设备处理量为750 m3/h,出水浊度可稳定在1 NTU左右,对COD的去除率达到了48.5%,大大降低了后续处理负荷,由此证明该设备具有较高的絮凝反应效率,出水水质良好,适用于钢厂废水回用工程。     

Application of gas-inducing reactor to obtain high oxygen dissolution in aeration process

The application of gas-inducing reactor to obtain high oxygen dissolution has been investigated at various operation conditions including agitation speed, temperature (20-40 degrees C), pressure (1.0-1.2 atm) and working liquid levels. Correlations regarding onset speed, agitation power consumption, gas holdup and oxygen mass transfer coefficient were established from experimental data. Onset speed can be accurately predicted with modified Froude number. The agitation power consumptions before and after onset speed is a function of Froude number and working liquid level. Gas holdup is an important factor influencing the mass transfer of oxygen after onset speed. In the study of mass transfer of oxygen (T=20 degrees C, P=1 atm), the highest dissolved oxygen concentration is as high as 39.34-39.92 mg x L(-1). The value of k(L)a is within 0.511-1.792 min(-1). The k(L)a is not affected by the oxygen gas pressure (1.0-1.2 atm). However, k(L)a increases with increasing temperature. The gas-inducing reactor of this study has higher k(L)a than the other type of gas-inducing reactor under the same unit volume power consumption. The pure oxygen utilization rate of this system can be as high as 100%.     

The intrinsic kinetics of nitrification in a continuous flow suspended growth reactor

The intrinsic rate of nitrification was observed in a continuous flow reactor by eliminating external and internal diffusional resistances. The former were minimized by means of intense agitation, and the latter by mechanical rupture of the activated sludge floc using high impeller rotational speeds. The experimental results obtained from the continuous flow experiments confirmed the applicability of Michaelis-Menten kinetics to the activated sludge nitrification process. A possible dependency of k on contact time was found, larger values of k being observed under shorter contact times. The Michaelis constant K, was found practically unaffected by the contact times used in this study.     

Effect of mechanical stress on biofilms challenged by different chemicals

In this study a methodology was applied in order to ascertain the mechanical stability of biofilms, by using a stainless-steel (SS) rotating device immersed in a biological reactor where biofilms formed by Pseudomonas fluorescens were allowed to grow for 7 days at a Reynolds number of agitation of 2400. The biofilms developed with this system were characterised in terms of amount of total, extracellular and intracellular proteins and polysaccharides, amount of mass, metabolic activity and mechanical stability, showing that the biofilms were active, had a high content of extracellular constituents and an inherent mechanical stability. In order to assess the role of chemical agents on the mechanical stability, the biofilms were exposed to chemical agents followed by mechanical treatments by submission to increase Reynolds number of agitation. Seven different chemical agents were tested (two non-oxidising biocides, three surfactants and two oxidising biocides) and their effects on the biofilm mechanical stability were evaluated. The increase in the Reynolds number increased the biofilm removal, but total biofilm removal was not found for all the conditions tested. For the experiment without chemical addition (only mechanical treatment), the biofilm remaining on the surface was about 76%. The chemical treatment followed by the subsequent mechanical treatment did not remove all the biofilms from the surface. The biofilm remaining on the SS cylinder ranged from 3% to 62%, depending on the chemical treatment, showing that the chemical treatment is far from being a cause that induces massive biofilm detachment and even the synergistic chemical and mechanical treatments did not promote biofilm removal. Some chemical agents promoted an increase in the biofilm mechanical stability such as glutaraldehyde (GTA), benzalkonium chloride (BC), except for the lower concentration tested, and sodium dodecyl sulphate (SDS), except for the higher concentration tested. Treatments that promoted biofilm removal, to an extent similar to the control experiment (without chemical treatment), were BC, for the lower and the higher concentration of SDS. Cetyltrimethyl ammonium bromide (CTAB), ortho-phthalaldehyde (OPA), sodium hydroxide (NaOH) and sodium hypochlorite (SHC) promoted the weakening of the biofilm mechanical stability.     

The Effect of Agitator Impeller Design on Maximum Shear Stress, and the Resulting Impact on the Flocculation Process

Although it is extensively researched, flocculation in the water-treatment industry lacks a design procedure to assess accurately the performance of the different types of agitator impeller which are available. New high-efficiency, hydrofoil-type impellers offer substantial potential for flocculation duties in many areas, provided that they are applied correctly. This paper highlights the importance of the 'velocity gradient'and the distribution of shear within the agitation system. The objective of the paper is to help engineers to evaluate different types of proprietary impeller designs, using various techniques to examine the shear distribution applied to the system.     

Kinetics of pneumatic flocculation

A mathematical model has been established to describe the kinetics of pneumatic flocculation in terms of the process variables: energy of agitation, volume of turbid water, temperature, water viscosity, amount of synthetic turbidity, flocculating time, amount of air flow, depth of water column and size of orifice. The mathematical model tested for both normal and taper types of flocculation. The experimental data vindicated the model relationship between the concentration ratio and the rate of air flow for the air flow rate above 50 cm³ min⁻¹. Accordingly, the developed mathematical model was then linearised.     

一体化涡旋网格澄清工艺的研制与应用

一体化涡旋网格澄清工艺是基于微涡旋混凝技术及浅池理论而提出的。该反应器在絮凝反应单元设置了涡旋网格絮凝反应器,在澄清分离室内设置了斜管(或斜板)沉淀器,增设了污泥浓缩单元,采用低回流或无回流技术,改进喷嘴及喉管结构,加大反应室的容积利用率,降低了能耗。工程实践表明,该工艺不仅提高了净水工艺的絮凝反应效率、降低了药耗、改善了净水水质,而且还提高了沉淀分离效率和污泥含固率,具有节省整体工程投资、降低制水成本等优点。     

PAC絮凝沉积藻量对水-底泥系统营养盐释放的影响

聚合氯化铝(PAC)絮凝除藻对降低水体藻密度效果显著,但絮凝形成的沉积藻量对水-底泥系统营养盐释放的影响鲜有报道。通过监测不同量的絮凝藻沉积于一定量的底泥表面时上覆水水质和底泥组成的变化,探究使用PAC絮凝除藻时沉积藻量对水体水质及底泥内源释放的影响。结果表明,沉积藻会显著增加底泥中的氮向上覆水释放,当泥与藻的干质量之比为167.2、83.6和41.8时,反应器上覆水中NH4^+-N浓度均值分别为控制反应器(CK)的2.86、2.42和1.43倍,对应TN浓度均值分别为CK的2.06、1.66和1.09倍。此外,沉积藻会促进泥水界面处的反硝化过程,促进效果与沉积藻量呈负相关。然而,沉积藻对于控制底泥磷释放具有积极作用,试验期间CK上覆水中TP和PO4^3--P浓度均值分别为0.35和0.22 mg/L,而覆有沉积藻的所有反应器中TP和PO4^3--P浓度均值分别都低于0.05和0.03 mg/L,且沉积藻量越大,对应的磷浓度越低。