臭氧接触反应器气液两相流数字图像处理方法与实验分析

在单相数字粒子图像测速度(PIV)技术的基础上,研究气液两相流动的PIV图像处理方法,采用数字掩模技术对不同相的流动信息进行标记、识别、提取与计算,编辑了相应的软件.运用改进后的PIV方法对臭氧接触反应器中气-液体两相流动进行了测试与分析.结果表明,臭氧接触反应器中液相轴向流速分布是决定反应器内水力特性的主导因素;进气流量直接影响反应器内液气两相的流速分布;随进气流量的提高,液气两相的轴向速度和横向速度均增大,同时反应器流动结构与流程分布会发生较大变化.     

内循环厌氧反应器多相流流场的三维数值分析

利用数值模拟的方法,引入欧拉双流体多相流模型及标准k-s紊流模型,模拟计算内循环厌氧反应器的三相流三维流场,并通过改变污泥颗粒密度及进水流量,针对固相流速及固含率的变化情况,分析条件的改变对流场的影响。研究结果表明,应用数值模拟方法可以获得内循环厌氧反应器内的流场特征;污泥颗粒密度及进水流量的改变对于反应器内污泥颗粒的流速及分布的均匀性有较为明显的影响。模拟结果对反应器的应用及优化设计具有一定的参考价值。     

气升式反应器气液两相流流态特性模拟

为了研究曝气强度对气升式反应器内气液两相流特性的影响,组合多相流Eulerian—Eulerian模型和液相Standardk-ε湍流模型,运用Fluent软件建立了气升式反应器内气液两相流的三维非稳态数值模拟。在曝气管布局方式一定的情况下,模拟计算获得了反应器内x轴截面处不同径向位置的气含率、液速分布情况,计算结果表明,在本文研究的曝气强度范围内,气含率随着曝气强度增加而增加,越靠近曝气池底部,升流区局部气含率越高,且气含率值波动较大;随着曝气强度的增加,曝气孔附近液速增加较明显,但随着气液两相流的上升,液速增加幅度降低;同时采用粒子图像测速（PIV）技术对液相速度进行了实验研究,实验结果与模拟结果吻合性较好。     

水流紊动特性对活性污泥沉降性能的影响

为优化活性污泥处理系统的设计和运行,在SBR反应器中通过改变搅拌浆的转速,调整水流的紊动条件,借助粒子图像测速技术分析了反应器内水流的紊动特性,研究了反应器内不同区域紊动强度对活性污泥沉降性能的影响.结果表明,搅拌浆叶周围15mm的范围内,紊动强度远高于距桨叶更远的区域,距离浆板5mm的1-1断面和距离浆板60mm的3-3断面搅拌轴心处的紊动强度值分别反映了反应器搅拌主体区和其他区的紊动特征.随搅拌浆转速的增加,反应器内各区域的紊动强度逐渐增加,活性污泥的沉降性能表现出先改善后恶化的规律.当反应器搅拌主体区紊动强度1.51%,其他区紊动强度0.31%时,本试验条件下形成的活性污泥沉降指数(SVI)达到最小值67mL/g,界面沉降速率(ZSV)达到最大值0.20mm/s,活性污泥的沉降性能最佳.搅拌主体区范围较小,紊动强度较高,增强该区的紊动强度会加剧污泥的侵蚀破坏;其他区范围较大,紊动强度较低,增强该区的紊动强度对改善污泥的沉降效果作用明显.工程中可通过降低搅拌主体区的紊动强度,选择其他区适当的紊动强度,改善活性污泥的沉降性能.     

常温下向ABR反应器中加入惰性载体促进颗粒污泥形成

常温条件下(21～25℃),用实验室规模的2个厌氧折流板反应器进行颗粒污泥培养实验,向其中一个反应器(称为B反应器)接种厌氧污泥的同时加入惰性载体,另一个反应器(称为A反应器)作为对照只接种厌氧污泥,考察了惰性载体对ABR反应器中颗粒污泥的形成和反应器运行效果的影响.结果表明,惰性载体的加入促进了反应器中颗粒污泥的形成,提高了反应器的处理效果.运行162 d后,B反应器每个隔室均出现大量颗粒污泥,4个隔室中粒径>0.5 mm的颗粒达到57.6%～72.7%;A反应器仅第1隔室中形成了大量颗粒污泥,其他3个隔室中粒径>0.5 mm的颗粒仅占11.3%～34.7%.COD去除率稳定保持在85%以上所需时间,B反应器比A反应器少用了51 d.     

Molecular characterization of bacterial community in aerobic granular sludge stressed by pentachlorophenol

To characterize the effects of pentachlorophenol (PCP) on the performance and microbial community of aerobic granular sludge in sequencing batch reactor (SBR), the web-based terminal restriction fragment length polymorphism (T-RFLP) and real-time PCR (RT- PCR) techniques were used to explore the bacterial community structure. When PCP increased from 0 to 50 mg/L, the COD removal rate changed little, while the ammonia removal rate dropped from 100% to 64.9%. The results of molecular characterization showed t...     

Preliminary evaluation of the electrochemical and chemical coagulation processes in the post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor

The main objective of this paper was to perform a preliminary comparative study between chemical and electrochemical coagulation processes, both followed by flocculation and sedimentation of an effluent from an upflow anaerobic sludge blanket (UASB) reactor treating simulated wastewater from an unbleached Kraft pulp mill. The electrochemical treatment removed up to 67% (with aluminum electrodes) and 82% (with stainless-steel electrodes) of the remaining chemical oxygen demand (COD) and 84% (stainless steel) and 98% (aluminum) of the color in the wastewater. These efficiencies were achieved with an energy consumption ranging from 14 to 20 Wh l(-1). The coagulation-flocculation treatment with ferric chloride and aluminum sulfate removed up to 87% and 90% of COD and 94% and 98% of color, respectively. The addition of a high molecular weight cationic polymer enhanced both COD and color removal efficiencies. The two post-treatment processes proved to be technically feasible; however the economical feasibility could not be assessed since the experiments were performed with small reactors that could distort scale factors.     

Oxidative destabilization of dissolved organics and E. coli in domestic wastewater through immobilized cell reactor system

Domestic wastewater contains a considerable amount of pathogenic organisms besides non-biodegradable organics. The conventional technologies followed for the treatment of domestic wastewater are less efficient in removing pathogenic organisms despite substantial removal of dissolved organics. The focal theme of the present investigation was to use a chemo-autotrophic activated carbon oxidation (CAACO) system, an immobilized cell reactor using chemoautotrophs (Bacillus sp.) for the treatment of domestic wastewater. The oxidation of organics and Escherichia coli in wastewater is controlled by the parameters space time, O(2)/COD, bed height and cod loading. The scheme comprised of anaerobic treatment, sand filtration and CAACO treatment removed BOD. COD, Total organic carbon (TOC), dissolved protein, total Kjeldhal nitrogen (TKN) and bacterial count (most probable number (MPN)) by 81%, 92%, 84%, 94%, 93% and 99.9997%, respectively. The low concentration of E. coli in the CAACO-treated wastewater was completely eliminated through UV irradiation in 3 min at 254 nm.     

Determination of model parameters for zinc (II) ion biosorption onto powdered waste sludge (PWS) in a fed-batch system

Biosorption of zinc (II) ions onto pre-treated powdered waste sludge (PWS) was investigated using a completely mixed tank operating in fed-batch mode instead of an adsorption column. Experiments with variable feed flow rate (0.05-0.5 L h(-1)), feed Zn(II) ion concentrations (37.5-275 mg L(-1)) and amount of adsorbent (1-6 g PWS) were performed using fed-batch operation at pH 5 and room temperature (20-25 degrees C). Break-through curves describing variations of aqueous (effluent) zinc ion concentrations with time were determined for different operating conditions. Percent zinc removal from the aqueous phase decreased, but the biosorbed (solid phase) zinc ion concentration increased with increasing feed flow rate and zinc concentration. A modified Bohart-Adams equation was used to determine the biosorption capacity of PWS (q'(s)) and the rate constant (K) for zinc ion biosorption. Biosorption capacity (q'(s)=57.7 g Zn kg(-1) PWS) of PWS in fed-batch operation was found to be comparable with powdered activated carbon (PAC) in column operations. However, the adsorption rate constant (K=9.17 m(3) kg(-1) h(-1)) in fed-batch operation was an order of magnitude larger than those obtained in adsorption columns because of elimination of mass transfer limitations encountered in the column operations. Therefore, a completely mixed tank operated in fed-batch mode was proven to be more advantageous as compared to adsorption columns due to better contact between the phases yielding faster adsorption rates.     

ABR成熟颗粒污泥的分形特征与尺度效应

建立了基于SEM照片研究ABR成熟颗粒污泥分形特征的操作程序,采用Photoshop、Newscan和Fips程序对该图形进行处理和分形维数计算.颗粒污泥的计盒维数值处于1.85以上,第3格室和第5格室形成的颗粒污泥较为致密.不同格室颗粒污泥边界的计盒维数的值在1.10左右,表明它们的边界或表面是不规则的,而且第1格室和第5格室形成的颗粒污泥的表面不规则程度高一些.颗粒污泥边界的圆规维数计算结果也表明其表面是不规则的,而且每一个颗粒污泥都存在2个分形维数的尺度区间,有的区间跨度达一个数量级.另外,不同的计算维数的方法会导致结果的差异.建立不同尺度域下的分形维数与颗粒污泥的组成、结构及物化特征的关系将具有重要意义.