Bubble performance of a novel dissolved air flotation(DAF) unit

ES-DAF, a novel DAF with low cost, high reliability and easy controllability, was studied. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied in detail by using a newly developed CCD imagination through a microscope. Compared with M-DAF under the same saturation pressure, ES-DAF can produce smaller bubble size and higher bubble volume concentration, especially in lower pressure. In addition, the bubble size decreases with the increase of reflux ratio or decrease of superficial air-water ratio. These results suggested that smaller bubbles will be formed when the initial number of nucleation sites increases by enhancing the turbulence intensity in the saturation system.

Dissolved Air Flotation in Combination with Ultrafiltration Membrane Modules in Surface Water Treatment

The primary purpose of this research is to evaluate the feasibility of dissolved air flotation(DAF) as pretreatment process for membrane modules in river water treatment.The performances of DAF in combination with an up-flow membrane biofilter(MBF) and a hollow-fiber ultrafiltration membrane(UFM) were investigated respectively.Removal efficiency of ultraviolet absorbance at 254 nm(UV254),ammonia nitrogen(NH3-N),particle counts and microbial index were measured for both systems.Results showed that DAF was a robust pretreatment process for floc particles separation despite of raw water quality fluctuations.For DAFUFM system,the monitoring data indicated bacteria breeding,nitrite accumulation in membrane vessel and the ammonia concentration of permeate water even exceeded regulatory limits.By contrast,DAF-MBF system was established via the introduction of multilayer filter media between DAF and curtain type ultrafiltration membrane.In MBF,the matured biological activated carbon(BAC) and zeolite particles guaranteed the efficient removal of both organic matters and ammonia.Moreover,the high dissolved oxygen levels in DAF effluent significantly improved bio-adsorption and degradation of pollutants in MBF.The retention of microorganisms by the membrane not only ensured a high concentration of biomass,but also eliminated the risk of microbes leaking out from MBF.In addition,compared with UFM,the curtain membrane exhibited obviously slower fouling development.These results suggested that the DAF-MBF system was more suitable for purifying raw waters seriously polluted by dissolved contaminants.

Strategy for Controlling the Level in a Dissolved Air Flotation Chamber

The aim of the present study was to implant an efficient strategy for controlling the level of the effluent-oily foam interface in a DAF （dissolved air flotation） chamber of a pilot-scale prototype. DAF has been successfully used in the treatment of oily water, which is one of the main environmental problems in different industrial facilities. Along with important operational parameters, such as microbubble size and flow rate, the control strategy for the automation of a DAF chamber may be an important tool for increasing efficiency. Controlling the level was the strategy chosen to enhance the separation efficiency in a pilot-scale DAF prototype, with monitoring performed using a computational program in LabVIEW （laboratory virtual instrument engineering workbench）. The findings demonstrate that it is possible to maintain the level of the fluid at a reference value established by the operator using the software program through the application of classic proportional integral derivative controllers. Using this control tool, the efficiency of water-oil separation in the pilot flotation chamber prototype was increased to nearly 98%.

Treatment of Wastewater Containing Heavy Metals Using Dissolved Air Released Flotation Column

A new type of dissolved air released flotation column is developed to treat wastewater containing Cr（Ⅵ） based on advantages of both dissolved air floatation and column floatation. By using a column with a diameter of 50 mm and a specially made dissolved air releaser, micro-bubbles inside the column can be formed. N2H4H2O was used as reductant, AlCl3 as flocculant, C12H25SO3Na（SDS） as surfactant in the experiment. The effects of pH of wastewater, pressure of dissolved air, ratio of return water, and concentration of flocculant and surfactant on the removal efficiency are studied. The results show that the efficiency of dissolved air released flotation column is much higher than that of other approaches after the operation parameters are optimized, with the reduction ratio of Cr（Ⅵ ） in wastewater reaching 98%. So this technique can be widely used in wastewater treatment

Comparison of Dissolved Air Flotation and Sedimentation in Treatment of Typical North China Source Water

The treatment of typical north China water by dissolved air flotation(DAF)and sedimentation process was examined.A pilot plant with a water treatment capacity of 120 m^3/d constructed in the Jieyuan Water Treatment Plant(JWTP) of Tianjin,China,was utilized for the comparison of the two processes.The results show that during the pilot test,DAF process can remove particles and organic mater more efficiently than sedimentation process.The removal rate for turbidity by DAF process is 5.5% higher than that by sedimentation in normal turbidity period,and 40% higher in low turbidity period,it is 5%～10% higher for removals of algae,total organic carbon(TOC),trihalomethane formation potential(THMFP)and bacteria in all periods.The removal rates for turbidity,TOC,THMFP,algae and bacteria by DAF process can reach 95%,30%, 20%,94% and 97% respectively.From the results of the pilot test,it can be concluded that DAF is a feasible clarification process,especially for source water with low turbidity and high algal blooming.

新型气浮装置ES-DAF中气泡粒径分布的表征

对ES DAF气浮装置进行了研究 .该装置取消了溶气灌 ,在循环泵的压水管和吸水管之间装有一个射流器和一个静态混合器进行吸气和溶气 .采用显微摄像系统 ,对该装置中气泡粒径分布进行了探讨 .结果表明 ,当环流比由 10 %增加到 4 0 %时气泡平均粒径由 5 2 9μm降低到 4 0 9μm ,当表观气水比由 12 %降低到 4 %时 ,气泡平均粒径由 5 5 9μm降低到 4 0 1μm .这说明提高溶气系统中的紊流强度能够形成更多的原始气泡核位 ,从而可以形成更小的气泡 .随着溶气压力由 30 0kPa增加到6 0 0kPa ,气泡粒径分布曲线变低变宽说明压力的升高加剧了气泡的碰撞与并聚作用 .

ADAF处理油田采出水的应用研究

介绍了新型ADAF溶气气浮的特点、关键技术及主要指标,并进行了油田采出水处理的试验。结果表明,该设备运行稳定,对含油废水中的油、SS的净化效率高,对其去除率分别达到94%和83%,可广泛用于油田采出水的处理。

JMS-CCDAF-NF工艺去除水中腐殖酸的研究

试验研究了JMS-逆流气浮-纳滤集成工艺去除水中腐殖酸的工艺特征和效果。试验结果表明:JMS-逆流气浮工艺去除水中腐殖酸时,在最佳投药点(PACl),出水水质符合纳滤系统预处理单元的要求。该预处理系统与纳滤系统组合的集成工艺可以使水中的腐殖酸有机物浓度大大降低,且含TQ56-36FC型纳滤膜的流程比含M-N1812A型纳滤膜的流程效果好。前者出水的TOC值可达0.28￣0.70mg/L。后者出水的TOC值在0.59￣1.30mg/L。另外,尽管保安过滤/活性炭预处理有利于纳滤膜出水水质的提高,但活性炭柱与纳滤膜能去除的有机物种类是有些重合。

DAF+MSBR联合法处理煤焦化废水实验研究

为了使焦化废水NH3-N能够达标排放,采用气浮法+改良式序列间歇反应器(DAF+MSBR)联合法处理榆林某焦化厂焦化废水。结果表明,进水CODcr平均质量浓度为1490 mg/L,NH3-N平均质量浓度为200 mg/L,挥发酚平均质量浓度为176 mg/L,CN平均质量浓度为17 mg/L,SS平均质量浓度为580 mg/L,DAF处理时间3 h,MSBR处理时间9 h。经DAF+MSBR法处理后,出水CODcr浓度为74.3 mg/L,NH3-N为10 mg/L,挥发酚为0.25 mg/L,CN为0.09 mg/L,SS为30 mg/L,去除率分别为93.8%、95%、99.8%、99.4%、95%,达到《炼焦化学工业污染物排放标准》排放标准。

CAF-DAF工艺在炼油污水预处理中的应用

通过涡凹气浮(CAF)和加压溶气气浮(DAF)组合工艺技术在炼油污水预处理中的实际应用,结果表明:对炼油污水中石油类和悬浮物去除率平均达到88.3%和76.4%,出水含油平均达到12.87 mg/L,装置运行稳定,应用效果显著。

DAF布气板的改进

本文结合DAF气浮池的部分回流溶气气浮法工作原理,分析了设备运行情况和常见问题,以改善溶气效果、提高气浮效率和降低维护费用为目的,对布气板实施改进,取得了一定的成效。

Research on DAF-BAF process in textile wastewater treatment

This experiment researches textile wastewater, adopts a BAF process that has developed quickly in recent years, and makes use of dissolved air flotation as a pretreatment process that can effectively make up for BAF’s lack of removing Chromaticity color. Performance effect, influencing factor, control condition have been reviewed and parameters of correlation have been analyzed in this experiment. The experiment and actual performance results indicate that this process is an effective way to remove the COD, suspended solid and colority with the value of 100 mg/L, 50 mg/L and 70 multiple respectively. The effluent meets the requirement of the standards of national sewage discharge. This process features a simple schematic, small location, continuous, reliable performance, strong shock and loading resistance and easy operation. Experimental data can provide scientific evidence and technical support for engineering practice of this process.

MBBR-DAF组合工艺处理生活污水的中试研究

为研究移动床生物膜反应器-加压溶气气浮组合工艺对生活污水的处理效果,本文构建了一套中试规模的试验装置,即MBBR-DAF系统。试验研究了此系统在不同水力停留时间、曝气强度、填料投加比、PAC和PAM的投加浓度等条件下对污染物的净化效果。结果表明,在MBBR单元的水力停留时间5~6 h,曝气强度4.5~6.0 m^3·m^-2·h^-1,填料投加比50%;DAF单元的PAC投加浓度30~60 mg·L^-1,PAM投加浓度0.2~0.5mg·L^-1等条件下,系统在夏季和冬季的出水CODCr,NH3-N、TP和SS等指标均能稳定达到《城镇污水处理厂污染物排放标准》(GB18918-2002)中的一级A标准。

常减压装置电脱盐污水治理的工艺改造与优化

针对常减压装置电脱盐污水中H2S和可燃气体含量高、水质因含油含渣的影响不能稳定达标的突出问题。采用常压闪蒸和高效旋流溶气气浮(CDFU)相结合技术路线配套原有重力沉降除油技术工艺,有效解决电脱盐污水中高含油含渣、可燃气和硫化氢含量较高的问题,改造后石油类降低73.6%,COD(化学需氧量)降低32.7%,H2S、可燃气体和VOCS体积浓度分别下降56.85%、57.93%和38.25%。电脱盐污水水质明显改善,减少对下游污水系统的影响,消除安全隐患。

铁路站段含油废水处理模式的碳排放研究

为提高铁路站段含油废水的去除效果,同时达到节能降耗减排的目的,以某铁路局车辆段含油废水为研究对象,对比研究传统方案“加压溶气气浮法”与新方案“平板陶瓷膜法”的去除效果和碳排放效果。此外,将传统方案中含油污泥的直接外运处理更改为掺入燃煤中焚烧,探讨其产生的环境效益。结果表明,平板陶瓷膜的整体碳排放强度仅占加压溶气气浮法的35.47%,年碳减排量可达70.2 tCO_(2)。平板陶瓷膜法电耗和药耗的碳排放量相较传统方案而言大幅降低,是因为处理过程所需能耗较小且反应无需添加药剂,仅需使用次氯酸钠对反应装置定期进行反冲洗,物耗使用量也大大降低。将含油污泥直接外运更改为掺入燃煤中焚烧法处理,能够在有效回收资源、实现污泥资源化利用的同时节约成本。整体而言,使用平板陶瓷膜法对铁路站段含油废水进行处理在碳减排方面具有明显优势,同时能够带来更好的处理效益和经济效益,是一项可行的方案,可以进行大范围推广使用。

溶气气浮中CFD方法发展和应用的研究进展

溶气气浮(DAF)工艺是水处理行业中一项重要的处理方法,其具有适应范围广、运营成本低等优势,但其复杂的三相体系使得对其内部研究较为困难。计算流体力学(CFD)技术采用数值模拟方式指导反应器设计,计算成本低,数据准确性高。通过对DAF工艺发展过程中CFD应用的文献全面综述,主要对浮选过程的原理、CFD方法的发展和气浮反应器优化等多方面进行研究,以突出目前使用的CFD方法特点和数值模拟工具的最新发展,并根据研究内容的总结,对今后的研究提出一些建议。

Feasibility of bubble surface modification for natural organic matter removal from river water using dissolved air flotation

A novel, functionalized bubble surface can be obtained in dissolved air flotation （DAF） by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter （NOM） removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the OAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for OAF to enhance NOM removal.

等静压石墨生产过程中洗烟废水处理技术分析

石墨烯生产过程中,碱洗塔会产生大量高浓度洗烟废水,其中COD>1000mg/L,TDS约14000mg/L,经过"混凝-气浮"+碟管式反渗透(DTRO)+机械式蒸汽再压缩(MVR)工艺进行处理后,一部分水可回用至生产车间,剩下的废水COD<500mg/L,TDS<1500mg/L,达到当地产业园区接管指标要求,直接排入园区污水管网。

THK引气气浮系统的研制与应用

在引进美国THK系统基础上 ,通过对THK系统的研究、消化和吸收 ,已实现THK的国产化生产 ,目前 ,国产化水平已达到 80 % - 90 %。工业废水处理应用表明 ,THK是一种简单、节能和高效的气浮设备 。

溶气气浮法采收盐藻(Dunalilla salina)细胞

初步探讨了不添加絮凝剂和表面活性剂时用溶气气浮法采收盐藻细胞的工艺条件,结果表明,藻液pH值、溶气压(PS)、溶气水进水流量(QW)、溶气水/原料藻液体积比(水液比αWF)对采收效果有重要影响. 本实验条件下,调节藻液pH值为11.5, 在PS＝0.39 MPa, QW＝7 ml/s, αWF＝1.5的气浮操作条件下,细胞采收率和浓缩倍数分别达86.4%～96.4%和2.38～5.57. 表明气浮法可以安全、高效地从培养液中采收盐藻细胞,无需添加絮凝剂.