池塘底部微孔曝气增氧试验及分析

随着水产养殖产业的持续升温、养殖密度的提高和高产高效养殖技术的推广,增氧装备越来越成为水产养殖必不可少的设备。鼓风曝气系统中的微孔曝气式增氧机因其曝气效率相对较高,适应性较强而广泛应用于水产养殖中。为了更好地了解和推广使用微孔曝气增氧系统,本文通过室内模型试验及数据分析,研究了曝气流量与曝气管长度对总氧体积传质系数的影响,构建了总氧体积传质系数预测模型。因此,本文的研究能为微孔曝气增氧系统在实际中的应用提供有价值的参考。     

微孔曝气器充氧性能变化对污水处理厂能耗的影响

以北京小红门污水处理厂的新、旧刚玉盘式微孔曝气器为例,进行曝气充氧性能的试验研究,并分析了更换曝气器对污水处理厂能耗的影响。结果表明:经过长期使用的曝气器充氧性能下降较大,氧总转移系数、氧的利用效率和动力效率分别下降了57%、58%和59%。旧微孔曝气器氧的利用效率为8.9%～14.1%,略高于中大气泡曝气器的性能参数,但由于微孔曝气器具有较大的阻力损失,使旧微孔曝气器的动力效率为1.5～2.1kgO2/(kW.h),低于中大气泡曝气器的性能参数。更换小红门全厂1/4的微孔曝气器后,鼓风机单耗降低21%,全厂能耗降低12%。因此,当微孔曝气器的充氧性能下降较大时,更换新的曝气器具有较高的节能和经济效益。     

基于微米气泡的臭氧强化传质技术研究

对臭氧微米气泡曝气和微孔曝气两种曝气方式在气泡直径分布、臭氧表观传质系数、臭氧吸收率和电能消耗进行了研究。结果表明,在微米气泡曝气方式下,随着水深的增加,气泡的索特直径减小,而臭氧的表观传质系数增加。当进水流量为15L/min,水深为2m时,微米气泡的表观传质系数是微孔曝气的2.4倍。在这两种曝气方式下,以某地下水作为水源,发现臭氧的吸收率随着臭氧投加量的增加而减小,随着水力停留时间和水深的增加而增大。在相同条件下,微米气泡曝气相比于微孔曝气,臭氧吸收率高10~25个百分点,并且受臭氧投加量的影响较小。然而,微米气泡曝气比微孔曝气至少多消耗29.8%的电能。该研究为臭氧微米气泡曝气技术在臭氧接触池中的推广应用提供了一定的理论依据。     

曝气对过饱和溶解氧消散过程影响的试验研究

为了促进曝气技术在减缓过饱和溶解氧(DO)影响中的应用,设计开展了无曝气工况和曝气工况下的过饱和DO释放试验,研究了曝气对过饱和DO消散过程的影响规律,分析了不同曝气条件下过饱和DO的释放过程和释放系数。试验结果表明,曝气能显著促进过饱和DO的消散,曝气工况下DO饱和度从170%左右消散至105%左右所需时间均小于11 min,而无曝气工况下所需时间最少为240 min；过饱和DO释放系数随曝气量的增大而增大,随曝气水深的增大而减小,与曝气孔径呈现较强的负相关幂函数关系。根据曝气对过饱和DO的释放规律建立了过饱和DO释放系数与曝气条件的定量关系,通过量纲分析建立了过饱和DO释放系数与曝气条件、模型尺寸、流体参数之间的定量关系,两种定量关系中,后者的均方根误差和平均绝对误差较小、相关系数较高,且参数较易获取,因此实用性更好。     

水射曝气的理论和应用

曝气是一种将气体传途到未饱和液体里去的过程。在活性污泥法中,曝气的目的是使氧有效地溶入混合液,并使混合液保持悬浮状态。曝气装置一直在不断改进着。总的说来,它可以分为四类,即机械曝气器(Mechanical aerator)、联合曝气器(Sparger turbine)、扩散曝气器(Airdiffuser)和水射曝气器(Jet aerator)。     

成都市三瓦窑污水处理厂工程设计介绍

成都市三瓦窑污水处理厂一期设计规模10万 m~3/d,远期规模40万 m~3/d,采用鼓风曝气活性污泥法二级生化处理工艺。在进厂水质 BOD_5=200mg/L,SS=260mg/L条件下,出厂水质可望达到 BOD_5≤20mg/L,SS≤30mg/L。为降低能耗,减少基建投资和便于运行管理,本工程还采用了钟氏沉砂池、微孔曝气器、周边进水周边出水二沉池、污泥气浮浓缩池等新技术。     

曝气生物滤池中气液两相流动特性模拟研究

掌握曝气生物滤池(biological aerated filter,BAF)中的流场分布特性,对该工艺的机理探讨及能耗优化具有重要意义。该文以上流式曝气生物滤池为研究对象,采用Fluent软件中的欧拉多相流模型、多孔介质模型及标准k-ε湍流模型,耦合计算解析了曝气量、滤料粒径和水力停留时间对滤料区域流场分布特性的影响。结果表明,曝气量、滤料粒径和水力停留时间(hydraulic retention time,HRT)均影响了滤料区域气液两相流动特性;在滤料区域表面区域,气相紊动程度显著增加;在曝气量为1.81×10~(-5)m~3/s、滤料粒径为10 mm条件下,气液两相流动有助于提高氧传质效率。该研究成果可为BAF的设计优化提供技术参考。     

双室(层)曝气生物滤池充氧性能及流态特征

研究了双室 (层 )曝气生物滤池 (DBAF)的充氧性能和流态特征 ,结果表明氧传质系数与曝气强度成正比 ,加滤料前后氧传质系数的差别与曝气强度的大小有关 ,曝气强度较低时 ,两者相差4 0 % ,随着曝气强度的增加 ,两者逐渐接近。DBAF可用n值为 8～ 10阶式CSTR描述 ,流态接近推流式反应器。降低水力负荷和增大滤料高度时 ,DBAF的流态更趋近于推流式     

微孔曝气器合理选用探讨

建立鼓风机轴功率与曝气器氧转移效率、阻力等性能参数和水池深度、曝气器安装高度、生物需氧量的关系式,提出在水深确定条件下的曝气器适用性评价指标系数a.结合某印染废水处理工程,从节能降耗的角度探讨如何选择能耗较低的曝气器.     

移动式曝气器曝气塘生态系统及充氧条件优化组合的试验研究

本试验采用移动式曝气器对曝气塘进行充氧,克 服了传统的固定式曝气的诸多缺点,可使塘体内DO分布均匀、充分,池内各处处于完全混合状态,避免了短流、死角现象的发生,具有设备投资省、低能耗、高效的特点.本文通过实际测量和实验分析,对移动式曝气器曝气塘的污水净化功能进行了探讨,结果表明,对有机物的净化功能较高,COD、BOD_5去除率分别在60～70%和78～88%之间,夏季则可高达76.5%和91%以上.本文还对该系统的水生生态系统的结构特点、水体生物群落的组成及空间分布的特点进行了研     

Prediction of alpha factor values for fine pore aeration systems.

The objective of this work was to analyse the impact of different geometric and operating parameters on the alpha factor value for fine bubble aeration systems equipped with EPDM membrane diffusers. Measurements have been performed on nitrifying plants operating under extended aeration and treating mainly domestic wastewater. Measurements performed on 14 nitrifying plants showed that, for domestic wastewater treatment under very low F/M ratios, the alpha factor is comprised between 0.44 and 0.98. A new composite variable (the Equivalent Contact Time, ECT) has been defined and makes it possible for a given aeration tank, knowing the MCRT, the clean water oxygen transfer coefficient and the supplied air flow rate, to predict the alpha factor value. ECT combines the effect on mass transfer of all generally accepted factors affecting oxygen transfer performances (air flow rate, diffuser submergence, horizontal flow).     

Improvement of oxygen transfer efficiency in aerated ponds using liquid-film-assisted approach.

In aerated ponds, oxygen is generally supplied through either diffused or mechanical aeration means. Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, a liquid-film-forming apparatus (LFFA) is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for LFFA alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for the liquid film aeration system increases by 37% in comparison with a conventional aeration system. Additionally, by tuning finely the structural parameters of the LFFA, it can also lead to high dissolved oxygen (DO) water with the DO percent saturation greater than 90%. More importantly, this result is accomplished by simply offering a single-pass aeration at a depth as shallow as 26 cm. As a result, the objective of economical energy consumption in aerated ponds can be realized by lowering the aeration depth without sacrificing the aeration efficiency. It is noteworthy that the data presented in this study are acquired either numerically or experimentally.     

THREE-DIMENSIONAL NUMERICAL SIMULATION OF BOD-DO FOR LARGE RESERVOIR

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粉煤灰水在土壤包气带中的垂直迁移规律

以太原二电厂阳坡沟粉煤灰场为例,建立灰水中污染物在土壤包气带的垂直迁移规律模型。通过数值计算可知,灰水污染物F-和As垂直入渗到达含水层中的浓度与包气带土壤渗透系数、吸附分配系数的关系均呈线性关系,灰水污染物F-到达含水层时的浓度与包气带土壤厚度的关系呈线性关系,污染物As的浓度与包气带土壤厚度的关系呈多项式曲线关系。     

Theoretical analysis and experimental study of oxygen transfer under regular and non-breaking waves

The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the d...     

细颗粒悬沙浓度分布的影响因素分析

从颗粒运动的PDF(概率密度分布函数)输运方程出发建立颗粒相的质量、动量和脉动速度二阶矩方程。对明渠二维恒定均匀流，利用垂向动量方程导出了修正的泥沙扩散方程，表明颗粒脉动强度梯度、升力、有效重力和紊动扩散都影响悬沙运动。理论和数值分析了细颗粒泥沙的密度、粒径、浓度，挟沙水流的水深和剪切流速等因素对泥沙扩散系数和浓度分布形状的影响，并定量分析了细颗粒试验资料，表明传统扩散方程在粒径、剪切流速相对较大、水深和水沙密度比较小的流动中存在较大误差，需要修正。     

Monitoring the variations of the oxygen transfer rate in a full scale membrane bioreactor using daily mass balances

Oxygen transfer in biological wastewater treatment processes with high sludge concentration, such as membrane bioreactor (MBR), is an important issue. The variation of alpha-factor versus mixed liquor suspended solids (MLSS) concentration was investigated in a full scale MBR plant under process conditions, using mass balances. Exhaustive data from the Supervisory Control And Data Acquisition (SCADA) and from additional online sensors (COD, DO, MLSS) were used to calculate the daily oxygen consumption (OC) using a non-steady state mass balance for COD and total N on a 24-h basis. To close the oxygen balance, OC has to match the total oxygen transfer rate (OTRtot) of the system, which is provided by fine bubble (FB) diffusers in the aeration tank and coarse bubbles (CB) in separate membrane tanks. First assessing OTR(CB) then closing the balance OC = OTRtot allowed to calculate OTR(FB) and to fit an exponential relationship between OTR(FB) and MLSS. A comparison of the alpha-factor obtained by this balance method and by direct measurements with the off-gas method on the same plant is presented and discussed.     

广州市大金钟水库浮游植物与环境因子的关系

对治理并维护运行了1年的大金钟水库进行5次采样实验,研究经修复后的水库中浮游植物的时空变化,并运用相关系数法分析了浮游植物变化与环境因子之间的关系.结果表明:随着水温降低,喜暖性的蓝藻数量急剧减少,与水温呈明显正相关关系(r＝0.986,p<0.05);其他藻类因不再受蓝藻抑制,数量呈上升趋势,特别是硅藻和绿藻代替蓝藻...