微孔曝气系统设计

结合最新发布的行业标准CJ/T 475—2015《微孔曝气器清水氧传质性能测定》,分析和叙述了曝气池微孔曝气系统的氧传质速率(OTR)、标准氧传质速率(SOTR)、风量和曝气器数量的计算方法;对标准氧转移效率(SOTE)的主要影响因素进行了分析,分析结果表明:SOTE主要与曝气池表观流速、曝气密度和曝气池水深有关,完整的曝气器SOTE性能曲线图应当包括SOTE与曝气器表观流速、曝气密度、曝气水深之间的关系曲线;并给出了具体计算例子,以期对微孔曝气系统的设计提供指导和参考。     

通气量及曝气密度对微孔曝气器充氧性能影响的中试研究

通气量及曝气密度是曝气系统重要的运行参数,在中试条件下,以充氧能力和氧利用率为评价指标,研究了橡胶膜及刚玉微孔曝气器在不同通气量及曝气密度下充氧性能的变化规律。结果表明:橡胶膜微孔曝气器的充氧能力随通气量及曝气密度的增大而增大,氧利用率随通气量及曝气密度的提高先增大后减小。刚玉微孔曝气器充氧能力随曝气密度的增大而增大,氧利用率随通气量的增大而减小,而随曝气密度的增大先增大后减小。橡胶膜微孔曝气器氧利用率最大时,其最佳通气量为3.0 m3/h时,最佳曝气密度为4.5%~5.5%,刚玉微孔曝气器最佳曝气密度为11%~15%。     

污水处理厂刚玉曝气器堵塞原因及清洗效果研究

以无锡市某污水处理厂刚玉曝气器为研究对象,论述了刚玉曝气器堵塞原因及堵塞特征,同时对刚玉曝气器进行酸洗实验,以保证污水处理厂曝气系统稳定运行。结果表明:新旧曝气头混合使用的曝气系统有效运行时间仅为160 d,远低于全新曝气头的曝气系统（840 d）,表明运行中的曝气系统曝气头容易堵塞,需及时清洗维护。微生物对刚玉曝气器的堵塞程度基本没有影响,但对判断刚玉曝气器的堵塞状态具有指示作用。刚玉曝气器堵塞程度与有机物、无机物的含量相关,且与总铁含量呈现正相关。酸清洗对恢复刚玉曝气器性能具有较好的提升效果,15% HCl溶液酸洗20 min能使刚玉曝气头氧传质系数由刮泥后的0.5 min-1左右恢复到0.7 min-1左右,接近于全新曝气头氧传质系数,清洗效果良好。     

新旧微孔曝气器氧转移速率试验研究

以某污水处理厂运行4年多的旧盘式曝气器和同型号的新盘式曝气器为试验对象,对其氧转移速率进行了对比试验,结果表明新旧曝气盘氧转移速率均明显分为两个阶段,运行了4年的旧曝气盘微孔数量减少、微孔孔径增大、气泡数量减少、气泡尺寸增大,氧转移速率比新曝气盘降低了29.2%。因此,污水处理厂在日常运行管理中要做好曝气器的保养工作,及时清洗更换破损、堵塞的曝气器避免能耗浪费。     

改性生物填料在水处理应用中氧传递的研究

研究了改性填料与普通填料在清水中的氧传质性能。根据反应器特征,建立了全混式反应器氧传质模型。分别测定了改性填料和普通填料在清水中连续曝气供氧的溶解氧值与曝气时间的关系。同一曝气流量下,改性填料反应器中清水的DO比普通填料反应器高;增大曝气流量,同一曝气时间反应器中清水的DO升高,直至饱和值Csat,并且前者比后者提前接近饱和值。采用全混式反应器氧传质模型,通过matlabprograms寻优求出连续曝气供氧时两种填料在清水中氧的液相总传递系数kLa。计算结果表明:曝气流量增大,氧传递系数kLa增大,其值约为22h-1～36h-1;在相同曝气流量下,改性填料的kLa均高于普通填料,约提高10%。试验表明改性填料增强了反应器的氧传递能力。     

微孔曝气国内外研究进展及趋势分析

分析比较了国内外微孔曝气研究和应用实例,指出了目前微孔曝气技术的研究重点。同时,综合国内外研究人员的研究成果,分别叙述了曝气量、安装水深、安装面积、孔径、水质和气孔堵塞状况对微孔曝气充氧性能的影响,对不同影响因素的作用效果做了总结,并指出目前研究存在的问题。以期对污水处理厂曝气系统的优化提供借鉴,对拟采用微孔曝气法进行生态修复的研究提供参考。     

常用曝气系统在城市给水工程中的应用对比

生物接触氧化法作为城市给水工程生物预处理工艺,近年来得到了日益广泛的实际应用。本文对给水生物接触氧化法预处理工艺中常用的两种曝气系统(微孔曝气器曝气和穿孔管曝气)作了简单介绍,并结合中试试验和工程实践对这两种不同曝气系统作了充氧性能、系统造价、运行成本及运行管理等方面的比较分析。研究表明,在实际污水处理厂生物池曝气系统应用中,采用微孔曝气器的曝气系统优于采用穿孔管的曝气系统。     

新型生物流化反应器氧转移的特性

气体的转移是废水处理过程中的重要环节,基于气体转移的“双膜理论”,采用在反应器中清水曝气的方法,对新型生物流化反应器进行了氧转移特性的研究.结果表明,在实验范围内,随着曝气量的增大,氧传质系数呈直线上升;投加载体后,随着载体量的增加,氧传质系数降低.在新型生物流化反应器不同运行方式下,随着A_d /A_r(降流区与升流区面积比)变大,反应器中氧传递效果变差.新型生物流化反应器氧利用率可以达到10%,充氧动力效率可以达到5.5kgO₂/(kWh).并且在载体浓度较高和空塔气速较大时,新型生物流化反应器氧利用率和充氧动力效率没有明显降低.     

曝气条件对等温层曝气器充氧性能的影响

分析了等温层曝气器曝气室内气泡—水接触界面的氧传质过程,确定了表征氧传质效果的各项参数,在双膜理论基础上建立了等温层曝气充氧动力学模型及其解析方法.应用本模型预测了美国Prince湖等温层曝气器的充氧效果.根据等温层曝气充氧动力学模型的预测结果,随曝气量的增加和气泡直径的减小,氧总传质系数和氧传质速率均增大;随曝气量和气泡直径的增大,曝气效率下降.在等温层曝气器结构固定的情况下,减小气泡直径和增加水深均有利于改善曝气室的充氧效果,尤其是当气泡直径达到μm级别时;当曝气量超过一定临界值0.06m3/s时,曝气室的充氧效果略有削弱.根据曝气量对氧传质速率、曝气效率和单位时间内曝气室的充氧量的影响特性曲线,可确定等温层曝气器的优化运行条件.     

固定螺旋曝气及组合填料技术的开发

大庆石化总厂炼油厂污水处理场自１９８９年以来，针对圆形合建式机械表面加速曝气池实际运行中的缺点，进行了合建式曝气池固定螺旋曝气技术和组合填料技术的开发与研究，并对本厂八座圆形合建式曝气池进行了改造。改造后，污水处理能力提高了２５％，提高了充氧能力，污泥回流好，回流缝不易堵塞。净化效率高、耐冲击能力强、能耗成本下降，操作维护方便。     

Evaluation of oxygen transfer parameters of fine-bubble aeration system in plug flow aeration tank of wastewater treatment plant

Knowledge of the oxygen mass transfer of aerators under operational conditions in a full-scale wastewater treatment plant (WWTP) is meaningful for the optimization of WWTP, however, scarce to best of our knowledge. Through analyzing a plug flow aeration tank in the Lucun WWTP, in Wuxi, China, the oxygenation capacity of fine-bubble aerators under process conditions have been measured in- situ using the off-gas method and the non-steady-state method. The off-gas method demonstrated that the aerators in different corridors in the aeration tank of WWTP had significantly different oxygen transfer performance; furthermore, the aerators in the same corridor shared almost equal oxygen transfer performance over the course of a day. Results measured by the two methods showed that the oxygen transfer performance of fine-bubble aerators in the aeration tank decreased dramatically compared with that in the clean water. The loss of oxygen transfer coefficient was over 50% under low-aeration conditions (aeration amount < 0.67 Nm 3 /hr). However, as the aeration amount reached 0.96 Nm 3 /hr, the discrepancy of oxygen transfer between the process condition and clean water was negligible. The analysis also indicated that the non-steady-state and off-gas methods resulted in comparable estimates of oxygen transfer parameters for the aerators under process conditions.     

Aeration optimization through operation at low dissolved oxygen concentrations: Evaluation of oxygen mass transfer dynamics in different activated sludge systems

In wastewater treatment plants(WWTPs)using the activated sludge process,two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics(such as concentrations of mixed liquor suspended solids(MLSS)and microbial communities)and operating conditions(such as air flow rate and operational dissolved oxygen(DO)concentrations). Moreover,operational DO is closely linked to effluent quality. This study,which is in reference to WWTP discharge class A Chinese standard effluent criteria,determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3 mg/L,and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions,as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model(determined using different air flow rate(Q′_(air))and mixed liquor volatile suspended solids(MLVSS)values),theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however,operating at low DO and low MLVSS could significantly reduce energy consumption. Finally,a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed,which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology.     

鼓风曝气系统氧利用率和动力效率的研究

研究了影响鼓风曝气系统氧利用率Eo 和动力效率Ep 的因素 ,给出了Eo 和Ep 与诸影响因素间的定量关系式。在鼓风曝气系统中 ,恰当地选取曝气器的浸没深度h和所产生气泡直径db 的组合 ,既可使氧气利用率高 ,又可使动力消耗少。这一结果对于指导曝气装置的设计和降低废水处理的能耗具有重要意义     

河道曝气提升河流水质的WASP模型研究

曝气充氧是修复受污染河道的重要技术,数学模型是预测、评估环境污染状况的重要方法.本研究应用WASP水质模型评价不同时段河道曝气对河流水质的提升作用.初期模型验证结果表明,WASP水质模型拟合结果与实际监测结果基本吻合,可为水污染治理工程提供参考依据.在此基础上,对不同曝气条件进行模拟分析,结果表明,河道曝气能够有效降低河水中的化学需氧量(COD)和氨氮(NH+4-N)浓度,改善水质;随着曝气河段内溶解氧(DO)水平的提升,水质虽不断改善,但改善幅度逐渐减小;全年不同月份曝气效果差异显著,5~9月曝气效果较好.结合经济投入和环境效益,最终确定夏季提升DO水平达到4 mg·L-1为河道曝气最优条件.     

污水厂曝气节能智能优化控制系统

针对国内大部分污水厂现有曝气控制中存在着溶解氧浓度波动大、曝气量冗余大、曝气单元能耗高等问题,提出曝气节能智能优化系统,该系统通过获得A/O工艺实时的在线数据不断进行模拟计算,然后按照生化池进水的污染物负荷状况,以曝气能耗最小为目标函数来获取最优的DO设定值及其PI控制器的参数Kp、Ki。该智能优化系统在沥滘污水厂的实际应用情况表明:该系统在盫こ鏊实那榭鱿拢唤鎏岣吡讼低车目垢汉沙寤髂芰Γ苯档土?曝气能耗。     

体积溶氧传递系数在好氧颗粒污泥系统中的变化特性初步分析

取成熟的好氧颗粒污泥,在同一测试装置中采用相同的曝气条件进行体积溶氧传递系数(kLa)的测试,当传统活性污泥和成熟好氧颗粒污泥浓度MLSS为2 000、4 000、6 000、8 000 mg·L-1时,其kLa(min-1)值分别为0.586 1±0.009 5、0.586 1±0.027 2、0.555 6±0.016 8、0.533 8±0.026 8和0.645 5±0.027 6、0.632 0±0.075 5、0.618 5±0.062 5、0.640 6±0.055 5,表明颗粒污泥kLa值高于同浓度条件下的絮体污泥,且随浓度增加,絮体污泥氧传递效率下降而颗粒污泥无明显变化.对好氧颗粒污泥进行筛分后,大颗粒和小颗粒在污泥浓度相同、体积相同、表面积相同以及个数相同的情况下二者的kLa值均无明显差别,由此可以推断,这些因素对好氧颗粒污泥kLa的影响可以忽略.研究结果对于污水处理厂节能运行具有一定的参考价值.     

基于降维状态观测器的曝气量最优控制仿真研究

为降低污水处理厂曝气过程的能耗,对曝气系统的优化控制进行了研究.首先,建立了基于活性污泥模型ASM1的曝气系统的简化模型;然后,利用降维状态观测器重构在线不可测状态,提出了基于降维状态观测器的曝气量最优控制策略;最后,将该优化控制策略应用于污水处理基准仿真模型BSM1,仿真采用晴天进水数据.结果表明,与溶解氧的PID控制相比,最优控制在保证出水氨氮浓度和化学需氧量等水质的情况下,降低了曝气量和出水总氮浓度,同时曝气能耗相比PID控制可下降5%以上,并且改善了出水指数.     

Biodegradation by bioaugmentation of dairy wastewater by fungal consortium on a bioreactor lab-scale and on a pilot-scale

A fungal consortium including Aspergillus niger, Mucor hiemalis and Galactomyces geotrichum was tested for the treatment of dairy wastewater. The bio-augmentation method was tested at lab-scale (4 L), at pilot scale (110 L) and at an industrial scale in Wastewater Treatment Plants (WWTP). The positive impact of fungal addition was confirmed when fungi was beforehand accelerated by pre-culture on whey (5 g/L lactose) or on the dairy effluent. Indeed, chemical oxygen demand (COD) removal yields increased from 55% to 75% for model medium, diluted milk. While after inoculation of an industrial biological tank from a dairy factory with the fungal consortium accelerated by pre-cultivation in a 1000 L pilot plant, the outlet COD values decreased from values above the standard one (100 mg/L) to values in the range of 50-70 mg/L. In addition, there was a clear impact of fungal addition on the ’hard’ or non-biodegradable COD owing to the significant reduction of the increase of the COD on BOD 5 ratio between the inlet and the outlet of the biological tank of WWTP. It was in the range of 451%-1111% before adding fungal consortium, and in the range of 257%-153% after bio-augmentation with fungi. An inoculated bioreactor with fungal consortium was developed at lab-scale and demonstrated successfully at pilot scale in WWTP.     

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O₂/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O₂/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O₂/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.