CFD在臭氧接触系统优化中的应用

利用计算流体力学（CFD）技术,通过计算流体的停留时间分布,模拟了深圳某水厂臭氧接触池的水力效率,对臭氧接触系统进行了优化.结果表明,未设置导流板的接触池水力效率较低,T10/HRT仅为0.40.通过设计优化,增加了导流板,可将接触池的水力效率提高73%,T10/HRT为0.66.     

基于CFD的海水淡化水矿化二氧化碳接触池优化研究

为解决海水淡化水矿化工艺中二氧化碳曝气效率较低的问题,利用CFD软件对二氧化碳接触池进行数值模拟与优化研究,考察了反应室数量对接触池水力效率的影响,并在此基础上对接触池池型进行了优化。结果表明:随着反应室数量的增加,池内流体流动越均匀,接近平推流。增设导流板和横挡板为优化接触池的最佳方案,接触池的水力效率T10/HRT达到0. 643。     

基于示踪试验的清水池水力效率影响因素研究

以优化清水池运行条件、提高水力效率为目的,通过建立中试模型进行不同工况下示踪试验,研究水深、流量、停留时间和穿孔挡板对清水池水力效率的影响。结果表明,在合理取值范围内,水力效率随着流量的增加而增加,随着水深、停留时间的增加而减少,水力效率随流量和水深的变化趋势均类似抛物线;对于停留时间较大的清水池,在进出口和廊道拐角处增设穿孔挡板可明显改善水体流态,提高水力效率,穿孔率为10%的穿孔挡板比无穿孔的挡板水力效率提高了13%~20%。     

应用计算流体力学优化清水池水力效率

为确定计算流体力学(CFD)用于清水池水力效率计算的可行性而建立了CFD中试模型,得到了清水池数学模型的液龄分布函数和累计液龄分布函数。改变模型流场设置,包括挡板数量、挡板长度、穿孔板和导流墙,分别建立相应的扩展数学模型对流场进行模拟和比较。通过对上述改进流场水力效率的措施进行整合,建立了四挡板和七挡板优化数学模型,明显提高了整个流场的水力效率,使得流场接近活塞流的理想状况。     

基于CFD的清水池水力特性研究

对清水池实例通过数值建模和CFD模拟,研究几何参数对清水池水力效率的影响,分析了其分散指数、Pe数、体积效率和短路指数等,并探讨了清水池的设计方法。结果表明:清水池的长宽比对其水力效率(T10/t)影响明显,水力效率随长宽比的增加而增大,但增速趋缓,函数相关系数较高。当T10/t0.5时,长宽比需在30以上。清水池分散度低,平移是传质的主要因素。设计实例的水力效率为0.537,MDI为2.00,若长宽比为150,则T10/t高达0.70。     

H_2O_2强化氧化/FLOPAC滤池用于工业园污水深度处理

上海某工业区污水处理厂一～四期提标改造工程,出水水质由上海市地方标准《污水综合排放标准》(DB 31/199—2009)的二级提高到一级排放标准。生化线改造规模为3. 25×10~4m~3/d,原采用混合均化池+缺氧池+曝气池+二沉池+气浮池+臭氧接触氧化池工艺,改造后深度处理工艺采用V型滤池+臭氧接触氧化池(臭氧与H_2O_2结合)+FLOPAC生物滤池;另外,用于处理高盐低有机污染废水的活性炭线改造规模为0. 4×10~4m~3/d,采用增加活性炭罐数量、降低处理负荷的方式,提高污染物去除率。实际运行表明,系统运行良好,出水水质达到了设计标准。     

基于CFD技术的腔体式紫外消毒反应器优化模拟

采用计算流体力学(CFD)建立了紫外消毒数值模拟模型,对现有腔体式紫外消毒反应器增加挡板前后的运行效果进行了模拟比较。结果表明:优化前后反应器的光强分布规律基本一致;在流场方面,挡板增强了反应器内水体的内部交换,有利于整体消毒效率的提高;优化后反应器的t10/HRT值由原来的22.0%提高到59.4%,且灭活范围内剂量分布更为均匀,70 m J/cm2以上的高剂量比例由3%提高到9%,最终使杀菌效率从优化前的1.73(微生物数量的lg差值)提高到2.02,有效提高了杀菌效果。     

臭氧对二沉池出水的氧化特性研究

采用臭氧处理北京市高碑店污水处理厂二沉池出水,就臭氧对二沉池出水的氧化特性进行了研究。结果表明,臭氧对二沉池出水中的COD、色度、UV254均有较好的去除效果,但对TOC的去除效果较差。试验条件下,臭氧的最佳投加量为10 mg/L、最佳接触时间为15 min,此时对COD的去除率为19.12%,去除单位COD的臭氧投加量为1.79 mg;对色度的去除率为58.59%,去除单位色度的臭氧投加量为1.46 mg;对UV254的去除率为39.57%,去除0.001 cm-1吸光度的臭氧投加量为2.82 mg;TOC/UV254提高到140.29,可生化性提高了1.59倍。     

给水厂常规消毒工艺的优化技术与应用

针对笔架山水厂示范工程提出的降低消毒剂消耗和消毒副产物生成量的目标,采取了改进药剂投加方式和对清水池结构进行优化的措施。结果表明,改变消毒剂投加方式后能节约氯耗约20%,节约能耗约15%;改进清水池结构后,使消毒剂与水的实际接触时间延长,在达到相同消毒效果的前提下降低了消毒剂的浓度,3个清水池的t10/T值分别提高了42%、21%和29%,清水池的流态也明显改善。     

泥位、HRT对高效初沉发酵池运行的影响

以高效初沉发酵池中试装置为试验对象,通过单因素控制,研究了泥位和HRT对其运行效果的影响。结果表明,在合理的运行条件下,高效初沉发酵池对改善生物段进水碳源有显著作用;不同泥位下高效初沉发酵池运行效果排序为:75%>60%>35%>90%,最佳泥位时的出水COD/SS、VSS/SS值分别比进水提高了23.0%、26.0%,而COD/TN值则降低了11.0%;当HRT为0.75 h时高效初沉发酵池的运行效果明显优于其他HRT的,此时出水COD/SS、VSS/SS值与进水相比分别提高了23.0%、22.7%,而COD/TN值降低了13.0%。     

Serial CSTR digester configuration for improving biogas production from manure

A new configuration of manure digesters for improving biogas production has been investigated in laboratory scale. A single thermophilic continuous-flow stirred tank reactor (CSTR) operated with a hydraulic retention time (HRT) of 15 days was compared to a serial CSTR configuration with volume distribution ratio of 80/20 and 90/10, and total HRT of 15 days. The results showed that the serial CSTR could obtain 11% higher biogas yield compared to the single CSTR. The increased biogas yield in the serial CSTR was mainly from the second reactor, which accounted for 16% and 12% of total biogas yield in the 90/10 and 80/20 configuration, respectively. VFA concentration in the serial CSTR was high in the first reactor but very low in the second reactor. The results from organic pulse load test showed that the second reactor in serial CSTR helped utilizing VFA produced from overloading in the first reactor, which improved the effluent quality and conversion efficiency of the serial CSTR.     

生物滤池/生态砾石床处理含氮微污染地表水

采用生物滤池/生态砾石床组合工艺进行了微污染地表水(含低碳、高NO3--N浓度)的脱氮研究,通过投加乙酸钠为碳源考察了C/N值、温度、水力负荷对反应器脱氮效能的影响。结果表明,C/N值对反应器的脱氮效能影响较大,在C/N值为10时可以取得较高的反硝化效率(>90%)。在低温下(2～10℃)反应器的反硝化效能受到严重抑制;在13～17℃条件下,反硝化效率恢复到60%左右;当水温>20℃时,在水力负荷为8 m3/(m2.h)的条件下(此时生物滤池和生态砾石床的水力停留时间分别为15、30 min),对NO3--N的去除率能够达到90%以上。生态砾石床能够将生物滤池出水中残余的碳源去除,保证了出水的水质安全。     

Treatment of anaerobically pre-treated domestic sewage by a rotating biological contactor.

The performance of a rotating biological contactor (RBC) for the post-treatment of the effluent of an up-flow anaerobic sludge blanket (UASB) was the subject of this study. Different hydraulic and organic loading rates have been investigated. The removal efficiencies of COD(total), COD(suspended), COD(colloidal) and COD(soluble) increased at a higher hydraulic retention time (HRT) and a lower influent organic loading rate. The results obtained indicated that a two-stage RBC reactor at an HRT of 10 h and an organic loading rate of 6.4g COD m(-2) d(-1) represents an effective post-treatment process. Most COD(suspended) and COD(colloidal) were removed in the first stage while nitrification proceeded in the second stage. The overall nitrification efficiency was 92% at an ammonia loading rate of 1.1 gm(-2) d(-1). Total E. coli removal at HRTs of 10, 5 and 2.5h were 99.5%, 99.0% and 89.0%. respectively. The major part of suspended E. coli ( >4.4 microm) was removed by sedimentation or by adsorption in the biofilm of the first stage of RBC (99.66%). However, E. coli in the colloidal fraction (<4.4 to >0.45 microm) was eliminated in the second stage of RBC (99.78%). A comparison of the performance of a one-stage versus two-stage RBC system, operated at the same total loading rate, revealed an improvement in the effluent quality of the two-stage effluent as compared to the one-stage effluent. The two stages RBC were used to examine the effect of hydraulic shock loads on reactor performance in terms of COD, nitrification and E. coli removal.     

Three-dimensional distinct element modeling of fault reactivation and induced seismicity due to hydraulic fracturing injection and backflow

This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on the geological data in Horn River Basin,Northeast British Columbia,Canada.The modeling results indicate that the maximum magnitude of seismic events appears at the fracturing stage.The increment of fluid volume in the fault determines the cumulative moment and maximum fault slippage,both of which are essentially proportional to the fluid volume.After backflow starts,the fluid near the joint intersection keeps flowing into the critically stressed fault,rather than backflows to the wellbore.Although fault slippage is affected by the changes of both pore pressure and ambient rock stress,their contributions are different at fracturing and backflow stages.At fracturing stage,pore pressure change shows a dominant effect on induced fault slippage.While at backflow stage,because the fault plane is under a critical stress state,any minor disturbance would trigger a fault slippage.The energy analysis indicates that aseismic deformation takes up a majority of the total deformation energy during hydraulic fracturing.A common regularity is found in both fracturing-and backflow-induced seismicity that the cumulative moment and maximum fault slippage are nearly proportional to the injected fluid volume.This study shows some novel insights into interpreting fracturing-and backflowinduced seismicity,and provides useful information for controlling and mitigating seismic hazards due to hydraulic fracturing.     

Effect of temperature, hydraulic residence time and elevated PCO2 on acid neutralization within a pulsed limestone bed reactor

Limestone has potential for reducing reagent costs and sludge volume associated with treatment of acid mine drainage, but its use is restricted by slow dissolution rates and the deposition of Fe, Al and Mn-based hydrolysis products on reactive surfaces. We evaluated a pulsed limestone bed (PLB) reactor (15 L/min capacity) that uses a CO2 pretreatment step to accelerate dissolution and hydraulic shearing forces provided by intermittent fluidization to abrade and carry away surface scales. We established the effects of hydraulic residence time (HRT, 5.1-15.9 min), temperature (T, 12-22 degrees C) and CO2 tension (PCO2, 34.5-206.8 kPa) on effluent quality when inlet acidity (Acy) was fixed at 440 mg/L (pH = 2.48) with H2SO4. The PLB reactor neutralized all H+ acidity (N = 80) while concurrently providing unusually high levels of effluent alkalinity (247-1028 mg/L as CaCO3) that allow for side-stream treatment with blending. Alkalinity (Alk) yields rose with increases in PCO2, HRT and settled bed height (BH, cm) and decreased with T following the relationship (R2 = 0.926; p<0.001): (Alk)non-filtered = -548.726+33.571.(PCO2)(0.5)+33.671.(HRT)+7.734.(BH)-5.197.(T). Numerical modeling showed CO2 feed requirements for a target Alk yield decrease with increases in HRT, T and the efficiency of off-gas (CO2) recycling.     

水平潜流人工湿地处理住宅灰水技术研究

以陶粒及天然沸石为基质,黄菖蒲为植物,构建新型水平潜流式人工湿地,研究其净化实际小区灰水的效果,进水流量50 L/d,水力停留时间2 d,进水COD、NH3-N、 TN、TP浊度为164、4.3、5.2、0.44 mg/L、82.4 NTU时,出水可分别降至70 、1.07 、2.07 、0.33 mg/L、7.27 NTU,去除率分别为57.32%、75.19%、60.26%、24.24%、91.18%,对实际灰水COD、NH3-N、TN、浊度有良好的去除效果。利用人工配水考察不同水力停留时间下湿地的去污效果。提高停留时间能有效提高湿地对COD、NH3-N的去除效果,停留时间为3 d时,该湿地的去污效果最好,COD、NH3-N、TN、TP浊度去除率分别为68.46%、81.75%、66.67%、34%、86.91%。     

Increased biological hydrogen production with reduced organic loading

An experimental matrix consisting of reactor hydraulic retention time (HRT) and glucose loading rate was tested to understand the effect of organic loading on H2 production in chemostat reactors. In order to vary the glucose loading rate over a range of 0.5-18.9 g/h, the glucose concentration in the feed was varied from 2.5 to 10 gCOD/L under conditions where the HRT varied from 1 to 10 h (30 degrees C, pH=5.5). Decreasing the glucose loading rate over this range increased the hydrogen yield from 1.7 to 2.8 mol-H2/mol-glucose. High yields of hydrogen were consistent with a high molar acetate:butyrate ratio of 1.08:1 as more hydrogen is produced with acetate as a product (4 mol-H2/mol-acetate) than with butyrate (2 mol-H2/mol-butyrate). It was thought that the decrease in yield with organic loading rate resulted from an overall decreased rate of hydrogen production. As the rate of gas production is reduced, H2 supersaturation in the liquid phase is likely reduced, relieving inhibition due to H2. Flocculation was also an important factor in the performance of the reactor. At the 5-10 gCOD/L influent glucose concentrations, substantial flocculation was observed particularly as the feeding rate was increased due to a reduction in the HRT from 10 to 2.5 h. At the HRT of 2.5 h, biomass concentrations reached as much as 25 g/L. The flocculant nature of the biomass allowed reactor operation at low HRTs with steady H2 production and >90% glucose removal. However, when the HRT was reduced to 1 h at a glucose feed concentration of 2.5 gCOD/L, there was little flocculation evident resulting in wash-out of the culture. These results suggest that hydrogen yields will be optimized for more dilute feeds and lower organic loading rates than have typically been used in biohydrogen reactor studies.     

UASB/MBR组合工艺处理抗生素废水的研究

采用UASB/MBR组合工艺处理抗生素废水,考察了其处理效果及影响因素.结果表明,当UASB的水力停留时间(HRT)为13 h、MBR的HRT为7.5 h时,系统对COD的去除效果最好,在进水COD为1 000～9 000 mg/L的条件下,出水COD可降至199 mg/L,对COD的总去除率可达80%以上.     

ABR处理低浓度有机废水的启动方式研究

对ABR处理低浓度有机废水的启动方式进行了试验研究.结果表明:固定HRT、逐步提高进水COD浓度的启动方式,可使ABR反应器于90 d内完成启动,其对COD的去除率达到80%,系统运行较稳定,但污泥颗粒比较松散;而固定进水COD浓度、缩短HRT的启动方式,49 d就可使ABR对COD的去除率达到80%,且污泥颗粒化程度较高.