计算流体力学法臭氧接触池水力条件优化

采用计算流体力学技术,模拟了北京某水厂臭氧接触池中水的流态分布及水力效率。通过流体停留时间分布（RTD）的分析,得知臭氧接触池的T10 /HRT为0.466,短流现象明显,水力效率低。在臭氧接触池中增加导流板后,T10 /HRT值可提高20.38%,但T90 /HRT高达1.316,回流现象明显;设置横挡板,可将T10 /HRT提高15.88%,同时T90 /HRT降至0.821,RTD更为集中,流场更接近理想活塞流。因此,增加横挡板有利于臭氧接触池水力效率的提高。     

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。     

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。     

混凝沉淀/水解酸化/接触氧化处理水产品加工废水

针对水产品加工废水的特点设计了混凝沉淀/水解酸化/接触氧化处理工艺,通过对水力停留时间(HRT)、温度和溶解氧这3个影响因素的考察,利用正交试验确定了最优工况.结果表明,当混凝剂(硫酸铁)投量为150 mg/L、助凝剂(PAM)投量为10 mg/L、水解酸化/接触氧化段的HRT为21 h(其中水解酸化池的HRT为6 h、接触氧化池的HRT为15 h)、温度为25℃、溶解氧为3.5 mg/L时,处理效果最好,出水COD的平均值<65 mg/L、出水氨氮的平均值<26 mg/L、出水总磷的平均值<1.0 mg/L.     

给水厂预臭氧接触池设计计算

探讨了水厂中预臭氧接触池各系统的设计计算方法,优化了接触池的管道布置方法。重点讨论了臭氧系统水射器增压水系统设计,给出了增压水泵的流量与扬程的计算方法,建议应优先选择沉后水作为增压水系统水源。提出了新建与改建水厂中预臭氧接触池的不同超越方式,分析了不同规模水厂预臭氧接触池更宜采用的叠合设计形式。     

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%。     

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。     

自来水厂后臭氧接触池进水流量的在线软测量方法

针对自来水厂后臭氧接触池进水流量无法在线测量的问题,提出了一种后臭氧接触池进水流量的在线软测量方法。首先,通过在线测试获得后臭氧接触池进水前提升泵房的各台提升泵运行在最大工作扬程和最小工作扬程下的频率-流量关系曲线;然后,计算生成当前工作扬程下的频率-流量关系曲线,并由此获得提升泵当前频率对应的实时流量;最后,计算提升泵房所有运转提升泵的出水流量之和,从而获得后臭氧接触池进水流量软测量值。实际应用结果表明,与先前的以活性炭滤池出水流量计的数值作为参考流量相比,提出的软测量方法能更准确地反映后臭氧接触池的实时进水流量,根据这一基准流量进行臭氧投加可使后臭氧接触池出水余臭氧浓度更加平稳,为后臭氧投加精确控制奠定了基础。     

纺织洗水回用作生活杂用水的中试研究

采用水解酸化/接触氧化/混凝工艺处理广东佛山某大型纺织厂的纺织洗水,并经臭氧消毒后回用作生活杂用水.结果表明,当水解酸化池和接触氧化池的水力停留时间分别为15、9h,接触氧化池的气水比为8:1,聚合氯化铝(有效浓度为15%)的投加量为75 mg/L时,COD从680～800 mg/L降至40～50 mg/L,再经3～5 mg/L的臭氧消毒处理后,各项指标均达到<城市污水再生利用城市杂用水水质>(GB/T 18920-2002)的要求.     

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.     

Extracellular biological organic matters in sewage sludge during mesophilic digestion at reduced hydraulic retention time

To operate an anaerobic digester at low hydraulic retention time (HRT) is welcome in practice. This study characterized the extracellular biological organic matter (EBOM) and supernatant organics for a sewage sludge digested in a lab-scale mesophilic digester (5 l) running at an HRT of 20, 15 or 10 d. The hydrophilic and hydrophobic acid fractions were the principal components in the sludge EBOM. The hydrolysis rates for hydrophobic acid fraction related EBOM at 10 d HRT and that of hydrophilic fraction related proteins in supernatant at 20 d HRT limited the anaerobic processes. Improved hydrolysis of soluble hydrophilic fraction assisted improving digester performance at 20 d HRT. To shorten digestion HRT, efficiency of hydrophobic acid fraction hydrolysis has to be practiced.     

Photocatalytic degradation of E. coliform in water

This study aims to further investigate the total mineralization of the bacteria to the extent of death and cell-mass inactivation using a TiO2-Fe2O3 membrane photocatalytic oxidation reactor. Experimental results clearly indicated that dissolved oxygen (DO), hydraulic retention time (HRT) and concentration of the model bacteria (Escherichia coliform) affected the removal efficiency. It was found that the ultimate removal efficiency was 99% at DO level of 21.34 mg/l, HRT at 60s and high concentration of E. coli at 10(9)CFU/ml. The morphologic studies also showed that E. coliform could be further mineralized into CO2 and H2O. Dissolved organic carbon, pH and gas chromatograph analysis had justified most importantly the evolution of CO2. Experimental results revealed that the photomineralization rate of E. coliform followed pseudo-first-order kinetics by the role of DO. The derived empirical models were found consistent with the proposed reaction pathways of a combined UV breakdown on mass cell and a dual-site Langmuir-Hinshelwood mechanism where the rate-controlling step is the surface interaction between the adsorbed cleavage bacterial cells and hydroxyl radicals.     

Hybrid reactor for priority pollutant-trichloroethylene removal

The present study was initiated to explore the potential of a hybrid biological reactor, combining trickling filter (TF) and activated sludge process (ASP), to treat wastewater containing trichloroethylene (TCE) at ambient temperature at different hydraulic retention time (HRT). The biofilm acclimation was achieved in 55-60 days with gradual increase in TCE concentration from 1 mg/l to 100 mg/l with a parallel increase in the concentration of substrate sodium acetate and other nutrients. COD and TCE concentration were taken as prime parameters for monitoring the growth of biofilm. During acclimation COD removal varied between 54.6-97.5% while TCE was removed 72.6-99.9%. HRT study was performed after acclimation. The removal efficiency increased with decreasing flow rate with maximum TCE removal (99.99%) at 6 l/d corresponding to an HRT of 28 h (TF 18 h + ASP 10 h). This was followed by a C:N:P ratio study. A ratio of 100:20:1 led to the sustenance of maximum TCE removal. Maximum TCE removal (99.99%) was observed at a substrate:cosubstrate ratio of 100:1. A pH of 7.4 +/- 0.2 was found to be optimum for degradation. Finally, volatilization losses were estimated to be 18.5%. A mass balance gave an efficiency of 81.51% for biological removal of TCE.     

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。     

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.     

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.     

Biological oxidation of arsenite in synthetic groundwater using immobilised bacteria

Biological oxidation of arsenite (As(III)) in synthetic groundwater was examined by using arsenite oxidising bacteria (AOB) isolated from an activated sludge. The phylogenetic analysis indicated that the isolated AOB was closely related to Ensifer adhaerens. Batch experiments showed that for an As(III) oxidation with the isolated AOB the optimum ratio of nitrogen source (NH₄-N) concentration to As(III) concentration was 0.5 (52 mg/L-110 mg/L) and the isolated AOB preferred pH values ranging from 6 to 8, and water temperatures greater than 20 °C. Further continuous experiments were conducted using a bioreactor with immobilised AOB. With an initial As(III) concentration of 1 mg/L at a hydraulic retention time (HRT) of 1 h, an As(III) oxidation rate was around 1 × 10⁻⁹ μg/cell/min and an As(III) oxidation efficiency of 92% was achieved. Although the maximum oxidation rate measured at an HRT of 0.5 h was 2.1 × 10⁻⁹ μg/cell/min, the oxidation efficiency decreased to 87%.These results advocate that a biological process involving immobilised AOB may be useful as an economical and environmentally friendly pre-treatment step for As removal from groundwater.     

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.