不同填料曝气生物滤池启动挂膜试验研究

不同填料曝气生物滤池在相同条件下进行挂膜试验。进水流向为上流式,挂膜方式为复合接种挂膜,即先用活性污泥闷曝接种,然后逐步提高进水流速,直到滤料表面形成稳定的生物膜。结果表明:33 d后挂膜成功,在温度为16～24℃,水力停留时间(HRT)为1 h,DO为6 mg/L的情况下,陶粒BAF对CODMn和NH3—N的去除率分别为23%和80%;沸石BAF的去除率分别为27%和84%;组合填料BAF去除效果最好,去除率分别为32%和92%。     

Interaction of oxygen concentration and retention of pollutants in vertical flow constructed wetlands for CSO treatment.

The EU Water Framework Directive (WFD) calls for a good quality of all water bodies. Retention soil filters (RSF) have been developed to treat discharges from combined sewers systems. RSF have proved over the past 15 years to be the most effective measure to meet the EU WFD standards, especially for small or particularly sensitive receiving waters, which require an enhanced reduction of emissions from combined sewer overflows (CSOs). The paper presents results from laboratory-scale experiments, in which the oxygen measurement in the filter plays a main role. The results show remarkable differences in oxygen concentrations in different filter depths. The highest oxygen consumption takes place in the upper part of the filter. In the lower part the re-aeration of sewage from the soil air dominates. This indicates that the biological activity is limited to the upper part of the filter. The availability of oxygen in the filter is a sign for degradation of wastewater compounds (ammonium, COD) under certain conditions and already takes place during the filter operation. The removal of ammonium especially cannot be strictly divided into phases of sorption during the loading and oxidation during the dry period any more.     

Monitoring of biological odour filtration in closed environments with olfactometry and an electronic nose.

Air treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and water. The prototype "ENQBE" electronic nose is based on an array of eight thickness shear mode resonators (TSMR), also known in the literature as quartz microbalance sensors. The chemical sensitivity is given by molecular films of metalloporphyrins and similar compounds. Chemical interaction of compounds in the air with the vibrating sensors induces a frequency change of the vibration that can be measured as a signal. The air from the mouse cage had a strong odour (3490 OUE/m3). The biological membrane filter performed well, achieving over 80% odour and ammonia reduction. The electronic nose signal could be correlated with the inlet and outlet air-quality of the biological filter, making it a promising method for monitoring air quality in closed environments.     

基于FVCOM模式的温排水三维数值模拟研究

为反映河口海湾温排水所具有三维结构特征,在基于三维非结构有限体积海岸和海洋模型(FVCOM 2004版)建立的三维潮流数值模型基础上,采用类似的有限体积法开发了一个三维温排水对流扩散模型用于模拟近岸海域温排水的扩散输运过程,并应用该模型对象山港内某滨海电厂的温排水进行了计算,模拟得到了温排水对流扩散过程的三维分布特征,即电厂冷却水温排放后,温差所产生的浮力效应使温排水趋于海水上层输移,海水上层温升与深层温升存在明显的垂向差异.     

波浪作用下悬移质泥沙运动的两相流数值模型

该文采用基于水沙两相紊流的数值模型对波浪作用下的悬移质泥沙运动进行研究。基本方程中将水相和颗粒相通过相间作用力进行耦合,合理地考虑了相间相对运动的影响。数值计算方法为有限体积法,对流项处理利用了三阶精度的QUICK格式,离散方程组求解采用的是TDMA迭代方法。计算得到的悬移质泥沙垂线时均计算值与不同尺度的水槽实验数据吻合很好,表明数学模型及其计算方法对于低浓度水沙两相问题是合理的。该研究还探讨了悬沙浓度、泥沙沉降速度以及各种相间作用力随时间的分布规律。     

Comparison of measured and simulated distribution of microbial biomass in subsurface vertical flow constructed wetlands.

The multi-component reactive transport module CW2D has been developed to model transport and reactions of the main constituents of municipal wastewater in subsurface flow constructed wetlands and is able to describe the biochemical elimination and transformation processes for organic matter, nitrogen and phosphorus. It has been shown that simulation results match the measured data when the flow model can be calibrated well. However, there is a need to develop experimental techniques for the measurement of CW2D model parameters to increase the quality of the simulation results. Over the last years methods to characterise the microbial biocoenosis in vertical subsurface flow constructed wetlands have been developed. The paper shows measured data for microbial biomass and their comparison with simulation results using different heterotrophic lysis rate constants.     

Nitrogen elimination from landfill leachates using an extra carbon source in subsurface flow constructed wetlands.

A three-stage constructed wetland for leachate treatment was monitored on a landfill at a pilot scale. The plant had been designed to achieve at least 75% nitrogen removal. NH4-N input concentration was 240 (median) up to 290 mgl(-1) and COD concentration was 455 to 511 mgl(-1), respectively. A 14 m2 vertical flow sand filter plus a 14 m2 horizontal flow sand filter followed by a 3.3 m2 vertical flow sand filter was chosen. Acetic acid was added to the horizontal flow system for denitrification. The results showed a very stable nitrification rate within the vertical flow system of 94% (median) at NH4-N loading rates of about 10 (median) up to 17 gm(-2)d(-1). Denitrification was mainly dependent on the dosing of acetic acid and could reach a maximum of 98%. One interesting effect was the production of nitrite in the horizontal flow sand filter. This could efficiently be eliminated by the subsequent vertical flow sand filter. The chosen concept proved to be very effective for nitrogen removal. In combination with a final activated carbon filter the COD effluent concentrations could be easily and safely controlled. The design of denitrification reed beds showed a further potential for optimization.     

The effect of a vertical flow filter bed on a hybrid constructed wetland system.

Data from 18 sampling wells in Kodij?rve horizontal subsurface flow (HSSF) constructed wetland (CW) (South Estonia) is presented and differences in purification efficiencies inside the HSSF CW are calculated. Temporarily anaerobic conditions in the Kodij?rve HSSF system did not allow efficient removal of BOD7, NH4-N, Ntot and Ptot. In 2002 a vertical subsurface flow filter was constructed to enhance aeration. The design of the system was based simply on the oxygen demand of the wastewater and on the aeration potential of vertical flow wetlands. The vertical flow system has shown satisfactory results. The purification efficiency of BOD7 in the Kodij?rve CW has improved significantly and there has been a slight increase in purification efficiencies of NH4-N and Ntot. On the ohther hand, the removal efficiency of Ptot has decreased significantly. Although, the mass loading rates have increased, mass removal rates of all four parameters have improved significantly. Nevertheless, optimization of the constructed wetland system is essential in order to meet effluent standards during wintertime.     

Nitrogen dynamics in a constructed wetland system treating landfill leachate.

A pilot scale treatment system was established in 2002 at the Laflèche Landfill in Eastern Ontario, Canada. The system consists of a series of treatment steps: a stabilisation basin (10,000 m3), a woodland peat trickling filter (5,200 m2), a subsurface flow constructed wetland planted in Phragmites sp. (2,600 m2), a surface flow constructed wetland planted in Typha sp. (3,600 m2) and a polishing pond (3,600 m2). The system operates from May to December with leachate being recycled within the landfill during the winter months. Hydraulic loading was increased three-fold over four operating seasons with nitrogen and organic mass loading increasing six-fold. Excellent removal efficiencies were observed with 93% BOD5, 90% TKN and 97% NH4-N removed under the highest loading conditions. Almost complete denitrification was observed throughout the treatment system with NO3-N concentrations never exceeding 5mg L(-1). The peat filter reached treatment capacity at a hydraulic loading of 4cm d(-1) and organic loading rate of 42 kg BOD ha(-1) d(-1), which is consistent with design criteria for vertical flow wetland systems and intermittent sand filters, The first order plug flow kinetic model was effective at describing TKN and ammonium removal in the SSF and FWS wetlands when background concentrations were taken into account. Ammonium removal k-values were consistent with the literature at 52.6 and 57.7 yr(-1) for the SSF and FWS wetlands, respectively, while TKN k-values at 6.9 and 7.7 yr(-1) were almost an order of magnitude lower than literature values, suggesting that leachate TKN could contain refractory organics not found in domestic wastewater.     

超空泡实验中的数字图像检测

在水洞实验中,高速摄像机以数十赫兹至数十千赫的速度记录空化过程的系列影像,是研究水中空化现象机理的有力工具。如何从众多的数字图像中准确获取空泡的外形、空泡波动周期等信息,同时克服背景干扰和光线在空气、水以及水洞观察窗面板中的折射效应,是进行超空泡非定常实验要解决的重要课题。文中应用现代数字图像分析理论,通过对图像的滤波、灰度拉伸、图像校准、边缘检测等操作,总结出一套适合在超空泡水洞实验中应用的自动图像获取技术。使用该方法能够自动获取高速摄像图像中的空泡外形和振动周期等参数,并形成数据文件。实验表明,该方法自动化水平高,并具有较好的精度,在实际应用中获得了良好的效果。     

典型污染场地含水层天然净化能力溶质模拟研究

根据典型石油类污染场地岩性、水文地质等特征,在长期观测、抽水试验及弥散试验等资料搜集与分析基础上,通过水流模型验证,构建了地下水水流运动及溶质迁移的数值模型。选取苯系物(BTEX)作为模拟因子,运用GMS软件中MT3DMS模块模拟地下水对流-弥散溶质迁移过程,运用RT3D模块模拟研究了地下水中移动、非移动的多种微生物共存的有机污染物生物降解过程。结果表明,生物降解化学反应具有明显的降低污染物峰值的作用,而研究区存在大量的好氧微生物作用和反硝化作用,据此提出可以采用原位生物修复技术来治理石油污染。     

Treatment of anaerobically digested dairy manure in a two-stage biofiltration system

High concentrations of ammonium and phosphate present a challenge to cost-effective treatment of anaerobically digested dairy manure. This study investigated the efficacy of a two-stage biofiltration system for passive treatment of digested dairy manure. The first stage pebble filters were batch loaded. When the slurry-like digested dairy manure was retained on pebble beds, soluble contaminants were removed before liquid infiltrated over 8-17 days. The pebble filters removed 70% of soluble chemical oxygen demand, 71% of soluble biochemical oxygen demand, 75% of ammonium, and 68% of orthophosphate. Nitrogen removal was attributed to the conventional nitrification - denitrification process and novel nitritation - anammox process. Aerobic ammonium oxidizing and anammox bacteria accounted for 25 and 23% of all bacteria, respectively, in the filtrate of the pebble filters. The longer it took for filtration, the greater the removal efficiency of soluble contaminants. The second stage sand filters had removal efficiencies of 17% for soluble chemical oxygen demand, 45% for soluble biochemical oxygen demand, 43% for ammonium, and 16% for orthophosphate during batch operations at a hydraulic retention time of 7 days. Aerobic ammonium oxidation and anammox were primarily responsible for nitrogen removal in the sand filters. Vegetation made an insignificant difference in treatment performance of the sand filters.     

Estimation and modeling of direct rapid sand filtration for total fecal coliform removal from secondary clarifier effluents

The filtration of fecal coliform from a secondary clarifier effluent was investigated using direct rapid sand filters as tertiary wastewater treatment on a pilot scale. The effect of the flocculation dose, flow loading rate, and grain size on fecal coliform removal was determined. Direct rapid sand filters can remove 0.6-1.5 log-units of fecal coliform, depending on the loading rate and grain size distribution. Meanwhile, the flocculation dose has little effect on coliform removal, and increasing the loading rate and/or grain size decreases the bacteria removal efficiency. A model was then developed for the removal process. Bacteria elimination and inactivation both in the water phase and the sand bed can be described by first-order kinetics. Removal was successfully simulated at different loading rates and grain size distributions and compared with the data obtained using pilot-scale filters.     

The effect of the scale of horizontal subsurface flow constructed wetlands on flow and transport parameters.

Horizontal subsurface flow constructed wetlands have proven their efficiency in treating wastewater and removing the pollutants of concern. Treatment efficiency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed filter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed filters using saturated horizontal flow at three scales (small and medium lab scales and full-scale system) using the same filter media is reported. Light-weight aggregate (filter media termed Filtralite-P) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA filters are evaluated from small-scale experiments.     

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     

任意平面流场中的湍流临界准则数

作者应用涡量对流及扩散(传输)的概念和理论建立了对任意平面流场中发生湍流流动的湍流临界准则数。这个准则数不同于熟知的雷诺数。如果应用此准则数在接近直管壁和平板边界层固壁处表明流动会诱发“猝发”现象;对毛细管内的流动而言它也会指出无论管中平均流速多大、它总不会发生湍流;而对多孔介质中的流动,湍流会出现。所有这些预示颇令人感兴趣和关注。     

Assessment of the Impact of Stormwater Characteristics on Clogging in Stormwater Filters

Hydraulic conductivity of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of stormwater characteristics on the clogging of stormwater filters. Effect of five different operational regimes has been tested in this study of sediment concentration; pollutant concentrations; stormwater sediment size; loading rate and stormwater loading/dosing regime and compared with the Base case. For each operational condition, five column replicates were tested. Results suggest that sediment concentration in stormwater is a significant parameter affecting hydraulic and treatment performance, eventually affecting longevity of these stormwater treatment systems. Further, the size of sediments (and their relation to the size of filter media grains) in stormwater was found to be an important parameter to be considered in design of coarse filters with high infiltration rates that are used for stormwater treatment. As expected, the addition of metals and nutrients had limited or no contribution to changes in hydraulic or sediment removal performance of the studied stormwater filters. Whilst loading rate was found to be an important parameter affecting the hydraulic and treatment performance of these systems, any variation in the stormwater loading regime had a limited effect on their performance. This study therefore develops an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs.     

荆江典型河弯河势变化三维数值模拟研究

分别建立了三维水沙数学模型及考虑纵向坍塌范围的二元结构河岸崩塌力学模型，并将两者结合，构建立了荆江典型河弯河势研究的三维数值模型。基于非正交网格采用局部网格可动技术处理由崩岸引起的河道摆动过程。模型采用有限体积法对方程进行离散，采用与动量插值技术相结合的SIMPLEC算法进行模型求解。对石首河弯进行了模拟研究，模拟结果表明：模型能够较好地模拟出蜿蜒河道的水沙运动规律，成功地复演了石首河弯1996年10月至1998年10月期间剧烈的河势变化（主、支汊易位及河道摆动等）过程，实测结果与模拟结果吻合较好；其中河岸坍塌是该河段河势变化剧烈的主要原因之一。