The influence of south Foehn on the ozone distribution in the Alpine Rhine valley—results from the MAP field phase

During the Mesoscale Alpine Programme (MAP) special observation period (SOP) between 7 September and 15 November 1999, ground-based and airborne measurements have been conducted in the Rhine valley south of the Lake of Constance to investigate the unstationary aspects of Foehn and related phenomena, like the impact of Foehn on the ozone concentrations in the valley. Foehn events occurred with above-average frequency and high diversity. Foehn induced ozone peaks in October and November are found to be much lower than the September Foehn case of the period. An inversion layer in the lake area with ozone concentrations below 10 ppb often shields the monitoring stations from the Foehn air aloft. Trajectory calculations for the Foehn period between 19 and 24 October 1999 reveal that the Foehn air originated from below 1 to 1.5 km above the Po Basin and the Mediterranean Sea. Tethered balloon soundings in the source area south of the Alps, ozone measurements at the mountain station Jungfraujoch (3580 m a.s.l.) and airborne measurements across the Alpine crests reveal that the ozone levels found in the Foehn air correspond to the concentrations just above the mixing height in the Po Basin and are transported across the Alpine crest within the lowest flow layer.     

模拟光伏曝气SBR除磷性能及其聚磷菌群落结构

基于村落生活污水排水、日光昼夜变化和SBR(序批式反应器)运行方式的特点及强化生物除磷所需的交替厌氧/好氧环境,采用模拟光伏曝气SBR处理生活污水,考察反应器的除磷效果及机理,并采用PCR(聚合酶链式反应)和TA克隆考察反应器内PAO(聚磷菌)的群落结构. 结果表明,反应器在12 d内成功启动,TP去除率从35.4%逐渐升至98.8%,此后TP去除率一直稳定在97%以上,出水ρ(TP)小于0.1 mg/L. 在反应段末期,反应器污泥中w(TP)达60 mg/g以上,其中w(complex-P)(complex-P为胞内聚合磷)达到55.0 mg/g,而w(EPS-P)(EPS-P为胞外聚合物结合磷)所占比例<10%,表明EPS吸附对除磷的贡献很小,除磷主要通过PAO的释磷/吸磷过程实现. 所有PAO均属于“Candidatus Accumulibacter”世系,Ⅱ型Candidatus Accumulibacter(包括Clade ⅡA-Clade ⅡD)是反应器内主要的PAO,其在3个克隆文库(d30、d60、d90)中所占比例分别为80.0%、80.0%和76.7%.      

Concentration levels of disinfection by-products in 14 swimming pools of China

Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products (DBPs) concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total trihalomethanes (TTHM), nine haloacetic acids (HAA9), chloral hydrate (CH), four haloacetonitriles (HAN4), 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 µg∙L⁻¹ and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could substantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids (THAA) levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon (TOC) contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant.     

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.     

曝气条件对等温层曝气器水力性能的影响

等温层曝气器内表观水流速度直接影响等温层曝气的充氧效果,针对表观水流速度难以准确计算的普遍问题,系统分析了曝气室内气水两相流运动所受的驱动能量与损失能量,提出了尾涡和顶部能量损失的无量纲表达式,建立了曝气室内水流的一维水动力学模型,以及基于MATLAB真域算法的模型求解方法.采用美国Prince湖等温层曝气器的实际运行数据,对该模型进行了验证,表观水流速度的预测误差在±8％以内,明显低于现有预测误差±20%.当曝气孔直径为2.6mm、曝气量从0.018m3/h增加到0.063m3/h时,曝气室内表观水流速度随曝气量的增加而增加;当曝气量固定,曝气孔直径从2.6mm减小至0.26mm时,表观水流速度随曝气孔直径的减小而增加,而当曝气孔直径进一步减小至0.026mm时,表观水流速度基本不受影响.计算了不同条件下的驱动能量和各项损失能量,揭示了引起表观水流速度变化的内因.建立的水动力学模型可用于指导等温层曝气器的设计和优化.     

曝气时间对美人蕉生态浮床去除水体中营养盐的影响

为有效去除水体中的营养盐,以美人蕉生态浮床为研究对象,将曝气时间设置为0(对照)、4、8、12 h/d,曝气量均为2.4 m3/(m2·d),研究曝气时间对植物生态浮床去除水体中营养盐的影响,在培养的0、3、5、7、18、28 d对美人蕉株高进行测量,同时监测水体中ρ(DO)、ρ(TN)、ρ(TP)、ρ(COD_Cr)、ρ(NH₃-N)、ρ(NO₃--N),试验结束后对美人蕉根际细菌总数进行测定. 结果表明:①与对照组相比,曝气4和8 h/d情况下ρ(DO)及TN、TP、NH₃-N、NO₃--N去除率均差异显著;②曝气4 h/d下美人蕉长势最好,并且在试验的第28天美人蕉株高达109 cm;③曝气4 h/d下ρ(DO)最高,并且对水体中营养盐的去除效果最好,试验至第28天,ρ(DO)为11.29 mg/L,TN、TP、COD_Cr、NH₃-N、NO₃--N去除率分别为75.10%、69.32%、65.75%、73.29%、78.79%;④试验至第28天,曝气4 h/d情况下美人蕉根际细菌总数达1.01×106 mL-1,显著高于曝气0、8和12 h/d下的细菌总数(分别为4.12×105、9.07×105、7.77×105 mL-1). 研究显示,该试验条件下,曝气4 h/d对水体中营养盐的去除效果最佳.      

Engineering practice of mechanical soil aeration for the remediation of volatile organic compound-contaminated sites in China: Advantages and challenges

In recent years, many industrial enterprises located in the urban centers of China have been relocated owing to the rapid increase in urban development. At the sites abandoned by these enterprises, volatile organic compounds have frequently been detected, sometimes at high concentrations, particularly at sites abandoned by chemical manufacturing enterprises. With the redevelopment of sites and changes in land-use type associated with these sites, substantial amounts of contaminated soils now require remediation. Since China is a developing country, soil remediation warrants the usage of techniques that are suitable for addressing the unique challenges faced in this country. Land shortage is a common problem in China; the large numbers of contaminated sites, tight development schedules, and limited financial resources necessitate the development of cost-effective methods for land reclamation. Mechanical soil aeration is a simple, effective, and low-cost soil remediation technique that is particularly suitable for the remediation of large volatile organic compound-contaminated sites. Its effectiveness has been confirmed by conducting laboratory studies, pilot tests, and full-scale projects. This study reviews current engineering practice and developmental trends of mechanical soil aeration and analyzes the advantages and disadvantages of this technology for application in China as an emerging soil remediation market. The findings of this study might aid technology development in China, as well as assist other developing countries in the assessment and implementation of costeffective hazardous waste site soil remediation programs.

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MBBR工艺中不同曝气方式充氧效率的比较及工程应用

通过设定不同的进水方式、曝气量、悬浮填料投加比,对比研究了MBBR工艺中三种曝气方式——均匀曝气、渐进曝气、单侧曝气的充氧效率,并且运用Matlab软件,采用非线性回归法计算测试条件下的饱和溶解氧浓度Cs和氧总传质系数KLα。得出:投加悬浮填料能明显提升原有曝气方式的充氧效率,但首先须保证填料在水中有一定活动强度,否则反会降低充氧效率;均匀曝气本身的充氧效率最佳,不过由于需要更大的气容比来带动填料运动,运行成本高于另外两种方式。     

竹园污水厂闭式双泥龄工艺活性污泥数学模型的参数研究

竹园第二污水厂采用一种闭式双泥龄新型工艺。以活性污泥1号模型(ASM1)为基础,测定污水厂的进水水质特性参数、异养菌产率系数(YH)和异养菌衰减系数(bH),为后续工艺模型的建立和校正提供基础数据。结果表明:竹园第二污水厂进水易生物降解有机物(Ss)、慢速生物降解有机物(Xs)、溶解态惰性有机物(SI)、异养菌(XBH)、颗粒态惰性有机物(XI)占总COD的平均比值分别为20.0%、32.1%、17.4%、9.6%、20.9%。进水氨氮(SNH)、溶解态可生物降解有机氮(SND)、颗粒态可生物降解有机氮(XND)占TN的平均比值分别为71.5%、10.0%、18.5%。闭式双泥龄工艺平行组合中的传统活性污泥池和A/O池分支的异养菌产率系数(YH)分别为0.68和0.78,异养菌衰减系数(bH)分别为0.501 d-1和0.621 d-1。     

Methanogenesis acceleration of fresh landfilled waste by micro-aeration

Introduction The key technology of bioreactor landfill ( Pohland,1995) and ecologically based landfill ( Bramryd, 2001 )consists in the initiative regulating of microbial activities inlandfill layers, so as to accelerate waste degradatio…