污水处理厂尾水细菌群落结构分析

城市尾水中含有大量的微生物,其中相当一部分为病原菌,其排入自然水体后给附近人群造成健康威胁.本研究采用建立16S rDNA克隆文库和PCR-RLFP技术对尾水的细菌群落结构进行分析,结果表明尾水中有59种细菌分别属于11个纲,其中44种细菌属于Proteobacteria门,约占85%(其中β-Proteobacteria和γ-Proteobacteria纲占绝对优势),7种细菌属于Clostridia纲占7.2%,而Actinobacteria、Bacteroidia、Gloeobacteria、Nitrospira、Planctomycetacia这5个纲的细菌所占数量都低于4%,尾水中的细菌大多来源于污水处理过程,因此各地区应该根据受纳水体的特点和净化能力选择合适的污水处理工艺;59种细菌中Legionella spp.占10%以上,其导致的退伍军人症可能成为尾水排放对附近人群健康的最大威胁,另外尾水中一些细菌能代谢次氯酸盐对氯气有一定抵抗能力,所以在选择消毒措施时应该选用氯气消毒与其他消毒工艺的组合;本研究中粪大肠杆菌、大肠埃希氏菌、沙门氏菌、志贺菌属、霍乱弧菌等致病菌在尾水中均未检出,因此对这些致病菌进行研究需要选择针对性更强的方法.     

JUSTIFICATION FOR A REDUCTION IN THE CREST-STAGE GAGE PROGRAM IN LOUISIANA1

The crest-stage gage program in Louisiana was evaluated to determine if the data were adequate for use in developing regional flood-frequency equations and to determine if any crest-stage gage stations could be discontinued. An abundance of data at many crest-stage gage stations and a lack of data for urban areas and flat-slope areas indicated a need for a shift in the number, type, and locations of gages. Correlations and comparisons of annual peak discharges and watershed characteristics of 96 existing stations resulted in the elimination of 72 stations and the addition of one new station, reducing the total network to 25 stations that could be used for future flood-frequency analyses. The adequacy of the reduced network for development and verification of regional flood-frequency equations was tested by comparing a set of regional flood-frequency equations developed using data from the full network with a set developed using data from the reduced network. The results indicate that the crest-stage gage network can be reduced to 25 stations and still provide adequate information for future flood-frequency analyses.     

FISH RESPONSES TO TEMPERATURE TO ASSESS EFFECTS OF THERMAL DISCHARGE ON BIOLOGICAL INTEGRITY1

ABSTRACT: The applicability of the U.S Environmental Protection Agency's (USEPA) water temperature criteria in evaluating the impact of a thermal discharge from the P. H. Glatfelter Paper Company, Spring Grove, Pennsylvania, is analyzed. A review of the literature relative to 11 temperature Criteria was conducted for six fish species designated by the USEPA as “representative important species” (RIS) of the West Branch Codorus Creek, Susquehanna River drainage. The species were: Notemigonus crysolcucas (golden shiner), Notropis analostanus (satinfin shiner), Rhinichthys atratulus (blacknose dace), Catostomus comme-soni (white sucker), Lepomis gibbosus (pumpkinseed). and Micropterous salmoides (largemouth bass). It was found that by applying only USEPA suggested criteria that a complete evaluation was not satisfactory. Temperature behavior data, specifically preference and avoidance information, coupled with field sampliug was needed to properly assess the effects of the thermal effluent. The final analysis indicated that the thermal discharge of the paper company should have minimal effect on the fish community of Codorus Creek.     

Minimum ignition energies of pure magnesium powders due to electrostatic discharges and nitrogen's effect

This paper experimentally investigated the relation between the minimum ignition energy (MIE) of magnesium powders as well as the effect of inert nitrogen (N₂) on the MIE. The modified Hartmann vertical-tube apparatus and four kinds of different-sized pure magnesium powders (median particle size, D50; 28.1 μm–89.8 μm) were used in this study. The MIE of the most sensitive magnesium powder was 4 mJ, which was affected by the powder particle size (D50; 28.1 μm). The MIE of magnesium powder increased with an increase in the N₂ concentration for the inerting technique. The magnesium dust explosion with an electrostatic discharge of 1000 mJ was suppressed completely at an N₂ concentration range of more than 98%. The experimental data presented in this paper will be useful for preventing magnesium dust explosions generated from electrostatic discharges.     

环境外部不经济性内部化手段的评价与筛选

分析环境外部不经济性产生的根本原因,提出环境外部不经济性内在化手段的评价指标,并据此对国内外常环境外部不经济性内化手段作系统评价,评价结果表明,排污收费制度是当前最合理的环境外部不经济性内的在化手段。     

高压脉冲放电降解水中苯乙酮的研究

进行了高压脉冲放电降解水中苯乙酮的实验,2.1×10^-3M苯乙酮溶液放电处理30min,苯乙酮的最高降解率达92％,另外还探讨了苯乙酮降解途径及气体的存在对放电效果和苯乙酮降解率的影响．研究表明,用高压脉冲放电处理有机废水是可行的．     

Experimental study on the relationship between the charge amount of polypropylene granules and the frequency of electrostatic discharges while silo loading

This paper is a report on the relationship between the charge amount (charge to mass ratio, q/m) of polypropylene (PP, 2–3 mm) granules and the frequency of electrostatic discharges that occur while loading a metal silo. The feedback control system was used in order to control the q/m of PP granules. The electrostatic discharges inside the silo were also observed using a conventional image-intensifier system. The charging control range for PP granules was from 0 to −12 μC/kg in the q/m. The results obtained from the experiments show that (1) two kinds of electrostatic discharges were clearly observed inside a metal silo while loading PP granules, i.e., brush discharges and incendiary bulk surface discharges; (2) the number of brush discharges and incendiary bulk surface discharges increased with the increase in the q/m of PP granules, almost reaching saturation; and (3) brush discharges and incendiary bulk surface discharges began to occur at the −1.16 μC/kg and −2.33 μC/kg points in the q/m, respectively, in this study.     

The Effect of Sewage Discharge On Water Quality Off the Coast of Alexandria in Spring and Summer

Water samples were taken from 7 transects at El-Anfushy, Eastern Harbour, El-Ebrahymea, Stanly, Gleem, Sidi-Bishr and El-Asafra along the coast off Alexandria. the area lies between latitude 31°10' and 31°20' N and longitude 29°55' and 30° E. Nitrate, nitrite, ammonium, urea, dissolved inorganic phosphate, silicate and pH values were measured with average values 1,13, 0.43, 1.41, 1.21, 1.71, 7.16 μmol l^-1, respectively. the investigated area is considered to be eutrophic. Levels of nutrients measured in 1991 are all significantly higher than those found in the same area in 1976.     

雾化电晕净化烹调油烟技术

对雾化电晕放电极雾化过程、荷电液滴的捕集原理、自清洗作用进行探讨,在相同电压下雾化负电晕放电电流高于干式负电晕放电电流,极间大量荷电液滴具有很高的荷质比,并高速向极板驱进,对烟尘具有静电凝并和动力凝并除尘作用,具有高效净化油烟、自清洗极板的功能,此项净化烹调油烟的新技术,优于传统油烟净化技术,具有很好的应用价值和前景。     

Integral Model for Turbulent Buoyant Jets in Unbounded Stratified Flows Part 2: Plane Jet Dynamics Resulting from Multiport Diffuser Jets

An integral model for the plane buoyant jet dynamics resulting from the interaction of multiple buoyant jet effluxes spaced along a diffuser line is considered as an extension of the round jet formulation that was proposed in Part I. The receiving fluid is given by an unbounded ambient environment with uniform density or stable density stratification and under stagnant or steady sheared current conditions. Applications for this situation are primarily for submerged multiport diffusers for discharges of liquid effluents into ambient water bodies, but also for multiple cooling tower plumes and building air-conditioning. The CorJet model formulation describes the conservation of mass, momentum, buoyancy and scalar quantities in the turbulent jet flow in the plane jet geometry. It employs an entrainment closure approach that distinguishes between the separate contributions of transverse shear and of internal instability mechanisms, and contains a quadratic law turbulent pressure force mechanism. But the model formulation also includes several significant three-dimensional effects that distinguish actual diffuser installations in the water environment. These relate to local merging processes from the individual multiple jets, to overall finite length effects affecting the plume geometry, and to bottom proximity effects given by a “leakage factor” that measures the combined affect of port height and spacing in allowing the ambient flow to pass through the diffuser line in order to provide sufficient entrainment flow for the mixing downstream from the diffuser. The model is validated in several stages: First, comparison with experimental data for the asymptotic, self-similar stages of plane buoyant jet flows, i.e. the plane pure jet, the pure plume, the pure wake, the advected line puff, and the advected line thermal, support the choice of the turbulent closure coefficients contained in the entrainment formulation. Second, comparison with data for many types of non-equilibrium flows with a plane geometry support the proposed functional form of the entrainment relationship, and also the role of the pressure force in the jet deflection dynamics. Third, the observed behavior of the merging process from different types of multiport diffuser discharges in both stagnant and flowing ambient conditions and with stratification appears well predicted with the CorJet formulation. Fourth, a number of spatial limits of applicability, relating to terminal layer formation in stratification or transition to passive diffusion in a turbulent ambient shear flow, have been proposed. In sum, the CorJet integral model appears to provide a mechanistically sound, accurate and reliable representation of complex buoyant jet mixing processes, provided the condition of an unbounded receiving fluid is satisfied.