Sulphadimethoxine and Azolla filiculoides Lam.: a model for drug remediation

Plants can be an interesting tool for in situ remediation of drug contaminated waters. In a laboratory model Azolla filiculoides Lam., an aquatic fern known to absorb pollutants, has been exposed to an environmental persistent antibiotic commonly used in intensive farming, sulphadimethoxine (S), to test its bioremediation capability. In a 5 week experiment, plants were cultivated outdoor at four drug concentrations (50, 150, 300 and 450 mg l(-1)) in N-free mineral medium. Drug affects growth rate (as biomass yield per week), N2-fixation, heterocyst frequency, but plants are able to survive. Notwithstanding, at all concentrations tested drug was actively removed from the medium and the accumulation in the biomass is in order of magnitude up to mg g(-1) plant dry weight (1000 ppm). Drug uptake and degradation rates increase with S concentrations in the culture medium. The efficacy of the model was very high. These results demonstrated that Azolla can be taken into consideration as a tool for sulphonamides environmental monitoring and decontamination.     

Water phytoremediation of cadmium and copper using Azolla filiculoides Lam. in a hydroponic system

The aim of this work was to evaluate the utility of Azolla filiculoides growing in a hydroponic system for the phytoremediation of continental water polluted with cadmium and copper during 7 days of exposure. Cadmium and copper chloride were added to the medium at concentrations of 0.5–10 mg/L and 0.1–25 mg/L, respectively. Cadmium and copper levels were measured in each plant using flame atomic absorption spectrophotometry. The analytical methodology used to measure cadmium and copper levels was validated with standard reference material (SRM) – 1570 (spinach) National Institute of Standards and Technology. The results indicated that cadmium and copper phytoremediation was statistically significant with a maximum increase in plant tissue of 1623.20 and 6013.1 μg/g, respectively. This photosynthetic efficiency was chronically damaged when Azolla filiculoides were exposed to 10 mg/L of Cd and 25 mg/L of Cu. The Azolla plants were not affected in the other phytoremediation treatments with copper.     

Azolla as a source of biomass: a comparison with water hyacinth

Aquatic weeds are known for their high growth potential. In this paper Azolla‐an aquatic free floating fern‐has been considered as a source of biomass. The five aspects, viz., habitat and distribution, habit and morphology, major chemical components, control measures and environmental influences, and utilization aspects have been focused and compared with those of the water hyacinth. The many advantages offered by Azolla over water hyacinth have been demonstrated. The possibility of using Azolla for biogas generation has also been emphasized.     

中小学研学旅行课程实施评价研究

中小学研学旅行作为研究性学习与旅行体验相结合的校外活动课程,在课程实施过程中容易产生“只旅不学”或“只学不旅”的问题,构建研学旅行课程实施评价指标是解决这一问题的突破口。为此,以课程要素分析为理论框架,根据我国中小学研学旅行政策文本,从准备要素、设计要素、过程要素、结果要素和反馈要素五个维度构建中小学研学旅行课程实施评价体系,为研学旅行课程设计、实施、评价提供理论和实践参考。     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—I. Growth potential of oxidation pond water and comparative optima for blue-green and green algal growth

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.     

The Use of the Water Velvet Azolla Filiculoides in Wastewater Treatment

Azolla filiculoides is a free-floating water fern which fixes atmospheric nitrogen in association with the nitrogen-fixing blue-green alga Anabaena azollae. It is used for nutrient-removal purposes because it can grow under a wide range of environmental conditions.
This paper describes a series of experiments which was carried out in Alexandria, Egypt, to elucidate the performance of Azolla for the treatment of sewage and nutrient removal.     

Treatment of stormwater using a detention pond and constructed filters

A stormwater treatment plant, consisting of a detention pond, a constructed filter system and a constructed wetland, has been investigated according to stormwater quality improvement, sediment and heavy metals accumulation and potential toxicity of the stormwater and sediment. The reduction of metal content in the detention pond was on average 26?–?84%. No acute toxicity in the stormwater was detected although heavy metal levels often exceeded guideline values during storm events. Pore water samples of the collected sediments were not toxic but the whole sediment was toxic when assessed with the Microtox^® Solid-phase test. The constructed filter system became clogged due to cementation of the filter substrate.     

某尾矿库渗流与稳定性的数值分析

运用数值分析方法,模拟计算某尾矿库的渗流与稳定性,得到了在正常水位运行和洪水水位运行两种工况条件下库区渗流浸润线的分布位置以及尾矿坝的安全系数,根据分析结果,对该尾矿库的渗流及静力稳定性分析进行了评价,得出了一些有益的结论。     

A compartmental model to describe hydraulics in a full-scale waste stabilization pond

The advancement of experimental and computational resources has facilitated the use of computational fluid dynamics (CFD) models as a predictive tool for mixing behaviour in full-scale waste stabilization pond systems. However, in view of combining hydraulic behaviour with a biokinetic process model, the computational load is still too high for practical use. This contribution presents a method that uses a validated CFD model with tracer experiments as a platform for the development of a simpler compartmental model (CM) to describe the hydraulics in a full-scale maturation pond (7 ha) of a waste stabilization ponds complex in Cuenca (Ecuador). 3D CFD models were validated with experimental data from pulse tracer experiments, showing a sufficient agreement. Based on the CFD model results, a number of compartments were selected considering the turbulence characteristics of the flow, the residence time distribution (RTD) curves and the dominant velocity component at different pond locations. The arrangement of compartments based on the introduction of recirculation flow rate between adjacent compartments, which in turn is dependent on the turbulence diffusion coefficient, is illustrated. Simulated RTD’s from a systemic tanks-in-series (TIS) model and the developed CM were compared. The TIS was unable to capture the measured RTD, whereas the CM predicted convincingly the peaks and lags of the tracer experiment using only a minimal fraction of the computational demand of the CFD model. Finally, a biokinetic model was coupled to both approaches demonstrating the impact an insufficient hydraulic model can have on the outcome of a modelling exercise. TIS and CM showed drastic differences in the output loads implying that the CM approach is to be used when modelling the biological performance of the full-scale system.     

Internal loading of phosphorus in a sedimentation pond of a treatment wetland: effect of a phytoplankton crash

Sedimentation ponds are widely believed to act as a primary removal process for phosphorus (P) in nutrient treatment wetlands. High frequency in-situ P, ammonium (NH₄⁺) and dissolved oxygen measurements, alongside occasional water quality measurements, assessed changes in nutrient concentrations and productivity in the sedimentation pond of a treatment wetland between March and June. Diffusive equilibrium in thin films (DET) probes were used to measure in-situ nutrient and chemistry pore-water profiles. Diffusive fluxes across the sediment-water interface were calculated from the pore-water profiles, and dissolved oxygen was used to calculate rates of primary productivity and respiration. The sedimentation pond was a net sink for total P (TP), soluble reactive P (SRP) and NH₄⁺ in March, but became subject to a net internal loading of TP, SRP and NH₄⁺ in May, with SRP concentrations increasing by up to 41 μM (1300 μl^− 1). Reductions in chlorophyll a and dissolved oxygen concentrations also occurred at this time. The sediment changed from a small net sink of SRP in March (average diffusive flux: − 8.2 μmol m^− 2 day^− 1) to a net source of SRP in June (average diffusive flux: + 1324 μmol m^− 2 day^− 1). A diurnal pattern in water column P concentrations, with maxima in the early hours of the morning, and minima in the afternoon, occurred during May. The diurnal pattern and release of SRP from the sediment were attributed to microbial degradation of diatom biomass, causing reduction of the dissolved oxygen concentration and leading to redox-dependent release of P from the sediment. In June, 2.7 mol-P day^− 1 were removed by photosynthesis and 23 mol-P day^− 1 were supplied by respiration in the lake volume. SRP was also released through microbial respiration within the water column, including the decomposition of algal matter. It is imperative that consideration to internal recycling is given when maintaining sedimentation ponds, and before the installation of new ponds designed to treat nutrient waste.     

Impact of western coal mining—I. Chemical investigations of a surface coal mine sedimentation pond

Chemical investigations of the sedimentation pond system at the West Decker Mine in southeastern Montana, U.S.A., were undertaken during an 18 month period from November 1975 to April 1977. Sedimentation pond water, essentially “altered” groundwater, differed chemically from the average groundwater in coal-bearing aquifers. The increase in certain chemical constituents (sodium, sulfate, bicarbonate and inorganic nitrogen) and the decrease in dissolved oxygen in pond water during autumn 1976 and winter 1977 was the result of erratic pond operation, dredging and increased nearby mining activity. Discharge from the pond complied with the guidelines advanced for effluents from surface coal mines. Levels of mercury in water samples collected from the sedimentation pond system were higher than those recommended for the protection of aquatic life and wildlife. The suitability of pond water for selected purposes and recommendations for improvement in pond design are discussed.     

Stability of a small solar pond with different salt gradient layers

A solar pond can be miniaturised for installing on a building's roof, which can bring more benefits. Different salt gradient layers affect the stability, heat absorption, and storage capacity of a solar pond. The study used the industrial NaCl as the working medium to prepare different kinds of salinity of a solar pond. Taking turbidity, salinity, and temperature as the key parameters, we studied the stability and thermal absorption of a solar pond. The results show that: When the volume proportion of upper convection, non-convection, and lower convection remains the same in the solar pond, the heat storage performance of the solar pond increases with an increase in the layer number of the solar pond. The optimal layers of non-convection are 4, and salt gradient layers of the solar pond are 6.     

Operation of a deep, well-mixed, high-rate photosynthetic oxidation pond

The maximum depth for the stable operation of a photosynthetic high-rate oxidation pond was found to be 90cm. At this depth, both the pH and the peak oxygen concentration were significantly lower than the values obtained in shallow high-rate oxidation ponds.     

压力分散型锚杆在某基础抗浮工程中的应用

为解决某地下车库基础抗浮问题,采用了压力分散型锚杆抗浮技术。通过锚杆极限承载力计算和锚杆结构设计,确定锚杆极限承载力为1300kN,锚杆的构造为在基础底板下土层内形成直径150mm、内设4个承载体、有效长度为23m的锚杆。本抗浮锚杆成孔采用泥浆护壁工艺,注浆采用常压注浆和二次高压注浆。通过现场试验研究,实测锚杆极限承载力大于设计值,为抗浮设计提供了合理依据。     

Environmental context of Cylindrospermopsis raciborskii (Cyanobacteria) blooms in a shallow pond in France

Cylindrospermopsis raciborskii, a potentially toxic blooming cyanobacterium (blue-green alga), responsible for public health problems in Australia, was identified in France in 1994 in a shallow pond south of Paris. A program monitoring the occurrence of C. raciborskii in this pond was conducted from July 1998 to October 1999. The phytoplankton assemblages were studied, and limnological parameters (water temperature, dissolved oxygen, pH, conductivity, and dissolved inorganic nutrients) were measured. By multivariate analysis (principal component analysis), we showed that sufficiently high temperatures to allow the germination of akinetes, relatively low nutrient concentrations (soluble reactive phosphorus with a mean concentration of 1 microM and nitrate between 0 and 5 microM, except in February 1999 (21 microM)) and a characteristic high and constant sulfate concentration (8981+/-471 microM) seemed to be the main factors involved in the proliferation of C. raciborskii in the "Francs-Pêcheurs" (FP) pond. In the light of these findings and of bibliographic data, C. raciborskii would seem to be characterized by good adaptability, but also by low competitiveness with other phytoplanktonic species in the temperate study area.     

Solar thermal modelling of a building with a roof pond and ventilation control systems

The paper proposes and presents thermal modelling of a ventilation-controlled, non-air-conditioned building with evaporative cooling (e.g. open water pond) over the roof for passive solar air conditioning. The ventilation rate, expressed in terms of number of air changes per hour, is assumed to be time-dependent, as should be the case in normal practice. A self-consistent periodic heat transfer analysis for a non-air-conditioned building with roof cooling and ventilation control systems, furnishing (assumed isothermal mass), windows, door and basement ground heat storage effects has been developed to assess the feasibility of the proposed passive space air-conditioning. It is shown that for no-ventilation summer nights the inside air temperature remains higher than the ambient air temperature even with an effective roof cooling system, and hence the windows should be opened to lose the internal heat and to introduce cool and fresh outside air. It is found that for a ventilation-controlled building with a roof pond the passive solar air conditioning can be achieved more effectively.     

大型工业水池混凝土控裂防渗技术研究

通过对某大型工业水池伸缩缝间距与极限抗拉强度验算,并对构造配筋、混凝土配合比等控裂防渗技术进行优化,成功实施了70m超长池体整体无缝(带)浇筑,实现了大型水池混凝土结构自防水无裂渗的目标。     

太钢二钢沉淀池喷粉桩施工工艺

喷粉桩适合各种成因的饱和软粘土、淤泥、淤泥质土,通过与设计人员共同研究,对二钢地质报告及施工现场环境进行分析,确定二钢沉淀池采用喷粉桩复合地基处理方式,解决了该工程施工场地狭小具工期紧,任务重,施工难度大的问题,达到了预期的效果。     

湖泊、池塘的水温模型与最大供冷能力的分析研究

借鉴分层水蓄冷方式,提出利用稳流器装置从水体底部取水、同温层回水的思路,建立了二维竖向水动力水温模型,与实测值的比较表明,该模型可以较准确地反映水体全年自然水温分布状态.利用该水温模型研究了水体的最大供冷能力,分析了供回水温差、气候和水深的影响.