3种短链脂肪酸对活性污泥储存PHA的影响

采用经乙酸钠驯化培养具有一定聚羟基烷酸酯(PHA)储存能力的活性污泥,考察乙酸、丙酸和丁酸3种短链脂肪酸,以及乙酸、丁酸分别与丙酸按1∶1、1∶2、2∶1比例组合成的6种混合酸作为碳源时对活性污泥中PHA的储存和转化的影响。实验结果表明,在3种短链脂肪酸中,以丁酸为碳源得到活性污泥PHA储存量最高,为40.53 mg/g;在混合酸中,乙酸与丙酸按1∶2组合时,系统PHA储存量最高,为773.4 mg/g。混合酸相对于单一的脂肪酸碳源更有利于活性污泥储存PHA。在混合酸总量一定的条件下,随着丙酸比例的增加,乙酸与丙酸混合比丁酸与丙酸混合更有利于微生物的PHA储存。     

Gold Mining: Is It Worth Its Weight?

Gold (Au) accounts for only 0.004 g/ton of the earth's crust and is the most desired element. With an average annual world production of approximately 2,500 tons, the current methods of Au mining in developing countries cause major environmental issues. These issues vary from deforestation to cyanide and mercury (Hg) contamination. This article presents several cases of environmental catastrophes caused by Au mining in different regions of the world (Africa, the Middle East, Eastern Europe, and South America). It discusses the currently available processes for the large-scale extraction of metallic Au grains and supports the need for an alternative sustainable process.     

Batch sorption dynamics and equilibrium for the removal of lead ions from aqueous phase using activated carbon developed from coffee residue activated with zinc chloride

Lignocellulosic materials are good precursors for the production of activated carbon. In this work, coffee residue has been used as raw material in the preparation of powder activated carbon by the method of chemical activation with zinc chloride for the sorption of Pb(II) from dilute aqueous solutions.The influence of impregnation ratio (ZnCl₂/coffee residue) on the physical and chemical properties of the prepared carbons was studied in order to optimize this parameter. The optimum experimental condition for preparing predominantly microporous activated carbons with high pore surface area (890 m²/g) and micropore volume (0.772 cm³/g) is an impregnation ratio of 100%. The developed activated carbon shows substantial capability to sorb lead(II) ions from aqueous solutions and for relative impregnation ratios of 75 and 100%, the maximum uptake is practically the same. Thus, 75% represents the optimal impregnation ratio.Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), solution pH, ionic strength and temperature. The maximum uptake of lead(II) at 25 °C was about 63 mg/g of adsorbent at pH 5.8, initial Pb(II) concentration of 10 mg/L, agitation speed of 200 rpm and ionic strength of 0.005 M. The kinetic data were fitted to the models of pseudo-first order and pseudo-second order, and follow closely the pseudo-second order model. Equilibrium sorption isotherms of Pb(II) were analyzed by the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model gives a better fit than the others.Results from this study suggest that activated carbon produced from coffee residue is an effective adsorbent for the removal of lead from aqueous solutions and that ZnCl₂ is a suitable activating agent for the preparation of high-porosity carbons.     

Methanogenic activity of woody debris

The paper is devoted to the phenomenon of methanogenic activity of woody debris, i.e., methane production in the course of wood decomposition by fungi, which are not directly involved in methane synthesis but form an initial link in the trophic chain leading to methanogenic archaea. Expert evaluation of probable amounts of methane emission is made. The results show that woody debris is an important global source of this greenhouse gas.     

Seasonal and spatial variability of Po,U and Pu levels in the river catchment area assessed by application of neural-network based classification

The present study deals with the application of self-organizing maps (SOM) in order to model, classify and interpret seasonal and spatial variability of ²¹⁰Po, ²³⁸U and ^239+240Pu levels in the Vistula river basin. The data set represents concentration values for 3 alpha emitters (²¹⁰Po, ²³⁸U and ^239+240Pu) measured in surface water samples collected at 19 different sampling locations (8 in major Vistula stream while 11 in right or left Vistula tributaries) during four seasons (winter, spring, summer and autumn) in the framework of a one-year quality monitoring study. The advantages of an SOM algorithm, its classification and visualization ability for environmental data sets, are stressed. The neural-network based classification made it possible to reveal specific patterns related to both seasonal and spatial variability. In the middle and upper part of Vistula catchment as well as in the right-shore tributaries, concentrations of ²¹⁰Po and ²³⁸U during summer and winter are the lowest. Concentrations of ²¹⁰Po and ²³⁸U increase significantly during spring and autumn in the Vistula river catchment, especially in the delta of Vistula river. High concentration of anthropogenic originated ^239+240Pu indicates “site-specific” character of pollution in two large left-shore tributaries located in the middle part of the Vistula drainage area. Efficient classification of sampling locations could lead to an optimization of river radiochemical sampling networks and to a better tracing of natural and anthropogenic changes along Vistula river stream.     

Experimental study of recycling lightweight concrete with aggregates containing expanded glass

The focus is on the issue of waste management when constructing and recycling lightweight concrete (LWC) with aggregates containing expanded glass. The paper analyses the recycling of concrete from lightweight aggregates, and on the important issue of environmental and waste management. The characteristics of recycling LWC such as density, compressive strength and thermal conductivity are investigated, and compared with normal existing concrete from lightweight aggregates. The results indicate that it is possible to recycle lightweight concrete construction waste. The described method shows great possibilities for increasing the use of construction waste materials from LWC containing expanded glass, in order to benefit from better use of the available capacity from existing construction waste. The characteristics of density, compressive strength and thermal conductivity from the new recycled material were compared with normal existing concrete from lightweight aggregates, such as changes in dependency on the type and parts of waste as well as its new binding components. Thus, a new recycled material has been created with new characteristics of density, compressive strength and thermal conductivity, which is conform to the compressive strength class and rules on heat protection and energy efficiency use in buildings (SI OJ RS No. 42/2002). Laboratory density, compressive strength, and thermal conductivity tests results showed that LWC can be produced by the use of waste LWC with aggregates containing expanded glass. However, the use of waste LWC with aggregates containing expanded glass seems to be necessary for the production of cheaper and environmentally friendly LWC.     

生活垃圾加载介质层填埋法对初期渗滤液污染抑制效果研究

以传统卫生填埋柱R2为对照,通过往生物反应器填埋柱R1内加载可渗透反应介质层1和2进行模拟试验,主要探讨了填埋柱R1垃圾渗滤液COD、总氮、氨氮及总磷的变化趋势,探索一种新型的加载介质层垃圾填埋处理方法。试验结果表明，填埋20周后, R1柱COD浓度基本维持在40 000～45 000 mg/L间,约为R2柱的20%～30%;第24周,R1柱总氮和氨氮分别为206.5 mg/L和167.3 mg/L,在16～24周内,R1总氮和氨氮分别约为R2的14.5%～17.5%和36.2%～43.6%;18周时,R1柱总磷达最大值1.704 mg/L,至第24周降为0.673 mg/L, 整个实验过程R1柱总磷约为R2的0.15%～0.56%。     

Enhanced resistance of yeast mutants deficient in low-affinity iron and zinc transporters to stannous-induced toxicity

Tin or stannous (Sn²⁺) compounds are used as catalysts, stabilizers in plastic industries, wood preservatives, agricultural biocides and nuclear medicine. In order to verify the Sn²⁺ up-take and toxicity in yeast cells we utilized a multi-elemental analysis known as particle-induced X-ray emission (PIXE) along with cell survival assays and quantitative real-time PCR. The detection of Sn²⁺ by PIXE was possible only in yeast cells in stationary phase of growth (STAT cells) that survive at 25 mM Sn²⁺ concentration. Yeast cells in exponential phase of growth (LOG cells) tolerate only micro-molar Sn²⁺ concentrations that result in intracellular concentration below of the method detection limit. Our PIXE analysis showed that STAT XV185-14c yeast cells demonstrate a significant loss of intracellular elements such as Mg, Zn, S, Fe and an increase in P levels after 1 h exposure to SnCl₂. The survival assay showed enhanced tolerance of LOG yeast cells lacking the low-affinity iron and zinc transporters to stannous treatment, suggesting the possible involvement in Sn²⁺ uptake. Moreover, our qRT-PCR data showed that Sn²⁺ treatment could generate reactive oxygen species as it induces activation of many stress-response genes, including SOD1, YAP1, and APN1.     

响应曲面法优化复合絮凝剂的制备工艺

为了提高染料废水中COD和色度的去除效果,采用响应曲面法对聚硅酸类新型复合絮凝剂的制备工艺进行了优化实验研究。在单因素实验基础上采用Box-Behnken Design(BBD)实验设计方法,设计出了影响染料废水处理效果的3因素3水平共15组实验,其中n(Fe+Al):n(Si)的摩尔比为4～6,n(B+Mg):n(Si)的摩尔比为0.3～0.7,熟化时间为1～3 d。根据15组实验结果,以COD去除率和色度去除率为响应值分别建立了二次多项式响应曲面模型。模型优化结果显示,在n(Fe+Al):n(Si)摩尔比为5∶1,n(B+Mg):n(Si)为0.5∶1,熟化时间为2 d的条件下,制备得到的新型复合絮凝剂聚硅酸铝铁硼镁具有最佳的絮凝处理性能和脱色效果,能有效去除染料废水中的COD和色度,其中出水色度接近于0,COD的去除率达到87.65%,模型验证实验进一步验证了本文所建立的响应曲面法在复合絮凝剂制备工艺优化中的有效性。