循环水排污水反渗透系统中溶解性有机物特征及其影响研究

循环水排污水回用是降低火电厂单位发电水耗与促进电厂水系统近零排放的关键.本研究以我国北方某电厂循环水排污水深度处理与回用系统为对象,针对夏季严重污堵的问题,分析了春、夏两季系统运行效能与溶解性有机物（DOM）变化特征及其对系统的影响.研究发现,系统预处理段运行效果较差,脱盐与COD的去除集中在反渗透（RO）段,导致RO系统污堵严重且夏季尤为明显,有机物是导致春、夏季水质差异的重要因素.进一步分析发现,排污水处理系统中DOM主要组分为蛋白质类、腐殖质类和可溶性微生物代谢产物类有机物;夏季RO过程的DOM腐殖化程度（HIX夏-RO1=0.620>HIX春-RO1=0.538）、组分复杂度、有机物聚合度均高于春季,从而造成系统夏季更为严重的污堵.夏季循环冷却系统及循环水排污水处理系统中的微生物和藻类的生长是有机物特性变化与夏季膜污堵的关键原因.因此,提升预处理段的运行效能、优化药剂投加策略、加强对DOM和微生物的控制是解决夏季系统污堵及稳定系统效能的关键.     

Effect of microbial activity on the mobility of chromium in soils

The effect of microbial activity on the chemical state of chromium, in a contaminated soil located in the Rh?ne-Alpes region (France), has been investigated. This soil contained 4,700 mg kg(-1) Cr, with about 40% present in the soluble hexavalent form. Indigenous microbial activity was found to significantly reduce Cr(VI) to the less mobile form (III) when the soil was incubated at 30 degrees C in an aqueous medium containing glucose and nutrients. A Cr(VI)-reducing strain of Streptomyces thermocarboxydus was isolated from the contaminated soil. The strain was found to metabolize Cr(VI) in a similar manner as an exogenous inoculum of Pseudomonas fluorescens LB300, and to precipitate chromium as a Cr oxyhydroxide with a gammaCrOOH-like local structure. The Cr(VI)-reducing activity of S. thermocarboxydus was induced, or significantly accelerated, by the aggregation of bacterial cells or their adhesion to suspended solid particles, and was stimulated in pure culture by glycerol and chromate.     

Legislative and environmental issues on the use of ash from coal and municipal sewage sludge co-firing as construction material

For the economy of any co-firing process, it is important that the common waste management options of ash remain practical. Ash from bituminous coal combustion is typically handed to the construction industry. This paper describes the current European legislation on use of ash for construction purposes. Also, it presents an experimental study on the suitability of fly ash from combustion of mixtures of bituminous coal and municipal sewage sludge as additive to cement and concrete, and for use in open-air construction works, based on the ash chemical composition and the characteristics of the extract of the ash. Presently, two European standards forbid the use of ash from co-firing as additive to cement or concrete. This study shows that ash derived from coal and sewage sludge co-firing contains generally less unburned carbon, alkali, magnesium oxide, chlorine, and sulfate than coal ash. Only the concentration of free lime in mixed ash is higher than in coal, even though, at least up to 25% of the thermal input, still below the requirements of the standards. This ash also meets the requirements for the use of fly ash in open-air construction works--concentration and mobility of few elements--although this management option is forbidden to ash from co-firing. The leaching of Cd, Cr, Cu, Ni, Pb and Zn was investigated with three leaching tests. The concentration of these metals in the extracts was below the detection limit in most cases. The concentration of Cu and Zn in the extract from fly ash was found to increase with increasing share of sewage sludge in the fuel mixture. However, the concentration of these two metals in the extract is not regulated. This study indicates that excluding a priori the use of ash from co-firing as a suitable additive for construction material could cause an unnecessary burden on the environment, since probably ash would have to be disposed of in landfill. However, allowing this requires the modification of current European standards to include limitations on all elements and compounds, absent in coal but which might be present in other fuels, that are deleterious for the quality of construction materials.     

Chemical investigations of aquifers affected by pyrite oxidation in the Bitterfeld lignite district

In a large area around the former open-pit lignite mines near Bitterfeld, Germany, groundwater taken from wells was analyzed for the major cations, anions, and trace elements. Quaternary and Tertiary sediments were collected from aquifers exposed on the sides of the pits and from boreholes outside the mines and analyzed for major and trace elements, as well as for carbonate, pyritic sulfur and total organic carbon. The pH and electrical conductivity of the sediments in suspension were measured. Significant differences were determined between the Tertiary sediments of the aquifers that were exposed to atmospheric oxygen during the lowering of the groundwater table and those outside the cone of depression. The greatest differences were found in the pyrite content, the pH values, and the electrical conductivity. In order to map the degree to which the mining of the lignite has affected the quality of the groundwater in the study area, the water samples were divided into six classes on the basis of their sulfate content. The neutralization potential was calculated to estimate the potential for acidification. Prediction of future groundwater quality is based on both (i) the present composition of the groundwater, surface water, and Quaternary and Tertiary aquifer sediments and (ii) the present and future groundwater flow directions. These studies have shown which parameters are important for future groundwater monitoring.     

Treatment of anti-osmotic drug based pharmaceutical effluent in an upflow anaerobic fluidized bed system

During the production of Cephradine (a main constituent of anti-osmotic drug) a large quantity of concentrated effluent was produced. The main polluting compounds in this effluent are osmotic drug, acetic acid and ammonia. The feasibility of using a fluidized bed reactor under anaerobic condition with bioaugmentation to treat anti-osmotic drug based pharmaceutical effluent was evaluated. The main objective of the study was to show that bioaugmentation could be used to promote biological treatment to applications where conventional operation might be difficult or unfavourable. The effluent with chemical oxygen demand (COD) of 14000-18000 mg/l was treated in a fluidized bed reactor with a hydraulic retention time of 3-12 h. The reactor was unable to maintain consistent removal in conventional mode of operation due to an inability to retain and grow biomass. The COD reduction (%) after inoculation from a sequencing batch reactor was related to influent concentration, mass of inoculum and hydraulic retention time characterized by calculating the initial food to microorganism ratio. The role of volatile fatty acid (VFA) as cosubstrate was assessed with respect to COD reduction (%). Continuous COD reduction (%) attained a maximum value of 88.5% using bioaugmentation through periodic addition of acclimated cells every 2 days with 30-73.2 g of cells from an off-line enricher reactor.     

Semi-volatile and particulate emissions from the combustion of alternative diesel fuels

Motor vehicle emissions are a major anthropogenic source of air pollution and contribute to the deterioration of urban air quality. In this paper, we report results of a laboratory investigation of particle formation from four different alternative diesel fuels, namely, compressed natural gas (CNG), dimethyl ether (DME), biodiesel, and diesel, under fuel-rich conditions in the temperature range of 800-1200 degrees C at pressures of approximately 24 atm. A single pulse shock tube was used to simulate compression ignition (CI) combustion conditions. Gaseous fuels (CNG and DME) were exposed premixed in air while liquid fuels (diesel and biodiesel) were injected using a high-pressure liquid injector. The results of surface analysis using a scanning electron microscope showed that the particles formed from combustion of all four of the above-mentioned fuels had a mean diameter less than 0.1 microm. From results of gravimetric analysis and fuel injection size it was found that under the test conditions described above the relative particulate yields from CNG, DME, biodiesel, and diesel were 0.30%. 0.026%, 0.52%, and 0.51%, respectively. Chemical analysis of particles showed that DME combustion particles had the highest soluble organic fraction (SOF) at 71%, followed by biodiesel (66%), CNG (38%) and diesel (20%). This illustrates that in case of both gaseous and liquid fuels, oxygenated fuels have a higher SOF than non-oxygenated fuels.     

Reactions of 2,4,6-trichlorophenol on model fly ash: oxidation to CO and CO2, condensation to PCDD/F and conversion into related compounds

Thermal treatment of 2,4,6-trichlorophenol on a magnesium silicate-based model fly ash in the temperature range between 250 degrees C and 400 degrees C leads predominantly to carbon monoxide and carbon dioxide. The fraction of 2,4,6-trichlorophenol which is oxidized to CO and CO2 increases from 3% at 250 degrees C to 75% at 400 degrees C. Further products are polychlorinated benzenes, dibenzo-p-dioxins, dibenzofurans and phenols. The homologue and isomer patterns of the chlorobenzenes suggest chlorination in the ipso-position of the trichlorophenol. The formation of PCDD from 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol on municipal solid waste incinerator fly ashes and model fly ash were compared and the reaction order calculated.     

不同部位梧桐生物质炭对水溶液中镉吸附的机理

为了探究梧桐不同部位废弃物所制备的生物质炭(皮、枝、叶)对Cd²⁺的吸附效率和稳定修复的机理,以此为园林废弃物炭化利用在重金属污染修复方面的应用提供科学依据.利用实验室模拟法,通过高温煅烧法制备梧桐不同部位生物质炭,采用元素分析仪、比表面积及孔隙分析(BET)、X射线衍射仪(XRD)、扫描电镜/能谱(SEM/EDS)及衰减全反射红外光谱(ATR-IR)等技术研究不同反应时间、重金属浓度和溶液初始pH条件下生物质炭对Cd²⁺吸附效果的影响,并运用四步萃取法和脱附实验分析生物质炭上Cd²⁺的吸附形态和稳定性.3种生物质炭都在8 h左右达到吸附平衡,最终吸附量依次为树皮炭>枝条炭>叶片炭;溶液初始浓度为0.5—2 g·L^-1时Cd²⁺的吸附量呈增长趋势,在2.5—3g·L^-1时逐渐平缓;生物质炭Cd²⁺吸附量均随着pH的升高而升高,但在pH值为5—8时,吸附的趋势逐渐平稳;树皮炭的酸溶态和非生物利用态的稳定Cd形态要高于枝条炭和叶片炭;比表面积不是影响梧桐生物质炭吸附Cd²⁺的主要影响因素,吸附动力学,ATR,XRD和重金属形态萃取均证实Cd碳酸盐类矿物生成是主导吸附机理;3种生物质炭的脱附量在4 h后逐渐趋于平衡,其中脱附量最大为叶片炭,最小为树皮炭.梧桐不同部位的初始性质对生物质炭吸附Cd²⁺具有明显的影响,其中梧桐皮具备更高的吸附量和重金属稳定形态,并且相比其他种类生物质炭有明显优势.因此,从吸附效果和生产成本的角度,本研究建议以梧桐皮为主,枝条和叶片为辅的生物质炭对重金属Cd进行修复治理.     

Masting mediated by summer drought reduces acorn predation in Mediterranean oak forests

Temporally variable production of seed crops by perennial plants (masting) has been hypothesized to be a valuable mechanism in the reduction of seed predation by satiating and starving seed consumers. To achieve these benefits, coexisting species subjected to the same predator would benefit from a similar pattern of seeding fluctuation over time that could lead to a reduction in predation at the within-species level. We tested for the existence of an environmental factor enforcing synchrony in acorn production in two sympatric Mediterranean oaks (Quercus ilex and Q. humilis) and the consequences on within-species and between-species acorn predation, by monitoring 15 mixed forests (450 trees) over seven years. Acorn production in Q. ilex and Q. humilis was highly variable among years, with high population variability (CVp) values. The two species exhibited a very different pattern across years in their initial acorn crop size (sum of aborted, depredated, and sound acorns). Nevertheless, interannual differences in summer water stress modified the likelihood of abortion during acorn ripening and enforced within- and, particularly, between-species synchrony and population variability in acorn production. The increase in CVp from initial to mature acorn crop (after summer) accounted for 33% in Q. ilex, 59% in Q. humilis, and 60% in the two species together. Mean yearly acorn pre-dispersal predation by invertebrates was considerably higher in Q. humilis than in Q. ilex. Satiation and starvation of predators was recorded for the two oaks, and this effect was increased by the year-to-year variability in the size of the acorn crop of the two species combined. Moreover, at a longer time scale (over seven years), we observed a significant reduction in the mean proportion of acorns depredated for each oak and the variability in both species' acorn production combined. Therefore, our results demonstrate that similar patterns of seeding fluctuation over time in coexisting species mediated by an environmental cue (summer drought) may contribute to the reduction of the impact of seed predation at a within-species level. Future research should be aimed at addressing whether this process could be a factor assisting in the coexistence of Q. ilex and Q. humilis.     

Constitutive and induced defenses to herbivory in above- and belowground plant tissues

A recent surge in attention devoted to the ecology of soil biota has prompted interest in quantifying similarities and differences between interactions occurring in above- and belowground communities. Furthermore, linkages that interconnect the dynamics of these two spatially distinct ecosystems are increasingly documented. We use a similar approach in the context of understanding plant defenses to herbivory, including how they are allocated between leaves and roots (constitutive defenses), and potential cross-system linkages (induced defenses). To explore these issues we utilized three different empirical approaches. First, we manipulated foliar and root herbivory on tobacco (Nicotiana tabacum) and measured changes in the secondary chemistry of above- and belowground tissues. Second, we reviewed published studies that compared levels of secondary chemistry between leaves and roots to determine how plants distribute putative defense chemicals across the above- and belowground systems. Last, we used meta-analysis to quantify the impact of induced responses across plant tissue types. In the tobacco system, leaf-chewing insects strongly induced higher levels of secondary metabolites in leaves but had no impact on root chemistry. Nematode root herbivores, however, elicited changes in both leaves and roots. Virtually all secondary chemicals measured were elevated in nematode-induced galls, whereas the impact of root herbivory on foliar chemistry was highly variable and depended on where chemicals were produced within the plant. Importantly, nematodes interfered with aboveground metabolites that have biosynthetic sites located in roots (e.g., nicotine) but had the opposite effect (i.e., nematodes elevated foliar expression) on chemicals produced in shoots (e.g., phenolics and terpenoids). Results from our literature review suggest that, overall, constitutive defense levels are extremely similar when comparing leaves with roots, although certain chemical classes (e.g., alkaloids, glucosinolates) are differentially allocated between above- and belowground parts. Based on a meta-analysis of induced defense studies we conclude that: (1) foliar induction generates strong responses in leaves, but much weaker responses in roots, and (2) root induction elicits responses of equal magnitude in both leaves and roots. We discuss the importance of this asymmetry and the paradox of cross-system induction in relation to optimal defense theory and interactions between above- and belowground herbivory.