低湿度表面的海洋附着细菌对厚壳贻贝附着的影响

从低湿度表面形成自然微生物被膜中分离和纯化出9株海洋附着细菌,并进行细菌16S rDNA基因序列的鉴定以确定其菌名;在18℃、黑暗条件下培养48h后形成单一菌株的微生物被膜,研究了细菌不同初始密度条件下形成微生物被膜的终密度变化及其对厚壳贻贝Mytilus coruscus稚贝附着的影响。同时,将获得的序列与有亲缘关系的序列用Mega软件的CLUSTALW程序进行序列比对和系统发育分析。结果表明:所有测试海洋附着细菌形成微生物被膜的最终密度随初始密度的增加而增加;9株海洋细菌均能不同程度地促进厚壳贻贝稚贝的附着,其中Bacillus sp.2诱导活性最高,其诱导稚贝的附着率为68%;除Pseudoalteromonas sp.3微生物被膜终密度与稚贝附着无显著相关性外(P>0.05),其余8株海洋细菌所形成的微生物被膜终密度与稚贝附着均呈显著相关性(P<0.05);系统发育分析表明,微生物被膜终密度对稚贝附着的诱导活性与细菌种属无关。研究表明,低湿度表面的海洋附着细菌对厚壳贻贝的附着有明显的促进作用,本研究结果对于今后开展厚壳贻贝稚贝的附着机制研究奠定了基础。     

Heterotrophic activity compromises autotrophic nitrogen removal in membrane-aerated biofilms: results of a modeling study

A 1-d multi-population biofilm model was constructed to study the effect of heterotrophic activity on completely autotrophic ammonium (NH4+) removal in membrane-aerated (counter-diffusion) versus conventional biofilm systems (co-diffusion). Growth of heterotrophic bacteria (HB) was supported either solely by biomass decay products or by organic carbon (as chemical oxygen demand (COD)) in the influent. Three scenarios were considered: influence of HB growing on biomass decay products on steady-state performance (total nitrogen (TN) removal efficiency); influence of the influent COD/N ratio on steady-state performance (supplying COD in the influent); and impact of dynamic changes in the influent COD/N ratio on TN removal efficiency. The results revealed that the TN removal efficiency in the counter-diffusion biofilm was significantly different when HB were included in the simulations at NH4+ surface loads of LNH4>2.7 g - N m(-2) d(-1). Influent COD significantly altered the microbial community composition in the counter-diffusion biofilm and anaerobic NH4+ oxidation could not be sustained at COD/N>2. The co-diffusion system, however, was less affected and more than 50% of the TN removal originated from anaerobic NH4+ oxidation at those ratios. Perturbation experiments showed that step increases to influent COD/N ratios of 2 or higher over a period of 50 d or longer caused a loss of anaerobic NH4+ oxidation capacity which could not be regained within a reasonable time frame (>1000 d) in the counter-diffusion system. In contrast, simulating a 1-d sloughing event only caused a disturbance of 200 d although a maximum biofilm loss of 90-95% occurred. These results clearly indicate the importance of heterotrophic activity in autotrophic N removal biofilms, especially in counter-diffusion systems where they may compromise N removal capacity.     

Effects of bacterial activity on estrogen removal in nitrifying activated sludge

The effects of bacterial activity on the degradation of estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2) in nitrifying activated sludge (NAS) were studied with different substrates and organic loading rates (OLRs) and low temperature conditions. Heterotroph was shown to have utilized glucose prior to E1 for metabolism. The co-metabolism of ammonia oxidizing bacteria (AOB) dominated the degradation of E1, E2 and EE2 in NAS. The higher the organic loading, the higher the rate of organic matter transformation, with less ammonia oxidation and less degradation of E1, E2 and EE2. The degradation of E3 in NAS was shown to be largely due to heterotroph metabolism. On the basis of the difference of apparent activity between heterotroph and AOB at 4 degrees C, the process of estrogen degradation via the co-metabolism of AOB was able to be identified.     

Uptake of cations under two different water regimes in a boreal scots pine forest

There is still much to find out about how trees react to changing nutrient conditions. In this cation uptake study, 134Cs and 22Na were injected between the humus and the mineral soil, and into a 20-cm depth in the mineral soil, respectively. Half of the experimental site was subjected to desiccation in 1995 and 1996, while the other half was subjected to irrigation in 1995, and desiccation in 1996. One month after the injections, the concentration of 134Cs in the xylem sap was higher in the irrigated plots (ID) than in the desiccated plots (DD). In August 1995, the difference in the 134Cs concentration in the xylem sap was even higher between the treatments. In 1995, 22Na was also higher in the xylem sap on the ID plots than on the DD plots, but not significantly. Exponential relationships were found between the amount of 134Cs and 22Na in the xylem sap; the relative water uptake from humus and 0-10-cm mineral soil (134Cs); and 10-25-cm mineral soil (22Na) in July 1995, when the tracers had not yet reached the top of the boles. The relative uptake of injected 22Na was larger than that of injected 134Cs, probably due to low exchangeability of Cs in the soil. One year after the injection (1996), more 134Cs was found in the wood, bark, needles and cones on the plots irrigated in 1995 than on the desiccated plots. The content of 134Cs in the stem wood and stump amounted to nearly 80% of the total uptake in the trees. The Cs distribution 1 year after the Chernobyl accident was dominated by Cs on/in needles and bark. After 10 years of redistribution, the Chernobyl Cs content of the different parts of the trees approached that of K.     

Investigation on the removal of natural and synthetic estrogens using biofilms in continuous flow biofilm reactors and batch experiments analysed by gas chromatography/mass spectrometry

The degradation of the natural estrogen 17β-estradiol and the synthetic steroid hormone 17α-ethinylestradiol, two estrogens already detected in surface waters at low concentration levels, was investigated using continuous flow biofilm reactors and batch experiments. Biofilms in continuous flow experiments were created by natural organisms from river systems of the national park Unteres Odertal, Germany, whereas batch experiments were performed with isolated bacterial strains derived from biofilms. The analytical method, including solid phase extraction, silylation of analytes and measurement with GC/MS, was optimised for the target compounds 17β-estradiol, 17α-ethinylestradiol and the possible metabolites estrone and estriol. The performance characteristics of the analytical method, namely recovery, standard deviations, method detection limits (MDL) and method quantification limits (MQL), were evaluated for accurate interpretation of degradation experiments. Continuous flow biofilm reactors were operated with two different nutrient media under dosage of estradiol and ethinylestradiol. Both estrogens were rapidly degraded within several hours; the metabolite estrone (from estradiol as well as from ethinylestradiol) was detected in significant amounts and was further decomposed. In additional batch experiments using isolated bacterial strains from the natural biofilms to decompose estradiol and ethinylestradiol, different metabolisms of isolates were explored. Five of the 15 isolated bacterial strains tested degraded estradiol and ethinylestradiol with different degradation rates. The results suggest that biofilms from national park Unteres Odertal possess a high capability to aerobically decompose natural and also synthetic estrogens so that these microorganisms could provide enhanced removal of pollutants in municipal water treatment plants.     

Retention of pesticides in soil columns modified in situ and ex situ with a cationic surfactant

A study of the effect of a clayey soil modified in situ and ex situ with the cationic surfactant octadecyltrimethylammonium bromide (ODTMA), on the retention of linuron, atrazine and metalaxyl was carried out. Leaching of these compounds was studied in columns of a natural clayey soil and the same clayey soil modified by direct injection of the surfactant in situ, and in columns of a natural sandy soil and the same sandy soil modified by intercalation of a barrier of the clayey soil saturated ex situ with the surfactant. Breakthrough curves indicated the total immobilization of linuron in modified soils and a decrease in the leaching kinetics of atrazine and metalaxyl compared to what was obtained in the natural soil. The results indicate the use of the clayey soil modified in situ or ex situ with the surfactant ODTMA could be of interest in the immobilization of pesticides of different hydrophobicities.     

Computational fluid dynamics modelling of different detention pond configurations in the interest of sustainable flow regimes and gravity sedimentation potential

This study presents the results of the flow regime evaluation, by means of computational fluid dynamics (CFD), of a vegetated detention pond located at Waterlooville, Hampshire, UK. Alternative pond layouts were assessed for the same flow conditions on the basis of recommendations made in the literature. The results were validated by comparing the maximum computational velocities for the same case using different numbers of mesh elements. It was found that the development of a CFD model of detention ponds is intricate but feasible. The main findings were: (i) The present design performed well in terms of flood risk management, but the flow patterns could result in questionable treatment efficiency; (ii) vegetation seems to promote horizontal recirculation and turbulence; (iii) triangular and elliptical pond designs showed very poor performance; (iv) the most appropriate design for the given location and hydrological regime is an elliptical pond with a central emergent/submerged island.     

Annual cycle of nitrogen removal by a pilot-scale subsurface horizontal flow in a constructed wetland under moderate climate

The annual course of nitrogen removal in a stable operating subsurface horizontal flow constructed wetland (SSF) in a moderate climate was evaluated using a large pool of data from 4 years of operation. In spring and autumn removal efficiencies were found to depend on the nitrogen load in a linear mode. The efficiencies in winter and summer differed extremely (mean removal rates of 0.15/0.7 g m(-2) d(-1) (11%/53%) in January/August) and were independent of the nitrogen load (0.7-1.7 g m(-2) d(-1)) in principle. Oscillations of the removal rates in spring, forming several maxima, suggest seasonal specific effects caused by the dynamics of the plant-physiology finally determining the nitrification efficiency, i.e. via O(2)-supply. Nitrification is limited by temperature during all seasons and surprisingly in midsummer additionally restricted by other seasonal aspects forming a clear-cut relative nitrification minimum (mean rate of 0.43 g m(-2) d(-1) (32%)) in July. The importance and the effect of the plants' gas exchange and oxygen input into the rhizosphere are discussed. Denitrification was nearly complete in midsummer and was clearly restricted at seasonal temperatures below 15 degrees C.     

Morphological and physicochemical characteristics of iron corrosion scales formed under different water source histories in a drinking water distribution system

The corrosion scales on iron pipes could have great impact on the water quality in drinking water distribution systems (DWDS). Unstable and less protective corrosion scale is one of the main factors causing “discolored water” issues when quality of water entering into distribution system changed significantly. The morphological and physicochemical characteristics of corrosion scales formed under different source water histories in duration of about two decades were systematically investigated in this work. Thick corrosion scales or densely distributed corrosion tubercles were mostly found in pipes transporting surface water, but thin corrosion scales and hollow tubercles were mostly discovered in pipes transporting groundwater. Magnetite and goethite were main constituents of iron corrosion products, but the mass ratio of magnetite/goethite (M/G) was significantly different depending on the corrosion scale structure and water source conditions. Thick corrosion scales and hard shell of tubercles had much higher M/G ratio (>1.0), while the thin corrosion scales had no magnetite detected or with much lower M/G ratio. The M/G ratio could be used to identify the characteristics and evaluate the performances of corrosion scales formed under different water conditions. Compared with the pipes transporting ground water, the pipes transporting surface water were more seriously corroded and could be in a relatively more active corrosion status all the time, which was implicated by relatively higher siderite, green rust and total iron contents in their corrosion scales. Higher content of unstable ferric components such as γ-FeOOH, β-FeOOH and amorphous iron oxide existed in corrosion scales of pipes receiving groundwater which was less corroded. Corrosion scales on groundwater pipes with low magnetite content had higher surface area and thus possibly higher sorption capacity. The primary trace inorganic elements in corrosion products were Br and heavy metals. Corrosion products obtained from pipes transporting groundwater had higher levels of Br, Ti, Ba, Cu, Sr, V, Cr, La, Pb and As.     

砖木结构古建筑不同风速下火灾蔓延规律研究

为探明砖木结构古建筑火场下火灾蔓延的变化规律,从火灾蔓延特性、热释放速率、温度的变化等方面探究不同风速影响下的火灾蔓延变化情况.选取中国典型砖木结构三原城隍庙为实例,通过古建筑BIM参数化建模,合理设置火灾场景进行火场模拟分析.结果表明:风速作用下,火焰蔓延过程变化波动较大,呈现一定的周期性,在一定范围内,风速越大,古...     

Partitioning of phenanthrene into surfactant hemi-micelles on the bacterial cell surface and implications for surfactant-enhanced biodegradation

Recent studies have suggested that the ability of a surfactant to enhance the bioavailability of hydrophobic organic compounds (HOC) requires the formation of surfactant hemi-micelles on the bacterial cell surface and subsequent partitioning of HOC into the hemi-micelles. However, the studies did not provide direct evidence of HOC partitioning into surfactant hemi-micelles on the bacterial cell surface. In this study, direct evidence is provided to demonstrate that the nonionic surfactant Brij 30 forms hemi-micelles on the bacterial cell surface and that phenanthrene sorption at the bacterial surface is enhanced by the surfactant. These results are in agreement with the current theory describing surfactant-enhanced HOC bioavailability. This enhanced bioavailability is put into context with microbial kinetics and system partitioning processes, and it is demonstrated that the addition of surfactant can enhance, have no effect, or inhibit HOC biodegradation depending upon surfactant concentration and microbial growth rate. Understanding these non-linear relationships between surfactant-enhanced HOC bioavailability, biodegradation kinetics, and system partitioning will assist in the design and implementation of surfactant-enhanced bioremediation programs.     

不同温度下矿物掺合料矿渣活性指数试验研究

对不同温度下矿渣矿物掺合料的水泥砂浆的力学性能进行了试验研究,利用同龄期比强度分析法,对不同温度不同龄期矿渣掺合料活性进行了数值分析,并比较了不同温度对活性指数的影响。结果表明,在龄期达到7 d时,(1)温度20℃:活性指数达到76%;(2)温度10℃:活性指数达到42%。在龄期达到28 d时,(1)温度20℃:活性指数达到109%;(2)温度10℃:活性指数达到76%。表明:(1)不同温度下,在20℃下,活性指数比较高,说明低温会阻碍掺合料的强度发展,使得其强度发展缓慢。(2)不同龄期下,28 d的活性指数比较高,20℃可以达到S95级矿渣,说明掺入矿渣的水泥砂浆后期强度高。     

微生物被膜形成因子及其对厚壳贻贝附着的影响

为调查环境因子对微生物被膜形成能力的影响以及在此条件下形成的微生物被膜对厚壳贻贝Mytilus coruscus稚贝(壳长为1.81 mm±0.13 mm)附着的影响,通过显微共聚焦技术和荧光染色技术,探讨了在18℃条件下盐度为10、20、30时和盐度为30的条件下温度为8、18、28℃时,环境因子对希瓦氏细菌Shewanella loihica ECSMB14101形成微生物被膜产生的影响,调查了上述环境下形成微生物被膜的细菌密度、分布、膜厚等生物学特性及其对厚壳贻贝稚贝附着的影响。结果表明:S.loihica ECSMB14101形成微生物被膜的最终密度随盐度的升高而增加;不同密度的微生物被膜诱导活性不同,且与盐度呈线性关系;微生物被膜上细菌密度随温度的升高而增多,在8℃和18℃时对稚贝的附着诱导活性有显著性差异(P<0.05),附着率分别为31%和68%,18℃与28℃时的微生物被膜诱导活性无显著性差异(P>0.05);随盐度和温度的上升,微生物被膜上的细菌分布逐渐密集,膜厚显著增加,且在盐度为30、温度为28℃条件下微生物被膜的膜厚达到最大值(4.4μm±0.1μm);在温度为18℃、盐度为30条件下,膜厚的最大值为(4.3±0.1)μm。研究表明,盐度和温度改变微生物被膜的生物学特性,并导致贻贝附着率的显著差异。     

微生物被膜形成因子及其对厚壳贻贝附着的影响

为调查环境因子对微生物被膜形成能力的影响以及在此条件下形成的微生物被膜对厚壳贻贝Mytilus coruscus稚贝(壳长为1.81 mm±0.13 mm)附着的影响,通过显微共聚焦技术和荧光染色技术,探讨了在18℃条件下盐度为10、20、30时和盐度为30的条件下温度为8、18、28℃时,环境因子对希瓦氏细菌Shewanella loihica ECSMB14101形成微生物被膜产生的影响,调查了上述环境下形成微生物被膜的细菌密度、分布、膜厚等生物学特性及其对厚壳贻贝稚贝附着的影响。结果表明:S.loihica ECSMB14101形成微生物被膜的最终密度随盐度的升高而增加;不同密度的微生物被膜诱导活性不同,且与盐度呈线性关系;微生物被膜上细菌密度随温度的升高而增多,在8℃和18℃时对稚贝的附着诱导活性有显著性差异(P<0.05),附着率分别为31%和68%,18℃与28℃时的微生物被膜诱导活性无显著性差异(P>0.05);随盐度和温度的上升,微生物被膜上的细菌分布逐渐密集,膜厚显著增加,且在盐度为30、温度为28℃条件下微生物被膜的膜厚达到最大值(4.4μm±0.1μm);在温度为18℃、盐度为30条件下,膜厚的最大值为(4.3±0.1)μm。研究表明,盐度和温度改变微生物被膜的生物学特性,并导致贻贝附着率的显著差异。     

Effect of biomass quantity and activity on TOC removal in a fixed-bed reactor

Experimental runs were carried out on an upflow fixed-bed reactor. The process cycle of 24 h was determined by following head losses used as an indicator of the clogging of the filter. The efficiency with which dissolved carbon pollution is eliminated, measured by the percentage of TOC removal decreases over the 24 h due to a decrease of 30% of the retention time, while the specific dehydrogenase activities of the biomass stay constant along the process cycle. The 50% increase in volatile matters at the end of the cycle does not induce a corresponding increase in the efficiency.     

SBR在三级A/O模式下不同运行条件对脱氮除磷的影响

研究了SBR在三级A/O模式下,不同的运行条件(COD/TN、排水比以及温度等)对脱氮除磷的影响,以期为SBR的过程控制提供依据。结果表明,排水比为50%的条件下,当COD/TN小于5.67时,TN去除率随着COD/TN的升高呈快速上升趋势;当COD/TN大于5.67时,TN去除率稳定在一个范围,基本不受COD/TN的影响。较小的排水比条件下有利于系统对TN的去除,而较大的排水比有利于对TP的去除。在系统温度低于11℃的情况下,硝化细菌的硝化功能受到严重影响,需延长停留时间,并且要经过相当长的一段时间才能恢复;当温度大于11℃时,硝化细菌的功能基本不受影响。     

Effect of vacuum removal on consolidation settlement under a combined vacuum and surcharge preloading

The combined vacuum and surcharge preloading technique is extensively used to accelerate the consolidation process of subsoils. The effect of vacuum pressure is often considered as a loading/unloading cycle of mean effective stress, such that elastic rebound occurs after vacuum removal, which cannot explain the observed postconstruction settlement in the field. In this study, the stress state of subsoils subject to vacuum and surcharge preloading is analyzed and decomposed into two components: (a) geostatic consolidation at a different depth, and (b) loading/unloading in the minor principal stress direction. A series of consolidated drained triaxial tests is conducted to simulate the soil behaviour after vacuum removal. Results show that the contribution of unloading in the minor principal stress direction outweighs the magnitude of elastic rebound after vacuum removal, and hence continued settlement dominates. A field case for highways is provided to further demonstrate the proposed mechanism.     

A novel separation of tritiated water formed by biodegradation of surfactant samples and its application to a sample preservation study

Primary biodegradation of a NEODOL^® ethoxylate labeled with tritium primarily in the α and γ positions of the alkyl chain and uniformly with ¹⁴C in the polyoxyethylene chain resulted in a very rapid release of tritiated water (HTO) by cleavage of the surfactant at the hydrophobe-hydrophile junction. This reaction was used to investigate the conditions necessary to preserve samples of biotreater clarifier effluent and mixed liquor suspended solids (MLSS). Treatment of the sample with granular activated carbon, followed by filtration, readily isolated the tritiated water. The amount of HTO formed indicated the extent of continued degradation of the surfactant. It was concluded that refrigeration alone was not adequate to prevent primary degradation of the surfactant. Refrigeration in combination with either formalin or 200 ppm HgCl₂ prevented short-term degradation of the surfactant. Formalin, but not HgCl₂, was found adequate for preventing degradation in samples of mixed liquor suspended solids preserved in excess of 14 days.     

Adsorption of anionic and cationic dyes on activated carbons with different surface chemistries

The influence of the surface chemical groups of an activated carbon on the removal of different classes of dyes is evaluated. Starting from the same material (NORIT GAC 1240 PLUS), the following treatments were carried out in order to produce a series of samples with different surface chemical properties but with no major differences in their textural properties: oxidation in the liquid phase with 6M HNO(3) and 10 M H(2)O(2) (acid materials) and heat treatment at 700 degrees C in H(2) or N(2) flow (basic materials). The specific micropores volume and mesopores surface area of the materials were obtained from N(2) adsorption equilibrium isotherms at 77K. The surface chemistry was characterised by temperature programmed desorption, by the determination of the point of zero charge (pH(pzc)) and by the evaluation of the acidity/basicity of the samples. Elemental and proximate analyses were also carried out. Equilibrium isotherms of selected dyes (an acid, a basic and a reactive dye) on the mentioned samples were obtained and the results discussed in relation to their surface chemistry. In general, the Langmuir model provided the best fit for the adsorption data. It is shown that the surface chemistry of the activated carbon plays a key role in dye adsorption performance. The basic sample obtained by thermal treatment under H(2) flow at 700 degrees C is the best material for the adsorption of all the tested dyes.