Rate constants of reactions of ozone with organic and inorganic compounds in water—III. Inorganic compounds and radicals

Second-order rate constants for reactions of ozone with 40 inorganic aqueous solutes are reported. Included are compounds of sulfur (e.g. H₂S, H₂SO₃, HOCH₂SO₃H), chlorine (e.g. Cl⁻, HOCl, NH₂Cl, HClO₂, ClO₂), bromine (e.g. Br⁻, HOBr), nitrogen (e.g. NH₃, NH₂OH, N₂O, HNO₂) and oxygen (e.g. H₂O₂), as well as free radicals (e.g. O₂⁻, OH^•). Most of these compounds exhibit an increase in rate constant with increasing pH corresponding to their degree of dissociation. Rate constants are based on ozone consumption rates measured by conventional batch-type or continuous-flow methods (10⁻³-10⁺⁶ M⁻¹ s⁻¹ range) and determinations of stoichiometric factors. Also listed are data determined by pulse-irradiation techniques using kinetic spectroscopy (10¹⁰ M⁻¹ s⁻¹ range). Additional literature data are reviewed for completeness. Results are discussed with respect to water treatment and environmental processes.     

Behavior of alkylphenol polyethoxylate metabolites during soil aquifer treatment

The attenuation of alkylphenol polyethoxylates (APEOs) metabolites was studied at a soil aquifer treatment (SAT) site located in Arizona, USA. Two parcels of water were monitored during infiltration; one parcel was predominantly oxic while the other was predominantly anoxic. In this study, only alkylphenol ethoxycarboxylates (APECs) and carboxyalkylphenol ethoxycarboxylates (CAPECs) were detected, no short-chained APEOs were observed-even under anoxic conditions. APEO metabolites were rapidly (<7 days) removed under both aerobic and anoxic conditions. In general, the length of the ethoxycarboxylate chain decreases with depth--at depths greater than 3m, only alkylphenoxy acetic acids (AP1ECs), carboxyalkylphenoxy acetic acids (CAP1ECs), and alkylphenols (APs) remain. Under aerobic conditions, octylphenol and nonylphenol concentrations decreased by approximately 80% (w/w) within 3m of the ground surface. Under anoxic conditions however, alkylphenol concentrations increased by approximately 200% during the first 1.5m and then decreased during the next 1.5m; overall, under anoxic conditions, alkylphenol concentrations increased by approximately 38% within 3m. During infiltration, APEC and CAPEC concentrations decrease by more than 95% within 3m of SAT. Alternate flooding and drying cycles appear to enhance overall APEO metabolite removal efficiencies.     

Removal of VUV pre-treated natural organic matter by biologically activated carbon columns

A potential alternative water treatment process using VUV (185 nm+254 nm) irradiation followed by a biological treatment is described. The system uses sufficient VUV radiation (16J cm(-2)) to significantly enhance the production of biologically degradable moieties prior to treatment with biologically activated carbon (BAC). Two similar activated carbons were used, one virgin and one taken from a water treatment plant with an established biofilm. The VUV-BAC process decreased the overall dissolved organic carbon (DOC) concentration of a natural water sample by 54% and 44% for the virgin carbon and previously used BAC, respectively. Furthermore, VUV-BAC treatment decreased the trihalomethane (THM) formation potential (THMFP) by 60-70% and the haloacetic acid (HAA) formation potential (HAAFP) by 74%. The BAC systems effectively removed the hydrogen peroxide residual produced by VUV irradiation. Although nitrite formation can result from VUV treatment of natural organic matter (NOM), none was detected before or after BAC treatment.     

750kV GIS中金属氧化物避雷器对VFTO影响的研究

随着超高压气体绝缘变电站(GIS)的广泛使用,由隔离开关(DS)和断路器(CB)操作引起的快速暂态过电压(VFTO)的危害越加明显。以西北地区750 kV官亭GIS变电站为计算原型,利用电磁暂态程序(EMTP)对不同运行方式下GIS设备上的VFTO进行数值仿真计算和分析。重点在于对不同运行方式下金属氧化物避雷器(MOA)的限制过电压效果进行分析。计算结果表明:DS无分合闸电阻时,MOA防护效果更明显;MOA主要的抑制效果体现在MOA附近的设备上,对于远离MOA的设备上的VFTO的抑制效果较小;由于VFTO持续的时间极短,通过MOA的能量很小。     

Formation of disinfection by-products in indoor swimming pool water: the contribution from filling water natural organic matter and swimmer body fluids

The contribution and role of different precursors in the formation of three class of disinfection by-products (DBPs) [trihalomethanes (THMs), haloacetic acids (HAAs), and halonitromethanes (HNMs)] in swimming pool waters were examined using filling waters obtained from five drinking water treatment plant (WTP) effluents and three body fluid analogs (BFAs). BFAs exerted higher chlorine demands as compared to natural organic matter (NOM) in filling waters. BFAs exhibited higher HAA formation potentials than THM formation potentials, while the opposite was observed for the filling water NOM. There was no appreciable difference in the HNM formation potentials of BFAs and filling water NOM. Different components in the BFAs tested exhibited different degree and type of DBP formation. Citric acid had significantly higher THM and HAA yields than other BFA components. The effect of temperature was greater on THM formation, whereas the effect of contact time had more impact on HAA formation. Experiments with filling waters collected from WTP effluents at three different times showed more variability in HAA than THM formation at the WTPs studied.     

膨润土对重金属离子Pb~(2+),Zn~(2+),Cr(VI),Cd~(2+)的吸附性能

试验研究了pH值、吸附时间和吸附剂用量对膨润土吸附重金属离子Pb2 ,Zn2 ,Cr(VI)和Cd2 的影响.结果表明,在本试验的pH值、吸附时间及吸附剂用量条件下,膨润土对Pb2 ,Zn2 ,Cd2 的吸附效果均优于其对Cr(VI)的吸附效果;pH值是影响上述吸附的重要因素,离子交换和表面络合是上述吸附的主要形式.     

集料碱活性检测方法评述

集料碱活性检测是预防碱集料反应(AAR)的重要措施。针对检测方法及其标准的建立,人们做了大量的研究工作。本文重点介绍了RILEM标准中检测集料AAR活性的方法及综合运用各种检测方法对集料进行检测的过程,同时对RILEM标准、ASTM标准、CSA标准中集料碱活性检测方法进行了比较。     

聚硅铁混凝去除腐殖酸的研究

考察了聚硅铁(PSF)对腐殖酸(HA)的去除效果及影响因素,并与聚合硫酸铁(PFS)、硫酸铁[Fe_2(SO_4)_3]进行了比较.结果表明,当5相似文献   

An energy-based partial pushdown analysis procedure for assessment of disproportionate collapse potential

A disproportionate (or progressive) collapse is triggered by localized structural damage that propagates throughout a large portion of a structural system. The current guidelines issued by the US Department of Defense use the alternative path method to assess the vulnerability of a structural system to disproportionate collapse. In this method, the capability of a structure to sustain local damage is evaluated by notionally removing primary load-bearing elements and checking whether the local damage can be absorbed. The assessment can be performed using linear or nonlinear static structural models or a nonlinear dynamic model. Although nonlinear dynamic analysis gives the most accurate results, it is computationally intensive and requires considerable skill to implement properly. In this paper, the vulnerability of three steel frames to disproportionate collapse is assessed using an energy-based nonlinear static pushdown analysis. The predictions are sufficiently close to the results of a nonlinear dynamic time history analysis that the method would be useful for disproportionate collapse-resistant design of buildings with regular steel framing systems.     

Data-driven estimation of joint roughness coefficient

Joint roughness is one of the most important issues in the hydromechanical behavior of rock mass. Therefore, the joint roughness coefficient (JRC) estimation is of paramount importance in geomechanics engineering applications. Studies show that the application of statistical parameters alone may not produce a sufficiently reliable estimation of the JRC values. Therefore, alternative data-driven methods are proposed to assess the JRC values. In this study, Gaussian process (GP), K-star, random forest (RF), and extreme gradient boosting (XGBoost) models are employed, and their performance and accuracy are compared with those of benchmark regression formula (i.e. Z₂, R_p, and SD_i) for the JRC estimation. To analyze the models’ performance, 112 rock joint profile datasets having eight common statistical parameters (R_ave, R_max, SD_h, i_ave, SD_i, Z₂, R_p, and SF) and one output variable (JRC) are utilized, of which 89 and 23 datasets are used for training and validation of models, respectively. The interpretability of the developed XGBoost model is presented in terms of feature importance ranking, partial dependence plots (PDPs), feature interaction, and local interpretable model-agnostic explanations (LIME) techniques. Analyses of results show that machine learning models demonstrate higher accuracy and precision for estimating JRC values compared with the benchmark empirical equations, indicating the generalization ability of the data-driven models in better estimation accuracy.     

Synthesis and characterisation of multi-walled carbon nanotubes (MWCNTs)

ABSTRACT

Carbon nanotubes are one of the major research areas in the field of nanotechnology, due to its mechanical and electro-conductive properties in the field of engineering and medical sciences. This paper focuses on preparation of multi-walled carbon nanotubes (MWCNTs) for the mass production using thermal catalytic chemical vapour deposition method. The synthesis of MWCNTs was made by breakdown of acetylene (C₂H₂) gas and Fe/MgO acting as catalyst. The surface morphology and structure of MWCNTs were characterised by scanning electron microscopy (SEM). Also phase identification and crystalline size of the nanopowder were determined by XRD. The particle size of MWCNTs was verified by SEM analysis and it was in the range of 20–30?nm and elemental analysis was carried out through energy dispersive analysis X-ray. Furthermore, thermal decomposition of the material property was studied by thermogravimetric analysis.     

A modification of the Trent Index for use in Denmark

A new pollution index based on macroinvertebrates has been devised which can be used as a surveillance system in Danish streams. The index is inspired by the Trent Index although it was necessary to incorporate two new principles. First, the pollution indicators Asellus aquaticus and Chironomus sp. are used as negative taxa, with a negative influence on the index value, thereby strongly enhancing the utility of the keygroups. Secondly, the taxonomic groups used in the Trent Index have been replaced by establishing positive and negative index groups, where the number of negative index groups is subtracted from the number of positive. Thus, the utility of the basic principle, increasing pollution effecting decreasing numbers of taxonomic groups, is enhanced.     

矿物掺合料对轻质高强混凝土性能的影响

研究了粉煤灰、矿渣和硅灰掺合料对大流动性高强轻集料混凝土性能影响.测试结果表明：在单掺情况下,矿渣和硅灰能有效地提高拌合物的粘聚性,从而改善了混凝土早期和后期强度,但对拌合物流动性有一定影响,掺加粉煤灰能有效提高流动性,但产生泌水对拌合物匀质性有不良影响.综合流动性和强度改善效果,复合掺加矿渣和粉煤灰对配制大流动性高强轻集料混凝土效果最佳.     

再生胶改性沥青性能及其微观结构研究

制备了普通橡胶沥青和再生胶改性沥青,测定了这2种橡胶沥青的各项技术指标,并对普通橡胶粉和再生胶颗粒的微观结构进行了研究.结果表明:与普通橡胶沥青相比,再生胶改性沥青的高温黏度大大降低,制备温度也稍微下调,且制备中无异味,更加环保.再生胶颗粒交联度低,活性化学键多,与沥青之间存在明显的化学作用;而普通橡胶粉交联度高,活性化学键少,与沥青之间几乎没有化学作用.     

PCE结构对硅酸三钙结构和形貌的影响

为了进一步了解减水剂与水泥矿物相的相互作用,分别采用X射线光电子能谱(XPS)和扫描电子显微镜(SEM)研究了聚醚型聚羧酸减水剂(PCE)结构对硅酸三钙(C_3S)水化产物表面电子状态和形貌的影响.结果表明:在吸附了PCE的样品中,C—H的C1s谱峰明显增强,并出现C—O的C1s谱峰,而Si2p谱峰明显减弱,PCE在C_3S表面的吸附膜厚度为0.94~1.40nm;由于Ca元素填充于PCE吸附膜中,导致C_3S表面的Ca2p谱峰强度变化较小;PCE结构对Si2p,Ca2p谱峰的化学位移影响显著,即PCE的羧酸根密度越大,样品的化学位移越明显;PCE结构不同,抑制C_3S水化的程度也不同,并且PCE还可阻止C_3S的水化产物相互黏结.     

MBR和SBR去除典型内分泌干扰物的对比研究

采用模拟生活污水,在相同的运行条件下,对比研究了MBR与SBR对7种典型内分泌干扰物及其内分泌活性的去除效果.结果表明,试验所投加的内分泌干扰物不影响MBR和SBR的稳定运行;对于目标物17β-雌二醇(E2)、雌三醇(E3)、双酚A(BPA)、4-壬基酚(4-NP)和4-辛基酚(4-OP),MBR和SBR对它们的去除效果没有明显差别;但MBR对壬基酚聚氧乙烯醚(NPnEO,n平均约为1.5)和17α-炔雌醇(EE2)的去除效果较SBR更佳且更稳定.此外,MBR对内分泌活性的去除效果也较SBR更优.     

Understanding soluble microbial products (SMP) as a component of effluent organic matter (EfOM)

Formation of soluble microbial products (SMP) during biological degradation of organic compounds in a sequencing batch reactor (SBR) was investigated using high performance liquid chromatography--size exclusion chromatography (HPSEC) as well as other organic matter characterization tools. Results showed that carbon compounds in a glucose feed solution were totally transformed to other organic products classified biomass-associated products (BAP). The SMP-BAP contained in the SBR effluent consisted mainly of high-molecular weight (MW) fractions of organic matter, possibly originating from cell lysis. These compounds exhibited a low specific ultraviolet absorbance (SUVA) and a hydrophilic character. In addition, the characteristics of bulk effluent organic matters (EfOM) samples from wastewater treatment facilities were studied. It was observed that EfOM consisted of humic-like and hydrophobic (HPO) compounds, derived from the corresponding drinking water source, in addition to SMP-BAP. A superimposition of SEC chromatograms of the SMP-BAP and humic-like compounds represented a fingerprint of EfOM.     

VRS—GPS网络RTK技术及其应用

本文介绍VRS-GPS网络RTK系统组成和工作原理,探讨了建设网络RTK有关技术要点和应用范围。     

Source apportionment of trichloroethylene in groundwater of the industrial complex in Wonju,Korea: a 15‐year dispute and perspective

The groundwater of an industrial complex has been contaminated with trichloroethylene (TCE) since 1995. High levels of TCE exceeding the Korean groundwater standard can still be found. However, ongoing controversial debate on the contamination source has hindered the remedial works. Wonju city suggested a single source, while the Gangwon Province considered multiple sources. The TCE plume appeared as two separate plumes rather than a single plume. Carbon tetrachloride (CT), a formerly used solvent, formed a plume but its extent was restricted to the left half of the overall TCE plume. The soil contamination survey revealed the existence of at least two contamination source areas. All the evidences pointed to the asphalt test laboratory as being one of the major sources, but the possibility of other sources cannot be excluded. The maximum extent of the TCE contamination caused by the asphalt laboratory may have been restricted to the left half of the overall TCE plume.     

Performance evaluation of cement-stabilized pond ash-rice husk ash-clay mixture as a highway construction material

This paper reports the results of an investigation carried out on clay soil stabilized with pond ash (PA), rice husk ash (RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio (CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%–45% and 5%–20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were carried out, respectively. The results obtained indicated a decrease in the maximum dry density (MDD) and a simultaneous increase in the optimum moisture content (OMC) with the addition of PA and RHA. Multiple linear regression analysis (MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.