基于BP神经网络的垃圾焚烧过程故障诊断

应用BP神经网络方法,建立了垃圾焚烧过程故障诊断的模型.该方法采用梯度下降法训练网络权值,利用最优停止法对网络进行了优化,避免了过拟合现象.提高了BP神经网络的训练速度和泛化能力.并以实际焚烧过程工况数据进行性能检验,检验结果表明了该BP网络具有较高的诊断精度.     

不同条件下高炉渣吸附水中无机磷的研究

高炉渣(BFS)是在冶炼生铁过程中产生的固体废弃物,开展高炉渣的资源化研究具有重要意义.为了对水淬高炉渣净化含磷污水的应用提供理论依据,采取等温吸附的实验方法,比较了不同水淬炉渣的吸附磷效果,研究了不同pH和不同温度下水淬炉渣吸附磷的特点,结果如下:利用Langmuir等温吸附方程炉渣吸附磷的过程进行拟合,其相关系数均能达到显著水平.炉渣的碱度越高,吸附磷的效果越好;炉渣对磷的吸附能力随溶液pH的增加而降低,且初始为酸性(pH=2、4)的溶液在吸附达到平衡后pH有所上升,而初始为碱性的溶液(pH=10、12)在吸附达到平衡后pH有所下降;炉渣对磷的吸附是一个自发放热过程.     

Seasonal and spatial occurrence and distribution of atmospheric polycyclic aromatic hydrocarbons (PAHs) in rural and urban areas of the North Chinese Plain

Passive air sampling (PAS) was employed to study the occurrence of gaseous and particle-bound PAHs in the North Chinese Plain. The averaged concentrations of gaseous and particle-bound PAHs were 485 ± 209 ng/m³ and 267 ± 161 ng/m³, respectively. The PAHs concentrations at urban sites were generally higher than those at rural ones with ratios <1.5 in spring, summer and fall, but differences between them were not significant for the wintertime and annually averaged concentrations. This urban-rural distribution pattern was related to the PAHs emission sources. PAHs spatial variation can be partially (49%) explained by emission with a simple linear regression method. Both the gaseous and particle-bound PAHs were highest in winter and lowest in summer, with winter/summer ratios of 1.8 and 8, respectively. Emission strength was the most important factor for the seasonality.     

污泥果肥利用中重金属迁移特征研究

为了厦门城市污泥的安全利用,将石渭头污水处理厂污泥经过好氧堆肥后施用于柚子树,对重金属元素在土壤、树叶及果肉中的迁移特征进行了研究。结果表明：Cd在土壤中的富集能力强;重金属元素从土壤向树叶迁移累积能力比向果肉的大得多,污泥肥料不能用于叶类食用植物的施用;Cr向树叶、Ni向果肉的迁移累积能力强;泥肥的施用加重了土壤中Cd的污染,提高了Cr向树叶、Ni向果肉的迁移能力;污泥果肥利用需降低Ni的浓度,对污泥中含量较高的Cu、Zn、Ni、Cr和Cd需进行跟踪检测。     

污泥加热预处理对中温厌氧消化的影响

对污泥加热预处理给中温厌氧混合消化和污泥单独消化带来的影响进行了研究.研究结果表明,污泥加热预处理有利于提高混合消化对 COD 的去除率,尤其是 SCOD 的去除率由 77%增长到 93%,但不利于 TS 和 VS 的去除;而对污泥单独消化,预处理则不利于有机物的去除.采用加热预处理后的污泥进样,混合消化和污泥单独消化的甲烷产气量均有所提高.     

Spatial and temporal variations and possible sources of dichlorodiphenyltrichloroethane (DDT) and its metabolites in rivers in Tianjin, China

Water, suspended solid (SS) and sediment samples were collected from nine water courses in Tianjin, China and analyzed for dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDXs, including o,p'-,p,p'-DDT, DDD and DDE). The average DDX concentrations in water, SS and sediment were 59+/-30 ng l(-1), 2690+/-1940 ng g(-1)dry wt. and 340+/-930 ng g(-1)dry wt., respectively. Due to the termination of the extensive agricultural application and industrial manufacture, DDXs in river sediment decreased by one order of magnitude since 1970's and low DDT fractions in these sediments were observed. Still, DDXs in the sediments near the outlets of the major manufacturers remained relatively high attributed to the historic input. DDXs in sediment were also positively correlated with organic matter content. Spatial distributions of DDXs in SS and water was different from that in sediment. For SS, a negative correlation between DDX concentration and SS content indicated a dilution effect in many rivers. Dissolved organic carbon content was the major factor affecting DDX concentrations in water phase. Wastewater discharged from dicofol manufacturers and likely illegal agricultural application were the primary reasons causing high DDT (DDE+DDD) ratios in SS and water.     

Catalytic hydrogenation of polyaromatic hydrocarbon (PAH) compounds in supercritical carbon dioxide over supported palladium

A series of supported palladium catalysts were evaluated for their ability to mediate the complete hydrogenation of polycyclic aromatic hydrocarbon (PAH) compounds. Benzo[a]pyrene (B[a]P) or phenanthrene (Phe) in hexane was merged with a hydrogen-carbon dioxide [5% (w/w) H(2)/CO(2)] stream and transferred to a flow through mini-reactor (capacity ca. 1 g) that was maintained at 90 degrees C under a back-pressure of 20.68 MPa. Effluent from the reactor trapped in hexane was monitored/quantified by gas chromatography-mass spectrometry. Catalyst formulations supported on iron powder, high density polyethylene (HDPE) or gamma-alumina were prepared and compared in terms of hydrogenation activity as measured by the quantity of substrate per unit time that could be perhydrogenated to toxicologically innocuous products. Both of the Pd preparations supported on gamma-alumina were more efficient than a commercial Pd(0) (5% w/w) on gamma-Al(2)O(3) formulation or preparations supported on HDPE or the iron powder. Bimetallic mixtures with Pd increased the hydrogenation activity when co-deposited with Cu or Ni but not with Ag or Co. However, increases in hydrogenation activity by increasing the loading of Pd (or bimetallic mixture) on this surface were limited. Despite using supercritical carbon dioxide (scCO(2)) to swell the surfaces of the polymer, the deposition of nanoparticles within the polyethylene formulation was appreciably less active than either the oxidic or the Fe(0) formulations.     

Sorption of organic contaminants by biopolymers: role of polarity, structure and domain spatial arrangement

Sorption behavior of hydrophobic organic contaminants (HOCs) (i.e., pyrene, phenanthrene and naphthalene) by native and chemically modified biopolymers (lignin, chitin and cellulose) was examined. Lignins (native and treated) showed nonlinear sorption for all compounds studied, emphasizing their glassy character. Chitins and celluloses had linear isotherms for phenanthrene and naphthalene, illustrating the dominance of partitioning, while pyrene yielded nonlinear isotherms. Sorption capacity (K(oc)) of HOCs was negatively correlated with the polarity [(O+N)/C] of the biopolymers. Aromatic and alkyl+aromatic C percentages, rather than alkyl C content, demonstrated a better correlation with K(oc) values, indicating the importance of aromatic structures for HOC affinity. Hydrophobicity (K(ow))-normalized K(oc) values decreased sharply with increasing percentage of O-alkyl C versus total aliphatic C (O-alkyl C/total aliphatic C) or with polar C/(alkyl+aromatic C) ratio of the biopolymers until their values reached 80% and 4, respectively, illustrating the effect of surrounding polar groups on reducing affinity for HOCs. Overall, the results of this study highlight the role of spatial arrangement of domains within biopolymers in sorption of HOCs, and point to sorbent properties, such as functionality, polarity and structure, jointly regulating the sorption of HOCs in biopolymers.     

Determining Sources of Fecal Bacteria in Waterways

The microbiological contamination of waterways by pathogenic microbes has been, and is still, a persistent public safety concern in the United States and in most countries of the world. As most enteric pathogens are transmitted through the fecal–oral route, fecal pollution is generally regarded as the major contributor of pathogens to waterways. Fecal pollution of waterways can originate from wastewater treatment facilities, septic tanks, domestic- and wild-animal feces, and pets. Because enteric pathogens are derived from human or animal sources, techniques capable of identifying and apportioning fecal sources have been intensively investigated for use in remediation efforts and to satisfy regulatory concerns. Pollution of human origin is of the most concern, since human feces is more likely to contain human-specific enteric pathogens. Fecal indicator bacteria have been used successfully as the primary tool for microbiologically based risk assessment. However measurement of fecal indicator bacteria does not define what pathogens are present, or define the sources of these bacteria. Microbial source tracking (MST) methods that have the ability to differentiate among sources of fecal pollution are currently under development. These methods will ultimately be useful for risk assessment purposes and to aid regulatory agencies in developing strategies to remediate microbiologically impaired waterways.     

Source apportionment of polycyclic aromatic hydrocarbons in surface soil in Tianjin, China

Principal component analysis and multiple linear regression were applied to apportion sources of polycyclic aromatic hydrocarbons (PAHs) in surface soils of Tianjin, China based on the measured PAH concentrations of 188 surface soil samples. Four principal components were identified representing coal combustion, petroleum, coke oven plus biomass burning, and chemical industry discharge, respectively. The contributions of major sources were quantified as 41% from coal, 20% from petroleum, and 39% from coking and biomass, which are compatible with PAH emissions estimated based on fuel consumption and emission factors. When the study area was divided into three zones with distinctive differences in soil PAH concentration and profile, different source features were unveiled. For the industrialized Tanggu-Hangu zone, the major contributors were cooking (43%), coal (37%) and vehicle exhaust (20%). In rural area, however, in addition to the three main sources, biomass burning was also important (13%). In urban-suburban zone, incineration accounted for one fourth of the total.