猪场废水处理中的沼气热电联产工程案例分析

中高浓度畜禽废水处理中的沼气热电联产是保障沼气工程常年稳定运行的有效手段.以典型猪场废水处理沼气热电联产工程为案例,在工程介绍的前提下,引入相关数学模型,对沼气热电联产相关工艺参数进行了计算分析,结果表明,该工程沼气产量最高为1 678 m3/d,沼气发电机组发电效率为31.3％,发热效率为38.8％,总发电效率为70.1％,该沼气工程投资回报期为3.6年;CSTR厌氧罐秋季可达温度为24.3℃,冬季为15.9℃,CSTR厌氧罐内温度分布为秋季罐内平均温度(T)5.4(换热器顶部温度)=25.4℃,平均温度梯度grad1=1.83℃/m,grad2=0.80℃/m;冬季(T)5.4=19.6℃,(grad)1=1.44℃/m,(grad)2=1.06℃/m;通过参数分析,搅拌器宜尽可能置于换热器所在区域,并控制进水量稳定以保证CSTR厌氧罐的消化效果.     

高家沟泥石流和深溪沟泥石流灾害特征

汶川地震之后,泥石流成为灾区最为严重的灾害类型之一,直接影响到灾后重建和灾区人民的生命财产安全.对汶川地震灾区7月初群发性泥石流进行野外考察,重点分析了高家沟和深溪沟两条泥石流的成因和特征.高家沟为由滑坡崩塌体引起的土力类粘性泥石流,容重约为2.07g/cm3,总量超过30万m3,分三次间歇性汇入主河,并堵断1/2河道,迫使岷江持续冲刷对岸路基,损毁213国道长达400m;深溪沟为山洪冲刷河道引起的水力类稀性泥石流,容重约在1.44～1.58 g/cm3之间,流量约在160～180 m3/s之间.对不同的泥石流沟应采用不同的防灾减灾措施,可有效降低泥石流灾害对人民生命财产的威胁.     

高梯度磁分离技术在水处理中的应用及发展

高梯度磁分离技术是一种新型的水处理技术,目前已经得到了大量应用,具有广阔的应用前景。本文介绍了它的基本原理,综述了该技术在水处理中的应用现状,并做出了展望。     

Suspended solid abatement in a conical fluidized bed flocculator

With the random movement of silica gel beads in a conical fluidized bed, micro-vortices resulting from the fluidization promoted the collision and aggregation of suspended fine kaolin powders. The abatement efficiencies of the suspended fine solids under several hydrodynamic conditions were studied, and a suitable control strategy for operating the conical fluidized bed flocculators was identified. The suspended solids abatement efficiency was found to increase with increasing Camp Number and flocculation time (T), but decreased with the increase of velocity gradient (G) within the range studied in this research (165.1–189.6 s^-1). The abatement efficiencies were all more than 60% at the range of G = 165–180 s^-1 and T = 15–33 s at an initial kaolin solid concentration of 150 mg·L^-1, polymer aluminum chloride dosage of 60 mg·L^-1 and sedimentation time of 20 min. However, the formation of flocs was influenced by the liquid backmixing. Excessive backmixing caused the breakup of flocs and resulted in difficulty for the fine powders to aggregate and sediment to the reactor bottom. The results of the calculated fractal dimension and measured free sedimentation velocity of flocs obtained at different runs showed similar flocs properties, and indicated an easy control strategy for sedimentation of the flocs.     

Urban forest landscape patterns in Ma'anshan City,China

The landscape pattern of Ma'anshan City was analyzed based on theories and methodologies of landscape ecology, remote sensing, global positioning, and a geographic information system (GIS). The study area encompassed the entire built-up area of 63.88 km²; a north–south transect 3-km wide and 13-km long was established along the long axis of the city. Five major landscape elements were assessed: urban land, urban forest, agriculture, water, and grass. Urban land was the dominant land cover type, and occupied 67% of total land area; while patches of urban forest occupied 16%, with a landscape element dominance of 0.42. Urban forest was classified according to land-use category and location into six types: scenic forest, yard forest, recreational forest, roadside forest, shelter forest, and nurseries. There were 2464 urban forest patches, the largest being 185.1 ha, with an average of 0.43 ha. The low nearest neighbor index and high patch density indicated that urban forest patches tend to be aggregated and have a high degree of fragmentation. This study also demonstrated that the spatial pattern of urbanization could be quantified using a combination of landscape metrics and gradient analysis. Urban forest has distinct spatial characters that are dependent on specific landscape metrics along the urbanization gradient.     

对水工构筑物设计的几点看法

探讨了水工构筑物设计中的地下水位确定、伸缩缝设置、总体布置及设计与施工配合等问题。设计在满足国家有关政策、规范要求的同时,要做到技术先进、安全适用、经济合理。     

Diffusive gradient in thin FILMS (DGT) compared with soil solution and labile uranium fraction for predicting uranium bioavailability to ryegrass

The usefulness of uranium concentration in soil solution or recovered by selective extraction as unequivocal bioavailability indices for uranium uptake by plants is still unclear. The aim of the present study was to test if the uranium concentration measured by the diffusive gradient in thin films (DGT) technique is a relevant substitute for plant uranium availability in comparison to uranium concentration in the soil solution or uranium recovered by ammonium acetate. Ryegrass (Lolium perenne L. var. Melvina) is grown in greenhouse on a range of uranium spiked soils. The DGT-recovered uranium concentration (C_DGT) was correlated with uranium concentration in the soil solution or with uranium recovered by ammonium acetate extraction. Plant uptake was better predicted by the summed soil solution concentrations of UO₂²⁺, uranyl carbonate complexes and UO₂PO₄⁻. The DGT technique did not provide significant advantages over conventional methods to predict uranium uptake by plants.     

Elevation-dependent genetic variation of plants and seed embryos in the Crimea Mountain population of Pinus pallasiana D. Don

In the Crimea Mountain population of Pinus pallasiana D. Don, the genetic structure of adult plants and embryos was studied along an elevation gradient (150, 400, 600, and 900 m a.s.l.). Ten polymorphic loci of six enzyme systems were examined. The degree of differentiation of plants from different elevations and their progeny with respect to genetic structure proved to be low, indicating the absence of strict isolation barriers that would interfere with gene flow along the elevation gradient.     

Distribution of plants differing in attitude toward thermal conditions in communities of the timberline ecotone on Mount Iremel’, the Southern Urals

Specific features in the distribution of plant species differing in their attitude toward thermal conditions have been studied in communities of the present-day timberline ecotone on Mount Iremel’ in the Southern Urals. It has been shown that the distribution of such species is characterized by significant spatial nonuniformity. Elevation above sea level, local conditions in habitats located at the same altitudinal level, and specific features of mountain slopes account for 13–84, 5–30, and 0.4–14% of the total variance of test parameters, respectively. The abundance of plants changes nonlinearly along the altitudinal gradient, whereas changes in the species diversity of different plant groups have an almost linear pattern. Marked differences between plant communities with respect to the proportions of species differently responding to changes in thermal conditions have been revealed on all slopes in the upper part of the timberline ecotone, upon transition from the slopes proper to the plateau-like areas of intermontane depressions.