垃圾压缩站污水的生物强化处理

垃圾压缩站污水是一种具有高COD、高NH3-N特点的有机污水.以厌氧/好氧组合工艺为基础,通过投加高效菌株对活性污泥系统进行生物强化.实验结果表明,与空白相比,厌氧出水COD去除率提高约30%,好氧出水NH3-N去除率提高约20%.最终出水COD《120 mg/L, NH3-N《25 mg/L,均达到《污水综合排放标准》(GB 8978-1996)二级排放标准.     

压力对填埋垃圾产甲烷的影响研究

压实作用被认为是影响填埋垃圾降解过程的一个重要因素,实验通过自制的压缩降解模拟填埋反应器装置,研究了阶梯增加式压力21k Pa→42 k Pa→84 k Pa(分别在垃圾填埋后的第75、103和131 d时施加)对填埋垃圾产甲烷这一资源化重要阶段的影响,包括产气特性、渗滤液性质及固体沉降等的变化.21 k Pa和42 k Pa分别恒定了4周,垃圾最后在84 k Pa恒定压力下降解,实验总共持续了170 d.结果表明,在初始21k Pa的压力作用下,由于接种物跟垃圾接触面积的增大,甲烷日产量从第75 d的1.85 L·d-1增加到了第76 d的2.95 L·d-1,产甲烷速率提高了59.82%,42 k Pa和84 k Pa时均有所增加,但增加程度均不明显.压力还使砾石层上部积留了一定水位高度的渗滤液,渗滤液的COD和含氮量在压力作用下都有了暂时的升高.压实作用还令垃圾体产生了较大的沉降,但压力进一步增大并没有使垃圾继续发生较多的沉降.实验结果有助于更好地了解压力对填埋垃圾降解过程的影响.     

A review of major factors influencing plant responses to recreation impacts

This article reviews some of the more important factors found to influence the susceptibility of plants to trampling impacts associated with recreational use of natural areas. A three-way interaction mediates plant responses to impacts: plant x environment x stress level(s). Plant responses vary in part according to the genetic constitution of the plant, life and growth form, the adaptive flexibility of the plant, and anatomical differences inherent to growth habit and morphology. Other factors that influence plant sensitivities to impacts are the habitat environments in which plants grow, since a number of conditions such as moisture excesses or deficiencies, nitrogen or oxygen starvation, late frosts, etc., cause physiological injury and may increase plant sensitivity to impacts. Among the environmental factors that may increase or lessen plant sensitivities to impacts are soil moisture levels, canopy density, elevation, aspect, microclimate, soil drainage, texture, fertility and productivity. Seasonal influences also bear consideration since environmental changes and phonological and physiological events are mediated by time of year. Stresses are caused by both direct and indirect forms of impact and vary according to season of use, frequency and amount of use, and the type of activity. These interactions are further complicated by evidence that inter- and intraspecific competition, antagonism, and commensalism may influence differences in the sensitivity of plant communities to impacts.     

油田污水处理水质影响因素与改善措施

随着油田开发阶段的延长,污水处理系统能力出现不足,排污系统和日常排污以及收油是影响油田污水处理水质的重要因素。针对这些因素提出利用人工湿地对洗井、修井污水进行处理,减轻水处理站压力,通过合理加药提高除油罐除油效率,从含油污水进口进行杀菌,防止对管线设备的腐蚀,防止细菌菌体堵塞过滤器,过滤后根据细菌监测结果再次进行杀菌,保证出水合格等改善措施。     

考虑采空区压实效应的沿空掘巷煤柱设计方法研究*

为建立1种相对科学的沿空掘巷煤柱尺寸设计方法,采用理论与数值试验研究、现场试验等手段,基于采空区压实效应,分析各尺寸煤柱沿空掘巷掘采全过程围岩应力分布与变形。研究结果表明:采空区压实效应模拟研究方法能够模拟采空区应力恢复;掘巷过程中,煤柱内应力由小到大依次为:工作面倾向水平应力、工作面推进方向水平应力、垂直应力,在小尺寸煤柱内呈偏向采空区一侧的单峰分布,小尺寸煤柱逐渐向大尺寸煤柱过渡期间,内部应力量值开始比原岩应力小,随后逐渐增加至出现一定的应力集中,而实体煤帮中峰值应力不断降低,位置逐步向巷帮转移;受超前采动作用后,更大面积的煤柱会受高应力作用,大尺寸煤柱内垂直及水平应力集中系数逐步提高,工作面倾向的高应力区范围更广,当煤柱宽度不超过一定数值时,内部应力大小均低于掘巷过程中相应数值,大煤柱则具有相反的规律,实体煤帮中应力集中系数与掘巷时相比更大,峰值点向围岩深处进一步转移;研究结果通过工程实践检验,可为合理煤柱尺寸设计提供1种新的方法。     

Ground flora trampling studies: Five years after closure

Trampling as an ecological factor is a major concern of the management of park, forest, nature preserves, and wilderness areas as recreational resources. Of particular importance to the management concept of carrying capacity is the relative resistance of native plant communities, to trampling and the resilience or the capacity of impacted communities to recover. This information can be used by management to establish seasonal use limits to prevent irreversible degradation of these resources. The purpose of this study was to follow the recolonizaton of experimental trail surfaces barren of vegetative cover and hiked at three levels of use intensity. Results of this study indicate that soil compaction as measured by soil penetration resistance increased progressively with use level while the total number of species, species diversity, and dominant index scores declined. A major finding was that the greatest degree of change occurred at the first level of hiking, indicating that major floristic measures were most affected by the least amount of hiking. Recolonization of impacted areas that received 100 trampling passes as measured by plant cover, dominant indices, floristic dissimilarity, and species diversity was similar to areas receiving four and eight times more trampling, despite major differences in soil penetration resistance. These data suggest limited use delivered at one time can be as damaging as increasing levels of use delivered at over time.     

风障联合压实防治煤堆自燃技术工艺参数优化

为提高煤堆自燃的防治效果,降低经济成本和提高施工的灵活性,基于煤堆自燃理论,使用COMSOLMultiphysics 5.0数值仿真软件,建立煤堆自燃模型,研究了煤堆最高温度和自然发火期变化及相关措施实施后最高温度降低规律,对比了单独压实、独立风障和风障联合压实的温度降低量,优化了联合措施的工艺。结果表明,煤堆孔隙率越小,自燃风速范围越宽,最小、最易、最大自燃风速越大;单独进行煤堆压实存在因孔隙率增加而降低的最低不宜风速;针对6 m高煤堆单独使用风障时,只有风障高12 m、距离煤堆25 m才能避免煤堆自燃;风障联合压实措施中,风障高7.5~9 m,设置距离煤堆10~30 m即能保证煤堆不自燃。说明联合的煤堆最高温度降低量更大,且能扩大压实的适用范围,降低风障高度,节约经济成本,增加风障现场施工的灵活性。     

Soil compaction--indicators for the assessment of harmful changes to the soil in the context of the German Federal Soil Protection Act

Soil compaction in agriculture induced by large-scale equipment is of growing concern. Heavy wheel loads used in arable cropping have the potential to cause irreversible damage to the subsoil structure and may lead to harmful soil compaction. In order to sustain or improve soil health or fitness on a sustainable basis, indicators are needed to assess the changes in the soil structure and the respective soil functions. This requires an adequate verification of methods for distinguishing between the impairment of soil structure and the disruption of soil functions, and for the respective subject of protection. In this article the link between existing models of soil physical prognosis, practical guidelines, and criteria for the identification of affected soil structure is demonstrated, and a viable concept to distinguish harmful changes to the soil is presented. The concept consists of methods for soil physical analysis such as "pre-compression stress" and "loading ratio", practical recommendations for best management practice, and an indicator-based model for the identification of harmful subsoil compaction derived from a research project for the German Federal Environmental Agency, making it possible to determine for a respective location the required level of action far beyond the common practice of precautions against harmful soil compaction.     

Settle3D软件在半填半挖黄土路基变形分析中的应用*

为揭示半填半挖黄土路基的变形规律及其影响因素,为高填方黄土路基稳定性的评估提供科学依据。以国道G310典型半填半挖黄土路基为例,运用Settle3D软件对不同工况条件下的黄土路基进行精确建模与系统分析。结果表明:自然条件下路基左右侧沉降量差别不大,而降雨条件下原状黄土侧的沉降大于压实黄土侧的沉降,土层交界处沉降差异显著;降雨条件下中心点的沉降曲线在原填土交界处发生转折,表明压实效果显著;各施工阶段间沉降量差值呈非线性减小趋势,但降雨条件下的稳定时间更长。因此施工中控制路基压实度和采取合理的路基防水排水措施非常重要。     

Polyelectrolyte Flocculation of Waste Activated Sludge in Decanter Centrifuge Applications: Lab Evaluation by a Centrifugal Compaction Test

Abstract This article introduces a centrifugal compaction (spin tube) test to thoroughly evaluate polyelectrolyte conditioning on lab scale. In contrast to the well-known and widely applied existing tests (e.g., the beaker, the Jar settling, the free drainage, and the [sheared] capillary suction time test), the proposed spin tube test has a clear relation with the dewatering process taking place in a decanter centrifuge. First, based on the theory of centrifugal compaction, the solids stress of separate layers of sludge cake (obtained after spinning sludge in a lab centrifuge) is calculated. Next, the test was applied to assess in the lab the performance of three different polymers by evaluating the obtained sludge dryness. To verify and/or compare the results obtained with the spin tube tests, sheared capillary suction time tests were conducted and floc size distributions were analyzed. Finally, two of the three polymers evaluated in the lab were applied in the industrial sludge dewatering and drying sys...