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411.
Technical developments have now made it possible to emplace granular zero-valent iron (Fe(0)) in fractured media to create a Fe(0) fracture reactive barrier (Fe(0) FRB) for the treatment of contaminated groundwater. To evaluate this concept, we conducted a laboratory experiment in which trichloroethylene (TCE) contaminated water was flushed through a single uniform fracture created between two sandstone blocks. This fracture was partly filled with what was intended to be a uniform thickness of iron. Partial treatment of TCE by iron demonstrated that the concept of a Fe(0) FRB is practical, but was less than anticipated for an iron layer of uniform thickness. When the experiment was disassembled, evidence of discrete channelised flow was noted and attributed to imperfect placement of the iron. To evaluate the effect of the channel flow, an explicit Channel Model was developed that simplifies this complex flow regime into a conceptualised set of uniform and parallel channels. The mathematical representation of this conceptualisation directly accounts for (i) flow channels and immobile fluid arising from the non-uniform iron placement, (ii) mass transfer from the open fracture to iron and immobile fluid regions, and (iii) degradation in the iron regions. A favourable comparison between laboratory data and the results from the developed mathematical model suggests that the model is capable of representing TCE degradation in fractures with non-uniform iron placement. In order to apply this Channel Model concept to a Fe(0) FRB system, a simplified, or implicit, Lumped Channel Model was developed where the physical and chemical processes in the iron layer and immobile fluid regions are captured by a first-order lumped rate parameter. The performance of this Lumped Channel Model was compared to laboratory data, and benchmarked against the Channel Model. The advantages of the Lumped Channel Model are that the degradation of TCE in the system is represented by a first-order parameter that can be used directly in readily available numerical simulators. 相似文献
412.
长江流域平原区水网密布、渔业发达,养殖池塘造成的氮磷污染问题突出,是河湖富营养化的重要污染源之一;从大空间尺度,精细化估算养殖池塘的氮磷污染负荷,对水污染的精准防控具有重要意义.以长江流域为研究区,依托Google Earth Engine遥感大数据平台,构建了基于机器学习算法的养殖池塘识别模型,精细化识别了长江流域养殖池塘的分布与类型;梳理养殖坑塘的氮磷污染研究案例,针对长江流域养殖坑塘的特征,构建氮磷污染负荷的估算方法,评估氮磷污染负荷的时空分布.研究结果表明:2021年,长江流域养殖池塘总面积为14567km2,包括鱼塘5820 km2、虾蟹塘8747 km2、氮磷排放量分别为95059、16224 t;中部地区的氮磷污染负荷最大,东部地区次之,西部地区最小.本研究是遥感大数据在大尺度污染负荷定量分析的尝试应用,方法适用于其它类型污染负荷的估算. 相似文献
413.
414.
在白银露天矿污染气象站五年的污染气象观测基础上,分析了采场粉尘浓度与污染源强度和气象因素之间的相关性,提出了粉尘污染预报的模式和方法,其准确率达到66.9%。并以粉尘污染预报模式为依据。提出了污染源控制管理模式。试验表明利用本模式对污染源实施控制管理具有实用意义和价值。 相似文献
415.
活性碳纤维在环境保护的应用 总被引:6,自引:0,他引:6
蔡体凯 《城市环境与城市生态》1992,5(3):44-47
活性碳纤维与普通活性碳相比,具有微孔多、孔径分布窄、比表面积大、吸附和脱附速度快,可制成纱、布、毡等形式,是吸附性、机械性能较好的新型吸附材料.可以广泛用于溶剂回收、脱臭装置、废水、废气处理、防毒面具等.活性碳纤维装置重量轻、占地少,回收溶剂质量高、操作简易,很有发展前途. 相似文献
416.
417.
Performance of Trickle-Bed Air Biofilter: A Comparative Study of a Hydrophilic and a Hydrophobic Voc
Two lab-scale trickle-bed air biofilters were operated for investigating the difference in performance between a hydrophilic
and a hydrophobic volatile organic compound (VOC). Methyl isobutyl ketone (MIBK) and styrene were selected as a model hydrophilic
and hydrophobic VOCs, respectively. Effects of loading rates, biofilter re-acclimation, removal profile along biofilter depth,
nitrogen consumption, and CO2 production were compared under three operating conditions, namely, backwashing and two non-use periods (starvation and stagnant).
Consistent over 99% removal efficiency up to loading rates of 3.26 kg COD/m3-day was obtained for the MIBK biofilter at 0.76 min empty bed retention time (EBRT) and 1.5 L/d nutrient flow. A similar
performance for the styrene biofilter was obtained for loading rates up to 1.9kg COD/m3-day at 2.02 min EBRT and 2.4 L/d nutrient flow. The MIBK biofilter required only an initial acclimation period of 16 days
while styrene biofilter required 46 days. Non-use periods can be used as another means of biomass control for both biofilters
when the employed loading rate did not exceed 1.27 and 2.17 kg COD/m3-day for styrene and MIBK biofilters, respectively. The re-acclimation of both biofilter was delayed with increase of loading
rate. MIBK biofilter re-acclimated in 90 min, while styrene biofilter re-acclimated in more than 600 min. Under similar loading
rates, MIBK biofilter utilized less biofilter depth than styrene biofilter. Nitrogen consumption behaviors were apparently
different between the two biofilters. Styrene biofilter had higher CO2 production than MIBK biofilter and its CO2 production was closely related to the theoretical complete chemical oxidation. 相似文献
418.
通过对溜矿井卸矿点产尘及其特点的研究 ,提出了一种独特的防尘思维模式 ,并有针对地设计出一种自净式喷雾装置 ,适用效果良好。 相似文献
419.
420.