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 共查询到10条相似文献,搜索用时 281 毫秒
1.
Gao W  Smith DW  Li Y 《Water research》2006,40(12):2321-2326
Inactivation capacity of E. coli (strain ATCC 15597) in water by natural freezing was examined via two freezing methods: spray freezing and freezing in a freezer. The effect of freezing temperature (-5, -15 and -35 degrees C), storage time, freeze-thaw cycles on the survival of the test organism were investigated. In addition, the number of cells injured by the freezing process was also examined by using different growth media. The bacteria frozen at the warmer temperature (-5 degrees C) was most sensitive to storage and freeze-thaw cycles as compared to those frozen at -15 and -35 degrees C. In general, greater inactivation efficiencies were achieved under longer storage time and warmer freezing temperature conditions. Freezing and thawing caused cell injury. More cells were injured when frozen at -15 degrees C. The percentage of cells injured decreased as freeze-thaw cycles increased. The spray-freezing process was found more effective in killing the cells. On average, the log reduction rate for the spray ice with two-day storage time was about 4 log units higher than those without any storage after freezing. The results indicated that the natural freezing processes are not only cost-effective techniques for chemical and physical contaminant removal from wastewater or enhancing sludge dewaterability in cold regions but also effective in reducing E. coli concentration.  相似文献   

2.
电镀中常用的酸铜工艺的水洗废水为强酸性,pH值超过了反渗透膜允许的范围,无法应用反渗透法进行浓缩回用于电镀槽。为此,采用全新的过冷水动态制冰技术,对酸铜工艺电镀水洗废水进行冷冻法处理。结果表明,一次冷冻结晶冰融水的溶质去除率超过90%,可满足一级水洗槽补充水洗水的要求;二次冷冻浓缩液达到电镀槽电镀液浓度的80%,可回用于电镀槽补充电镀液。  相似文献   

3.
Rolf Halde 《Water research》1980,14(6):575-580
Attention is drawn to the exceedingly useful, but often neglected freezing method for the concentration of aqueous solutions and suspensions or sludges. The use of freezing is based on the fact that when ice is crystallized from an aqueous solution or suspension, the crystal is built up by pure water, leaving the impurities in the remaining liquid.The fundamental phenomenon of the interaction between a solute or suspended particle and an ice-water interface during freezing is described extensively. The presented experimental work reveals the fact that particles of different kinds, sizes and shapes interact in different ways with the solid-liquid interface. Variables such as freezing rate, applied shear forces, and added chemicals strongly affect the impurity migration.  相似文献   

4.
When wastewater containing only soluble pollutants is frozen gradually, ice crystals grow from the pure water only, while pollutants are rejected into the liquid phase thus increasing their concentration. In this way, pure water can be removed from various wastewaters. Two kinds of wastewater were studied: synthetic wastewater containing water and one or more soluble pollutants, and industrial wastewaters (urban wastewater and cutting oil wastewater). In most cases, separation efficiency close to 100% was achieved. A large range of pollutant concentrations was studied in order to determine the limits of freezing separation.  相似文献   

5.
原状土冻融过程中水分迁移试验研究   总被引:7,自引:0,他引:7       下载免费PDF全文
赵刚  陶夏新  刘兵 《岩土工程学报》2009,31(12):1952-1957
为了量化原状土中水分在冻融过程中的迁移,试验采取在其他试验条件相同的条件下,改变初始含水率或温度模式的方法,研究了单个因素对水分迁移的影响。经冻结并融化到设定位置后,从试验中观察到试样未融化部分存在有横向和竖向的裂缝现象、明显的冻融分界线、水分积聚层和融化锋面并不在同一个层面内、土中水的冻结温度各不相同、冻结后含冰不均匀现象等结果,进而对冻融过程中进行温度场分析以及冻融前后含水率的变化分析,用具体试验数据得出如下结论:控制不同顶板温度时,不同含水率的试样中各点处温度的变化趋势基本相同;在顶板控温相同的情况下,初始含水率大的试样,水分迁移量大,水分积聚多;不同冻结温度和融化温度对试样中水分的迁移影响非常明显,顶板冻结时温度越高,水分积聚层位置处的含水率越大,水分积聚越多等。  相似文献   

6.
通过对小清河(济南段)流域内干、支流水量及水质的实地排查和检测,分析了小清河(济南段)水质污染规律,并采用MIKE11软件对小清河(济南段)进行了河道水动力和水质模拟,构建了小清河流域的降雨径流模型(NAM)、一维水动力模型(HD)和对流扩散模型(AD)。通过模型运算分析了小清河各类污染源的污染权重值,结果如下:小清河现状水源(污染源)中,污染贡献程度排序为污水厂(站)尾水(34.0%)>雨水径流(33.0%)>直排污水(29.1%);水量贡献程度排序为污水厂(站)尾水(58.8%)>雨水径流(26.1%)>直排污水(5.5%);削减难易程度排序为直排污水>污水厂(站)尾水>雨水径流。  相似文献   

7.

Water-bearing porous rocks can be greatly strengthened by freezing; its microscopic mechanisms lie in how subzero temperature modifies pore structure but have not yet been clearly defined. In this study, we link the mechanical properties of frozen sandstone to phase composition of pore water (i.e., relative amount of unfrozen water and ice). Both the strength (uniaxial compressive strength and tensile strength) and the phase composition of pore water (tested through the nuclear magnetic resonance (NMR) method) of frozen sandstone at nine subzero temperatures were measured. The results showed the following: (1) subzero temperature strengthened saturated sandstone significantly, both the strengths increased in a three-stage mode and each stage showed an approximately linear trend as temperature decreased from 0 to – 20 °C; and (2) change of phase composition with freezing displayed two distinct stages: the rapid decreasing stage of unfrozen water content (0 to – 4 °C), when bulk water and capillary water froze almost completely, and the slow decreasing stage (? 4 to – 20 °C), when adsorbed water froze partially. Based on direct observations on microscopic pore structure of sandstone and detailed discussion on the mechanical interactions between water, ice, and pore wall, phase composition may modify the mechanical properties of frozen rocks through the following effects: the supporting effect of ice under compression, the crack-filling effect of ice, the cementing effect of unfrozen water film under tension or under shearing load, and the frost damage effect. The former three are strengthening effects, while the latter one is weakening effect.

  相似文献   

8.
混凝土盐冻破坏机理(Ⅱ):冻融饱水度和结冰压   总被引:3,自引:1,他引:2  
研究了冻融循环条件下NaCl浓度(质量分数)对混凝土内部吸入溶液量和饱水度、溶液结冰膨胀率和结冰压的影响,继而对混凝土盐冻破坏机理进行分析.结果表明:随着NaCl浓度的增加,溶液结冰膨胀率和结冰压平衡值显著降低,但溶液结冰产生结冰压的临界饱水度显著提高;在NaCl溶液中进行冻融循环时,混凝土内部饱水度明显高于水中,且饱水度的增长主要取决于冷冻阶段吸入溶液量,与融化阶段关系很小;2%~6%NaCl溶液将产生最大结冰压,因此中低盐浓度引起的混凝土盐冻破坏最严重.  相似文献   

9.
冻融循环导致洛川黄土边坡剥落病害产生机制的试验研究   总被引:3,自引:0,他引:3  
 冻融循环作用导致洛川黄土边坡剥落病害的发生。作为对比,在洛川剥落边坡及铜川未剥落边坡分别采样,模拟自然坡面冻融过程,在开放不补水条件下,开展冻融循环试验,测定在冻融循环作用下土样表面的变化特征及土样高度、干密度、含水率、黏聚力及内摩擦角的变化情况。试验结果表明:洛川土样在初始几次冻融过程中,土样体积稍有增大,含水率变化较大,冻结过程中冰晶冻胀力破坏土体结构,融化时结构不可恢复,反复冻融导致土体强度弱化。冻融循环10次左右后,土体物理力学状态趋于稳定。融化时,在水的软化作用和冰的促化效应下,沿着水冰交界面易产生剥落病害;铜川土样在冻结过程中,在冻结缘处产生负孔隙水压力,土体密度增大,体积减小,强度增大;融化时,有效应力减小,总应力不变,融沉量大于冻胀量,土体黏聚力略有增强,不易产生剥落。  相似文献   

10.
为了探究大尺寸富水卵砾石样冻结状态下单轴抗压强度与冻结温度的关系,以南宁市地铁1号线民族大学—青川站区间联络通道富水卵砾石样为研究对象,自研大尺寸模具制备试样,通过GCTS试验平台对试样进行单轴抗压试验,探究试样强度与冻结温度的相互作用关系。试验结果表明:试样抗压强度随着冻结温度的降低不断增加,试样承载能力不断增强,由2.18 MPa增长到3.1 MPa,试验轴应变随着冻结温度的降低不断减小;冻结状态下,卵砾石试样强度主要受冰的强度、冰卵砾石连接强度以及试样中未冻水含量的影响,在一定范围内,降低冻结温度冰强度增强、冰卵砾石连接强度增强、未冻水含量减小,黏聚力提高,内摩擦角略微增大,造成卵砾石试样随着冻结温度的降低强度不断增强;卵砾石试样达到最大抗压强度时轴应变随着冻结温度的降低不断减小,由7.4%降低到3.2%,表明试样随着冻结温度的降低,脆性增强延性减弱,试样破坏趋向于脆性破坏。  相似文献   

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