Effects of iron surface pretreatment on sorption and reduction kinetics of trichloroethylene in a closed batch system

The decline of trichloroethylene (TCE) in a metallic iron-water system results from the combination of reduction reaction and sorption onto iron surfaces. Sorption, particularly by highly impure iron, accelerates the removal of TCE from the aqueous phase, but delays the prevalence of steady-state conditions. In this case, an overly high value of reaction rate constant in the design of a treatment system would be used. In this work, the effects of an iron surface with 8.0% C, 6.1% O and 0.8% Si separately following HCl-washing and H2-reducing pretreatment on sorption and reduction rates were examined. The amounts of both aqueous and sorbed TCE were measured using a modified solvent-extraction method. TCE sorption onto an iron surface, as quantified by the Langmuir sorption maximum, followed the trend H2-reduced Fe0 > HCl-washed Fe0 > untreated Fe0 (0.887, 0.365 and 0.311 mg/g, respectively). Measurements of the concentration of sorbed TCE revealed that about 34-37% of the initial mass of TCE in the aqueous phase was removed by sorption by H2-reduced Fe0, 16-19% was removed by HCl-washed Fe0 and 13-16% was removed by untreated Fe0. A combination of new and previously reported data on cast iron's capacity to sorb TCE revealed a linear relationship between this capacity and the C fraction in the surface of the iron, with the coefficient of determination (r2) exceeding 0.99. The first-order observed rate constants (k(obs)) of the reduction of TCE in contact with Fe0 were obtained from the slope of a plot of total TCE loss rate (-dC(T)/dt) versus the amount of TCE in the aqueous phase (C(w)) using linear least-squares analysis. The k(obs) values were 0.080, 0.148 and 0.191 h(-1) for untreated, HCl-washed and H2-reduced Fe0, respectively. Normalized to iron surface area concentration, the specific rate constants (k(SA)) were 2.3 7x 10(-3) , 2.31 x 10(-3) and 5.62 x 10(-3) h(-1) m(-2) L, respectively. The results indicated that HCl-washing approximately doubled k(obs), primarily because of the increase in the surface area of the iron, and it slightly decreased k(SA) due to rapid corrosion during the rinsing process. Both the number of reactive sites and the sorption capacity per unit iron surface area through the H2-reducing pretreatment were increased due to the reduction of iron oxide layer and the carbonization of carbon-containing subjects on the iron's surface. Hence, the H2 reduction of cast iron promotes the removal of TCE from contaminated water by the concurrent sorption and reduction.     

高锰酸钾预处理微污染地表水研究

通过生产性试验考察了高锰酸钾预处理工艺对地表水中有机物、氨氮、铁、锰等污染物的去除效果,并与预氯化工艺进行了对比。结果表明,高锰酸钾预处理在减少铁锰污染、去除氨氮、降低有机物含量等方面具有比预氯化更好的效果。     

混凝/微滤用于反渗透海水淡化的预处理

考察了混凝/微滤工艺用于反渗透海水淡化预处理的可行性,并通过调整FeCl3和粉末活性炭(PAC)投量来确定最佳运行条件。结果表明,当FeCl3投量为2.5mg/L(以Fe3 计)、PAC耗量为40mg/L时处理效果最好,出水浊度<0.1NTU,污泥淤塞指数SDI<1.5,CODMn平均去除率为24%,满足反渗透的进水水质要求。此外,混凝及PAC的吸附作用可使海水中粒径<0.22μm的颗粒物变大,从而被微滤膜截留,这是出水水质良好的保证。     

瓷珠曝气生物滤池去除源水中氨氮研究

采用以瓷珠为填料的曝气生物滤池(BAF)预处理某高氨氮源水,结果表明,在气水比为1∶1、滤速为5. 5m/h、水温>10℃的条件下,当进水氨氮<5mg/L时BAF对氨氮的去除率为70% ~90%,反应器中存在一定的亚硝酸氮积累;反冲洗周期对氨氮的去除率有较大影响。     

深度处理污染河水的反渗透膜污染特性与防治

对以受污染河水为原水的反渗透系统膜污染问题进行了分析，初步认定反渗透膜污染是以生物粘泥、铁的氧化物及有机物为主的综合污染，而预处理的不完善、清洗方案选择不合理以及杀菌措施不够是导致膜污染的主要原因，最后提出了相应的解决办法。     

取样扰动对土的工程性质指标影响的试验研究

本文报道了取样扰动对土的工程性质指标影响的一批研究成果。采用100mm和75mm两种直径的取土器取样作对比试验以研究取土器扰动的影响。试验证明取土器直径对试样的孔隙比、压缩系数、超固结比和天然强度等指标都有明显的影响。采用两种预固结处理的方法以恢复原生应力状态,用不固结不排水试验比较了应力状态对天然强度的影响。对取土过程中土体应变的分布及其对土样扰动的影响用有限元方法进行了模拟。     

炼油废水的物化预处理工艺研究

对炼油废水的物化预处理工艺进行了研究，比较了分别投加5种不同混凝剂的混凝沉淀效果。结果表明：SHY-Ⅲ型混凝剂与PAM配合投加时对浊度和COD的去除效果最好；投加电解质CaCl2后破乳效果显著；混凝剂和CaCl2的投加量对混凝效果均有影响。对混凝沉淀出水采用气浮或超滤工艺进行处理可进一步去除废水中的乳化油，但对溶解性COD的去除作用微弱。经过物化预处理后，废水中大量有毒、难降解的有机物被去除，可生化性大大提高。     

生物接触氧化/气浮、生物滤地/沉淀处理地表水比较

为筛选出合适的滴水湖补充水的处理工艺,开展了"生物接触氧化+气浮"(工艺1)和"生物滤池+沉淀"(工艺2)两种组合工艺处理地表源水的中试研究(规模为20 m3/h).结果表明,生物接触氧化池对藻类、叶绿素a和氨氮的去除效果比生物滤池好,但二者对浊度、总磷、CODMn的去除效果相差不大;工艺1去除浊度、藻类、叶绿素a、总磷、氨氮和CODMn的效果较工艺2好,且对污染物的去除效果受混凝剂投加量的影响较小.     

浅谈游泳池设计

本文就游泳池设计中水源预处理、水循环处理、恒温手段等三个方面进行比较, 讲述了现在游泳池设计中的主要作法以及各自的优缺点。     

基于小波预处理的EMD算法静态寻北信号分析

针对直接应用EMD算法处理寻北信号的不可靠性,提出了基于小波预处理的EMD分解方法,并对传统小波阈值去噪分析方法做一改进,提出一种相关系数和3.0准则的自适应阈值方法。新方法规避了直接应用EMD过程中存在的模态混叠问题,并有效提取了寻北信号的误差信息和有用信息,能够用于某型磁悬浮陀螺寻北仪的寻北研究中。