该【环境科学专业外语Unit13市公开课一等奖省赛课微课金奖PPT课件 】是由【286919636】上传分享，文档一共【20】页，该文档可以免费在线阅读，需要了解更多关于【环境科学专业外语Unit13市公开课一等奖省赛课微课金奖PPT课件 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。Unit 13 Text：Water Treatment Processes 自来水处理过程 1/20 One of the great achievements of modern technology has been to drastically reduce the incidence of waterborne of diseases such as cholera and typhoid fever. 当代化技术所取得伟大成就之一就是极大降低了霍乱和伤寒等水源性疾病发生。 These diseases are no longer the great risks to pubic health that they once were. 这些疾病曾经对人类健康产生过巨大威胁，但现在不是了。 The key to this advance was the recognition that contamination of pubic ware, supplies by human wastes was the main source of infection，and that it could be eliminated by more effective water treatment and better waste disposal. 进步关键在于人们认识到被人为污染公共水供给是主要传染源，这能够经过更主动更先进水处理技术所消除。 2/20 Today's water treatment plants are designed to provide water continuously that meets drinking water standards at the tap. 今天水处理厂被设计为能连续提供符合饮用水标准水。 There are four man considerations involved in accomplishing this：sour selection, protection of water quality，treatment methods to be used，and prevention of recontamination. 有四个主要方面要考虑：水源选择、水质保护、所使用处理方法和怎样预防二次污染。 Common precautions to prevent groundwater and surface water pollution include prohibiting the discharge of sanitary and storm sewers close to the water reservoir, installing fences to prevent pollution from recreational uses of water, and restrictions on the application of fertilizers and pesticides in areas that drain to the reservoir. 普通预防地下水污染和地表水污染办法包含预防排泄物管道和雨水管道排放口靠近蓄水池，安装栅栏预防娱乐用水污染，限制在水库流域使用化肥和杀虫剂。 3/20 Screening，coagulation/flocculation，sedimentation, filtration，and disinfection are the main unit operations involved in the treatment of surface water. 隔离、混凝/絮凝、沉淀、过滤是地表水处理四个主要步骤。 Water treatment operations fulfill one or more of three key tasks: removal of particulate substances such. as sand and clay，organic matter, bacteria，and algae；removal of dissolved substances such as those sing color ; and removal or destruction of pathogenic bacteria and viruses. 水处理要实现一到三个目标：去除沙和尘土等颗粒物质、有机物质、微生物和藻类；去除引发色度和硬度溶解物质；去除或破坏致病细菌和病毒。 4/20 The actual selection of treatment processes depends on the type of water source and the desired water quality. 实际处理工艺选择有赖于水源类型和所需要水质。 Occasionally，raw water with low turbidity can be treated by plain sedimentation (no chemicals) to remove larger particles and then filtration to remove the few particles that failed to settle out. 有时，不太混浊进水能够经过自然沉降来去除较大颗粒，在利用过滤去除剩下颗粒。 Usually, however, particles in the raw water are too small to be removed in a reasonably short time through sedimentation and simple filtration alone. 但通常，进水颗粒物非常小，在短时间内仅仅依靠沉淀和简单过滤无法去除。 5/20 To remedy this，a chemical is added to coagulate/flocculate the small particles, called colloids, into large ones, which can then be settled out in sedimentation tanks or removed directly in filters. 作为补救，将会加入胶体这种化学药品来吸附小颗粒，形成大颗粒在沉淀池里析出，或在过滤池里直接去除。 Removal of Particulate Matter 颗粒物质去除 The unit operations employed for the removal of particulate matter from water include screening, sedimentation, coagulation/flocculation, and filtration. 从水中去除颗粒物操作步骤包含隔离、混凝/絮凝、沉淀、过滤。 6/20 Screening to remove large solids such as logs，branches, rags，and small fish is the first stage in the treatment of water. 隔离 去除像木屑、树枝、碎布和小鱼这么大固体物隔离过程是水处理第一步。 Allowing such debris into the treatment plant could damage pumps and clog pipes and channels. 碎片万一进入处理厂可能会损坏水泵，阻塞管道。 For the same reasons，water intakes are located below the surface of the lake or river in order to exclude floating objects and minimize physical damage from ice. 一样原因，进水口普通设置在湖面和河水面以下，以免吸入漂浮物，最大程度降低冰破坏作用。 7/20 Sedimentation，the oldest and most widely used form of water and wastewater treatment uses gravity settling to remove particles from water. 沉降是水和废水处理中使用最古老最广泛处理方式，它是利用重力作用从水中去除颗粒物。 It is relatively simple and inexpensive and can be implemented in basins that are round，square，or rectangular. 它工艺相对简单，造价低廉，能够造成圆形、正方形、矩形。 As noted earlier, sedimentation may follow coagulation and flocculation (for highly turbid water) or be omitted entirely (with moderately turbid water). 就像前面提到，对于浊度高水，沉淀能够放在混凝后面，对于浊度不高水，则能够完全省去该过程。 Particulates suspended in surface water can range in size from 10- to 10- mm in diameter, the size of fine sand and small clay particles，respectively. 地表水中悬浮颗粒物粒径在10-1和10-7毫米之间，分别是细沙和微尘尺寸。 8/20 Turbidity or cloudiness in water is caused by those particles larger than 10-4 mm, while particles smaller than 10-' contribute to the water's color and taste. 浊度和不透明度是由那些粒径大于10-4mm颗粒引发，小于10-4mm颗粒主要对色度和臭味有贡献。 Coagulation/flocculation is a chemical-physical procedure whereby particles too small for practical removal by plain sedimentation are destabilized and clustered together for faster settling． 混凝/絮凝 当颗粒太小而用普通沉淀法无法去除时，利用混凝或絮凝化学-物理过程，就能够让这些颗粒物失去稳定性，凝结成团，从而更加快得到沉降。 9/20 A significant percentage of particulates suspended in water are so small that settling to the bottom of a tank would take days or weeks. 水中相当百分比悬浮颗粒物粒径非常小，沉淀到池底需要数天甚至数周。 These colloidal particles would never settle by plain sedimentation. 这些胶体状颗粒物都不能用普通沉淀法处理。 Coagulation is a chemical process used to destabilize colloidal particles. 混凝是使胶体颗粒失去稳定一个化学过程。 The exact mechanism is not well understood，but the general idea is to add a chemical which has positively charged colloids to water containing negatively charged colloids. 准确机理不太好了解，但大致意思就是添加一个含有正电荷胶体化学药品到含有负电荷胶体水中。 10/20
