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1、,*,*,*,單擊此處編輯母版標題樣式,單擊此處編輯母版文本樣式,第二級,第三級,第四級,第五級,單擊此處編輯母版標題樣式,單擊此處編輯母版文本樣式,第二級,第三級,第四級,第五級,*,*,*,Unit 13 Text：Water Treatment Processes,自來水處理過程,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.
2、,現(xiàn)代化技術(shù)所取得的偉大成就之一就是極大的降低了霍亂和傷寒等水源性疾病的發(fā)生。,These diseases are no longer the great risks to pubic health that they once were.,這些疾病曾經(jīng)對人類的健康產(chǎn)生過巨大威脅，但現(xiàn)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 cou
3、ld be eliminated by more effective water treatment and better waste disposal.,進步的關(guān)鍵在于人們認識到被人為污染的公共水供應(yīng)是主要的傳染源，這可以通過更積極更先進的水處理技術(shù)所消除。,Todays water treatment plants are designed to provide water continuously that meets drinking water standards at the tap.,今天的水處理廠被設(shè)計為能持續(xù)的提供符合飲用水標準的水。,There are four man c
4、onsiderations involved in accomplishing this：sour selection,protection of water quality，treatment methods to be used，and prevention of recontamination.,有四個主要的方面要考慮：水源的選擇、水,質(zhì),的保護、所使用的處理方法和如何防止二次污染。,C,ommon precautions to prevent groundwater and surface water pollution include prohibiting the discharg
5、e 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.,一般的預(yù)防地下水污染和地表水污染的措施包括防止排泄物管道和雨水管道的排放口靠近蓄水池，安裝柵欄防止娛樂用水的污染，限制在水庫流域使
6、用化肥和殺蟲劑。,Screening，coagulation/flocculation，sedimentation,filtration，and disinfection are the main unit operations involved in the treatment of surface water.,隔離、混凝/絮凝、沉淀、過濾是地表水處理的四個主要步驟。,Water treatment operations fulfill one or more of three key tasks:removal of particulate substances such.as sand
7、 and clay，organic matter,bacteria，and algae；removal of dissolved substances such as those sing color and.Hardness;and removal or destruction of pathogenic bacteria and viruses.,水處理要實現(xiàn)一到三個目標：去除沙和塵土等顆粒物質(zhì)、有機物質(zhì)、微生物和藻類；去除引起色度和硬度的溶解物質(zhì)；去除或破壞致病細菌和病毒。,The actual selection of treatment processes depends on th
8、e type of water source and the desired water quality.,實際的處理工藝的選擇有賴于水源的類型和所需要的水質(zhì)。,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.,有時，不太混濁的進水可以通過自然沉降來去除較大的
9、顆粒，在利用過濾去除剩余的顆粒。,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，進水的顆粒物非常小，在短時間內(nèi)僅僅依靠沉淀和簡單的過濾無法去除。,To remedy this，a chemical is added to coagulate/flocculate the small particles,called colloids,in
10、to large ones,which can then be settled out in sedimentation tanks or removed directly in filters.,作為補救，將會加入膠體這種化學(xué)藥品來吸附小顆粒，形成大顆粒在沉淀池里析出，或在過濾池里直接去除。,Removal of Particulate Matter,顆粒物質(zhì)的去除,The unit operations employed for the removal of particulate matter from water include screening,sedimentation,coag
11、ulation/flocculation,and filtration.,從水中去除顆粒物的操作步驟包括隔離、混凝/絮凝、沉淀、過濾。,Screening,to remove large solids such as logs，branches,rags，and small fish is the first stage in the treatment of water.,隔離 去除像木屑、樹枝、碎布和小魚這樣的大的固體物的隔離過程是水處理的第一步。,Allowing such debris into the treatment plant could damage pumps and cl
12、og pipes and channels.,碎片萬一進入處理廠可能會損壞水泵，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.,同樣的原因，進水口一般設(shè)置在湖面和河水面以下，以免吸入漂浮物，最大程度的減少冰的破壞作用。,Sedimentation,，the oldest and most widely used
13、 form of water and wastewater treatment uses gravity settling to remove particles from water.,沉降是水和廢水處理中使用最古老最廣泛的處理方式，它是利用重力作用從水中去除顆粒物。,It is relatively simple and inexpensive and can be implemented in basins that are round，square，or rectangular.,它工藝相對簡單，造價低廉，可以造成圓形、正方形、矩形。,As noted earlier,sediment
14、ation may follow coagulation and flocculation(for highly turbid water)or be omitted entirely(with moderately turbid water).,就像前面提到的，對于濁度高的水，沉淀可以放在混凝后面，對于濁度不高的水，則可以完全省去該過程。,Particulates suspended in surface water can range in size from 10-to 10-mm in diameter,the size of fine sand and small clay part
15、icles，respectively.,地表水中的懸浮顆粒物的粒徑在10-1和10-7毫米之間，分別是細沙和微塵的尺寸。,Turbidity or cloudiness in water is caused by those particles larger than 10-4 mm,while particles smaller than 10-contribute to the waters color and taste.,濁度和不透明度是由那些粒徑大于10-4mm的顆粒引起的，小于10-4mm的顆粒主要對色度和臭味有貢獻。,Coagulation/flocculation,is a c
16、hemical-physical procedure whereby particles too small for practical removal by plain sedimentation are destabilized and clustered together for faster settling,混凝/絮凝 當(dāng)顆粒太小而用普通沉淀法無法去除時，利用混凝或絮凝的化學(xué)-物理過程，就可以讓這些顆粒物失去穩(wěn)定性，凝結(jié)成團，從而更快的得到沉降。,A significant percentage of particulates suspended in water are so small that settling to the bottom of a tank would take days or weeks.,水中相當(dāng)比例的懸浮顆粒物粒徑非常小，沉淀到池底需要數(shù)天甚至數(shù)周,。,These colloidal particles would never settle by plain sedimentation.,這些膠體狀的顆粒物都不能用普通沉淀法處理。,Coagula
環(huán)境科學(xué)專業(yè)外語Unit
