污水處理外文翻譯---污水的生物處理過程

1、<p><b>　　附錄Ⅰ：</b></p><p>　　Wastewater Biological Treatment Processes</p><p>　　The objective of wastewater treatment is to reduce the concentration of specific pollutants to the

2、level at which the discharge of the effluent will not adversely affect the environment or pose a health threat. Moreover , reduction of these constituents need only be to some required level.</p><p>　　For an

3、y given wastewater in a specific location , the degree and type of treatment are variables that require engineering decisions . often the degree of treatment depends on the assimilative capacity of the receiving water .

4、DO sag curves can indicate how much BOD must be removed from wastewater so that the DO of receiving water is not depressed too far . The amount of BOD that must be removed is an effluent standard and dictates in large pa

5、rt the type of wastewater treatment required .</p><p>　　To facilitate the discussion of wastewater , assume a “ typical wastewater ”and assume further that the effluent from this wastewater treatment must me

6、et the following effluent standards :</p><p>　　BOD≤15mg/L</p><p><b>　　SS≤15mg/L</b></p><p><b>　　P≤1mg/L</b></p><p>　　Additional effluent standar

7、d could have been established , but for illustrative purposes we consider only these three . The treatment system selected to achieve these effluent standards includes </p><p>　　1. Primary treatment : physic

8、al processes that nonhomogenizable solids and homogenize the remaining effluent .</p><p>　　2. Secondary treatment : biological process that remove most of the biochemical demand for oxyen .</p><p&

9、gt;　　3. Tertiary treatment : physical , biological , and chemical processes to remove nutrients like phosphorus and inorganic pollutants , to deodorize and decolorize effluent water , and to carry out further oxidation .

10、</p><p>　　Primary treatment </p><p>　　The most objectionable aspect of discharging raw sewage into watercourses is the floating material . Thus screen were the first form of wastewater treatment

11、 used by communities , and they are used today as the first step in treatment plants .Typical screens consist of a series bars that might be about 2.5 cm apart . A screen in a modern treatment plant removes might damage

12、equipment or hinder further treatment . in some older treatment plants are cleaned by hand , but mechanical cleaning equipme</p><p>　　In many plants , the second treatment step is a comminutor , a circular g

13、rinder designed to grind the solids coming through the screen into pieces about 0.3 cm or less in diameter .</p><p>　　The third treatment step is the removal of grit or sand from the wastewater . Grit and sa

14、nd can damage equipment like pumps and flow meters and must be removed . The most common grit chamber is a wide place in the channel where the flow is slowed enough to allow the dense grit to settle out . Sand is about 2

15、.5 times dense than most organic solids and thus settles much faster . The objective of a grit chamber is to remove sang and grit without removing organic material .Organic material must be t</p><p>　　Most w

16、astewater treatment plants have a settling tank after the grit chamber , to settle out as much material as possible . Accordingly , the retention time is long and turbulence is kept to a minimum .</p><p>　　T

17、he solids settle to the bottom of the tank and are removed though a pipe , while the clarified liquid escapes over a V-notch weir that distributes the liquid discharge equally all the way around a tank . Settling tanks a

18、re also called sedimentation tank or clarifiers . The settling tank that immediately follows screening and grit removal is called the primary clarifier . The solids that drop to the bottom of a primary clarifier are remo

19、ved as raw sludge .</p><p>　　Raw sludge generally has a powerfully unpleasant odor , is full of pathogenic , and is wet , three characteristics that make its disposal difficult . It must be stabilized to ret

20、ard further decomposition and dewatered for ease of disposal .</p><p>　　The objective of primary treatment is the removal of solids , although some BOD is removed as a consequence of the removal of decomposa

21、ble solids .</p><p>　　A substantial fraction of the solids has been removed , as well as some BOD is a little P , as a consequence of the removal of raw sludge . After primary treatment the wastewater may mo

22、ve on to secondary treatment .</p><p>　　Secondary Treatment</p><p>　　Water leaving the primary clarifier has not lose much of the solid organic matter but still contains high-energy molecules th

23、at decompose by microbial action , creating BOD . The demand for oxygen must be reduce (energy wasted ) or else the discharge may create unacceptable condition in the receiving waters . The objective of secondary treatme

24、nt is to remove BOD , where the objective of primary treatment is to remove solids .</p><p>　　The trickling filter consists of a filter bed of fist-sized rocks or corrugated plastic blocks over which the was

25、te is trickled . The name is something of a misnomer since no filtration takes place . A very active biological growth forms on the rocks , and these organisms obtain their food from the waste stream dipping through the

26、rock bed . Air either is forced through the rocks or circulates automatically because of the difference between the air temperature in the bed and ambient temperatures</p><p>　　Trickling filtration was a wel

27、l-established treatment system at the beginning of the twentieth century . in 1914 , a pilot plant was built for a different system that bubbled air through free-floating aerobic microorganisms , a process which became k

28、nown as the activated sludge system . The activated sludge process differs from trickling filtration in that the microorganisms are suspended in the liquid .</p><p>　　An activated sludge system includes a ta

29、nk full of waste liquid from the primary clarifier and a mass of microorganisms . Air bubbled into this aeration tank provides the necessary oxygen for survival of the aerobic organisms . The microorganisms come in conta

30、ct with dissolved organic matter in the wastewater . adsorb this material , and ultimately decompose the organic material to CO2 , HO2 ,some stable compounds , and more microorganisms .</p><p>　　When most of

31、 the organic material , that is , food for the microorganisms , has been used up , the microorganisms are separated from the liquid in a settling tank , sometimes called a secondary or clarifier . The microorganisms rema

32、ining in the settling tank have no food available , become hungry , and are thus activated-hence the term activated sludge . The clarified liquid escapes over a weir and may be discharged into the receiving water . The s

33、ettle microorganisms , now called return activat</p><p>　　Activated sludge treatment produces more microorganisms than necessary and if the microorganisms are not removed , their concentration will soon incr

34、ease and clog the system with solids . Some of the microorganisms must therefore be wasted and the disposal of such waste activated sludge in one of the most difficult aspects of wastewater treatment .</p><p&g

35、t;　　Activated sludge system are designed on the basis of loading , or the amount of organic matter , or food , added relative to the microorganisms available . The food-to-microorganisms (F/M) ratio is major design param

36、eter . Both F and M are difficult to measure accurately , but may be approximated by influent BOD and SS in the aeration tank , respectively . The combination of liquid and microorganisms undergoing aeration is known as

37、mixed liquor , and the SS in the aeration tank are mixed liquid </p><p>　　Relatively small F/M ,or little food for many microorganisms , and a long aeration period (long retention time in the tank ) result i

38、n a high degree of treatment because the microorganisms can make maximum use of available food . Systems with these features are called extended aeration systems and are widely used to treat isolated wastewater source ,

39、like small developments or resort hotels . Extended aeration systems create little excess biomass and little excess activated sludge to dispose of </p><p>　　The success of the activated sludge system also de

40、pends on the separation of the microorganisms in the final clarifier . when the microorganisms do not settle out as anticipated , the sludge is said to be a bulking sludge , Bulking is often characterized by a biomass co

41、mposed almost totally of filamentous organisms that from a king of lattice structure within the sludge floes which prevents settling . A trend toward poor settling may be the forerunner of a badly upset and ineffective s

42、ystem . Th</p><p>　　Tertiary Treatment </p><p>　　The effluent from secondary treatment meets the previously established effluent standards for BOD and SS . only phosphorus content remains high .

43、 The removal of inorganic compounds , including inorganic phosphorus and nitrogen compounds , requires advanced or tertiary wastewater treatment .</p><p>　　Primary and secondary (biological) treatment are a

44、part of conventional wastewater treatment plants . However , secondary treatment plant effluents are still significantly polluted . some BOD and suspended solids remain , and neither primary nor secondary treatment is ef

45、fective in removing phosphorus and other nutrients or toxic substances . A popular advanced treatment for BOD removal is the polishing pond , or oxidation pond , commonly a large lagoon into which the secondary effluent

46、flows . s</p><p>　　BOD may also be removed by activated carbon adsorption , which has the added advantage of removing some is a completely enclosed tube , which dirty water is pumped into bottom and clear wa

47、ter exits at the top . microscopic crevices in the carbon catch and hold colloidal and smaller particles . As the carbon column becomes saturated , the pollutants must be removed from the carbon and the carbon reactivate

48、d , usually by heating it in the absence of oxygen . Reactivated or regenerated carbon is so</p><p><b>　　附錄Ⅱ：</b></p><p><b>　　污水的生物處理過程</b></p><p>　　物水處理的目的是

49、降解特定污染物的濃度使其達到污水排放不影響環(huán)境或形成健康威脅的程度，而且降低這些成分僅僅需要達到要求大的水平即可。</p><p>　　應(yīng)為任何給定的污水在來源，處理程度和類型方面是變化的，而這種變化是由工業(yè)決定的，而且處理程度往往依賴接納水體的同化能力。氧垂曲線能顯示多少BOD必須從污水中去除以致于使接納水體的溶解氧不致降低太多。在大部分的污水處理要求的類型中，必須被去除的BOD數(shù)量是污水的一個標準和指標。&l

50、t;/p><p>　　為了便于討論污水，假定一種“典型的污水”而且假定這種污水通過處理必須達到以下的污水標準：</p><p>　　BOD ≤ 15 mg/L</p><p>　　SS ≤ 15 mg/L</p><p>　　P ≤ 1 mg/L</p><p>　　增加的污水標準應(yīng)該被列出，但是為了說明目的我們僅僅考慮這

51、三項。能達到這些污水標準的處理系統(tǒng)包括：</p><p>　　初級處理：固體物質(zhì)非均勻化和污水排放均勻化的物理過程。</p><p>　　二級處理：依靠氧去除大部分生化物質(zhì)的生物處理過程。</p><p>　　三級處理：物理，生物和化學過程的目的就是去除營養(yǎng)物質(zhì)，像磷和有機物等，而且去除污水的臭味，色度和更多的氧化物。</p><p><

52、;b>　　初級處理</b></p><p>　　排放原污水到水域中最厭惡的一個方面是其中的漂浮物，因此，格柵被用在社區(qū)污水處理的首要位置，現(xiàn)在它們被作為處理方案的第一步，典型的格柵由一系列的鋼條組成，這些鋼條之間大約相距2.5cm，在現(xiàn)代的處理方案中，格柵攔截了那些可能對設(shè)備造成破壞或者影響后續(xù)處理的物質(zhì)，在過去的一些舊的處理方案中，格柵通過人工清洗；但是現(xiàn)在幾乎所有的方案中都用機械清洗設(shè)備。當

53、格柵被阻塞使水位上升到柵條以上時，清洗設(shè)備被啟動。</p><p>　　在許多方案中，第二步是粉碎，循環(huán)擠壓固體物質(zhì)通過格柵形成大約3.0cm或更小直徑的小塊。</p><p>　　第三步處理是去處污水中的沙粒和石子，沙粒和石子會損壞設(shè)備，像水泵和流量計，因此必須被去除。大部分沉沙池是個很寬的空間，在這個渠道內(nèi)水流慢到足夠大密度的沙粒沉淀下來，沙粒的密度是大部分有機物密度的2.5倍，因此沉

54、淀的比較快。沉沙池的目的就是去除沙粒和石子，而不去除有機顆粒，在處理過程中有機物必須被進一步處理而分離除的出的沙?？梢员挥米魈畛湮锒鵁o需額外處理。</p><p>　　大部分污水處理方案中在沉沙池后面都有一個沉淀池，目的就是盡可能的去除固體顆粒，因此，停留時間比較長，水流速度保持比較慢。</p><p>　　固體沉淀到池子底部，然后通過管道被清除，而被澄清的液體則通過均勻布置在池子周圍的V

55、型溢流堰排放，沉淀池也被稱為沉積池或澄清池，緊隨在清渣和除沙之后的沉淀池也被叫作初次澄清池，沉淀在初次澄清池底部而被排放的固體稱為原污泥。</p><p>　　原污泥通常有很強的令人不快的氣味，含有病原有機體，而且含水率高，這三個特點增加了它處理的困難，它必須被穩(wěn)定為了防止它進一步腐化，也為了容易脫水處理。</p><p>　　初級處理的目的就是去除固體顆粒，然而一些BOD也在分離固體物質(zhì)

56、的一系列過程中被去除了。相當?shù)囊徊糠止腆w物質(zhì)，還有一部分BOD和少量的P作為原污泥的產(chǎn)物而被去除了，被初級處理之后污水可能繼續(xù)進行二級處理。</p><p><b>　　二級處理</b></p><p>　　水離開初次澄清池并沒有去除多少固體有機物，而且仍含有能通過微生物作用分解的高能量分子，成為BOD。要求氧必須減少，否則，在接納的水體中排放可能出現(xiàn)不能接受的情況。

57、二級處理的目的就是去除BOD，而初級處理的目的則是去除固體顆粒。</p><p>　　慮池由拳頭大小的礫石或波紋塑料板的慮床組成，通過它污物被慮掉，命名可能有錯誤，因為根本沒有過濾發(fā)生?；钚晕⑸锔街诘[石上，空氣被強制通過礫石或自動循環(huán)，因為慮床空氣溫度和周圍溫度的差異，慮池用一個循環(huán)調(diào)節(jié)系統(tǒng)降低它的能耗，像一個均勻布水裝置，能均勻的在整個慮床上分布污水，而通常水流是循環(huán)的，因而更高程度的處理被實現(xiàn)。</

58、p><p>　　在20世紀初，滴慮是一種被證實了的處理系統(tǒng)。1914年，一個試驗方案確立了一個不同系統(tǒng)，空氣泡通過自由漂浮的好氧微生物，一種變的出名的活性污泥系統(tǒng)的處理方案?；钚晕勰嗵幚聿煌诘螒]在于滴慮過程中微生物是懸浮在液體中的。</p><p>　　一個活性污泥處理系統(tǒng)包括一個充滿來自初次澄清池的污染液體的池子和一團微生物, 空氣泡進入曝氣池提供存活好氧有機物所必須的氧氣，微生物進入與在

59、污水中的溶解性有機物混合，吸附這些物質(zhì)，最終將有機物分解成，等一些穩(wěn)定的化合物和更多的微生物。</p><p>　　當大部分作為微生物食物的有機物被消耗掉，在一個沉淀池里微生物被從液體中分離，有時叫二次澄清池，在沉淀池里微生物仍舊沒有食物可利用，變得饑餓，變成失去活性的活性污泥，澄清的液體從溢流堰流出而排入接納水體。沉淀的微生物現(xiàn)在叫回流污泥，被抽送至曝氣池前端，在那里它們從初次澄清池進入曝氣池的液體的有化合物中

60、找到更多的食物，處理再一次開始?；钚晕勰嗵幚硎且粋€連續(xù)的過程，連續(xù)的污泥回流和連續(xù)的清水排放。</p><p>　　活性污泥處理產(chǎn)生的微生物多于需要的，如果微生物不被清除，它們的濃度將很快增加而形成固體物阻塞系統(tǒng)，因此，一部分微生物必須被去除，而處理這樣多余的活性污泥也是污水處理中一個最困難的方面。</p><p>　　活性污泥處理系統(tǒng)設(shè)計依據(jù)負荷，有機物數(shù)量或營養(yǎng)物，而且聯(lián)系到微生物的易

61、變性，營養(yǎng)物與微生物（F/M）之比是一個主要的設(shè)計參數(shù)，F(xiàn)和M難于精確測定的，但是可以通過曝氣池中的BOD和SS分別被估算，液體和微生物的混合物被稱為混合液。在曝氣池內(nèi)SS是混合液懸浮固體（MLSS），BOD/MLSS，F(xiàn)/M是系統(tǒng)負荷，以計。</p><p>　　相對小的F/M，或者少的營養(yǎng)物，而且一個長的曝氣周期（長的停留時間在池中）產(chǎn)生一個高的處理效果，因為微生物能最大限度的利用營養(yǎng)物，有這些特點的系統(tǒng)被稱

62、為延時曝氣系統(tǒng)，而且被用于單獨的污水處理工藝，像小的工業(yè)部門或用于應(yīng)急處理的旅館。延時曝氣系統(tǒng)產(chǎn)生少的剩余生物團，而且只有少的剩余活性污泥需要處理。</p><p>　　活性污泥處理系統(tǒng)的成功也依賴微生物最終在澄清池里的分離。當微生物沒有像預(yù)期中的沉淀去除，則污泥被稱為膨脹污泥，膨脹被描述為生物團有大量的絲狀菌組成，形成了一個由污泥附著其上的空架結(jié)構(gòu)而阻止了沉淀，低的沉淀率可能是一個低效率系統(tǒng)的先兆?；钚晕勰喑恋?/p>

63、能力經(jīng)常用污泥容積指數(shù)描述（SVI），SVI值的測定是通過在一個1L的圓筒內(nèi)讓污泥沉淀數(shù)分鐘，如果SVI值是100或更低，則污泥固體沉淀快而且最終從澄清池流出的污泥可能被保持在一個高的固體濃度，然而，SVI值大約是200時，顯示污泥膨脹而導致低的處理效果。</p><p><b>　　三級處理</b></p><p>　　來自二級處理的污水能達到前續(xù)要求的BOD和SS

64、排放標準，僅僅磷含量仍舊是高的，去除無機化合物，包括無機磷和氮化合物，就要求先進的或廢水三級處理系統(tǒng)。</p><p>　　初級和二級處理是傳統(tǒng)廢水處理方案的一部分，而且二級處理后污水被污染的程度仍然很高，一定程度的BOD和懸浮固體仍然存在，既不是初級也不是二級處理是有效的去除磷，氮或者碳的化合物的方法。一種流行的先進的BOD去除處理是人工塘或氧化塘，通常是二級污水流入一個大的環(huán)礁湖，像這樣的塘有一個長的停留時間