過(guò)濾英漢互譯

1、filtrationdefinetionthe term filtration has different meaning or connotations to various people. outside the water works profession, even in other technical disciplines, filtration is commonly thought of as a mechanical straining process. it may also have this same basic meaning in water works pract

2、ice as applied to the passage of water through a very thin layer of porous material deposited by flow on a support septum. this type of alter has a few rather specialized applications to water treatment as described later. however, most frequently in water works parlance, filtration refers to the us

3、e of a relatively deep(1.5 to 3 ft) granular bed to remove impurities from water. this general type of filter has a wide range of applications. in contrast to mechanical strainers which remove only part of the coarse suspended solids, the newest types of filters used in water purification remove all

4、 suspend solids, including virtually all colloidal particles. over the years the meaning of the term filtration as used by the water works industry has changed as improved filters have been developed and as the nature of the physical and chemical processes involved in filtration have become better u

5、nderstood. in an effort to distinguish recent new and improved filters from older conventional types, the term “separation bed” has sometimes been applied to mixed media alters which incorporate: (1)coarse-to-fine in-depth filtration,(2)the application to the filter influent of a polymer, alum, or a

6、ctivated silica as a filter aid,(3)continuous monitoring of filter effluent turbidity, and(4)pilot filter control of coagulant dosage. however, separation beds are still referred to.by many as ”filters” and the important distinctions in functions and efficiency are often overlooked or not understood

7、.water filtration can be further defined as a physical-chemical process for separating suspended and colloidal impurities from water by passage through a bed of granular material. water fills the pores of the filter medium, and the impurities are absorbed on the surface of the grains or trapped in t

8、he openings. in nature, filtration is an active and important process in the purification of underground waters, and in water purification plants, it is an indispensable unit process.filter types there are several ways to classify filters. they can be described according to the direction of though t

9、he bed, that is, downflow, upflow, radial flow, horizontal flow, fine-to-coarse, or coarse-to-fine. they may be classed according to the type of filter media used such as sand, coal(or anthracite),coal-sand, multilayered, mixed-media, or diatomaceous earth, filters are also classed by flow rate. slo

10、w sand filters operate at rates of 0.05 to 0.13gpm/ft2. another flow characteristic of filters is pressure or gravity flow. gravity filter units are usually built with open top and constructed of concrete or steel while pressure filters are ordinarily fabricated from steel in form of a cylindrical t

11、ank. available head for gravity flow usually is limited to about 8 to 12ft, while it may be as high as 150 psi for pressure filters. because pressure filters have a closed top, it is not possible to routinely maintain a visual condition of the filter media. further, it is possible to violently distu

12、rb the media in a pressure filter by sudden changes in pressure. these two factors have in the past tended to limit municipal application of pressure filters to treatment of relatively unpolluted waters such as the removal of hardness, iron, or manganese from well waters of good bacterial quality. t

13、he susceptibility to bed upset and the inability to see the surface of the media in pressure filter have been compensated for to some extent at least by the use of quick-opening manholes and particularly by the recent development and application of recording turbidimeters for continuous monitoring o

14、f the filter effluent turbidity. the introduction of a 3 in layer of coarse(1mm)high density(specific gravity 4.2)garnet or ilmenite between the fine media and the gravel supporting bed has virtually eliminated the problem of gravel upsets and another of the concerns about the use of pressure filter

15、s for production of potable water.rapid or high rate alters operate at about 30 times the rate of slow filters, so they must be cleaned about 30 times as often. a common method for cleaning slow sand filters is to scrape a thin layer of media from the surface of the bed, wash it, and return it to th

16、e bed. rapid filters are washed in place by reversing the flow through the media to expand and scour the media. this hydraulic leaning process can be supplemented in various ways as necessary such as water jet agitation of the expanded media, mechanical stirring by rakes, or by injecting air into th

17、e bed before or during backwashing. with the scraping method used to clean slow sand filters, it was advantageous to collect as much of the foreign material as possible at the top surface of the bed. this favored the use of a fine-to-coarse filter medium. with modern hydraulic backwashing supplement

18、ed by water or air jet agitation, it is possible to thoroughly clean granular beds at all depths, making it feasible to tailor the graduation of the fine media(coarse-to-fine)for optimizing the filter cycle rather than the cleaning cycle of filter operation. 待添加的隱藏文字內(nèi)容3過(guò)濾定義過(guò)濾這個(gè)專業(yè)術(shù)語(yǔ)不同的人有不同的理解。水處理以外的其

19、他技術(shù)領(lǐng)域，過(guò)濾普遍被認(rèn)為是一種簡(jiǎn)單的機(jī)械過(guò)程。在水處理過(guò)程中，如果只是使水流通過(guò)架起的過(guò)濾層將水中雜質(zhì)截流在多孔介質(zhì)薄層上，這樣的濾池也具有同樣的基本概念。專門(mén)應(yīng)用于水處理方面的改型濾池有不少，后文將詳細(xì)敘述。然而，在水處理的常用術(shù)語(yǔ)中，過(guò)濾就是利用相對(duì)較厚的粒床（1.5到3英尺）出去水中雜質(zhì)。這種普通類型的濾池已得到廣泛的應(yīng)用，與能除去水中部分粗大懸浮固體的機(jī)械過(guò)濾相比，應(yīng)用于水體凈化的新型的濾池的發(fā)展革新以及對(duì)過(guò)濾過(guò)程中物理化學(xué)作用的進(jìn)一步認(rèn)識(shí)，應(yīng)用于水處理工業(yè)中的過(guò)濾一詞的含義也在變化。為了把近期改進(jìn)的過(guò)濾方式與老式的傳統(tǒng)方式區(qū)別開(kāi)來(lái)，有時(shí)用“分離床”表示綜合一下四種功能的過(guò)濾形式，（

20、1）在深度上從粗到細(xì)的過(guò)濾，（2）進(jìn)水中加了聚合物、礬、活化硅酸等助濾劑的過(guò)濾，（3）可連續(xù)監(jiān)測(cè)濾后水的濁度，（4）由此控制混凝劑用量。然而，分離床仍然被很多人看做是濾池，人們經(jīng)常忽視或者不知道兩者功能和效率方面的顯著差異。過(guò)濾可以進(jìn)一步的定義為當(dāng)水流通過(guò)顆粒物質(zhì)層時(shí)，將水中懸浮的或膠狀的雜質(zhì)分離的物理化學(xué)過(guò)程。當(dāng)水流充滿濾料的細(xì)孔時(shí)，水中的雜質(zhì)就被吸附到顆粒的表面或被孔口截留下來(lái)。實(shí)際上，在地下水處理過(guò)程中，過(guò)濾是一個(gè)有效而又重要的過(guò)程，因此，在水處理廠過(guò)濾是一個(gè)不可或缺的單元。濾池類型濾池的分類有幾種不同的方式。根據(jù)水流流經(jīng)濾層的方向，可以將濾池分為降流式、升流式、輻流式、平流式、細(xì)粗式、粗細(xì)式；根據(jù)所用濾料的不同，濾池可分為砂型、煤（或無(wú)煙煤）型、煤砂型、多層濾料型、混合型及硅藻土型等。濾池也可以按濾速分類，慢速砂濾池的運(yùn)行濾速為0.050.13加侖/平方英尺，快速砂濾池的運(yùn)行濾速為12加侖/平方英尺，高速砂濾池的運(yùn)行濾速為315加侖/平方英尺.濾池也可按水流特點(diǎn)分為壓力流或重力流濾池。重力流濾池一般敞口修建，通常是混凝土或鋼結(jié)構(gòu)；壓力流濾池往往建成圓柱形的鋼罐。重力流濾池的可利用水頭通常不會(huì)超過(guò)8到12英尺，而壓力流濾池的可用水頭可能高達(dá)1