In the past several years the number of processes utilized in wastewater treatment hasincreased rapidly. Many of these processes have been developed with the specific purpose oftransforming nitrogen compounds or removing nitrogen from the wastewater stream. Otherscan remove several compounds, including significant amounts of nitrogen. Still others mayremove only a small amount of nitrogen or a particular form of nitrogen which is a smallfraction of the total. In determining which method is most suitable for a particular application, considerationmust be given to six principal aspects: (1) form and concentration of nitrogen compounds inthe process influent, (2) required effluent quality, (3) other treatment processes to beemployed, (4) cost,(5) reliability, and (6) flexibility. Great care must be taken indeveloping and evaluating alternatives. Presented below are brief descriptions of the various processes employed in wastewatertreatment facilities which, to varying degrees, remove nitrogen from the waste stream.Process characteristics, compound selectivity, and normal range of efficiency are presented.It is stressed that this discussion is descriptive and is intended only to provide anintroduction to the following chapters of this manual.
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在過去的數(shù)年間，廢水處理中使用的處理過程數(shù)量迅速增加。很多這樣的過程是針對(duì)轉(zhuǎn)化氮化合物或從廢水流中去除氮的特定目的而開發(fā)的。其他過程則可去除多種化合物，包括大量的氮。還有一些過程可能只去除少量的氮或一種特定形式的氮，而這種形式只是總氮的一小部分。在確定哪種方法最適合特定應(yīng)用時(shí)，必須考慮六個(gè)主要方面：（1）處理原料中氮化合物的形式和濃度，（2）要求的出水水質(zhì)，（3）其他要使用的處理過程，（4）成本，（5）可靠性和（6）靈活性。必須十分謹(jǐn)慎地發(fā)展和評(píng)估替代方案。以下是污水處理設(shè)施中使用的各種過程的簡(jiǎn)要說明，這些過程在不同程度上都可去除廢水流中的氮。介紹了其特性、化合物的選擇性和正常效率范圍。強(qiáng)調(diào)這討論僅僅是描述性的，并旨在為本手冊(cè)的下一章節(jié)提供引言。

2.5.1常規(guī)處理工藝

Nitrogen in raw domestic wastewaters is principally in the form of organic nitrogen, bothsoluble and particulate, and ammonia. The soluble organic nitrogen is mainly in the form ofurea and amino acids. Primary sedimentation acts to remove a portion of the particulateorganic matter. This generally will amount to less than 20 percent of the total nitrogenentering the plant.
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生活污水中的氮主要以有機(jī)氮形式存在，包括可溶性有機(jī)氮和顆粒有機(jī)氮以及氨?？扇苄杂袡C(jī)氮主要以尿素和氨基酸的形式存在。初級(jí)沉淀作用能夠去除一部分的顆粒有機(jī)物，通常只占進(jìn)一廠總氮負(fù)荷的不到20%。

Biological treatment will remove more particulate organic nitrogen and transform some toammonium and other inorganic forms A fraction of the ammonium present in the wastewili be assimilated into organic materials of cells formed by the biological process. Solubleorganic nitrogen is partially transformed to ammonium by microorganisms, but concentrations of? to 3 mg/l are usually found in biological treatment effluents.24 Through theseprocesses, an additional 10 to 20 percent of the total nitrogen is removed when biologicaltreatment and secondary sedimentation follows primary sedimentation. Thus, total nitrogenremoval for a conventional primary-secondary facility will generally be less than about 30percent.
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生物處理將去除更多顆粒狀有機(jī)氮并將一部分轉(zhuǎn)化為銨和其他無(wú)機(jī)形式。廢水中存在的銨的一部分將被生物過程形成的細(xì)胞有機(jī)材料吸收?？扇苄杂袡C(jī)氮部分通過微生物轉(zhuǎn)化為銨，但是生物處理出水中通常僅發(fā)現(xiàn)3mg / l的濃度。通過這些過程，在化學(xué)處理和二級(jí)沉淀跟隨初級(jí)沉降時(shí)，附加10％至20％的總氮可被去除。因此，對(duì)于傳統(tǒng)的初級(jí)-次級(jí)設(shè)施，總氮去除通常不超過30％。

2.5.2廢水深度處理工藝

Advanced treatment processes designed to remove wastewater constituents other thannitrogen often remove some nitrogen compounds as well Removal is often restricted toparticulate forms, and overall removal efficiency is rarely high.
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設(shè)計(jì)用于去除廢水中除氮以外其他成分的高級(jí)處理工藝，通常也會(huì)去除一些氮化合物。去除通常限于顆粒形式，總體去除效率很少是高的。

Tertiary filtration can remove a significant fraction of the organic nitrogen present. Overallremoval depends on the amount of nitrogen in the suspended organic form, As noted above.most of the organic nitrogen in secondary effluent is insoluble, but ammonium usuallyaccounts for the majority of the total nitrogen. Carbon adsorption, used to remove residualorganics, will also remove organic nitrogen. The amount of organic nitrogen remaining atthat point in the treatment scheme will generally be quite small.
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高等過濾技術(shù)可以有效去除有機(jī)氮的顯著比例?？偟娜コ咳Q于含懸浮有機(jī)物形式的氮的數(shù)量，如前所述，大多數(shù)二級(jí)廢水中的有機(jī)氮是不溶性的，但氨通常占總氮的大部分。碳吸附技術(shù)用于去除殘留的有機(jī)物也可以去除有機(jī)氮。在處理過程中，剩余的有機(jī)氮通常會(huì)很小。

Electrodialysis and reverse osmosis are tertiary processes used primarily for reduction oftotal dissolved solids. Nitrogen entering such systems is mainly in the ammonjum or nitrateform. Electrodialysis can be expected to remove about 40 percent of these forms; reverseosmosis, 80 percent. However, these processes are not currently in use for treatment ofmunicipal wastewater.
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電滲析和反滲透是主要用于降低總?cè)芙夤腆w的三級(jí)處理過程。進(jìn)入這些系統(tǒng)的氮主要以銨或硝酸鹽形式存在。電滲析可以預(yù)期去除約40％的這些形式，而反滲透可以去除約80％。然而，這些過程目前不適用于處理市政污水。

Chemical coagulation, often utilized for phosphate removal, also aids in removal ofparticulate matter,including particulate organic nitrogen. While chemical coagulation doesnot remove ammonium directly, lime addition is used prior to ammonia stripping (discussedin Section 2.5.3.4) in order to raise the pH and allow the process to proceed.
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化學(xué)混凝是通常用于磷的去除的方法，同時(shí)也有助于去除顆粒物，包括顆粒性有機(jī)氮。雖然化學(xué)混凝不能直接去除銨，但在銨中和之前添加石灰以提高 pH 值，使該過程得以進(jìn)行，是常見的銨去除方法（如第2.5.3.4章節(jié)所述）。

Land disposal may be used to remove nitrogen. Removal occurs when the effluent is usedfor irrigation purposes with the nitrogen assimilated by growing crops which aresubsequently harvested. However, nitrogen removal by land treatment systems is not withinthe scope of this manual.
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土地處置可以用于去除氮。當(dāng)廢水用于灌溉目的時(shí)，氮被吸收到種植作物中，隨后被收獲收取實(shí)現(xiàn)去除。然而，土地處理系統(tǒng)的氮去除不在本手冊(cè)的范圍內(nèi)。

2.5.3主要脫氮工藝

The major processes considered in this manual are nitrification-denitrification, breakpointchlorination (or superchlorination), selective ion exchange for ammonium removal, and air stripping for ammona removal (ammonia stripping). These are the processes which aretechnically and economically most viable at the present time.
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本手冊(cè)所討論的主要過程包括硝化反硝化、斷點(diǎn)氯化（或超氯化）、針對(duì)銨離子的選擇性離子交換和氨氣去除的氣體脫附（氨氣蒸發(fā)）等。這些是目前技術(shù)上和經(jīng)濟(jì)上最為可行的過程。

2.5.3.1生物硝化-反硝化

Biological nitrification does not increase the removal of nitrogen from the waste stream overthat achieved by conventional biological treatment. The principal effect of the nitrificationtreatment process is to transform ammonia-nitrogen to nitrate. The nitrified effluent canthen be denitrified biologically. Nitrification is also used without subsequent biologicaldenitrification when treatment requirements cal for oxdation of ammonia-nitrogenOxidation of ammonium can be as high as 98 percent. Overall transformation to nitratedepends on the extent to which organic nitrogen is transformed to ammonia-nitrogen in thesecondary stage or is removed by another process. Nitrification can be carried out inconjunction with secondary treatment or in a tertiary stage;in both cases, either suspendedgrowth reactors (activated sludge) or attached growth reactors (such as trickling filters) canbe used.
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生物硝化并不能比傳統(tǒng)的生物處理方式更有效地去除廢水中的氮。硝化處理的主要效果是將氨氮轉(zhuǎn)化為硝酸鹽。硝化后的出水可以通過生物脫氮來(lái)處理。當(dāng)需要處理氨氮氧化時(shí)，也可以使用硝化而無(wú)需進(jìn)行后續(xù)的生物脫氮。氨的氧化率可以高達(dá)98％?？偟南趸D(zhuǎn)化取決于有機(jī)氮在二次處理階段被轉(zhuǎn)化為氨氮還是被另一個(gè)過程去除。硝化可以在二次處理階段或第三級(jí)階段進(jìn)行。在兩種情況下，都可以使用懸浮生長(zhǎng)反應(yīng)器（活性污泥）或固定生長(zhǎng)反應(yīng)器（如滴濾池）進(jìn)行處理。

Biological denitrification can also be carried out in either suspended growth or attachedgrowth reactors. As previously noted, an anoxic environment is required for the reactions toproceed. Overall removal efficiency in a nitrification-denitrification plant can range from 70to 95 percent.
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生物反硝化可以在懸浮生長(zhǎng)反應(yīng)器或附著生長(zhǎng)反應(yīng)器中進(jìn)行。如前所述，需要一種缺氧環(huán)境來(lái)促進(jìn)反應(yīng)的進(jìn)行。在硝化-反硝化工廠中，總體去除效率可在70至95％之間變化。

2.5.3.2折點(diǎn)加氯

Breakpoint chlorination (or superchlorination) is accomplished by the addition of chlorineto the waste stream in an amount sufficient to oxidize ammonia-nitrogen to nitrogen gasAfter sufficient chlorine is added to oxidize the organic matter and other readily oxidizablesubstances present, a stepwise reaction of chlorine with ammonium takes place. The overalltheoretical reaction is as follows:
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斷點(diǎn)氯化（或超氯化）是通過向廢水中添加足夠的氯，使氨氮氧化為氮?dú)舛鴮?shí)現(xiàn)的。在添加足夠的氯氣氧化有機(jī)物和其他易于氧化物質(zhì)后，氯氣會(huì)逐步與銨發(fā)生反應(yīng)，從而實(shí)現(xiàn)氮?dú)庋趸??？傮w的理論反應(yīng)式如下：

In practice, approximately 10 mg/l of chlorine is required for every 1 mg/l ofammonia-nitrogen, In addition, acidity produced by the reaction must be neutralized by theaddition of caustic soda or lime. These chemicals add greatly to the total dissolved solids andresult in a substantial operating expense. Often dechlorination is utilized followingbreakpoint chlorination in order to reduce the toxicity of the chlorine residual in theeffluent.
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實(shí)際操作中，每1毫克/升氨氮需要約10毫克/升氯。此外，反應(yīng)產(chǎn)生的酸度必須通過加入氫氧化鈉或石灰進(jìn)行中和。這些化學(xué)物質(zhì)大大增加了總?cè)芙馕锏暮?，?dǎo)致了大量的運(yùn)營(yíng)費(fèi)用。通常，在進(jìn)行斷點(diǎn)氯化處理后，會(huì)采用脫氯技術(shù)，以減少排放物中殘留的氯毒性。

An important advantage of this method is that ammonia-nitrogen concentrations can bereduced to near zero in the effluent The effect of breakpoint chlorination on organicnitrogen is uncertain, with contradictory results presented in the literature. Nitrite andnitrate are not remoyed by this method.
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這種方法的一個(gè)重要優(yōu)勢(shì)是，在廢水中氨氮濃度可以降至接近于零。而斷點(diǎn)氯化對(duì)有機(jī)氮的影響尚不確定，文獻(xiàn)中也存在著相互矛盾的結(jié)果。此方法無(wú)法去除亞硝酸鹽和硝酸鹽。

2.5.3.3選擇性離子交換除

Selective ion exchange for removal of ammonium from wastewater can be accomplished bypassing the wastewater through a column of clinoptilolite, a naturally occurring zeolitewhich has a high selectivity for ammonium ion. The first extensive study was undertaken in1969 by Battelle Northwest in a federally sponsored demonstration project, Regeneration ofthe clinoptilolite is undertaken when all the exchange sites are utilized and breakthroughoccurs.
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通過將廢水通過自然產(chǎn)生的沸石之一的斜十字沸石的柱體中，可以實(shí)現(xiàn)有選擇性地進(jìn)行銨離子去除的離子交換。斜十字沸石因具有極高的銨離子選擇性而被廣泛應(yīng)用，關(guān)于其首次廣泛研究是在1969年由Battelle Northwest進(jìn)行的聯(lián)邦贊助演示項(xiàng)目。當(dāng)所有交換位點(diǎn)被利用完畢并出現(xiàn)突破時(shí)，便對(duì)斜十字沸石進(jìn)行再生。

Filtration prior to ion exchange is usually required to prevent fouling of the zeolite.Ammonium removals of 90-97 percent can be expected. Nitrite, nitrate, and organicnitrogen are not affected by this process.
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在離子交換之前，通常需要進(jìn)行過濾以防止沾污分子篩。預(yù)計(jì)可達(dá)到90-97％的銨離子去除率。該過程不會(huì)影響亞硝酸鹽、硝酸鹽和有機(jī)氮。

2.5.3.4氣相吸附去除氨

Ammonia in the molecular form is a gas which dissolves in water to an extent controlled bythe partial pressure of the ammonia in the air adjacent to the water. Reducing the partialpressure causes ammonia to leave the water phase and enter the air. Ammonia removal fromwastewater can be effected by bringing small drops of water in contact with a large amountof ammonia-free air. This physical process is termed desorption, but the common name isammonia stripping.
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氨分子形式的氣體可溶于水中，且溶解度由氨在水旁的空氣中產(chǎn)生的分壓控制。降低分壓會(huì)導(dǎo)致氨從水相離開，進(jìn)入空氣中。通過將小水滴接觸大量無(wú)氨氣體，可實(shí)現(xiàn)將氨從廢水中去除。這種物理過程被稱為解吸，常用名為氨氣剝離。

In order to strip ammonia from wastewater, it must be in the molecular form (NH3) ratherthan the ammonium ion (NH4 form. This is accomplished by raising the pH of thewastewater to 10 or 1l, usually by the addition of lime. Because lime addition is often usedfor phosphate removal, it can serve a dual role. Again, nitrite, nitrate, and organic nitrogenare not affected.
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為了從廢水中剝離出氨，必須將其轉(zhuǎn)化為分子形式（NH3），而非銨離子（NH4）形式。通常通過加入石灰，將廢水的pH值升至10或11來(lái)實(shí)現(xiàn)此目的。由于石灰補(bǔ)加常常用于磷的去除，因此它可以發(fā)揮雙重作用。需要重申的是，亞硝酸鹽、硝酸鹽和有機(jī)氮不會(huì)受到影響。

The principal problems associated with ammonia stripping are its inefficiency in coldweather, required shutdown during freezing conditions, and formation of calcium carbonatescale in the air stripping tower.
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氨脫除的主要問題包括其在寒冷天氣下的低效率、需要在冰凍條件下停機(jī)以及空氣脫除塔中鈣碳酸鹽形成。

The effect of cold weather has been well documented at the South Lake Tahoe PublicUtility District where ammonia stripping is used for a 3.75 mgd tertiary facility. Thestripping tower is designed to remove 90 percent of the incoming ammonium during warmweather. During freezing conditions, the tower s shut down. One echanism of scaleformation is attributed to the carbon dioxide in the air reacting with the alkaline wastewaterand precipitating as calcium carbonate. In some instances, removal with a water jet hasbeen possible; in other applications the scale has been extremely difficult to remove. Somefactors which may affect the nature of the scale are: orientation of air flow, recirculation ofsludge, pH of the wastewater, and chemical makeup of the wastewater.
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南萊克塔霍公共事業(yè)區(qū)使用氨氣脫除法處理污水，冷天氣的影響已有充足的文獻(xiàn)記錄。這座處理廠緊急脫氨設(shè)備在炎熱天氣中的目標(biāo)是脫除進(jìn)水中90%的銨。在冰冷的氣溫下，設(shè)備必須關(guān)閉。由于空氣中的二氧化碳與堿性廢水反應(yīng)并析出碳酸鈣，這是結(jié)垢的一個(gè)機(jī)制。有時(shí)可以用水噴射法去除結(jié)垢，而在其他情況下，結(jié)垢非常難以去除。影響結(jié)垢特性的因素包括：氣流方向、污泥再循環(huán)、廢水pH值和化學(xué)成分。

2.5.4其他脫氮工藝

In addition to the processes listed above, there are other methods for nitrogen removalwhich might usefully be discussed. Most are in the experimental stage of development oroccur coincidentally with another process.
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除了上述列出的過程外，還有其他一些氮去除方法值得探討。這些方法大多處于實(shí)驗(yàn)開發(fā)階段或與其他過程偶然出現(xiàn)。

Use of anionic exchange resins for removal of nitrate was developed principally fortreatment of irrigation return waters. Two major unsolved problems are the lack of resinswhich have a high selectivity for nitrate over chloride and disposal of nitrogen-ladenregenerants.
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離子交換樹脂是一種主要用于處理灌溉回灌水中硝酸鹽去除的方法。其中，存在兩個(gè)主要的未解決問題：一是缺乏高選擇性去除氯化物的樹脂，二是氮負(fù)荷再生劑的處置。

Oxidation ponds can remove nitrogen through microbial denitrification in the anaerobicbottom layer or by ammonia emission to the atmosphere. The latter effect is essentiallyammonia stripping but is relatively inefficent due to a low surface-volume ratio and low pHIn a study of raw wastewater lagoons in California, removals of 35-85 percent were reportedfor welloperated lagoons.
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氧化池可以通過微生物反硝化在厭氧底層將氮去除，或通過氨排放到大氣中去除氮。后一種效應(yīng)本質(zhì)上是氨剝離，但由于低表面積-體積比和低pH而相對(duì)低效。在加利福尼亞對(duì)原始廢水塘的研究中，對(duì)于運(yùn)營(yíng)良好的池塘，報(bào)道了35-85％的去除效果。

Nitrogen in oxidation ponds is assimilated by algal cultures. If the algal cells are removedfrom the pond effluent stream, nitrogen removal is thereby effected. Methods for removalof algae are summarized in the EPA Technology Transfer Publication, UpgradingLagoons,
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氧化池中的氮被藻類文化同化。如果從池的排放流中移除藻細(xì)胞，則從而實(shí)現(xiàn)了氮的去除。除藻的方法總結(jié)在EPA技術(shù)轉(zhuǎn)移出版物《升級(jí)沼澤》中。

It was noted previously that in secondary biological treatment and in nitrification, somenitrogen is incorporated in bacterial cells and is removed from the waste stream with thesludge. If an organic carbon source such as ethanol or glucose is added to the wastewaterthe solids production will be increased and a greater nitrogen removal will be effectedDisadvantages are that large quantities of sludge are produced and that difficulties occur inregulating the addition of the carbon source, with high effluent BODs values or highnitrogen levels resulting.
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先前已經(jīng)指出，在第二級(jí)生物處理和硝化過程中，部分氮被細(xì)菌細(xì)胞吸收并隨著污泥從廢水中去除。如果添加可作為有機(jī)碳源的乙醇或葡萄糖到廢水中，則會(huì)增加固體產(chǎn)量并促進(jìn)更大的氮去除。缺點(diǎn)是會(huì)產(chǎn)生大量污泥，并且在調(diào)節(jié)碳源添加時(shí)會(huì)出現(xiàn)困難，從而導(dǎo)致出水BOD或氮含量較高。

2.5.5 總結(jié)

Table 2-3 summarizes the effect of various treatment processes on nitrogen removal. Shownis the effect that the process has on each of the three major forms: organic nitrogen.ammonium, and nitrate. In the last column is shown normal removal percentages which canbe expected from that process. Overall removal for a particular treatment plant will dependon the types of unit processes and their relation to each other For example, while manyprocesses developed for nitrogen removal are ineffective in removing organic nitrogenincorporation of chemical coagulation or multimedia filtration into the overall flowsheetcan result in a low concentration of organic nitrogen in the plant effluent. Thus, theinterrelationship between processes must be carefully analyzed in designing for nitrogenremoval. Further discussion of process interrelationships is presented in Chapter 9
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表2-3總結(jié)了各種處理工藝對(duì)氮去除的影響。顯示了處理過程對(duì)三種主要形式（有機(jī)氮、銨和硝酸鹽）的影響。最后一列顯示的是該過程可以期望的正常去除百分比。對(duì)于特定處理廠的總體去除效果將取決于單元處理類型及其相互關(guān)系。例如，盡管為了氮去除而開發(fā)的許多處理過程在去除有機(jī)氮方面無(wú)效，但將化學(xué)凝聚或多介質(zhì)過濾體系納入總流程中可以使工廠廢水的有機(jī)氮濃度降低。因此，在設(shè)計(jì)氮去除時(shí)必須仔細(xì)分析處理過程之間的相互關(guān)系。詳細(xì)討論處理過程的相互關(guān)系將在第9章中進(jìn)行。