It was previously noted that nitrogenous compounds discharged from wastewater treatmentfacilities can have several deleterious effects. Although biostimulation of receiving watershas generated the most concern in recent years, other less well publicized impacts can be ofmajor importance in particular situations. These impacts include toxicity to fish lifereduction of chlorine disinfection efficiency, an increase in the dissolved oxygen depletionin receiving waters, adverse public health effects - principally in groundwater, and areduction in the suitability for reuse.
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先前已指出，從廢水處理設(shè)施排放出來的含氮化合物可能產(chǎn)生多種有害影響。雖然最近幾年接收水體的生物刺激引發(fā)了最大的關(guān)注，但在特定情況下，其他不太為人知的影響可能具有重要作用。這些影響包括對魚類生命的毒性、氯消毒效率降低、接收水體中溶解氧消耗增加、對公共健康的不良影響——主要出現(xiàn)在地下水中，以及減少再利用的適用性。

2.4.1 Biostimulation of Surface Waters
A major problem in the field of water pollution is eutrophication, excessive plant growthand/or algae “bloomsresulting from over-fertilization of rivers, lakes, and estuaries. Resultsof eutrophication include deterioration in the appearance of previously clear waters, odorproblems from decomposing algae, and a lower dissolved oxygen level which can adverselyaffect fish life.
Four basic factors are required for algal growth: nitrogen, phosphorus, carbon dioxide, andlight energy. The absence of any one will limit growth. In special cases, trace micronutrientssuch as cobalt, iron, molybdenum and manganese may be limiting factors under naturalconditions.
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2.4.1 表面水的生物刺激作用

水污染領(lǐng)域中的主要問題是富營養(yǎng)化，即由于對河流、湖泊和河口的過度施肥導(dǎo)致植物生長和/或藻類“水華”過度增長。富營養(yǎng)化的結(jié)果包括先前清澈水體的惡化外觀，由腐爛藻類產(chǎn)生的異味問題，以及溶解氧水平降低，可能對魚類生命產(chǎn)生不利影響。

藻類生長需要四個基本因素：氮、磷、二氧化碳和光能。缺乏其中任何一個都會限制生長。在特定情況下，微量營養(yǎng)元素，如鈷、鐵、鉬和錳，可能是自然條件下的限制因素。

Good generalizations concerning which factor is growth limiting and at what concentrationare difficult to make. Light and carbon dioxide are essentially impossible tocontrol. Bothnitrogen and phosphorus are present in waste discharges and hence subject to control. Thequestions which must usually be answered when faced with a eutrophication problem are: isnitrogen or phosphorus (or neither) the limiting nutrient, and if either one is, can theamount entering the receiving water be significantly reduced by removing that nutrient fromthe waste stream? In some cases algal assay procedures may allow a conclusion as to whichnutrient is limiting. Under some circumstances, however, removal of both nitrogen andphosphorus may be undertaken to limit algal growth.
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關(guān)于哪種因子是生長限制因素以及何種濃度為限制因素的充分歸納總結(jié)是困難的。光和二氧化碳基本上是無法控制的，而氮和磷則存在于廢水排放中，因此受到控制。通常面臨營養(yǎng)過度問題時必須回答的問題是：氮或磷（或兩者皆是）是否為限制養(yǎng)分，如果是，則是否可以通過從廢水中去除這些養(yǎng)分顯著降低污水處理后排放的進水中的限制養(yǎng)分含量？在某些情況下，藻類鑒定過程可以確定是哪種養(yǎng)分限制因素。但是，在某些情況下，需要同時去除氮和磷以限制藻類生長。

Eutrophication is of most concern in lakes because nutrients which enter tend to berecycled within the lake and build up over a period of time.9 A river, by contrast, is aflowing system, Nutrients are always entering or leaving any given section. Accumulationstend to occur only in sediment or in slack water, and the effects of these accumulations arenormally moderated by periodic flushing by floods.
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富營養(yǎng)化對湖泊的影響最為關(guān)注，因為流入湖泊的營養(yǎng)物質(zhì)在湖內(nèi)循環(huán)并逐漸積累。與之相反，河流是一個流動的系統(tǒng)，任何給定區(qū)域營養(yǎng)物質(zhì)都在進出。積累往往僅出現(xiàn)在沉積物或緩流水中，并且這些積累的影響通常會被洪水的周期性沖刷所緩解。

In estuaries and oceans, nitrogen compounds are often present in very low concentrationsand may limit the total biomass and the types of species it contains.9 Thus, upwelling,which brings nutrient-rich waters to the surface, may result in periodic blooms of algae orother aquatic life. While in some estuaries discharges from wastewater treatment plants mayincrease nitrogen concentrations to the level where blooms occur, the high dilution providedby a direct ocean discharge probably eliminates the danger of algae blooms caused by sucldischarges.In summary, while nitrogen in wastewater treatment plant effluents can inparticular cases cause undesirable aquatic growths, determination of the limiting constituentand other sources of that constituent (such as feedlot runoff or fixation) should be madebefore the decision is made to require nitrogen removal from municipal wastewaters.
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在河口和海洋中，氮化合物通常存在非常低的濃度，可能會限制總生物量和其中包含的物種類型。因此，上升流將營養(yǎng)豐富的水帶到表面，可能會導(dǎo)致周期性的藻類或其他水生生物的繁殖。雖然在一些河口中，來自廢水處理廠的排放可能會增加氮濃度，并導(dǎo)致藻類繁殖，但直接向海洋排放的高稀釋率可能會消除由此類排放引起的藻類繁殖的危險。

總之，在某些情況下，廢水處理廠排放的氮可能會導(dǎo)致不良的水生生長現(xiàn)象，但在決定要求從市政污水中去除氮之前，應(yīng)確定限制構(gòu)成因素和其他來源（如飼料料場徑流或固定）。
2.4.2 Toxicity
The principal toxicity problem is from ammonia in the molecular form (NHa) which canadversely affect fish life in receiving waters. A slight increase in pH may cause a greaincrease in toxicity as the ammonium ion (NHn is transformed to ammonia in accordancewith the following equation.
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2.4.2 毒性問題
主要毒性問題來自于分子形式下的氨（NH3），它可能會對接受水域中的魚類生命產(chǎn)生負面影響。pH值的輕微增加可能會導(dǎo)致毒性的急劇增加，因為氨鹽離子（NH4+）會根據(jù)如下反應(yīng)式轉(zhuǎn)化為氨。

Factors which may increase ammonia toxicity at a given pH are: greater concentrations ofdissolved oxygen and carbon dioxide; elevated temperatures; and bicarbonate alkalinity.Reported levels at which acute toxicity is detectable have ranged from 0.01 mg/19 to over2.0 mg/120 of molecular ammonia-nitrogen.
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在特定的 pH 值下可能增加氨毒性的因素包括：溶解氧和二氧化碳的濃度更高；溫度升高；以及碳酸鹽堿度。報道的急性毒性可檢測水平范圍從 0.01mg/19到超過 2.0 mg/1分子氨氮。

2.4.3 Effect on Disinfection Efficiency
When chlorine, in the form of chlorine gas or hypochlorite salt, is added to wastewatelcontaining ammonium, chloramines, which are less effective disinfectants, are formed.Themajor reactions are as follows;
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2.4.3 消毒效率影響
當(dāng)氯以氯氣或次氯酸鹽的形式被添加到含有氨、氯胺等物質(zhì)的廢水中時，會產(chǎn)生一種消毒效果較差的化合物——氯胺。其主要反應(yīng)如下：

Only after the addition of large quantities of chlorine does free available chlorine exist. Ifthe effluent ammonia-nitrogen concentration were 20 mg/l, about 200 mg/l of chlorinewould be required to complete the reactions with ammonium and organic compounds. Onlrarely in wastewater treatment is this level of chlorine addition (“breakpoint” chlorination)used. Therefore, as a practical matter, the less effective combined chlorine residuals(monochloramine and dichloramine) must be relied upon for disinfection. This results irincreased chlorine dose requirements for the same level of disinfection. Further informationon the relative effectiveness of free chlorine and combined residuals is presented in Section
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只有添加大量氯氣后才會存在可用自由氯。如果廢水中氨氮濃度為20毫克/升，則需要約200毫克/升的氯氣與銨離子和有機物反應(yīng)。在廢水處理中很少使用這種氯氣添加水平（“斷點”氯化），因此，作為實際問題，必須依靠不太有效的復(fù)合氯余量（一氯胺和二氯胺）來進行消毒。這會導(dǎo)致相同消毒水平需要增加氯氣用量。有關(guān)自由氯和復(fù)合余量相對有效性的進一步信息請參見本節(jié)6.2.7.

2.4.4 Dissolved Oxygen Depletion in Receiving Waters
Ammonium can be biologically oxidized to nitrite and then to nitrate in receiving watersand thereby add to the oxygen demand imparted by carbonaceous materials. Table 2-2shows a typical example of the removal of total oxygen demand obtainable with varyingdegrees of treatment. If either conventional biological treatment or physical-chemica!treatment is utilized to provide 90 percent BODs removal, an effluent will be dischargedwhich still contains over 100 mg/l of oxygen demand. This high level of oxygen demandmay cause significant oxygen depletion in the receiving water if insufficient dilution isavailable. Nitrification (or ammonia nitrogen removal) will reduce the total oxygen demandof the effluent to less than 40 mg/l.
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2.4.4 溶解氧在受納水體中的耗竭問題
氨可以在受納水體中被生物氧化為亞硝酸鹽，接著再被氧化為硝酸鹽，從而增加碳質(zhì)材料所施加的氧需求。表2-2展示了在不同程度的處理下總氧需求的去除典型例子。如果采用傳統(tǒng)的生物處理或物理-化學(xué)處理實現(xiàn)90%的BOD去除率，則排放出的廢水中仍包含100 mg/l以上的氧需求。如果受納水體中的稀釋不足，則這種高水平的氧需求可能會導(dǎo)致顯著的氧耗竭。硝化（或氨氮去除）可將廢水的總氧需求降至少于40 mg/l。

The Potomac Estuary in the United States and the Thames Estuary in Great Britain areexamples of estuaries which are greatly affected by nitrification. Figure 2-4 shows, as afunction of the degree of nitrification provided by wastewater treatment facilities, theestimated discharge into the Thames Estuary which will cause the maximum oxygendepletion to be 10 percent of saturation, The calculation assumes an effluent BODs of 20mg/l, an effluent organic plus ammonia-nitrogen concentration of 19 mg/l, and discharge ata point 10 miles above London Bridge. From the figure, the allowable discharge fornon-nitrified effluent is about 12 mgd, while for completely nitrified effluent, over 40 mgdcan be discharged.
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波托馬克河口在美國和泰晤士河口在英國是受硝化作用影響較大的河口的例子。圖2-4顯示，根據(jù)污水處理設(shè)施提供的硝化程度，估計向泰晤士河口排放將導(dǎo)致最大氧飽和度降至10％的排放量。該計算假定出水BOD為20mg/l，出水有機物加氨氮濃度為19mg/l，并在倫敦橋上游10英里的一點排放。從圖表中可以看出，未經(jīng)硝化處理的出水允許排放量約為12 mgd，而完全經(jīng)過硝化處理的出水可以排放超過40 mgd。

2.4.5 Public Health
The public health hazard from nitrogen is associated with the nitrate form and is limitedprincipally to groundwater where high concentrations can occur. Nitrate in drinking water was first associated in 1945 with methemoglobinemia, a sometimes fatal blood disorderwhich affects infants less than three months old. When water high in nitrate is used fororeparing infant formulas, nitrate is reduced to nitrite in the stomach after ingestion. Thenitrites react with hemoglobin in the blood to form methemoglobin, which is incapable ofcarrying oxygen. The result is suffocation accompanied by a bluish tinge to the skin, whichaccounts for the use of the term “blue babies”in conjunction with methemoglobinemia. Insuspect areas water should be analyzed for both nitrite and nitrate since either form willcause methemoglobinemia.
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2.4.5 公共衛(wèi)生學(xué)
氮的公共衛(wèi)生風(fēng)險主要與硝酸鹽形式有關(guān)，其限制性主要在地下水中高濃度存在。飲用水中的硝酸鹽最初與一種有時會影響3個月以下嬰兒的致命血液疾病——高鐵血紅蛋白癥關(guān)聯(lián)。當(dāng)富含硝酸鹽的水用于制備嬰兒配方奶粉時，硝酸鹽在攝入后在胃中被還原為亞硝酸鹽。然后，亞硝酸鹽與血液中的血紅蛋白反應(yīng)形成高鐵血紅蛋白，該物質(zhì)不能傳遞氧氣。其結(jié)果是窒息并伴有皮膚呈藍色，這就是“藍色嬰兒”術(shù)語在高鐵血紅蛋白癥中的使用原因。在可疑的地區(qū)，應(yīng)分析水中的亞硝酸鹽和硝酸鹽，因為任一形式都會導(dǎo)致高鐵血紅蛋白癥。

Since 1945 about 2,000 cases of methemoglobinemia have been reported in the U.S. andEurope, with a mortality rate of seven to eight percent. Because of difficulty in diagnosingthe disease and because no reporting is required, the actual incidence may be many timeshigher.10
The EPA's interim primary drinking water standard (40 CFR Part 141) for nitrate is 10 mg/las nitrogen, This standard is exceeded most often in shallow wells in rural areas.
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自1945年以來，在美國和歐洲大約報告了2,000例的高鐵血紅蛋白血癥，其中死亡率為7%至8%。由于該疾病的診斷困難，而且沒有報告要求，實際發(fā)病率可能高出許多倍。環(huán)保局的暫行飲用水主要標準（40 CFR第141部分）中亞硝酸鹽的濃度為10毫克/升作為氮。這一標準最常在農(nóng)村地區(qū)的淺井里被超過。

2.4.6 Water Reuse
While direct wastewater reuse for domestic water supply is not yet a reality because ofpublic health considerations, plans for industrial reuse are being carried out in several areasWhen reclaiming wastewater for industrial purposes, ammonia may need to be removed inorder to prevent corrosion. Further, nitrogen compounds can cause biostimulation incooling towers and distribution structures.
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2.4.6 水的再利用
盡管受制于公共健康考慮，直接將廢水再利用于生活用水目前還未成為現(xiàn)實，但在幾個領(lǐng)域中已經(jīng)開始執(zhí)行廢水產(chǎn)業(yè)再利用計劃。在回收廢水用于工業(yè)目的時，為了防止腐蝕，可能需要去除氨。此外，氮化合物可能會在冷卻塔和配水結(jié)構(gòu)中引起生物刺激反應(yīng)。