飲用水處理過程中溴酸鹽的生成特性及優(yōu)化控制研究_圖文_百度文庫

1、博士學(xué)位論文飲用水處理過程中溴酸鹽的生成特性及優(yōu)化控制研究BROMATE FORMATION CHARACTERISTICS AND OPTIMAL CONTROL IN DRINKING WATERTREATMENT PROCESS朱琦哈爾濱工業(yè)大學(xué)2012年6月國內(nèi)圖書分類號:TU991.2學(xué)校代碼:10213 國際圖書分類號:628.1 密級:公開工學(xué)博士學(xué)位論文飲用水處理過程中溴酸鹽的生成特性及優(yōu)化控制研究博士研究生:朱琦導(dǎo) 師:崔福義教授申請學(xué)位:工學(xué)博士學(xué)科:城市水資源所在單位:市政環(huán)境工程學(xué)院答辯日期:2012年6月授予學(xué)位單位:哈爾濱工業(yè)大學(xué)Classified Index:

2、TU991.2Dissertation for the Doctoral Degree in EngineeringBROMATE FORMATION CHARACTERISTICS AND OPTIMAL CONTROL IN DRINKING WATERTREATMENT PROCESSCandidate:Zhu QiSupervisor:Prof. Cui FuyiAcademic Degree Applied for:Doctor of Engineering Speciality:Urban Water Resource Affiliation:School of Munici. &

3、amp; Envir. Engrg Date of Defence:June, 2012Degree-Conferring-Institution:Harbin Institute of Technology摘要摘要在微污染飲用水處理中,臭氧氧化技術(shù)已越來越多地被選擇應(yīng)用到飲用水處理過程中。含溴水在臭氧氧化時會生成2B級致癌物溴酸鹽,溴酸鹽濃度的控制是確保水質(zhì)安全的重要問題。目前,相關(guān)研究主要集中于應(yīng)用各種外加方法去除水中的溴酸鹽,忽略了常規(guī)水處理工藝環(huán)節(jié)的自身作用,未見溴酸鹽在常規(guī)工藝中是否可以得到去除的相關(guān)研究。在現(xiàn)有水處理的工藝中解決溴酸鹽的污染問題,是最切合實際,最易應(yīng)用、最經(jīng)濟(jì)合理的

4、方法。針對整套飲用水處理工藝流程,論文研究了水中溴酸鹽的生成特性,常規(guī)處理對溴酸鹽及其前驅(qū)物溴離子的控制,臭氧-活性炭工藝中的溴酸鹽控制,紫外輻射處理對水中溴酸鹽的控制,含溴飲用水處理工藝的構(gòu)建與優(yōu)化等內(nèi)容。通過水中溴酸鹽的生成特性的研究,明確了在水中常見的0500g/L的初始溴離子濃度范圍內(nèi)溴酸根和中間產(chǎn)物的數(shù)量關(guān)系,從而探明了04mg/L 的臭氧投量下溴酸鹽生成量較低的原因。臭氧劑量及水中初始溴離子濃度直接關(guān)系到水中溴酸鹽生成量。水中氨氮存在形式對pH值和溴酸鹽生成量有影響,與不含氨氮的水樣相比,pH值接近的含氨氮的水樣的溴酸鹽的生成量相對較低。在同一氨氮含量下,提高pH值,溴酸鹽的生成量

5、有小幅升高,氨氮對溴酸鹽的生成量的影響要大于pH值的影響。水樣投加銨鹽和投加氨水的實驗表明,對于含有銨根離子的水樣,由于其pH較低,所以對溴酸鹽生成的抑制作用更大。通過對含溴水進(jìn)行氯化實驗,探明了飲用水氯化消毒處理對溴離子及溴酸鹽的影響。含溴水樣加氯后,溴酸鹽的生成總量很小,加氯量5mg/L時,溴離子向溴酸根的轉(zhuǎn)化率不足 1.3%。次氯酸鈉長時間與溴離子接觸后,溴酸根的生成量只有小幅增加。在有機(jī)物濃度較高的水中,氯化不會導(dǎo)致溴酸鹽產(chǎn)生。含溴原水氯化時,加氯量1mg/L和3mg/L都未檢出溴酸鹽,加氯量達(dá)到5mg/L時,原水中只是檢出了非常少量的溴酸鹽。在飲用水余氯濃度為0.11 0.26 mg

6、/L,TOC為1.41.8 mg/L條件下,均未檢出溴酸根,說明飲用水中較低濃度的余氯不會將溴離子氧化為溴酸根,不存在使溴酸鹽超標(biāo)的風(fēng)險。通過以聚合氯化鋁和三氯化鐵作混凝劑的實驗,明確了混凝沉淀對溴酸鹽和溴離子有一定的控制作用,其效果受到混凝劑投量、pH、水樣濁度、水溫等條件的影響。三氯化鐵比聚合氯化鋁混凝沉淀對溴酸鹽及溴離子的控制效果- I -哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文更好,70mg/L 三氯化鐵投量下,對原水中溴酸鹽的平均去除率為58.5%。研制了具有除濁和控制溴酸鹽雙重功能的硅酸改性聚合亞鐵混凝劑,通過紅外光譜表征,證明改性聚合亞鐵混凝劑的制備效果可靠。改性聚合亞鐵混凝劑的除濁性能強(qiáng)

7、于普通鐵鹽和亞鐵鹽,改性聚合亞鐵混凝去除溴酸鹽和溴離子的效果很好。硅鐵比1:2的改性聚合亞鐵控制溴酸鹽的效果最佳,其投量為16.8mg/L時,溴酸鹽的平均去除率為83.8%,說明改性聚合亞鐵可作為控制水中溴酸鹽的有效混凝劑。明確了過濾對溴酸鹽和溴離子的控制作用有限,在水樣初始濁度為40NTU,pH=6.86,T=23條件下,濾層深度 1.2m時,溴酸鹽去除率為14.4%。溴離子去除率為13.6%。濾層厚度對溴酸鹽和溴離子濃度影響最大,其次是水樣的濁度,而在50200g/L范圍內(nèi),溴酸根和溴離子初始濃度的影響可以忽略。在中試的基礎(chǔ)上,確定了優(yōu)化臭氧-活性炭工藝參數(shù)控制溴酸鹽的方法。一方面,通過控

8、制臭氧氧化工藝參數(shù)限制溴酸鹽的生成量不超標(biāo)。另一方面,若溴酸鹽生成量已經(jīng)超標(biāo),通過控制活性炭運(yùn)行參數(shù)使得出水溴酸鹽的量不超標(biāo)。水中初始溴離子濃度、臭氧投量和接觸時間是控制溴酸鹽生成量的關(guān)鍵因素。在臭氧處理單元,建立了控制溴酸鹽生成量數(shù)學(xué)模型。在活性炭處理單元,炭柱接觸時間和進(jìn)水溴酸鹽濃度是控制溴酸鹽去除的關(guān)鍵因素,建立了控制溴酸鹽去除率數(shù)學(xué)模型?？疾炝?2個月連續(xù)運(yùn)行的活性炭表面微生物的情況及生物量的變化。證明了生物活性炭對水中溴酸鹽的去除效能強(qiáng)于活性炭,探明了生物活性炭對水中溴酸鹽的作用機(jī)理,明確了微生物在活性炭表面的作用。通過紫外輻射含溴酸鹽水樣的研究,確定了短波紫外線UVC輻射可以作為去

9、除飲用水中溴酸鹽的有效手段,但輻射的劑量要求較大。長波紫外線UV A是紫外還原溴酸鹽的一個干擾因素,應(yīng)當(dāng)減少其輻射劑量以確保水中溴酸鹽的還原效果。本文揭示了溴酸鹽及溴離子在水處理過程中的變化規(guī)律,構(gòu)建了全流程協(xié)同溴控制酸鹽的方法體系,探明了各個處理單元中控制溴酸鹽風(fēng)險的工藝參數(shù)。優(yōu)化了針對溴酸鹽控制的工藝運(yùn)行條件,為溴酸鹽控制技術(shù)在飲用水處理中的實際工程應(yīng)用提供了理論與技術(shù)指導(dǎo)。關(guān)鍵詞:飲用水;溴酸鹽;生成特性;優(yōu)化控制AbstractAbstractIn the micro-polluted drinking water treatment, ozone oxidation technolo

10、gy has been increasingly applied to drinking water treatment process. Containing bromide water in the ozone oxidation can generate bromate, which belongs to 2B level carcinogen,and the bromate concentration control is important to ensure the water quality security. At present, the relevant studies w

11、ere mainly on Application of various applied methods in the removal of bromate, which ignoring the conventional water treatment process itself. It has not been reported that the bromate in the conventional process could be removed in the recent related research. In the existing water treatment techn

12、ology, to solve the pollution problem of bromate is the most practical and easily applied and the most economical method.For the whole system of drinking water treatment, this paper investigated water bromate formation characteristics, conventional treatment on bromate and controlling its precursor

13、bromide ion, controlling bromate in ozone-activated carbon process, ultraviolet radiation treatment on the control of bromate in water, construction and optimization of bromine containing drinking water treatment technology.Through the research on the characteristics of bromate formation in water, w

14、e ascertained the quantitative relation between BrO3- and intermediate within the conventional range of 0 500g/L initial concentration of bromide ions in water, so as to find out the reason for low bromate production with 0 4mg/L ozone dosage. Ozone dosage and the initial concentration of bromide io

15、n in water are directly related to the formation of bromate in water quantity. Ammonia nitrogen forms have influence on pH and formation amount of BrO3-. Compared with water samples which contained no ammonia nitrogen, the formation amount of BrO3-was relatively lowe in pH value close to the ammonia

16、 water samples. In the same ammonia nitrogen content, when improved pH value, the formation amount of BrO3- was slightly elevated. It means that the influence of the ammonia nitrogen on the formation amount of BrO3- was more than pH value. The experiment of adding ammonium salt and adding ammonia to

17、 water respectively showed that the influence of ammonium group on bromide ion converting to bromate ion in water is哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文more than that of free ammonia due to its low pH.Based on the experiment with bromine chloride, we ascertained the effect of chloridizing disinfection of drinking water

18、on bromine and bromate. Water adding chlorine within 360min, the formation amount of bromate was small. When chlorine dosage was 5mg / L, the conversion rate of bromine ion to bromate was less than 1.3%. After long time for Sodium hypochlorite contacted with bromide ions, the formation amount of BrO

19、3- was slightly elevated. In the water with higher concentration of organic matter, chlorination did not lead to bromate. When chloridizing bromine water, bromate were not detected with chlorine dosage of 1mg/ L and 3mg/ L. With chlorine dosage up to 5mg / L, bromate was detected by very small amoun

20、t in raw water. When chlorine residual level was 0.110.26 mg/L and TOC was 1.4 1.8 mg/ L, BrO3- were not detected in drinking water. That meant the existence of low concentration of residual chlorine could not oxidize the bromide ions to bromate, let alone bromate exceed standard .By experiment of P

21、AC and FeCl3 as coagulant, the article made clear that coagulation and sedimentation have certain control effect on bromate and bromide ions, and its effect by coagulant dosage, pH, turbidity, water temperature and other conditions. The control effect of FeCl3 on bromate and bromide ions was better

22、than that of PAC coagulation sedimentation. With the dosage of FeCl3 of 70mg/L, the average removal rate of bromate was 58.5% in the raw water.A silicic acid modified polymerized ferrous coagulant was developed, which had turbidity removal and control of bromate in the dual function. characterized b

23、y infrared spectroscopy, we found that the modified polymerized ferrous coagulant preparation effect was reliable. The operty of turbidity removal of modified polymerized ferrous coagulant was stronger than common salt and ferrous salt. The effect of polymer modified ferric coagulation on removal of

24、 bromate and bromide ions was very good. Modified polymerized ferrous with ferrosilicon ratio 1:2 had best effect on control of bromate.When the dosage of 16.8mg/ L, bromate average removal rate was 83.8%, that meant modified polymerized iron could be used as efficient coagulant for the control of b

25、romate in water.The Control Action of filtration on bromate and bromide ion was limited. When the initial turbidity water was 40NTU, pH = 6.86, T=23, filter depth 1.2m, bromate removal rate was 14.4%, bromide ion removal rate was13.6%. The filter layer thickness had most important influence on broma

26、te and bromide ionsAbstractconcentration. Next came the water turbidity, in the range of 50200g/L, the initial concentration of bromate and bromide ion effect can be ignored.Based on the pilot experiment,we determined the method which controlled bromate by ozone-activated carbon process with the opt

27、imal parameter. On one hand, by controlling the ozone oxidation process parameter limits the bromate formation amount to not exceed the standard. On the other hand, if the bromate production had already exceed the standard, by controlling the operating parameters of the active carbon water bromate a

28、mount to not exceed the standard. The initial concentration of bromide ion in water, ozone dosage and contact time were the control of bromate production key elements. In the ozone processing unit, established the mathematical model of controlling bromate production. In the activated carbon processi

29、ng unit, an activated charcoal column contact time and water bromate concentration were the key factors of controlling bromate removal, established control of bromate removal rate mathematical model. We Studied 12months of continuous operation of the activated carbon surface microorganisms and bioma

30、ss change,and proved that the biological activated carbon for water bromate removal efficiency was better than activated carbon, It was ascertained that the mechanism of action of biological activated carbon on bromate in water , and the effect of microorganisms on activated carbon surface.Ultraviol

31、et radiation containing bromate in water was researched, then determined the shortwave ultraviolet UVC radiation can be used as effective means in the removal of bromate in drinking water, but the radiation dose required larger. UVA was a disturbance factor for reducing bromate, so we should reduce

32、the radiation dose to ensure water bromate reduction effect.This paper revealed the change law of bromate and bromide ions in water treatment process, and built the control technology system of bromate, proved the parameters combination in bromate processing unit for safety. We optimized process ope

33、rating conditions for bromate control, provided theoretical and technical guidance for bromate control technology in drinking water treatment in the actual project application.Keywords: drinking water, bromate, Formation characteristics, optimal control哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文目錄摘要.I ABSTRACT.III 第1章緒論 (11.1

34、課題研究背景 (11.2 溴酸鹽控制研究現(xiàn)狀 (51.3 本課題的來源及意義 (91.4 研究內(nèi)容及技術(shù)路線 (10第2章試驗材料與方法 (122.1 試驗?zāi)Ｐ脱b置設(shè)計 (122.2檢測指標(biāo)及分析方法 (15第3章水中溴酸鹽的生成特性 (23目錄3.1 溴離子向溴酸根的轉(zhuǎn)化規(guī)律 (233.2 pH值變化對溴酸鹽生成的影響 (293.3 氨氮和pH值對溴酸鹽生成的綜合影響 (313.4 水中有機(jī)物含量對溴酸鹽生成的影響 (333.5 氯化消毒對溴酸鹽生成的影響 (343.6 本章小結(jié) (37第4章常規(guī)水處理和強(qiáng)化混凝控制溴酸鹽及溴離子 (394.1混凝沉淀去除溴酸鹽的影響因素 (394.2 混凝

35、沉淀對水中溴離子的去除 (444.3 混凝沉淀對原水中溴酸鹽和溴離子的去除 (454.4 改性聚合亞鐵強(qiáng)化混凝對溴酸鹽和溴離子的去除 (494.5 過濾對溴酸鹽和溴離子的去除作用 (614.6 本章小結(jié) (62第5章臭氧-活性炭工藝中的溴酸鹽控制 (645.1優(yōu)化臭氧處理條件對溴酸鹽生成的控制 (64哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文5.2 優(yōu)化活性炭處理條件對溴酸鹽的去除 (705.3 生物活性炭對溴酸鹽的去除 (775.4本章小結(jié) (85第6章紫外輻射對溴酸鹽的控制 (876.1 UVC輻射對水中溴酸鹽的作用 (876.2 UVA對溴酸鹽的影響 (896.3 水質(zhì)條件對UVC輻射溴酸鹽的影響

36、(916.4 本章小結(jié) (93第7章飲用水處理工藝中溴酸鹽的控制對策 (957.1 全流程協(xié)同控制溴酸鹽的方法體系構(gòu)建 (957.2 水處理各單元環(huán)節(jié)控制溴酸鹽及溴離子的效能 (967.3 針對不同工藝情況的運(yùn)行條件優(yōu)化 (101目錄7.4 本章小結(jié) (105結(jié)論 (106參考文獻(xiàn) (108攻讀學(xué)位期間發(fā)表的學(xué)術(shù)論文及其他成果 (119哈爾濱工業(yè)大學(xué)學(xué)位論文原創(chuàng)性聲明及使用授權(quán)說明 (121致謝 (122個人簡歷 (123哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文ContentsAbstract (In Chinese.Abstract (In English. (Chapter 1 Introducti

37、on (11.1 Research background (11.2 Research situation for control of bromate (51.3 Source and significance of the project (91.4 Research contents and technical route (10Chapter 2 Test materials and methods (122.1 Design of test model device (122.2 Detection indexes and analytical methods (15by scann

38、ing electron microscope (20ContentsChapter 3 Formation characteristics of bromate in the water (233.1 Transformation rule between Br- and BrO3- (23on bromate formation (273.2 The effect of water pH value variation on BrO3- generation (293.3 Comprehensive influence of ammonia nitrogen and pH value on

39、BrO3- generation (313.4 Influence of organic matter content on BrO3- in water (333.5 The effect of chlorination disinfection on bromate formation (343.6 The chapter summary (37Chapter 4 The control of bromate and bromide ions by conventionalwater treatment and enhanced coagulation (394.1 Influence f

40、actors of coagulation sedimentation for removing the bromate (394.2 Removal of bromide ion by coagulation and sedimentation (444.3 The removal of Bromate and bromide by coagulation and sedimentationin raw water (454.4 The removal of Bromate and bromide by modified polymerized ferrous (49ferrous (51哈

41、爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文4.6 The chapter summary (62Chapter 5 The control of bromate in ozone-activated carbon process (645.1 The effect of optimization of ozone treatment conditions on thecontrol formation of bromate (645.2 Bromate removal by optimizing activated carbon treatment conditions (70treatment unit

42、(765.3 The removal of bromate by biological activated carbon (77biomass increasing (78continuous operation (83on bromate (845.4 The chapter summary (85Chapter 6 The control of bromate by ultraviolet radiation (876.1 The effect of UVC radiation on bromate in water (876.2 The effect of UVA on bromate

43、(896.3 The effect of water quality on the removal of bromate of UVC (91Contents6.4 The chapter summary (93chapter 7 bromate Control Countermeasures of drinking watertreatment process (957.1 The construction of whole process collaborative control of bromatemethod system (957.2 The control effectivene

44、ss of bromate and bromide in water treatment unit (967.3 The optimization of the operating conditions (101combined with process (101carbon combined with process (102ozone-activated carbon combined with process (1037.4 The chapter summary (105Conclusions (106References (108Papers published in the per

45、iod of Ph.D. education (119Statement of copyright and Letter of authorization (121Acknowledgements (122Resume (123第1章緒論第1章緒論1.1課題研究背景我國的水源水大部分受到了一定程度的污染1,如何保障飲用水安全是人們共同關(guān)注的問題。針對水中重要污染物的水處理技術(shù)急待發(fā)展和進(jìn)步,同時,逐步提高的飲用水衛(wèi)生標(biāo)準(zhǔn)也給水處理行業(yè)提出了一些新的要求。2006年,我國發(fā)布了新的生活飲用水衛(wèi)生標(biāo)準(zhǔn),比原來的水質(zhì)標(biāo)準(zhǔn)增加和修訂了多項水質(zhì)指標(biāo),新增的溴酸鹽、氯化氰、亞氯酸鹽、氯酸鹽等毒理指標(biāo),由于

46、其可能具有較大的毒性而受到人們的廣泛關(guān)注。溴酸鹽被國際癌癥研究機(jī)構(gòu)認(rèn)定為2B級潛在致癌物,有研究表明,如果長期飲用溴酸鹽濃度較高的水,患癌的可能性很高,而且溴酸鹽具有遺傳毒性2。目前,世界衛(wèi)生組織、歐盟、美國和中國都對飲用水中的溴酸鹽做出了限值10g/L的規(guī)定。在我國的很多江河入?？诟浇貐^(qū),地表水體有可能被海水入侵3,從而使得淡水水源中混入溴化物或溴酸鹽。據(jù)文獻(xiàn)報道,有些地區(qū)確實存在飲用水中含有溴酸鹽或溴酸鹽超標(biāo)的問題4-6,甚至在某些瓶裝礦泉水中溴酸鹽也被檢出7,而這些礦泉水的由水源是某些地區(qū)的地下水。因此,溴酸鹽問題成為飲用水安全中的重要問題。在我國的飲用水深度處理中,臭氧氧化除微污染技

47、術(shù)正在被逐步推廣和應(yīng)用8,臭氧氧化出水水質(zhì)的安全性已受到水處理行業(yè)的普遍關(guān)注9。在臭氧氧化技術(shù)應(yīng)用研究中發(fā)現(xiàn),往往因原水中有機(jī)物或溴化物的本底濃度高,導(dǎo)致臭氧出水中氯化消毒副產(chǎn)物或溴酸鹽存在超標(biāo)風(fēng)險,且國內(nèi)尚缺乏具有針對性的化學(xué)安全評價方法和關(guān)鍵控制技術(shù),各文獻(xiàn)的對此方面評價均不全面和清晰,大多數(shù)只對溴酸鹽的形成和危害進(jìn)行評價。本課題突出特點是考慮北方水體,由于沿海地區(qū)飲用水源受季節(jié)性咸潮影響或海水浸滲影響很大,及其農(nóng)業(yè)污染問題,沿海地區(qū)水體中均發(fā)現(xiàn)存在溴離子含量過高問題,水體中的溴離子濃度高達(dá)400g/L。當(dāng)采用臭氧工藝作為給水深度處理時,如水中含有溴離子,其和水中天然有機(jī)物作用,臭氧氧化后

48、會生成很多溴類副產(chǎn)物,包括無機(jī)溴化物溴酸鹽和有機(jī)溴化物。且由于大量的溴離子和水中天然有機(jī)物反應(yīng)。臭氧和天然有機(jī)物與水中溴離子存在相互競爭反應(yīng),使得生成物更加復(fù)雜。臭氧氧化過程中,溴離子分配關(guān)系及各溴類物質(zhì)如何變化,鮮有研究和報道。因此,很有哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文必要開展全面系統(tǒng)的臭氧氧化出水溴酸鹽安全性控制原理和技術(shù)研究。,我國已經(jīng)自2010年起開始執(zhí)行生活飲用水衛(wèi)生標(biāo)準(zhǔn)GB5749-2006,而目前大多數(shù)凈水廠的水質(zhì)和規(guī)定的106項指標(biāo)的要求還有較大的差距。作為有效的飲用水深度處理工藝,臭氧-活性炭工藝越來越多地被凈水廠采用,那么,溴酸鹽的生成及控制問題必將成為各個凈水廠關(guān)注的焦點。

49、臭氧氧化技術(shù)應(yīng)用最廣泛、最成功的領(lǐng)域是飲用水處理。臭氧作為一種強(qiáng)氧化劑,應(yīng)用于水處理已有90多年歷史。利用臭氧的主要作用是消毒和氧化,例如,嗅味和氣味的控制,脫色,微污染物的去除等等10,11。在飲用水處理工藝中,臭氧技術(shù)主要應(yīng)用在工藝最前端的預(yù)臭氧處理和過濾之后的主臭氧處理。預(yù)臭氧處理的主要作用是氧化分解水中的部分有機(jī)物和有害的無機(jī)物12,改善混凝處理的原水水質(zhì)條件。主臭氧處理通常會與活性炭吸附處理相聯(lián)合,臭氧-活性炭工藝的主要作用是繼續(xù)降低水中的微污染有機(jī)物濃度,去除三鹵甲烷及其前驅(qū)物質(zhì)13,提高飲用水出水水質(zhì)。臭氧氧化在水處理中的功能可概括為以下幾方面:(1臭氧消毒。臭氧可應(yīng)用于滅活細(xì)菌

50、、病毒和孢子 14,可對水體的微生物污染進(jìn)行控制15。(2水中無機(jī)物和有機(jī)物的氧化。臭氧可將水中的低價態(tài)的鐵、鎂、硫化物、氰化物、重金屬、亞硝酸鹽等物質(zhì)氧化,同時,臭氧可通過氧化水中有機(jī)物來降低水的色度,減輕水的味道和氣味,去除某些洗滌劑、農(nóng)藥及酚類等物質(zhì)16-18。(3去除氯化消毒的副產(chǎn)物。飲用水處理中典型的氯化消毒副產(chǎn)物主要是三鹵甲烷和鹵乙酸,在處理工藝前段采用預(yù)臭氧化技術(shù),可以通過直接去除氯化消毒副產(chǎn)物的前驅(qū)物質(zhì)或者轉(zhuǎn)化其前驅(qū)物質(zhì)來控制氯化消毒的副產(chǎn)物,從而減輕后續(xù)處理工藝的處理壓力19-22。(4控制水中的藻類。預(yù)臭氧氧化可將藻細(xì)胞溶裂,也可以直接殺藻,從而減輕藻類對后續(xù)工藝處理效果的

51、影響23。(5助凝。在混凝處理之前設(shè)置預(yù)臭氧處理單元,混凝劑的投量可適當(dāng)減少,同時,還可能提高混凝除濁的效果,改善濾池的進(jìn)水水質(zhì)。臭氧氧化可以與許多水處理技術(shù)聯(lián)合應(yīng)用以解決相應(yīng)的難題,如過濾、離子交換、活性炭吸附和反滲透等24。臭氧的氧化性很強(qiáng),可以與水中多種有機(jī)物和無機(jī)物發(fā)生反應(yīng)。在不同的水質(zhì)條件和臭氧劑量下,臭氧氧化的產(chǎn)物種類也不同。不過,水中腐植酸等有機(jī)物在臭氧的作用下不易被完全氧化。有機(jī)物第1章緒論徹底氧化的產(chǎn)物主要是水和二氧化碳,而已有研究證明臭氧對有機(jī)物的主要作用是將大分子物質(zhì)分解為小分子物質(zhì),同時,還可能生成一些新的含氧官能團(tuán)及飽和的化學(xué)鍵25。經(jīng)臭氧處理后的水,其水質(zhì)有利于活性

52、炭吸附和微生物降解。有研究表明,在對微污染水進(jìn)行處理的過程中,發(fā)現(xiàn)了多種對人類健康有害的副產(chǎn)物,這些有害物質(zhì)的出現(xiàn)使得臭氧氧化后的水質(zhì)受到影響26,27。臭氧氧化的副產(chǎn)物有有機(jī)物和無機(jī)物,水中腐殖酸類有機(jī)物可被臭氧氧化為甲醛和乙醛等有毒物質(zhì)28,水中無機(jī)溴化物被臭氧氧化為溴酸鹽的過程非常復(fù)雜,水質(zhì)條件對反應(yīng)過程有較大影響。溴離子存在于飲水中不會危害人體健康,但溴離子在強(qiáng)氧化劑的作用下可能會轉(zhuǎn)化為溴酸根29-31。天然水體中的溴離子可能的來源主要是咸潮入侵地表淡水水體或滲入地下水的潛水水層32,以及各種礦物在水體中的溶解33。水中溴離子的濃度還與人類的工業(yè)生產(chǎn)有關(guān)34,在礦業(yè)開采和各種無機(jī)鹽類藥

53、劑的生產(chǎn)過程中有可能造成部分溴離子排入水體中35。在一些城市冬季使用的融雪劑中也可能含有溴離子,用于農(nóng)業(yè)生產(chǎn)的化肥中可能含有含溴物質(zhì),這些含溴物質(zhì)有可能通過污水排放或地表徑流進(jìn)入天然水體。根據(jù)國外的調(diào)查研究結(jié)果,歐洲地表河流中溴離子平均濃度為150µg/L;地下水中溴離子平均濃度為102µg/L36。美國的地表水體中溴離子的平均濃度為110µg/L;地下水中溴離子濃平均濃度為96µg/L;受海水入侵的影響,沿海地區(qū)水體中溴離子濃度偏高,平均濃度為210µg/L37。我國深圳水庫中溴離子濃度平均值為24µg/L,最大值為73.3

54、1;g/L,深圳市的流域面積較大的河流中溴離子平均濃度在60.81056µg/L之間,地下水中溴離子濃度在60250µg/L之間38。黃河水中溴離子平均濃度為200µg/L39。黃浦江上游三大支流的溴離子平均濃度為200µg/L40。長江口處的青草沙水庫中溴離子濃度約為500µg/L41。水中存在溴離子是導(dǎo)致溴酸鹽產(chǎn)生的主要因素之一。溴離子可能被一些氧化劑氧化為溴代副產(chǎn)物 42,43,這些溴代物質(zhì)可能被臭氧等強(qiáng)氧化劑氧化為溴酸鹽44,45,在一些高級氧化聯(lián)用技術(shù)應(yīng)用中,也可能將溴離子氧化為溴酸鹽46,47。當(dāng)溴離子濃度較大時,生成溴酸鹽的濃度存

55、在超標(biāo)的可能。溴酸鹽對人體的毒害作用很強(qiáng),若長期飲用含有溴酸鹽濃度較高的飲用水,會嚴(yán)重危害健康48。有研究表明,溴酸鹽可導(dǎo)致動物體產(chǎn)生腫瘤,小白鼠哈爾濱工業(yè)大學(xué)工學(xué)博士學(xué)位論文喂養(yǎng)實驗證明長期食用溴酸鹽的小鼠出現(xiàn)了甲狀腺、腹膜及腎小管的損傷41。小白鼠連續(xù)食用溴酸鹽100周后,導(dǎo)致癌變的幾率為10%49。若一次性食用大量的溴酸鹽,短時間內(nèi)就會出現(xiàn)腹痛、腹瀉和嘔吐癥狀,還可能會引發(fā)耳聾失聰?shù)炔“Y50。此外,動物體內(nèi)溴酸鹽劑量較高時,可能會使DNA被氧化破壞,溴酸鹽可能伴有遺傳毒性51-53。作為一種強(qiáng)氧化劑,臭氧的氧化還原電位很高,因而臭氧可將水中的多種物質(zhì)氧化。溴酸鹽形成的過程非常復(fù)雜54,所

56、涉及的化學(xué)反應(yīng)多達(dá)幾十個55。在溴離子轉(zhuǎn)化為溴酸鹽的過程中,可能會生成一些其他含溴物質(zhì)56,57。主要中間產(chǎn)物有:亞溴酸鹽(BrO2- 、溴氧自由基(BrO·、次溴酸(HOBr、次溴酸鹽(OBr- 和溴自由基(Br·等58,59。目前,被研究人員普遍認(rèn)可的溴酸鹽的形成途徑有:溴離子直接被臭氧分子氧化和溴離子被羥基自由基氧化生成溴酸鹽60,61,在具體反應(yīng)中究竟是以哪種途徑為主,取決于反應(yīng)體系的很多條件因素62,63。(1臭氧分子直接氧化過程Gunten U V認(rèn)為,水中投加臭氧后,溴離子被氧化為次溴酸和次溴酸根58,不過,這是一個可逆反應(yīng),次溴酸根還可能轉(zhuǎn)化為溴離子64,65。在氨氮存在的條件下,次溴酸可能會轉(zhuǎn)化為溴銨66,67。在臭氧濃度增加的過程中,次溴酸根會繼續(xù)氧化為亞溴酸根和溴酸根68,69。臭氧分子直接氧化溴離子生成溴酸鹽的過程如圖1-1所示。 圖1-1 臭氧氧化Br-生成BrO3-的過程70Fig.1-1 The process of Br- transformed into BrO3- by ozone oxidation 70(2羥基自由基氧