PCBs在城鎮(zhèn)污水處理過程中的分布規(guī)律及去除特性研究
發(fā)布時間：2018-08-30 07:47
【摘要】：持久性有機(jī)污染物(POPs)被UNEP視為 世界面臨的最大環(huán)境挑戰(zhàn)之一‖,因其具有持久性、生物累積性、高毒性和半揮發(fā)性,對人體和生態(tài)系統(tǒng)具有不可估量的危害。多氯聯(lián)苯(PCBs)作為最具代表性的POPs之一,由于曾經(jīng)大量生產(chǎn)和應(yīng)用于多種工業(yè)領(lǐng)域,其在各種環(huán)境介質(zhì)中廣泛存在,包括城鎮(zhèn)污水。由城鎮(zhèn)污水傳播到水環(huán)境中或回用水中的PCBs是人類健康和安全的巨大隱患。本文以EPA推薦的7種多氯聯(lián)苯(PCB28、PCB52、PCB101、PCB118、PCB138、PCB153、PCB180)為目標(biāo)物,采用固相萃取(SPE)、索氏提取(SOX)前處理技術(shù)和氣相色譜-質(zhì)譜連用法(GC-MS),考察北京市城鎮(zhèn)污水、污泥中PCBs的存在現(xiàn)狀及污染水平,分析污水處理過程中PCBs在污水、污泥中的分布,比較三種活性污泥法污水處理工藝(AO、A/A/O、SBR)對PCBs的去除規(guī)律和效果,研究粉末活性炭(PAC)和4種碳納米管(SWCNT、MWCNT-8、MWCNT-30、MWCNT-50)對水中PCBs的吸附動力學(xué)和吸附等溫線,采用擬一級、擬二級動力學(xué)吸附模型以及Langgmuir、Freundlich吸附等溫線模型對實(shí)驗(yàn)數(shù)據(jù)進(jìn)行擬合,分析粉末活性炭和碳納米管對水中PCBs的吸附特性。研究結(jié)果表明:(1)本市城鎮(zhèn)污水中ΣPCBs濃度為18.67 ng?L~(-1)~56.28 ng?L~(-1)之間,活性污泥中ΣPCBs含量在43.13~176.41 ng?g~(-1)之間,與國內(nèi)外其他地區(qū)相比均處于中等水平。(2)PCBs在污水處理過程中的去除主要依靠固體懸浮顆粒和活性污泥的吸附作用,初沉池對PCBs有較好的去除效果,二級處理中的好氧階段是去除主體,厭氧階段高氯聯(lián)苯可能發(fā)生降解生成氯代程度較低的中間產(chǎn)物。相比于A/O和A/A/O的普通二沉池,SBR的沉淀階段對PCBs有較高的去除作用。相對于進(jìn)水,二沉池出水中低氯聯(lián)苯的比例增加、高氯聯(lián)苯的比例下降;初沉池污泥中高氯聯(lián)苯的比例較高,二沉池污泥中PCBs的分布與進(jìn)水中相似。(3)粉末活性炭和碳納米管都能實(shí)現(xiàn)對PCBs的快速吸附,對不同PCBs單體的吸附效果有所差異。粉末活性炭對PCBs的吸附在100 min以后趨于平衡,碳納米管對PCBs的吸附在80 min以后達(dá)到平衡。相比之下,CNTs更早達(dá)到吸附平衡,且平衡吸附量更大。(4)擬一級和擬二級動力學(xué)吸附模型均能較好地擬合PAC和CNTs對PCBs的吸附過程,擬一級模型的Adj-R~2均大于0.95,擬二級模型的Adj-R~2均大于0.98。擬二級吸附模型的擬合效果更好,說明PAC和CNTs對PCBs的吸附是較為復(fù)雜的多步過程。(5)Freundlich和Langmuir吸附等溫線模型都能較好的描述PAC和四種CNTs對PCBs的吸附等溫過程,Langmuir模型的Adj-R~2都在0.98以上,Freundlich的模型的的Adj-R~2都在0.99以上,擬合結(jié)果較好。SWCNT對水中PCBs的最大吸附容量最大,MWCNTs次之,PAC最小,與吸附動力學(xué)結(jié)論一致。
[Abstract]:Persistent organic pollutant (POPs) is regarded as one of the biggest environmental challenges facing the world by UNEP because of its persistence bioaccumulation high toxicity and semi-volatility which has incalculable harm to human body and ecosystem. Polychlorinated biphenyls (PCBs) (PCBs), as one of the most representative POPs, is widely used in various environmental media, including municipal sewage, because of its mass production and application in a variety of industrial fields. PCBs, which is transmitted from urban sewage to water environment or recycled water, is a great hidden danger to human health and safety. In this paper, seven kinds of polychlorinated biphenyls (PCB28,PCB52,PCB101,PCB118,PCB138,PCB153,PCB180) recommended by EPA were used as the target materials, the pretreatment of (SOX) extracted by solid phase extraction of (SPE), Soxhlet and the continuous use of gas chromatography-mass spectrometry (GC-MS) were used to investigate the existing situation and pollution level of PCBs in municipal sewage and sludge in Beijing. The distribution of PCBs in sewage and sludge during sewage treatment was analyzed, and the removal law and effect of PCBs by three activated sludge wastewater treatment processes (AO,A/A/O,SBR) were compared. The adsorption kinetics and isotherm of PCBs in water by powdered activated carbon (PAC) and four kinds of carbon nanotubes (SWCNT,MWCNT-8,MWCNT-30,MWCNT-50) were studied. The experimental data were fitted by pseudo-first-order, pseudo-second-order kinetic adsorption model and Langgmuir,Freundlich adsorption isotherm model. The adsorption characteristics of powdered activated carbon (AC) and carbon nanotubes (CNTs) for PCBs in water were analyzed. The results showed that: (1) 危 PCBs concentration in municipal sewage was between 18.67 ng?L~ (-1) and 56.28 ng?L~ (-1), and 危 PCBs content in activated sludge was between 43.13 and 176.41 ng?g~ (-1). Compared with other regions at home and abroad, the removal of PCBs mainly depends on the adsorption of solid suspended particles and activated sludge, and the primary settling tank has better removal effect on PCBs. The aerobic stage of secondary treatment is the removal of the main body, and the degradation of high chlorinated biphenyls in anaerobic stage may produce intermediate products with lower chlorination degree. Compared with the precipitation stage of ordinary secondary settling tank SBR of A- O and A/A/O, it has higher removal effect on PCBs. Compared with the influent, the proportion of low and low chlorinated biphenyls in the effluent of secondary sedimentation tank increased, while the proportion of high chlorinated biphenyl in sludge of primary sedimentation tank decreased, and the proportion of high chlorinated biphenyl in sludge of primary settling tank was higher. The distribution of PCBs in the sludge of secondary settling tank is similar to that in influent. (3) both powdered activated carbon and carbon nanotubes can realize the rapid adsorption of PCBs, and the adsorption effects of different PCBs monomers are different. The adsorption of PCBs on powdered activated carbon tends to balance after 100 min, and the adsorption of PCBs on carbon nanotubes reaches equilibrium after 80 min. By comparison, the adsorption equilibrium was achieved earlier and the adsorption capacity was larger. (4) the pseudo-first-order and pseudo-second-order kinetic adsorption models could better fit the adsorption process of PCBs by PAC and CNTs. The Adj-R~2 of pseudo-first-order model was greater than 0.95.The Adj-R~2 of pseudo-second-order model was all greater than 0.98. The fitting effect of pseudo-two-order adsorption model is better. (5) the isotherm model of Freundlich and Langmuir can describe the isotherm process of PAC and four CNTs adsorption isotherms for PCBs. The Adj-R~2 of PAC model is more than 0.98 and the Adj-R~2 of Freundlich model is more than 0.99, which shows that the adsorption of PCBs by PAC and CNTs is more complicated. (5) the isotherm model of Freundlich and Langmuir can well describe the isotherm process of PAC and four CNTs adsorption isotherms of PCBs and the Adj-R~2 of Freundlich model is more than 0.99. The fitting results showed that the maximum adsorption capacity of PCBs in water was the largest and the second was the lowest, which was consistent with the adsorption kinetics.
【學(xué)位授予單位】：北京建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X703
本文編號：2212421
[Abstract]:Persistent organic pollutant (POPs) is regarded as one of the biggest environmental challenges facing the world by UNEP because of its persistence bioaccumulation high toxicity and semi-volatility which has incalculable harm to human body and ecosystem. Polychlorinated biphenyls (PCBs) (PCBs), as one of the most representative POPs, is widely used in various environmental media, including municipal sewage, because of its mass production and application in a variety of industrial fields. PCBs, which is transmitted from urban sewage to water environment or recycled water, is a great hidden danger to human health and safety. In this paper, seven kinds of polychlorinated biphenyls (PCB28,PCB52,PCB101,PCB118,PCB138,PCB153,PCB180) recommended by EPA were used as the target materials, the pretreatment of (SOX) extracted by solid phase extraction of (SPE), Soxhlet and the continuous use of gas chromatography-mass spectrometry (GC-MS) were used to investigate the existing situation and pollution level of PCBs in municipal sewage and sludge in Beijing. The distribution of PCBs in sewage and sludge during sewage treatment was analyzed, and the removal law and effect of PCBs by three activated sludge wastewater treatment processes (AO,A/A/O,SBR) were compared. The adsorption kinetics and isotherm of PCBs in water by powdered activated carbon (PAC) and four kinds of carbon nanotubes (SWCNT,MWCNT-8,MWCNT-30,MWCNT-50) were studied. The experimental data were fitted by pseudo-first-order, pseudo-second-order kinetic adsorption model and Langgmuir,Freundlich adsorption isotherm model. The adsorption characteristics of powdered activated carbon (AC) and carbon nanotubes (CNTs) for PCBs in water were analyzed. The results showed that: (1) 危 PCBs concentration in municipal sewage was between 18.67 ng?L~ (-1) and 56.28 ng?L~ (-1), and 危 PCBs content in activated sludge was between 43.13 and 176.41 ng?g~ (-1). Compared with other regions at home and abroad, the removal of PCBs mainly depends on the adsorption of solid suspended particles and activated sludge, and the primary settling tank has better removal effect on PCBs. The aerobic stage of secondary treatment is the removal of the main body, and the degradation of high chlorinated biphenyls in anaerobic stage may produce intermediate products with lower chlorination degree. Compared with the precipitation stage of ordinary secondary settling tank SBR of A- O and A/A/O, it has higher removal effect on PCBs. Compared with the influent, the proportion of low and low chlorinated biphenyls in the effluent of secondary sedimentation tank increased, while the proportion of high chlorinated biphenyl in sludge of primary sedimentation tank decreased, and the proportion of high chlorinated biphenyl in sludge of primary settling tank was higher. The distribution of PCBs in the sludge of secondary settling tank is similar to that in influent. (3) both powdered activated carbon and carbon nanotubes can realize the rapid adsorption of PCBs, and the adsorption effects of different PCBs monomers are different. The adsorption of PCBs on powdered activated carbon tends to balance after 100 min, and the adsorption of PCBs on carbon nanotubes reaches equilibrium after 80 min. By comparison, the adsorption equilibrium was achieved earlier and the adsorption capacity was larger. (4) the pseudo-first-order and pseudo-second-order kinetic adsorption models could better fit the adsorption process of PCBs by PAC and CNTs. The Adj-R~2 of pseudo-first-order model was greater than 0.95.The Adj-R~2 of pseudo-second-order model was all greater than 0.98. The fitting effect of pseudo-two-order adsorption model is better. (5) the isotherm model of Freundlich and Langmuir can describe the isotherm process of PAC and four CNTs adsorption isotherms for PCBs. The Adj-R~2 of PAC model is more than 0.98 and the Adj-R~2 of Freundlich model is more than 0.99, which shows that the adsorption of PCBs by PAC and CNTs is more complicated. (5) the isotherm model of Freundlich and Langmuir can well describe the isotherm process of PAC and four CNTs adsorption isotherms of PCBs and the Adj-R~2 of Freundlich model is more than 0.99. The fitting results showed that the maximum adsorption capacity of PCBs in water was the largest and the second was the lowest, which was consistent with the adsorption kinetics.
【學(xué)位授予單位】：北京建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X703
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