【作者】 冯琳；

【导师】 黄玉明；

【作者基本信息】 西南大学 ， 分析化学， 2009， 博士

【摘要】 人工湿地（Constructed wetland,简称CW）是20世纪50、60年代开始研究并发展起来的水处理生态系统。自从1972年Kickuth提出“根区理论”以来,人工湿地作为一种独特的新型污水处理技术进入水污染控制领域。人工湿地是一个完整的生态系统,具有高效、操作简单、维护和运行费用低廉等优点,尤其适合广大城镇及农村的污水处理,具有极广阔的应用前景。但是,由于人工湿地处理污水机理的复杂性及湿地处理的“黑箱效应”,目前尚缺乏深入的机理研究,加之水力学复杂性及对工艺动力学缺乏深入的了解,因此,人们正投入大量精力以改良人工湿地技术。在绝大多数研究中,人们主要是通过检测出口及入口水中化学需氧量（COD）及生物化学需氧量（BOD）的变化来评价人工湿地去除有机污染物的效果,而对COD、BOD的化学构成以及在人工湿地运行过程中有机物降解中间产物研究很少。众所周知,溶解有机质在废水生物化学处理过程中具有重要作用,因此,系统分析研究人工湿地处理过程中有机物及其降解中间产物对于进一步提高人工湿地的处理效能是至关重要的。固相微萃取是在固相萃取的基础上发展起来的绿色萃取技术,它无需有机溶剂,大大简化了分析过程,特别适用于复杂的湿地废水中有机物及其降解中间产物,尤其是对挥发性有机物的分析测定。本文是国家自然科学基金（No.20477033）资助下的部分研究内容,重点研究潜流人工湿地中有机污染物降解及其机理,主要研究内容如下:1、顶空固相微萃取（HS-SPME）-气相色谱（GC）-火焰离子检测法（FID）测定废水中挥发性脂肪酸（VFAs）的分析方法研究,利用短链的VFAs在聚丙烯酸脂（PA）萃取头上的选择性吸附,建立了SPME-GC-FID对湿地废水中VFAs的分析方法;2、设计及运行参数对潜流人工湿地中挥发性脂肪酸去除的影响研究,通过湿地设计参数和运行参数对湿地处理后的废水中VFAs的影响,讨论了各参数对短链VFAs去除的影响及规律:3、中试规模人工湿地中有机负荷、温度、硫酸盐、及水力停留时间对挥发性短链脂肪酸去除的影响,通过湿地中的几个影响因素的变化和湿地中VFAs的去除关系,探讨了湿地中有机污染物降解中间产物VFAs的去除机理;4、顶空固相微萃取结合气相色谱-火焰光度检测器（FPD）测定废水中烷基硫醇化合物,通过优化SPME条件,利用对硫选择性的监测器FPD,建立了分析小分子硫醇的新方法。通过研究,得到以下主要的结果:一、顶空固相微萃取-GC-FID测定废水中挥发性脂肪酸的分析方法研究建立了顶空固相微萃取-气相色谱结合火焰离子检测器直接测定人工湿地废水中VFAs的分析方法。通过研究VFAs在不同涂层的萃取行为和在Stabilwax-DA毛细管柱（内经30m×0.32mm,膜厚0.25μm）及氮气为载气条件下的色谱行为,选择聚丙烯酸脂PA涂层的纤维头富集VFAs,获得了优化的色谱条件。GC炉温的程序升温条件:炉温70℃停留2 min,然后以4℃/min的速率升温到180℃,保持2min,再以20℃/min的速率升温到200℃,保持最后的温度3min。通过研究不同的参数包括萃取时间,萃取温度,pH值,离子强度,样品体积及解吸条件对萃取效率的影响,以优化HS-SPME对废水中VFAs的分析测定。实验结果表明:方法的线性范围为10-45000μg/L,对不同链长的VFAs,线性范围分别为2-4个数量级。VFAs的检测限（3σ）低至μg/L,相对标准偏差低于10%,回收率达85%-117%。以2-乙基丁酸为内标物,该方法用于人工湿地废水中VFAs的分析测定,结果满意。二、设计及运行参数对潜流人工湿地中挥发性脂肪酸去除的影响研究以中试规模的潜流人工湿地（SSFW）水处理系统为对象,研究了床体长宽比、填料粒径、水位和水力负荷（HLR）等设计及运行参数对废水中VFAs去除的影响。通过一年的运行及监测分析,结果表明,当湿地系统水力负荷为12-86 cm’d^-1时,人工湿地系统对所研究的VFAs具有很好的去除作用,VFAs中重要的乙酸和丙酸的去除率分别为64%及86%左右;方差分析表明水力负荷和温度是影响所研究的污染物去除的两个主要因素;水力负荷对出口水中乙酸、异戊酸及己酸的浓度有显著性影响（p＜0.05）;温度（季节）对出口水中的VFAs浓度有显著性影响（p＜0.05）。较深水位（70cm）的床体对乙酸及丙酸的去除效果较浅水位床体（50cm）的好;而床体长宽比、填料粒径大小及水位对出口水中的VFAs浓度没有显著性影响（p＞0.05）。通过沿程样品中溶解氧和氧化还原电位的测定分析,发现本湿地系统有着极强的还原环境（Eh＜-300mV）,结合硫酸盐、硝酸盐、亚硝酸盐等电子受体及溶解有机物（TOC）浓度在湿地系统中的变化趋势,推测VFAs的去除主要是通过硫酸盐还原菌及产甲烷菌作用进行的。三、中试规模人工湿地中有机负荷、温度、硫酸盐、及水力停留时间对挥发性短链脂肪酸去除的影响以中试规模的SSFW水处理系统为对象,研究评价了在SSFW运行期间,湿地水中有机负荷（OLR）、温度、硫酸盐、及水力停留时间（HRT）等因素对挥发性短链脂肪酸（VFAs）影响。结果表明,OLR和COD/SO₄^2-比是影响VFAs去除效率的重要因素。较高的OLR、高温、较长的HRT（2.62d）有利于VFAs的去除。本研究的SSFW水中COD/SO₄^2-比为6,表明该SSFW中乙酸的降解可能以产甲烷菌降解为主,在此基础上讨论了SSFW中VFAs可能的去除机理。四、顶空固相微萃取GC-FPD测定废水中烷基硫醇化合物建立了顶空固相微萃取-气相色谱法测定人工湿地废水中烷基硫醇化合物的分析方法。采用顶空固相微萃取（HS-SPME）为样品前处理方法及对含硫化合物有选择性的FPD为检测器,详细研究了萃取参数如萃取涂层、萃取时间、萃取温度、样品体积、盐效应、样品pH值等对HS-SPME萃取乙硫醇（EtSH）、2-甲基-2-丙硫醇（Me-PrSH）、1-丙硫醇（1-PrSH）、2-丙硫醇（2-PrSH）、1-丁硫醇（1-BuSH）、环戊硫醇（CycloPeSH）（内标）的影响。富集的硫醇化合物经DB-VRX（60m×0.25mm×1.40μm）毛细管色谱柱分离,FPD检测。在优化的实验条件下,本法测定乙硫醇、2-甲基-2-丙硫醇、1-丙硫醇、2-丙硫醇、1-丁硫醇的线性范围介于0.12～16.21μg/L之间,检出限（3σ）介于0.97～7.89ng/L之间,相对标准偏差介于2.8～7.5%之间。以环戊硫醇为内标物质,将本法用于废水中硫醇化合物的测定,获得满意结果。更多还原

【Abstract】 Constructed Wetland（CW） is one of wastewater treatment systems developed since 50 to 60’s in the 20th century.Since the appearance of the root zone theory,which was firstly proposed by Kickuth in 1972,the constructed wetland as a new wastewater treatment technology has entered into the field of water pollution control.CW promises high efficiency for removal of contaminants in wastewaters,easy operation,low cost for operation and maintenance.And it is especially suitable for wastewater treatment in the area of the small town and countryside.However,due to the complication and the“black box”mechanism involved in contaminant removal in CW,knowledge regarding the fate and dynamics of contaminants and their fate in constructed wetland system is highly limited.And great efforts have been paid to modification of CW technology.Currently,the available information on the performance of these systems is limited to common contaminants,such as chemical oxygen demand（COD）,biochemical oxygen demand（BOD₅）.Very little study on the chemical constitutes of COD,BOD₅,and specific degradation intermediates of organic contaminants in the operation process of constructed wetlands.It is well known that the dissolved organic matter plays an important role in the process of biochemical wastewater treatment.Therefore,it is essential to systematically study the organic matter and its degradation intermediate products in the constructed wetland system in order to improve its performance.Solid-phase microextraction is a green extraction technology derived from the solid-phase extraction.Solid-phase microextraction is organic solvent-free.Using solid-phase microextraction can greatly simplify the analytical processes.It is suitable to analysis and determination of organic compounds and their degradation intermediates in complex wastewaters,and especially for the analysis of volatile organic compounds. Under the financial support of the Natural Science Foundation of China（No.20477033）,this dissertation focused on the degradation and mechanism of the organic contaminants in the subsurface constructed wetlands,and the main contents are as follows:（1） Headspace solid-phase microextraction in combination with GC-FID for quantification of the volatile free fatty acids in wastewater from constructed wetlands has been developed.It is based on the selective adsorption of VFAs onto polyacrylate（PA） fiber.（2） Effect of design and operation parameters on removal of volatile fatty acids in the subsurface constructed wetlands were investigated through the statistic analysis of parameters effects.（3） Effect of organic loading rate,sulfate,temperature and hydraulic retention time on the behavior of volatile short chain fatty acids was investigated in a pilot-scale constructed wetlands system.The removal mechanism of degradation intermediates of organic contaminants in the constructed wetland has also been studied.（4） A new method for the determination of small molecule organic sulfur such as alkanethiols has been developed based on the headspace solid-phase microextraction combined with gas chromatography-flame photometric detector（FPD）.The optimized conditions for the analysis of alkanethiols were obtained.The major conclusions are summarized as follows:1.Solid-Phase Microextraction in Combination with GC-FID for Quantification of the Volatile Free Fatty Acids in Wastewater from Constructed WetlandsA headspace solid-phase microextraction（HS-SPME） followed by gas chromatography coupled to flame ionization detector（GC-FID） has been developed for the direct determination of volatile fatty acids（VFAs） in wastewater from constructed wetlands.Through the investigation on extraction behavior of different coatings for VFAs and the chromatographic behavior of VFAs in Stabilwax-DA capillary column（30m×0.32mm i.d.,0.25μm film thickness） using nitrogen as carrier gas,the polyacrylate（PA） fiber was selected as the satisfactory coating for VFAs analysis, and optimum chromatographic conditions were obtained.The oven temperature was programmed at 70℃for 2 min,then a 4℃/rain rate until 180℃,holding 2 min,and then a 20℃/min rate until 200℃,holding the final temperature for 3 min.The various parameters including extraction time,extraction temperature,pH value,ion strength,sample volume and desorption conditions were investigated for optimization of HS-SPME performance for VFAs in the wastewater.The experimental results show that the linear dynamic ranges were 10-45000μg/L,and over two to four orders of magnitude depending on different acids.The detection limit（3σ） for VFAs were low toμg/L levels and the RSDs were less than 10%,and the recoveries were between 85%and 117%. By using 2-ethylbutyric acid as internal standard,the proposed method has been successfully applied to determination of VFAs in wastewater from the constructed wetlands.2.Effect of Design and Operation Parameters on Removal of Volatile Fatty Acids in Subsurface Flow Constructed WetlandsA pilot-scale subsurface constructed wetland wastewater treatment system was sampled for one year to study the effect of bed aspect ratio,substrate medium size,water depth,HLR（hydraulic loading rate） and temperature（season） on removal of VFAs.The yearly experimental results demonstrated that the system showed good performance for VFAs removal in wastewater under different HLR ranging from 12 cm d^-1 to 86 cm d^-1.The system removed 64%of acetic,86%of propionic acid,respectively.The results showed that HLR and water temperature（season） were major factors that controlled the system performance for the target analytes.According to ANOVA test,the HLR caused significant differences（p＜0.05） on the average acetic,isopentanoic, hexanoic acids effluent concentrations.And temperature caused significant differences（p＜0.05） on the average effluent concentrations of all target analysts.Deep water depth caused better removal for acetic and propionic acids.However,bed aspect ratio,substrate medium size and water depth did not cause significant differences（p＞0.05） on the average VFAs effluent concentrations. The survey of dissolved oxygen and redox potential（ORP） indicated that the constructed wetlands system showed strong reduced condition.On the basis of investigations of electron acceptors(such as SO₄^2-,NO₃^- and NO₂^-) and dissolved organic pollutants（such as TOC） concentrations along with the length of constructed wetlands,it can be concluded that anaerobic biology processes such as sulfate reduction and methanogenisis were the main mechanism for VFAs removal in constructed wetland beds.3.Effects of Organic Loading Rate,Temperature,Sulfate,Hydraulic Retention Time On the Removal of the Volatile Short Chain Fatty Acids in a Pilot-Scale Constructed WetlandsThis study investigated the effect of organic loading rate（OLR）,temperature,sulfate concentration and hydraulic retention time（HRT） on the removal of volatile short chain fatty acids （VFAs） in a pilot-scale subsurface constructed wetland wastewater treatment system.The results indicated that OLR and COD/SO₄^2- ratio are two important factors affecting the VFAs removals. Higher OLR,higher temperature,and relative longer retention time（i.e.2.6 d） favored the VFAs removal in the studied wetland during the sampling period.Influent COD/SO₄^2- ratio was about 6, suggesting that methanogensis was probably a dominant pathway for acetic acid degradation in the present SSFW system.The possible mechanism for VFAs removal in SSFW was also discussed.4.Headspace Solid-Phase Microextraction Combined with Gas Chromatography -Flame Photometric Detection for the Analysis of Alkylthiols in WastewaterA headspace solid-phase microextraction combined with gas chromatography/flame photometric detection has been developed for the analysis of alkylthiols in wastewater from constructed wetlands.The effect of various extraction parameters such as extraction coatings, extraction time,temperature,sample volume,salt effect,sample pH value on the extraction of alkylthiols,namely,EtSH,Me-PrSH,1-PrSH,2-PrSH,1-BuSH and CycloPeSH were investigated and optimized.The enriched alkylthiols were separated by DB-VRX（60m×0.25 mm×1.40μm） capillary column and detected by FPD.Under the optimized conditions,the linear dynamic ranges for EtSH,Me-PrSH,1-PrSH,2-PrSH,1-BuSH were in the range of 0.12～16.21μg/L.The detection limit（3σ） for the studied five alkylthiols were 0.97～7.89 ng/L with RSD（n＝11） ranging from 2.8%to 7.5%.By using CycloPeSH as internal standard,the proposed method has been applied successfully to the analysis of alkylthiols in wastewater from constructed wetlands with satisfactory results.更多还原