pH值对“Fe^0．厌氧微生物”体系去除2，4，6-三氯酚过程的影响

考察了pH值对“Fe^0一厌氧微生物”体系降解2，4，6，一三氯酚（2，4，6．TCP）效果的影响，结果表明：pH值是影响“Fe^0-厌氧微生物”体系降解2，4，6-TCP效果的重要参数，初始pH值直接影响微生物活性和铁腐蚀，进而影响过程pH值变化，反过来又影响铁腐蚀和微生物活性，pH7．0～9．0的中性偏碱范围较适于厌氧微生物生长。Fe^0与微生物对目标污染物的降解具有协同促进作用，其协同促进机制表现在3方面：Fe^0与微生物对体系过程pH值具有互补调节作用，可将体系的pH值调节值适于微生物生长的中性范围；Fe^0腐蚀产生的Fe2＋和H2可为微生物代谢提供电子对和营养物质，从而促进生物还原脱氯的进行；Fe^0的腐蚀过程直接对氯代有机物还原脱氯，而微生物又可促进Fe^0腐蚀。     

Fe0/厌氧微生物联合体系处理2,4,6-三氯酚影响因素的研究

利用Fe0/厌氧微生物联合体系对2,4,6-三氯酚(2,4,6-TCP)进行降解研究.结果表明,Fe0/厌氧微生物联合体系可以有效降解2,4,6-TCP,Fe0与厌氧微生物之间存在明显的协同效应.Fe0/厌氧微生物联合体系处理2,4,6-TCP的最优条件为:微生物接种量0.434 g VSS/L,Fe0投加量15 g/L,体系初始pH值7.0～8.0.     

Fe0/厌氧微生物联合体系处理2,4,6-三氯酚影响因素的研究

利用Fe⁰/厌氧微生物联合体系对2,4,6-三氯酚(2,4,6-TCP)进行降解研究。结果表明，Fe0/厌氧微生物联合体系可以有效降解2,4,6-TCP，Fe⁰与厌氧微生物之间存在明显的协同效应。Fe⁰/厌氧微生物联合体系处理2,4,6-TCP的最优条件为：微生物接种量0.434 g VSS/L，Fe⁰投加量15 g/L，体系初始pH值7.0～8.0。     

零价铁与厌氧微生物协同还原地下水中的硝基苯

通过间歇式实验,考察了零价铁与厌氧微生物协同还原地下水中硝基苯的效果。实验结果表明,由零价铁腐蚀为厌氧微生物提供H2电子供体还原硝基苯的效果明显优于零价铁和微生物单独作用,硝基苯去除率分别提高21.8%和57.0%。弱酸性条件有利于协同反应进行,当初始pH为5.0和6.0时,4 d后硝基苯去除率比初始pH为7.0时的提高74.4%和35.2%。增加零价铁投加量可提高协同还原的效果,零价铁最佳投加量为250 mg/L。零价铁腐蚀产生的Fe2+无法作为电子供体被微生物利用,但可作为无机营养元素促进协同过程。由于零价铁产H2速率受表面覆盖物影响不明显,在地下水修复过程中可保证协同效果并延长零价铁的使用寿命。     

Fe0-厌氧微生物体系处理活性艳红X-3B的试验研究

采用间歇式摇床试验,研究了葡萄糖共基质条件下Fe0-厌氧微生物体系中Fe0投加量、pH值、染料初始浓度对活性艳红X-3B模拟废水脱色率的影响,比较了Fe0-厌氧微生物、纯厌氧微生物及纯Fe03种体系中废水的脱色效果.结果表明:Fe0-厌氧微生物体系中初始浓度(50～500 mg/L)对活性艳红X-3B的脱色率影响不大;而Fe0投加量、pH值存在一个最佳范围;当Fe0投加量为260 mg/L,pH值为6.0,污泥浓度为0.35 g VSS/L,停留时间约为30 h时,体系中活性艳红X-3B的脱色率可达90%左右,比相同试验条件下纯Fe0、纯厌氧微生物体系达到此脱色率所需时间分别缩短了约1/2、7/10.在Fe0-厌氧微生物体系中,由紫外可见分光光度分析可推测活性艳红X-3B的脱色机理主要是其偶氮键发生断裂,生成苯胺和萘类物质,而且苯胺和萘类物质能得到进一步降解.     

超声波和零价铁联用对氯代苯酚脱氯降解作用的研究

采用超声波和零价铁联用对氯代有机物3氯苯酚(CP)、2,4-二氯苯酚(DCP)和2,4,6-三氯苯酚(TCP)模拟废水进行了脱氯处理研究。以单因素法, 考察了铁粉初始投加量、溶液的初始浓度、超声波功率和溶液的pH值等因素对氯代酚降解的影响，并探讨了降解反应动力学。结果表明，超声波和零价铁联用对氯酚具有显著的降解效果，当水样初始浓度为25 mg/L，溶液pH呈弱酸性，超声波功率为200 W时，氯代酚的脱氯效率达到最大值。降解反应符合准一级反应，CP、DCP和TCP的反应速率常数分别0.0613 h^-1、0.374 h^-1和0.197 h^-1。     

Pd/Fe催化脱氯水中PCE的动力学研究

以GC-MS为分析方法，采用Pd／Fe双金属对水溶液中四氯乙烯（PCE）进行了催化还原脱氯处理，考察了PCE初始浓度、钯含量、Pd／Fe用量和溶液初始pH值等各因素对脱氯效果影响及还原动力学规律。结果表明，Pd／Fe双金属对PCE有较好的还原脱氯效率，反应遵循准一级反应动力学规律，以反应物PCE浓度为参照的反应速率常数K变化范围为0．019min^-1～0．16min^-1，对应的PCE半衰期从6min到36min，揭示反应有可能是在过量的Pd／Fe双金属表面进行。当PCE溶液初始浓度为1mmol／L，投加1．2g钯含量为0．03％的Pd／Fe双金属，在25℃下反应60min，PCE的脱氯率达到95％以上。增大钯含量和Pd／Fe用量可有效提高脱氯率，在初始pH值为弱酸性条件下有利于还原脱氯反应进行。     

Fe^0-厌氧微生物体系处理活性艳红X-3B的试验研究

采用间歇式摇床试验，研究了葡萄糖共基质条件下Fe^0-厌氧微生物体系中Fe^0投加量、pH值、染料初始浓度对活性艳红X-3B模拟废水脱色率的影响，比较了Fe^0-厌氧微生物、纯厌氧微生物及纯Fe^0 3种体系中废水的脱色效果。结果表明：Fe^0-厌氧微生物体系中初始浓度（50～500mg／L）对活性艳红X-3B的脱色率影响不大；而Fe^0投加量、pH值存在一个最佳范围；当Fe^0投加量为260mg／L，pH值为6．0，污泥浓度为0．35gVSS／L，停留时间约为30h时，体系中活性艳红X-3B的脱色率可达90％左右，比相同试验条件下纯Fe^0、纯厌氧微生物体系达到此脱色率所需时间分别缩短了约1／2、7／10。在Fe^0-厌氧微生物体系中，由紫外可见分光光度分析可推测活性艳红X-3B的脱色机理主要是其偶氮键发生断裂，生成苯胺和萘类物质，而且苯胺和萘类物质能得到进一步降解。     

产酸克雷伯氏菌Klebsiella oxytoca对硝基苯及4-氯硝基苯的降解

硝基苯类化合物生物降解菌的筛选及性能研究，是制药、染料等行业废水达标的重要基础。以浓度梯度升高法筛选到一株硝基苯厌氧降解菌Klebsiella oxytoca NBA-1。考察了该菌对氧气的需求，以及在厌氧条件下，温度、pH值、外加葡萄糖及硝基苯初始浓度等环境因子对菌株降解硝基苯能力的影响，并进一步讨论菌株对氯取代硝基苯类化合物的降解情况。结果表明，该菌在厌氧条件下生长比好氧条件下慢，但降解速度更快；厌氧降解硝基苯的最佳pH值和温度和分别为8．3和30～35℃；加入0．3％～0．5％的葡萄糖可促进降解，且对300mg／L以下的硝基苯均有降解能力；该菌能将4-氯硝基苯转化为4-氯苯胺，并进一步脱氯为苯胺。研究结果可为硝基苯及含氯硝基苯的处理工艺选择提供相关的参考依据。     

零价铁对土壤中2-氯硝基苯的还原作用

在常温常压下利用零价铁(Fe0)还原土壤中的2-氯硝基苯(o-CNB),研究反应条件对还原率的影响以及反应产物在不同反应阶段的变化.GC-MS检测结果显示,o-CNB在还原过程中先生成2-氯亚硝基苯,最终生成2-氯苯胺.反应时间、Fe0用量、温度和土壤初始pH值等均会对o-CNB的还原率产生影响,其中土壤初始pH值控制在偏酸性、土壤温度较高时能显著提高其还原率.当o-CNB的初始浓度约为2.5×10-6 mol/g,Fe0加入量是25 mg/g时,经过4 h反应,o-CNB的还原率可达99%以上.此外,还初步探讨了Fe0还原o-CNB的反应机理.     

Reductive dechlorination and biodegradation of 2,4,6-trichlorophenol using sequential permeable reactive barriers: laboratory studies

The reductive dechlorination and biodegradation of 2,4,6-trichlorophenol (2,4,6-TCP) was investigated in a laboratory-scale sequential barrier system consisting of a chemical and biological reactive barrier. Palladium coated iron (Pd/Fe) was used as a reactive barrier medium for the chemical degradation of 2,4,6-TCP, and a sand column seeded with anaerobic microbes was used as a biobarrier following the chemical reactive barrier in this study. Only phenol was detected in the effluent from the Pd/Fe column reactor, indicating that the complete dechlorination of 2,4,6-TCP was achieved. The residence time of 30.2-21.2h was required for the complete dechlorination of 2,4,6-TCP of 100 mg l(-1) in the column reactor. The surface area-normalized rate constant (k(SA)) is 3.84 (+/-0.48)x10(-5)lm(-2)h(-1). The reaction rate in the column tests was one order of magnitude slower than that in the batch test. In the operation of the biobarrier, about 100 microM of phenol was completely removed with a residence time of 7-8d. Consequently, the dechlorination prior to biodegradation turns out to increase the overall treatability. Moreover, the sequential permeable reactive barriers, consisting of iron barrier and biobarrier, could be recommended for groundwater contaminated with toxic organic compounds such as chlorophenols.     

Enhanced reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide

The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (α-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of α-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe²⁺ + α-FeOOH and the system of DIRB + α-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of α-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments.     

An integrated anaerobic/aerobic bioprocess for the remediation of chlorinated phenol-contaminated soil and groundwater.

An investigation of biodegradation of chlorinated phenol in an anaerobic/aerobic bioprocess environment was made. The reactor configuration used consisted of linked anaerobic and aerobic reactors, which served as a model for a proposed bioremediation strategy. The proposed strategy was studied in two reactors before linkage. In the anaerobic compartment, the transformation of the model contaminant, 2,4,6-trichlorophenol (2,4,6-TCP), to lesser-chlorinated metabolites was shown to occur during reductive dechlorination under sulfate-reducing conditions. The consortium was also shown to desorb and mobilize 2,4,6-TCP in soils. This was followed, in the aerobic compartment, by biodegradation of the pollutant and metabolites, 2,4-dichlorophenol, 4-chlorophenol, and phenol, by immobilized white-rot fungi. The integrated process achieved elimination of the compound by more than 99% through fungal degradation of metabolites produced in the dechlorination stage. pH correction to the anaerobic reactor was found to be necessary because acidic effluent from the fungal reactor inhibited sulfate reduction and dechlorination.     

Microbial dechlorination of 2,4,6-trichlorophenol in anaerobic sewage sludge

The dechlorination of 2,4,6-trichlorophenol (TCP) in municipal sewage sludge with a chlorophenol (CP)-adapted consortium was investigated. Results show that dechlorination rates differed according to the source of the sludge samples used in the batch experiments. No significant differences in 2,4,6-TCP dechlorination were observed following treatment with inoculum at densities ranging from 10% to 50% (V/V), but a significant delay was noted at 5% (V/V) density. Overall, results show that the higher the 2,4,6-TCP concentration, the slower the dechlorination rate. The addition of acetate, lactate, pyruvate, vitamin B12 or manganese dioxide did not results in a significant change in 2,4,6-TCP dechlorination. Data collected from a bioreactor experiment revealed that pH 7.0 and a total solid concentration of 10 g/L were optimal for dechlorination. Dechlorination rates decreased significantly at higher agitation speeds. 2,4,6-TCP dechlorination was enhanced under methanogenic conditions, but it was inhibited under denitrifying and sulfate-reducing conditions.     

Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species

2,4,6-Trichlorophenol (2,4,6-TCP) is a common chemical intermediate and a by-product of water chlorination and combustion processes, and is a priority pollutant of the aquatic environment in many countries. Although information on the toxicity of 2,4,6-TCP is available, there is a lack of information on the predicted no-effect concentration (PNEC) of 2,4,6-TCP, mainly due to the shortage of chronic and site-specific toxicity data. In the present study, acute and sub-chronic toxicity of 2,4,6-TCP on six different resident Chinese aquatic species were determined. PNEC values were calculated and compared by use of two approaches: assessment factor (AF) and species sensitivity distribution (SSD). Values for acute toxicity ranged from 1.1 mg L⁻¹ (Plagiognathops microlepis) to 42 mg L⁻¹ (Corbicula fluminea) and the sub-chronic no observed effect concentrations (NOECs) ranged from 0.05 mg L⁻¹ (Mylopharyngodon piceus) to 2.0 mg L⁻¹ (C. fluminea). PNECs obtained by the assessment factor approach with acute (AF = 1000, 0.001 mg L⁻¹) or chronic (AF = 10, 0.005 mg L⁻¹) toxicity data were one order of magnitude less than those from SSD methods (0.057 mg L⁻¹). PNEC values calculated using SSD methods with a 50% certainty for 2,4,6-TCP was less than those obtained by use of the USEPA recommend final chronic value (FCV) method (0.097 mg L⁻¹) and the one obtained by use of the USEPA recommend acute-to-chronic (ACR) methods (0.073 mg L⁻¹). PNECs derived using AF methods were more protective and conservative than that derived using SSD methods.     

Polychlorinated biphenyl (PCB) anaerobic degradation in marine sediments: microcosm study and role of autochthonous microbial communities

Polychlorobiphenyl (PCB) biodegradation was followed for 1 year in microcosms containing marine sediments collected from Mar Piccolo (Taranto, Italy) chronically contaminated by this class of hazardous compounds. The microcosms were performed under strictly anaerobic conditions with or without the addition of Dehalococcoides mccartyi, the main microorganism known to degrade PCBs through the anaerobic reductive dechlorination process. Thirty PCB congeners were monitored during the experiments revealing that the biodegradation occurred in all microcosms with a decrease in hepta-, hexa-, and penta-chlorobiphenyls (CBs) and a parallel increase in low chlorinated PCBs (tri-CBs and tetra-CBs). The concentrations of the most representative congeners detected in the original sediment, such as 245-245-CB and 2345-245-CB, and of the mixture 2356-34-CB+234-245-CB, decreased by 32.5, 23.8, and 46.7 %, respectively, after only 70 days of anaerobic incubation without any bioaugmentation treatment. Additionally, the structure and population dynamics of the microbial key players involved in the biodegradative process and of the entire mixed microbial community were accurately defined by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) in both the original sediment and during the operation of the microcosm. The reductive dehalogenase genes of D. mccartyi, specifically involved in PCB dechlorination, were also quantified using real-time PCR (qPCR). Our results demonstrated that the autochthonous microbial community living in the marine sediment, including D. mccartyi (6.32E+06 16S rRNA gene copy numbers g^?1 sediment), was able to efficiently sustain the biodegradation of PCBs when controlled anaerobic conditions were imposed.     

超声波／零价铁降解水中双酚A

研究了超声波／零价铁（US／Fe^0）工艺对水中双酚A（BPA）的降解效果及影响因素。结果表明，US／Fe^0工艺可以有效降解水中的BPA，具有协同作用，且降解过程符合一级动力学规律；Fe^0具有促进和抑制的双重作用；超声功率越大，越有利于BPA的降解；初始浓度较低时，BPA的降解效果较好；弱酸性条件有利于BPA的降解；加入一定量的自由基捕获剂（正丁醇）可以抑制BPA的降解；联合作用2h后，TOC的去除率较低，说明其矿化程度不完全。     

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid

The combination of zero-valent iron (Fe⁰) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe⁰ or IOCS alone, the Fe⁰-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe⁰ and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage.