混合PAHs生物降解过程中的竞争和协同作用解析

通过恒温摇床实验研究5株PAHs优良细菌对3种多环芳烃(PAHs)在单一基质和混合基质下的生物降解特征,并对优良菌降解混合PAHs时底物之间的竞争和协同代谢作用进行解析。结果表明:5株细菌对混合PAHs好氧降解效果由大到小依次为菲、蒽、芘;反应初期简单PAHs和难降解的复杂PAHs存在竞争代谢,造成短期内难降解PAHs的降解率偏低,随着反应的进行,复杂PAHs的降解率最终被提高,且对降解能力越强的菌株,这种提高作用越明显;施氏假单胞菌(Pseudomonas stutzeri sp)HY7对混合基质中的蒽、芘的降解率分别比单一基质蒽、芘的降解率提高12.7%、5.5%。     

氯代酚类化合物的生物降解与污染控制技术研究

本文针对环境危害较大的氯代酚类化合物的生物降解和污染的好氧生物控制技术进行了较为系统深入的研究。试验中,首先从驯化活性污泥中分离出一批降解菌,通过优化组合得到一组能利用4-氯代酚(4-MCP)作为唯一碳源且具有协同作用的复合菌,然后通过摇瓶试验对复合菌的最适生长条件、氯代酚类化合物的降解特性和降解途径以及共代谢降解机制分别进行了研究。在此基础上,通过模拟试验 对氯代酚废水处理的生物强化技术和氯代酚污染土壤的生物修复技术进行了探讨。上述研究结果表明: (1)复合茵由三种菌组成,分别是:假单胞菌(Pseudomonas sp.),鞘氨酸单胞菌(Sphingomonas sp.)和寡养单胞菌(Stenotrophomonas sp.);它们的最适宜配比是10:1:1:1;在试验条件下复合菌的最佳生长条件是:pH 6,温度35℃,摇床转速240r/min。 (2)复合菌对4-MCP具有良好的降解能力。4-MCP被复合菌最有效降解的浓度范围是150～190mg/L。在浓度为150mg/L时,平均降解速率达到最大值2.28 mg/(L·h)。 (3)复合菌对2-氯代酚(2-MCP)也具有较好的降解能力。复合菌在一定程度上也可以降解2,4-二M氯代酚(2,4-DCP)。三种氯代酚生物可降解性顺序为:4-MCP>2-MCP>2,4-DCP。 (4)4-MCP在复合菌的作用下降解得较为彻底,降解过程中存在脱氯现象,并形成关键中间     

灌溉水质对土壤和夏玉米多氯联苯含量影响的试验研究

为明确不同灌溉水质对土壤和夏玉米中多氯联苯PCBs含量的影响,2015年在北京市通州区永乐店镇北京市灌溉试验中心站布置了田间灌溉试验,设置了再生水灌溉、再生水和清水(地下水)交替灌溉和清水灌溉等3个处理,每个处理设置3个重复。采用气相色谱-质谱仪分析了土壤和夏玉米籽粒中7大类PCBs含量。研究结果表明采集的表层土壤和夏玉米籽粒仅四氯联苯含量高于实验检出限,一氯联苯、二氯联苯、三氯联苯、五氯联苯、六氯联苯和七氯联苯均未检测出。表层土壤PCBs含量为ND(未检出)至0.06μg/kg,各处理间没有显著差异;土壤PCBs含量远低于加拿大农业土壤质量指导值和荷兰土壤质量标准中的干预值,且其生态风险概率小于10%。供试5个品种夏玉米籽粒产量为1.03~5.92t/hm~2;与清水灌溉相比,再生水灌溉条件下夏玉米籽粒产量增加52%~116%。甜玉米2000除外,其他品种夏玉米再生水灌溉条件下籽粒产量显著高于清水灌溉。夏玉米籽粒PCBs含量为ND至1.74μg/kg,总体上同一品种不同灌溉水质条件下籽粒PCBs含量无显著差异。夏玉米籽粒PCBs含量低于美国卫生及公共服务部建议指标。     

汾河流域沉积物中多氯联苯的分布及生态风险评价

对汾河流域沉积物中国际公认的7种指示性多氯联苯(PCBs)的质量浓度进行测定,分析其组成、空间分布、可能的污染源和生态风险。结果表明:7种PCBs全部被检出,水相PCBs的质量浓度范围为0. 008~0. 485μg/L,沉积相PCBs的质量比范围是4. 44~79. 42 ng/g;沉积相PCB28和PCB180的平均质量比和检出率均比较高,是汾河流域沉积物中的优势污染物,其空间分布表现为从上游到下游干流PCBs质量比先升后降的趋势,PCBs主要来自汾河流域中下游地区分布的大量工业企业及工业园区的排放,汾河流域中游沉积物PCBs的生态风险较高,上游和下游沉积物PCBs的生态风险较低。     

表面活性剂LAS高效降解菌的筛选及降解性能的研究

从洗涤剂污泥中分离到一株对LAS活性很高的降解菌Wg~(-1)。该菌初步鉴定为假单胞菌(Pseudomonas sp.)。其最适生长pH为 7,温度为30℃,LAS浓度为 800mg/L。当LAS初始浓度高于800mg/L时,Wg~(-1)对LAS的降解率随底物浓度的增加而降低。该菌对LAS具有很强的耐受性,在LAS浓度达4000 mg/L时,仍能较好地生长并发挥降解作用。Wg~(-1)的生长速度及降解能力均是空白对照(CK)的几倍甚至几十倍。     

表面活性剂对土壤中多氯联苯洗脱影响研究进展

多氯联苯(PCBs)作为典型的持久性有机污染物(POPs),在环境中广泛分布且具有生物毒性,土壤中的多氯联苯可通过食物链在生物体中富集,对生物体产生危害.多氯联苯易与土壤紧密结合,由于其难以降解,故去除土壤中多氯联苯非常困难.利用表面活性剂的亲水性和亲油性,可促进土壤中PCBs释放到水体中,水体中的多氯联苯便于进一步处...     

熔盐电化学处理多氯联苯的技术研究

采用碱性熔盐电化学方法处理多氯联苯(PCBs)污染物,该处理技术通过电解的方式原位产生氧化剂和还原剂,并以碱性高温熔盐作为反应介质促进分解反应的发生。通过考察PCBs浓度、熔盐体系、反应温度、工作时间、电解电压等工艺参数对PCBs处理效率的影响,探索最佳PCBs处理工艺条件。试验结果表明:PCBs的去除效率随反应温度和电解电压的升高而提高,随进样量的增多和运行时间的延长而降低;此外,不同熔盐组分也会影响PCBs的去除效率;在优化后的工艺参数条件下,采用1 h预电解的方式,多氯联苯的去除效率达到了99%以上。研究成果为PCBs等氯代芳香烃的治理提供了新的途径。     

纳米ZnO处理含Pb~(2+)废水的实验分析

Pb~(2+)是一种对人体危害较大的重金属离子,常规方法难以将其降解。纳米ZnO是一种半导体材料,具有良好的光催化性能。实验中,通过改变实验条件,进而得到纳米ZnO降解Pb2+的最适条件。研究发现:当pH=5时,利用高压汞灯作为光源,光照2h条件后,对于4g/L的模拟含铅废水,10mg的纳米ZnO能够降解33.89mmol的Pb~(2+),降解率为70.6%。     

苯酚降解菌筛选及降解特性研究

针对焦化废水生物难降解有机物含量高、实际生产过程中的水质和水量变化大的特点,开展了高效菌株处理含酚废水的试验研究。从某焦化厂水处理车间生物处理装置曝气池活性污泥中驯化、分离和筛选得到4株以苯酚为唯一碳源的高效降解菌,并对其进行鉴定及降解特性研究。结果表明:初步鉴定h32a2、b31B、h31A和b41a为假单胞菌属(Pseudomonas sp.);通过溴化容量法测定苯酚含量,确定了菌株的最佳降解条件为:温度32℃,p H值7.5,培养时间16 h,接种密度1%,且单一菌株h32a2的苯酚最大降解率可达90.55%。通过单一和组合高效菌株对苯酚的降解特性可知,4株高效菌混合的降解效果最佳。因此,混合高效苯酚降解菌处理含酚废水具有一定的可行性。     

生活污水高效降解混合菌群的研究

从下水道中筛选5株COD高效降解菌,经初步鉴定,这5株菌分属于假单胞菌属(2株)、芽孢杆菌属(2株)和短杆菌属(1株)。将这5株高效菌组成混合菌群,对该菌群的COD和BOD降解能力及其生长条件进行了研究。结果表明,该菌群对有机物的降解效率很高,CODCr的降解率平均为92.94%,BOD5的降解率平均为92.36%。该菌群的最适碳源为甘蔗汁,最适氮源为蛋白胨;其pH和温度范围较广,适宜pH为5～8,最适pH为7;温度为25℃～40℃,最适温度为35℃。该菌群适于好氧处理。     

Biodegradation of phenolic compounds by an acclimated activated sludge and isolated bacteria

The degradation of a mixture of phenol, 4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP) and 2,4,6-trichlorophenol (246TCP) by acclimated activated sludge and by isolated bacteria was studied. Activated sludge was acclimated for 70 days to 40 mg phenols/1 then the microorganisms responsible for the CP degradation were isolated and identified. Four types of Gram-negative bacteria (Aeromonas sp., Pseudomonas sp. Flavomonas oryzihabitans, and Chryseomonas luteola) were identified. Also, two acid-fast bacilli with distinct glycolipid patterns were isolated. From their chemical composition and their growth characteristics, both isolates appeared to be mycobacteria closely related to Mycobacterium peregrinum. The degradation kinetics of each phenol by Aeromonas sp., Pseudomonas sp. Flavomonas oryzihabitans, Chrvseomonas luteola and activated sludge were determined. The acclimated activated sludge degradation rates were from one to two orders of magnitude higher than those of pure strains when uptake rates were calculated in terms of the viable biomass (CFU). The specific substrate uptake rate for acclimated activated sludge varied between 8.2 and 15.8 ß 10⁻⁷ mg/CFU·d (407-784 mg/BVSS·d). Aeromonas sp. had the highest specific substrate uptake rate of the pure strains, based on a VSS basis (33–57 mg/gVSS·d) but, in terms of viable biomass (5.0–15.6 × 10⁻⁸ mg/CFU·d), the Pseudomonas sp. rate was the highest. Specific substrate uptake rates were 1.8 mg chlorinated phenoWg VSS-d for unacclimated activated sludge.     

表面活性剂对土壤中多氯联苯洗脱影响研究进展

多氯联苯（PCBs）作为典型的持久性有机污染物（POPs）,在环境中广泛分布且具有生物毒性,土壤中的多氯联苯可通过食物链在生物体中富集,对生物体产生危害。多氯联苯易与土壤紧密结合,由于其难以降解,故去除土壤中多氯联苯非常困难。利用表面活性剂的亲水性和亲油性,可促进土壤中PCBs释放到水体中,水体中的多氯联苯便于进一步处理,以减轻对生态的危害。该文综述了近年来国内外对于表面活性剂促进多氯联苯从土壤向水体中释放的研究进展,在阐释了表面活性剂促进土壤中多氯联苯洗脱机理的基础上,具体分析了影响促进作用的各种因素。     

Decontamination of wastewater contaminated by polychlorinated biphenyls (PCBs).

Wastewater contaminated by PCBs obtained from three different sources was treated at both laboratory and pilot plant scale conditions by ultraviolet oxidation of organics at the presence of hydrogen peroxide after partial adsorption of impurities and PCBs on activated carbon and/or activated bentonite. The procedure was conducted both with and without a Fe(II) catalyst and considerable reduction of PCB concentration was achieved in both cases. In pilot plant scale experiments, activated carbon polishing step followed UV oxidation. The following three types of contaminated waste water were examined: a) aqueous extracts originated in the course of clean-up of contaminated soil by extraction with aqueous solvents. Concentrations of PCBs in extracts were between 1 microg/L to 3,000 microg/L; b) wastewater condensates originated in the process of thermal desorption of PCB from soils. Concentrations of PCBs in condensates were between 300 microg/L and 5,000 microg/L. c) underground water contaminated by PCBs extracted from the sites of old contamination. The content of PCBs was up to 50,000 ng/L. Biodegradation of PCBs with a mixture of indigenous soil bacteria (selected strains of Pseudomonas and Acitenotobacter) was also tested. It was carried out in a reactor with volume of 1.5 m3 by application of the bacteria in a slurry of bentonite with adsorbed PCBs.     

Evaluation of performance and microbial ecology of sequencing batch reactor and membrane bioreactor treating thin-film transistor liquid crystal display wastewater

In Taiwan, a substantial amount of thin-film transistor liquid crystal display (TFT-LCD) wastewater is produced daily due to an increasing production of the opto-electronic industry in recent years. The main components of TFT-LCD wastewater include dimethyl sulphoxide (DMSO), monoethanolamine (MEA), and tetra-methyl ammonium hydroxide (TMAH), which are recognized as non-or slow-biodegradable organic compounds and limited information is available regarding their biological treatablility. This study was conducted to evaluate the long-term performance of two bioreactors, anaerobic-aerobic (A/O) sequencing batch reactor (SBR) and aerobic membrane bioreactor (MBR), treating synthetic TFT-LCD wastewater containing DMSO, MEA, and TMAH with different loadings. For the A/O SBR, the influent wastewater was composed of 800 mg MEA/L, 430 mg DMSO/L, and 90 mg TMAH/L, respectively. After reaching steady-state, SBR was able to achieve more than 99% degradation efficiencies for the three compounds examined. For the case of aerobic MBR, the influent wastewater was composed of 550 mg MEA/L, 270 mg DMSO/L, and 330 mg TMAH/L, respectively, and degradation efficiencies for the three compounds achieved more than 99%. Although both different reactors shared similar and satisfactory degradation efficiencies for DMSO, MEA, and TMAH, the microbial ecology of these two reactors, as elucidated with molecular methods, was apparently different. The 16S rDNA-based cloning/sequencing results indicated that the dominant sequences retrieved from the aerobic MBR, including Hyphomicrobium denitrificans, Hyphomicrobium zavarzinii, Rhodobacter sp., and Methyloversatilis universalis, showed a clear linkage to their physiological properties of DMSO and TMAH degradation. On the other hand, Zoogloea sp., Chlorobium chlorochromatii, Agricultural soil bacterium, and Flavosolibacter ginsengiterrae were proliferated in the A/O SBR Run1, while Thiobacillus sp., Nitrosomonas sp., Thauera aromatica and Azoarcus sp. became dominant in Run2. Furthermore, the sequences retrieved from different reactors were used to establish the terminal restriction fragment length polymorphism (TRFLP) fingerprint methodology for monitoring the dynamics of dominant degrading bacteria in the aerobic MBR treating TFT-LCD wastewater.     

Dioxin-like and non-dioxin like effects of polychlorinated biphenyls: Implications for risk assessment

Polychlorinated biphenyls (PCBs) are persistent, bioaccumulative and toxic contaminants in the environment. Individual PCB congeners exhibit different physicochemical properties and biological activities that result in different environmental distributions and toxicity profiles. The variable composition of PCB residues in environmental matrices and their different mechanisms of toxicity complicate the development of scientifically based regulations for risk assessment. Various approaches for the assessment of risks of PCBs have been critically examined. Recent developments in the toxic equivalency factor (TEF) approach for the assessment of toxic effects due to dioxin‐like PCBs have been examined. The PCB exposure studies that describe non‐dioxin‐like toxic effects, particularly neurobehavioural effects and their effective doses in animals, were compiled. A comparative assessment of effective doses for dioxin‐like and non‐dioxin‐like effects by PCBs has been made to evaluate the relative significance of non‐ortho and ortho‐substituted PCBs in risk assessment. Using mink as an example, relative merits and implications of using TEF and total PCB approaches for assessing the potential for toxic effects in wildlife were examined. There are several advantages and limitations associated with each method used for PCB risk assessment. Toxic effects due to coplanar PCBs occur at relatively smaller concentrations than those due to non‐dioxin‐like PCBs and, therefore, the TEF approach derives the risk assessment of PCBs in the environment. The need for the refinement of the TEF approach for more accurate assessment of risks is discussed.     

PCBs in Lake Superior, 1978–1980

Polychlorinated biphenyls (PCBs) were measured in the water column of Lake Superior during the summers of 1978 to 1980. The total PCB water concentrations were relatively uniform areally and vertically within any one year: 1978, 1.3 ± 1.3 ng/L; 1979, 3.8 ±1.9 ng/L; 1980, 0.9 ±0.4 ng/L. The volume-weighted abiotic PCB burden in the water column fluctuated with climatic conditions between ～10,000 and 40,000 kg, but would be in the range of 10,000 to 20,000 kg most of the time. Analysis of 24 large volume, filtered samples from 1980 showed that 27±12% of the PCBs were in the paniculate phase. The distribution coefficient for PCBs, defined by use of a glass-fiber filter, ranged from 10⁴ to 10⁷ L/kg, exhibiting a strong, inverse log relationship to the suspended solids concentration. This behavior is partially attributed to the differences in the organic carbon content of the sampled particles in different regions of the lake and to artifacts of the filtration process. The elevated total PCB concentrations in the summer of 1979 in conjunction with the previous winter's severe weather conditions are evidence of seasonal fluctuations of PCBs in the water column resulting mostly from sediment resuspension.     

Optimization of a bacterial consortium for nitrobenzene degradation

Three bacterial strains, Arthrobacter sp. NB1, Serratia sp. NB2 and Stenotrophomonas sp. NB3, were isolated from contaminated sludge by using nitrobenzene as a sole source of carbon and nitrogen. It was observed that all three strains could degrade nitrobenzene at 400 mg/L initial concentration and mixed-cultivation of these strains could enhance the degradation of nitrobenzene compared with mono-cultivation. Mixture design was used for adjusting the proportions of each strain and the optimal ratio of inoculation size was NB1:NB2:NB3 = 4:4:5, where the nitrobenzene degradation percentage was two times higher than for by the single strain. The results of Plackett-Burman design indicated that Mg(2+), Ca(2+), Fe(2+), Zn(2+) and Mn(2+) had a positive effect on the degradation of nitrobenzene, while Cu(2+) and Co(2+) had a negative effect on it.     

PCB concentrations in walleyes and their prey from the Saginaw River,Lake Huron: A comparison between 1990 and 2007

Concentrations of polychlorinated biphenyls (PCBs) were measured in composited samples of walleyes Sander vitreus and their prey during 2005–2007 from Saginaw Bay, Lake Huron. There was a linear relationship between fish length and PCB concentrations in walleyes between 356 and 608 mm, but fish 680 mm had lesser concentrations than 608-mm fish. When fish 222–550 mm from 1990 were compared with those from 2007, there was a decrease of 1315 ng PCBs/g wet wt (ww). Concentrations of PCBs in gizzard shad Dorosoma cepedianum (190 ng PCBs/g ww) were three-fold less than fish collected in 1990 (516 ng PCBs/g ww). Round gobies Neogobius melanostomus collected from the Saginaw River had the greatest concentrations of PCBs (range: 200–350 ng PCBs/g ww) compared with other prey fishes (45–190 ng PCBs/g ww). Concentrations of PCBs in Saginaw River round gobies were three-fold greater than those from Saginaw Bay. Zooplankton from 1990 and 2008 contained 8.0 and 32 ng PCBs/g ww, respectively, while zebra mussels Dreissena polymorpha from 2008 contained 351 ng PCBs/g ww. Principal components analysis showed that PCB congeners differed between the largest walleyes and other fish. There are several possible explanations for lesser concentrations of PCBs observed in 2007. These include effects of dredging, changes in the food web related to round gobies, loss of alewife Alosa pseudoharengus, which was a major walleye prey item in 1990, and replacement by yellow perch Perca flavescens, or decreases in release of PCBs from sediments due to weathering, burial, or diffusion.