膜生物反应器处理甲苯废气的降解特性及传质过程强化

设计了一种气相空间带方形扰流柱结构的平板膜生物反应器,进行了甲苯降解废气净化实验,并与未加入方形扰流柱结构的反应器进行了对比。实验研究了甲苯入口浓度和气体流量对甲苯降解效率和传质速率的影响,结果表明,随着甲苯入口浓度和气体流量的增加,膜生物反应器降解效率降低,甲苯的传质速率增大,气相空间加入方形扰流柱后,甲苯在反应器中的传输得到了强化,降解效率最大提高了8%。     

盆栽植物净化甲苯废气

采用动态模拟法模拟盆栽植物对甲苯污染气体的净化,考察吊兰和金绿萝两种盆栽植物在净化甲苯过程中,甲苯入口浓度与植物对甲苯净化速率的关系。结果表明,2种盆栽植物对低浓度甲苯废气具有长期明显的净化效果。在相同条件下,吊兰茎叶和土壤的净化速率优于金绿萝体系。在植物的耐受浓度范围内,2种植物茎叶和土壤的净化速率均随着甲苯入口浓度的升高而增大,且白天的净化速率明显高于黑夜时的净化速率。在实验过程中,吊兰土壤体系的降解率随着甲苯浓度的升高逐渐下降;金绿萝土壤体系的降解率基本不受甲苯入口浓度的影响。吊兰盆栽体系的降解率明显大于金绿萝的降解率。两种植物盆栽体系的降解率随甲苯进口浓度的影响可以忽略。     

有机复合填料生物滤床对甲苯气体的净化

利用一种新型有机复合填料作为生物滤床中微生物的附着载体,接种经过驯化筛选的专性甲苯降解菌,填装于生物过滤塔中净化低浓度甲苯气体。研究了新型有机复合填料在长期运行时的情况,考察了进气流量、入口浓度、床层温度和填料湿度对生物滤床的影响,最终经过优化得出,此种填料的生物滤床能够为微生物提供良好的附着生长环境,并能保持滤床的高效稳定运行,当进气流量为0.4 m3/h,入口浓度为400 mg/m3,床层温度为30℃,填料湿度为50%时,生化去除量达到30.6 g/(m3.h),并且在此条件下滤床具有良好的耐冲击性能。     

腐殖填料生物滤池氨氮降解特征

根据腐殖填料生物滤池及石英砂普通生物滤池的氨氮去除效率、表面水力负荷及微生物量差异,比较两者氨氮降解速率及比降解速率,对腐殖填料生物滤池的氨氮降解特征进行分析。结果表明,在相同运行方式及外界环境下,腐殖填料滤池表面水力负荷数倍于石英砂普通生物滤池;腐殖填料生物滤池单位体积平均氨氮降解速率高达31.5 g NH4+-N/(m3.d),是石英砂普通生物滤池的5.4倍;腐殖填料生物滤池氨氮比降解速率为4.1×10-2μg NH4+-N/(g微生物碳.d),约为石英砂普通生物滤池的4倍。腐殖填料生物滤池能负载较高的生物量,抗堵塞性能较强,系统内特异微生物对氨氮降解能力较高,是一种优良的降解氨氮的生物滤池。     

几种腐殖填料生物滤池COD去除效能比较研究

分别采用腐殖垃圾、泥炭、煤炭等腐殖填料及河沙构筑生物滤池,处理模拟废水,比较研究其COD去除效能及降解特征,为工艺填料改性提供理论依据。几种填料的扫描电镜分析图显示腐殖垃圾及泥炭以团聚体三维空间结构为主;煤炭与河沙表面粗糙程度较小,且主要由颗粒状物质构成。稀释平板涂布法分离出各生物滤池中发挥主要作用的微生物共3种,各系统菌落数量有差异,但种类相同。3种腐殖填料生物滤池在进水有机物浓度为500 mg/L及1000 mg/L时均有较理想的有机物去除效率。3种腐殖填料生物滤池中泥炭构筑的腐殖填料生物滤池有机物比降解速率最小,因而微生物比增长速率最小,微生物增长和自身氧化最易趋向于动态平衡,对应的饱和水力渗透系数最大,滤池最不易发生堵塞,最有利于腐殖填料生物滤池长期稳定运行,证明泥炭是一种优良的生物介质。     

低温等离子体联合技术降解甲苯气体的研究

以自制的纳米钛酸钡基介电材料为催化剂,以电工陶瓷拉西环为载体,利用介质阻挡放电产生的低温等离子体对常压下流动态含甲苯的空气进行处理,研究了电场强度、空塔气速、甲苯初始浓度及不同填料情况下甲苯的降解及臭氧产生情况,初步探讨了等离子体联合技术降解甲苯的机制,并进行了产物分析.实验结果表明,甲苯降解率随电场强度的提高而上升,随空塔气速和甲苯初始浓度的增加而降低;随反应器内填料变化,甲苯降解率表现为催化剂填料》普通填料》无填料,其降解率最高可达95%.当电场强度》13.0 kV/cm时,臭氧浓度因受到过量的高能电子攻击而发生分解,表现为臭氧浓度随电场强度的继续增加而降低,故最佳电场强度为13.0 kV/cm.当9.0 kV/cm＜电场强度＜13.0 kV/cm,臭氧产量表现为催化剂填料＞普通填料＞无填料,纳米钛酸钡基介电材料大大增强了臭氧的产量.     

生物膜填料塔SO2废气净化性能研究

采用生物膜填料塔净化SO2废气,研究结果表明:当气体流量从100L/h增加到300L/h时,SO2净化效率由86.4%下降到73.2%;生化去除量随着入口SO2气体浓度的升高而增大;随着温度的升高,SO2净化效率和生化去除量都随之提高,且20℃以上时,净化效率可达90.9%以上,生化去除量可达75 mg/L·h以上,更利于微生物降解SO2.     

活性污泥对甲醛废水的净化性能

采用微生物法处理低浓度甲醛废水达标排放是比较经济的方法之一.在研究中采用序批式活性污泥法(SBR)工艺,考察了曝气时间、进水甲醛浓度、进水 pH 和水温对微生物净化低浓度甲醛废水的影响.结果表明,随着曝气时间的延长,活性污泥对甲醛的去除率增大.进水甲醛浓度在 40～120 mg/L 范围内,随着浓度升高甲醛污泥负荷增加,微生物对甲醛的降解速率增加,但对甲醛的去除率降低.活性污泥在 pH 为 5～7 的中性和弱酸性环境中对甲醛的降解速率较高.在15～35℃范围内,污泥对废水中甲醛的去除率随温度升高而上升,微生物对甲醛的降解速率随温度升高呈指数递增趋势.     

间歇运行式生物滴滤池处理油漆废气中试研究

为研究间歇运行式生物滴滤池对油漆生产厂废气净化能力，建立一座中试规模生物滴滤池（BTF），接种降解菌群，采用8 h/d运行方式净化某油漆厂包装车间废气，并用PCR-DGGE技术揭示BTF细菌群落结构与工艺运行条件间的联系。油漆厂包装车间废气中挥发性有机物（VOCs）主要为甲苯、乙苯、混合二甲苯（间、对和邻二甲苯），BTF对甲苯、乙苯、混合二甲苯最大去除率分别为88.8%、83.7%和86.3%。DGGE分析显示，BTF稳定运行时，主要优势菌相对丰度较为稳定（F，P>0.05），其细菌多样性显著低于启动期（F，P>0.05）；同时，下层填料细菌多样性高于上层填料，其细菌结构变化也较上层明显；另外，提升培养液浓度至2倍和4倍对菌群结构亦无显著影响。     

膜生物反应器中生物膜的生长特性

实验采用经甲苯培养驯化而成的单一假单胞菌菌种,通过分析平板式生物膜反应器内,不同阶段假单胞细菌生物膜干重、厚度、活性生物量和生物种群分布的变化,研究生物膜特性与降解效率之间的关系。实验结果表明,在挂膜初期生物膜迅速生长,生物量以及生物膜干重增长很快,有利于甲苯及营养物质的传输,降解效率也快速提升。随着生物膜的生长,生物量及干重也逐步增加,厚度逐渐增加使传质阻力不断增大,生物膜上层微生物的有机底物供应不足,使生物膜上层结构稀疏,最终维持一个甲苯的总传输量与生化降解量的平衡,生物量的生长与衰亡也达到动态平衡,形成了一个较高且稳定的降解效率。     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.