利用螺旋切割强化臭氧氧化降解苯酚废水的研究

针对臭氧在水中不易溶解的现象,采用自制静态螺旋切割装置强化臭氧氧化苯酚废水,考察了臭氧进气流量、液体流量以及初始pH对苯酚降解率的影响,并对比了不同气液混合方式下臭氧传质效果及苯酚降解率。结果表明,静态螺旋切割装置可以强化臭氧在水中的传质,9min后液相臭氧质量浓度可达12mg/L左右,远高于常规曝气及循环气液混合方式下的液相臭氧浓度。在臭氧进气流量为2.0L/min、液体流量6L/min、初始pH为7时,反应12min,螺旋切割强化臭氧氧化的苯酚降解率可达97.09%,比常规曝气和循环气液混合下的苯酚降解率分别提升64.21百分点和35.53百分点。     

微气泡曝气中氧传质特性研究

气泡曝气过程中氧传质对于好氧生物处理过程具有重要意义。采用水力旋转剪切微气泡发生装置,考察了运行条件和水质特性对微气泡曝气中氧传质特性的影响。结果表明,微气泡曝气可获得较高的气含率和气泡停留时间;表面活性剂十二烷基磺酸钠(SDS)可以提高微气泡曝气的气含率和气泡停留时间。微气泡曝气中氧的总体积传质系数明显高于传统气泡曝气。总体积传质系数随着空气流量的增加而增加;氧传质效率随着空气流量的增加而减小,且对空气流量的变化更为敏感。在温度15~35℃范围内,微气泡曝气中氧的总体积传质系数随着温度的增加而增加,变化关系与传统气泡曝气基本相同,但对温度的变化更为敏感。微气泡曝气中,表面活性剂SDS会使氧的总体积传质系数略有降低,其不利影响明显小于传统气泡曝气;氧的总体积传质系数随盐度(NaC l浓度)增加而逐渐增加,并在NaC l浓度5 000 mg/L后趋于稳定。     

臭氧在柱式反应器中的强化传质过程

结合理论分析,提出了影响臭氧在水中传质效率的三大因素:表观气速μobs、初始气泡直径d、液位高H。通过实验设计,以臭氧氧化柱式反应器中气泡的行为为研究对象,以废水COD去除率及臭氧利用率为指标,考察了这三大因素对臭氧传质效率的影响,且探讨了体系中引入搅拌对强化臭氧传质的贡献。结果表明,适当地提高表观气速μobs、初始气泡直径d及液位高H都可强化气液传质、提高废水处理效果,而对于传质控制型反应效果更为显著。在低、中表观气速下,搅拌能促使气泡均匀分散,从而提高气液传质效率;而在高表观气速下,搅拌作用的强化能力是有限的。通过对搅拌作用下反应器内流体热视图分析可知,反应器内中心气泡密度、尺寸均高于近壁面位置。n=100 r·min~(-1)时,反应器内气泡直径小且分布均匀;n=200 r·min~(-1)时,反应器内气泡破碎严重,搅拌杆有气穴生成;n=500 r·min~(-1)时,反应器中心出现明显旋流与气液分层现象。     

pH对微气泡臭氧氧化处理染料废水影响

微气泡技术有助于改善废水臭氧氧化处理效果,p H值是影响微气泡臭氧氧化处理性能的重要因素。考察了不同初始p H值条件下,微气泡臭氧氧化处理酸性大红3R废水性能。结果表明,p H值对微气泡曝气中臭氧分解速率具有显著影响,强酸性和碱性条件下,微气泡曝气中臭氧分解速率均明显高于中性条件。同时,酸性和碱性条件下,微气泡臭氧氧化处理酸性大红3R的脱色速率和TOC去除速率明显高于中性条件。酸性条件下臭氧微气泡氧化能力最强,TOC去除速率约为中性条件的2倍,TOC去除率可达83.1%。酸性、碱性和中性条件下TOC去除量与臭氧消耗量的比值(R)分别为0.0372、0.0298和0.0180 mg/mg。不同初始p H值下微气泡臭氧氧化处理酸性大红3R过程中,臭氧利用率均高于99%。     

微孔分布器对光催化臭氧氧化反应器传质的影响

为了开发高效的光催化臭氧氧化反应器,以不同孔径钛微孔气体分布器对臭氧气液传质性能进行了研究.考察了表观气速和表观液速对液相总传质系数的变化影响规律,获得了液相总传质系数与表观气速的关联公式和微孔板孔径与表观气速对液相总传质系数的经验关联公式.利用无因次吸收数对微孔分布器的性能进行了分析,得到不同表观气速下微孔分布器的性...     

膜接触反应器臭氧传质及其对模拟印染废水的降解

对膜接触反应器传质过程及其在模拟印染废水降解中的应用进行了研究。实验表明,产水臭氧浓度随着液相雷诺数、气相臭氧浓度和膜长的增加而升高,随着温度升高而下降。在膜接触反应器中,臭氧体积传质系数kLa可达0.317s~(-1),比鼓泡反应器大15~62倍。对模拟印染废水的降解速率常数ka可达0.336 s~(-1),比鼓泡反应器大65%,而比臭氧消耗量为鼓泡反应器的45%。实验表明,膜接触反应器具有体积较小,臭氧利用效率较高等优势。     

臭氧微气泡深度处理染料废水生化出水

采用臭氧氧化法对某厂染料废水生化出水进行深度处理，考察了废水初始pH值和臭氧气泡大小对废水处理效果的影响，研究了臭氧微气泡对气液传质的影响。结果表明，在pH 2.5~11范围内，废水初始pH值越大，处理效果越好；加载微孔膜片后，臭氧气泡粒径变小，增大了臭氧的传质比表面积，延长了臭氧气泡在反应柱内的停留时间，强化了传质效果，处理废水的臭氧利用率可增大10%~30%，强化了臭氧氧化作用。加载5 μm孔径的膜片相比无膜片的情况，COD去除率提高了近30%，TOC去除率提高了16%。     

微气泡臭氧强化污泥碳源的释放过程

臭氧处理污泥后释放的碳物质可作为低碳市政污水生物处理的重要碳源补充。为突破传统臭氧处理效率低等问题,研究采用微气泡臭氧技术以强化污泥碳源释放效果。结果表明,在臭氧投加量为200 mg O_3·(g SS)~(-1)时,污泥SCOD增长了1 964 mg·L~(-1),为传统臭氧处理的2.1倍,DDCOD由18.1%上升至41.5%,污泥碳源释放效果显著提高。同时确定了微气泡臭氧处理在臭氧浓度为100.0 mg·L~(-1),污泥浓度为5 g·L~(-1),污泥初始p H为9的条件下,污泥碳源矿化损失较小且污泥碳源释放效果较好,在臭氧投加量为160 mg O_3·(gSS)~(-1)时污泥SCOD增长了1 923 mg·L~(-1),DDCOD达到41.2%。与传统臭氧处理相比,微气泡臭氧处理能提高臭氧传质效率与间接反应强度,更有利于污泥碳源的释放。     

基于电催化疏水膜的新型膜接触臭氧氧化工艺

膜接触臭氧氧化(MCO)工艺以疏水膜为臭氧提供丰富的气液接触界面,具有较高臭氧传质效率。然而,MCO工艺以臭氧直接氧化为主,对废水中有机污染物的去除有较强的选择性,氧化能力有待提高。通过电催化疏水膜将MCO工艺与电化学技术相结合,构建了新型的膜接触电催化臭氧氧化(ECMCO)工艺。ECMCO工艺以高级氧化过程为主,对水中硝基苯的去除效率明显增强,同步提高了臭氧传质效率和体系的氧化能力。ECMCO工艺对酒厂废水的生化出水进行深度处理后,水中COD降至50 mg·L-1以下,色度完全脱除,总运行能耗明显低于MCO和MCO+H2O2工艺。针对臭氧工艺在水处理应用中传质效率低、矿化能力差、运行能耗高的问题,ECMCO技术提供了可行的解决方案,有较好的研究价值和应用前景。     

填料塔中Na_2CO_3吸收高浓度H_2S的传质特性

在填料吸收塔中考察了Na2CO3溶液吸收高浓度H2S气体的气液传质特性。通过测量填料塔进出口气体中H2S浓度计算了Na2CO3溶液吸收高浓度H2S气体的总体积传质系数(KGa),并研究了进气流速、吸收液流量、吸收温度和吸收液浓度对KGa的影响。结果表明,KGa随Na2CO3浓度、吸收液流量的增加而增加,随吸收温度、进气流速的升高而降低;在高浓度H2S吸收过程中液相传质阻力不能忽略。     

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.     

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.     

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.     

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.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

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.     

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.     

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.