短程硝化处理炼油催化剂废水

炼油催化剂生产过程中产生的高盐度、高无机质的高氨氮废水难以处理。研究将短程硝化反硝化生物脱氮技术应用于该种废水的处理。实验同时控制反应器温度(31℃)、溶解氧(≤1.5 mg/L)、pH值(7.8~8.7)和污泥龄(30 d),较快地实现催化剂废水短程硝化污泥的驯化,亚硝酸盐平均积累率达到了97.4%。在此基础上,结合在线监控ORP、pH值变化情况及短程硝化反应动力学研究,较好地实现了炼油催化剂废水的短程硝化。     

纯种氨氧化菌短程反硝化特性

以Comamonas aquatica LNL3为研究对象,根据其既能短程硝化又能短程反硝化的特性,采用好氧方式富集和固定化菌种,再以厌氧方式驯化,得到具有高效短程反硝化特性的纯种氨氧化菌。采用扫描电镜对固定化前后的载体进行表征,且用正交试验考察了不同环境因子(温度、pH、碳氮比、溶解氧)对Comamonas aquatica LNL3短程反硝化的影响。结果表明,所用载体与Comamonas aquatica LNL3有良好的亲和性,适于微生物的固定化;环境因子对Comamonas aquatica LNL3短程反硝化影响大小顺序为:温度>pH>DO>C/N;在环境条件改变过程中当温度为35℃,pH=8,C/N=3,DO=2.5 mg/L时,Comamonas aquatica LNL3短程反硝化速率达到最大,为32.63 mg/(L.h);研究结果还表明,Comamonas aquatica LNL3具有好氧反硝化特性,适宜处理低碳氮比废水。     

包埋活性污泥和反硝化污泥全程硝化反硝化脱氮

将活性污泥和驯化所得的反硝化污泥菌泥按适当比例混合后,用聚乙烯醇(PVA)将其包埋,制成直径为3～4mm的颗粒小球.以模拟废水为处理对象,在流化床反应器内进行实验.结果表明,包埋颗粒小球对氮素和COD的去除效果良好,当包埋颗粒填充率为7％～8％(体积比),控制其他条件,12h的NH4+-N和TN去除率均在95％以上,对COD的去除率大于95％.整个过程中NO2--N未见明显积累,因此为全程硝化反硝化脱氮.最后,通过单因素实验得出的最佳温度、pH值和溶解氧浓度分别为30℃、7.5和4 mg/L.     

固定化氨氧化细菌短程硝化特性研究

以高分子聚合物为载体,采用固定化细胞增殖技术固定氨氧化细菌,研究温度、pH、碱度和溶解氧等因素对短程硝化过程的影响.实验结果表明,最适宜的温度、pH分别是30℃和8.5;当碱度/NH4 -N(质量比)=6.75时,亚硝化率为87.5%;溶解氧浓度影响氨氧化速率,但对亚硝化率影响不大,溶解氧的适宜质量浓度为403 mg/L.     

不同温度对SBBR同步短程硝化反硝化处理炼油催化剂废水的影响

采用SBBR在溶解氧1.0 mg/L条件下考察了不同温度对实际炼油催化剂废水脱氮系统效能的影响.结果表明,SBBR容积负荷及同步硝化反硝化(SND)三氮去除率与进水氨氮浓度正相关.不同进水浓度下,反应器SND三氮去除率最高可达40％左右.33、30及28℃条件下,反应器亚硝积累率均可稳定保持在90％以上.不同温度下短程硝化反硝化pH值及ORP变化趋势基本一致,结合在线监控pH值及ORP变化规律调控反应时间,最大限度保证短程硝化的稳定性.     

实时控制SBR系统中的短程硝化反硝化

以人工模拟高氨氮废水为研究对象,采用循环间歇式曝气方式,以溶解氧浓度(DO)和pH值为过程控制参数,对SBR系统进行实时控制、全程跟踪.根据此过程中COD、NH4 -N、NO2--N和NO3--N 4项水质指标的变化情况,研究SBR系统中的短程硝化反硝化工艺.实验结果表明,在短程硝化反硝化工艺中,采用较高曝气量,并且在曝气过程中用DO和pH值作为过程控制参数是可行的.     

压力式接触氧化法同步硝化反硝化脱氮性能研究

研究了压力式接触氧化法的脱氮性能,分析了容积负荷、溶解氧和停留时间等因素对反应器脱氮效果的影响.研究表明,压力式接触氧化法具有明显的同步硝化反硝化现象,当HRT=1.8 h时,DO高达5.4 mg/L,可获得90%以上的反硝化率.当HRT=1.8 h,溶解氧4～5 mg/L,容积负荷为10～12 kg COD/(m3·d)时,氨氮去除率80%左右,总氮去除率达70%～80%.     

好氧反硝化菌TAD1的同步硝化反硝化性能

研究发现嗜热螯台球菌(Chelatococcus daeguensis)TAD1具有同步硝化反硝化性能,可将水中的氨氮去除。重点考察50℃下,碳氮比、碳源、初始pH值、DO浓度等因素对菌株TAD1同步硝化反硝化脱氮性能的影响规律及菌株TAD1的耐氨能力,最后用Minitab软件进行综合优化。结果表明,菌株TAD1在高浓度氨氮(500～3 000 mg/L)下仍具有很高的脱氮能力,pH值和碳源用量是影响TAD1同步硝化反硝化最显著的因素,综合优化后总氮最大去除率达到了70%,证实利用菌株TAD1的同步硝化反硝化性能具有潜在的废水脱氮应用前景。     

高浓度氨氮废水同步硝化反硝化性能研究

利用序批式反应器研究了溶解氧浓度和进水碳氮比对高浓度氨氮废水脱氮性能的影响.结果表明,溶解氧浓度降低实现了短程同步硝化反硝化,并提高了反应器脱氮效率.反应器运行经历了外部碳源的摄取、PHB储存、PHB有氧氧化和同步硝化反硝化作用,PHB作为同步硝化反硝化过程中反硝化的电子供体.     

同步硝化反硝化生物脱氮技术研究

讨论了影响同步硝化反硝化反应的各参数,并进行了单因素实验与正交实验,获得了同步硝化反硝化生物脱氮工艺运行的最佳条件:DO浓度控制在0.5～2 mg/L,COD浓度为600～800mg/L,混合液悬浮固体(MLSS)为5000 mg/L,pH值在8.0左右,反应时间为6 h.在此条件下,氨氮及COD的去除率都较高,分别达85%和95%,总氮去除率为68 5%.     

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.