反硝化生物滤池深度脱氮机理

研究了反硝化生物滤池对污水中硝酸盐氮的脱氮机制及其影响因素。结果表明,在实验室小试条件下,反硝化生物滤池启动14 d后出水基本达到稳定,NO3--N和TN的去除率分别为80%～88%和76%～80%,COD的去除率达到80%以上。稳定运行期,在室温20～29℃、水力负荷为1.5～2 m3/(m2.h)、COD/TN为3.7～4.5的条件下,反应器对NO3--N和TN的去除率分别为70%～85%和47%～64%,且在运行过程中出现了少量NO2--N的积累。分析反硝化生物滤池沿水流方向有机物浓度及氮形态分布发现,沿水流方向NH4+-N浓度基本保持不变;NO2--N浓度在滤层底部至40 cm高处积累较为明显,其后浓度基本不变。     

天津津南污泥处理厂两段式PN/A工艺处理污泥脱水液的成功启动与运行分析

污泥脱水液的经济高效脱氮处理已成为污水处理中的重要环节.依托天津津南污泥处理厂采用两段式部分亚硝化/厌氧氨氧化(PN/A)脱氮工艺处理污泥脱水液,在35℃下,对工程规模的工艺启动和稳定运行特性进行了研究.结果表明:接种活性污泥可成功启动部分亚硝化(PN)反应器,PN反应器出水NO2--N/NH4+-N为1.1时,可实现...     

ASBR厌氧氨氧化反应器的快速启动及脱氮原理分析

以城市生活污水为基本水质进行配水,采用ASBR研究了厌氧氨氧化反应器的快速启动过程及脱氮性能。实验条件如下:T为(35±1)℃、HRT为24 h、pH为7.2～7.5,进水NH4+-N、NO2--N浓度为40～160 mg/L,TN负荷为0.08～0.34 kg TN/(m3.d),按2∶1比例混合接种好氧短程硝化污泥和厌氧氨氧化污泥,经49 d运行成功启动厌氧氨氧化反应器,并实现稳定运行。实验结果表明:稳定运行期NH4+-N、NO2--N去除率分别达96%和98%;NH4+-N、NO2--N去除量与NO3--N生成量比值为1∶1.05∶0.29,较为接近理论值;成功启动的反应器出水pH高于进水;系统TN去除率平均值为79.7%;反应器内存在反硝化与厌氧氨氧化的协同作用,实现了部分COD去除;污泥由深棕色絮状变成红褐色颗粒状,经SEM扫描电镜观察污泥菌群种类单一,多为球状菌,有漏斗状缺口,具有典型氨氧化菌形态特征。     

城市污水条件下ASBR厌氧氨氧化的启动与脱氮性能

采用ASBR在城市污水条件下进行厌氧氨氧化的启动与脱氮性能研究。实验接种好氧硝化污泥,在温度为(35±1)℃、HRT为24 h、pH为7.3～8.5的条件下经过130 d的培养,成功启动了厌氧氨氧化反应。实验结果表明,厌氧氨氧化反应稳定运行时,TN容积负荷平均为0.179 kg/(m3.d),NH4+-N、NO2--N和TN去除率分别达到了95.30%、91.30%和76.28%。启动期和稳定运行期NH4+-N、NO2--N去除量和NO3--N生成量的比值分别达到1∶1.54∶0.25和1∶1.27∶0.27;稳定运行期进出水pH差值由启动时的0.85下降到0.24。启动期反硝化和厌氧氨氧化反应同时存在而在稳定运行期厌氧氨氧化发展成为主导反应。MLSS和MLVSS/MLSS先减少后增加,反映了启动过程中硝化细菌、反硝化细菌的衰亡和厌氧氨氧化菌逐渐富集的过程,这与反应器的宏观运行效果相一致。     

琼脂碳源生物反硝化去除水源水中硝酸盐

针对受硝酸盐污染的水源水,以琼脂为反硝化细菌的碳源和微生物载体,通过生物反硝化作用脱除水源水中的硝酸盐,并利用曝气生物滤池(BAF)去除琼脂反应器出水中残留的少量CODMn和NO2--N等污染物。实验结果表明,水源水自然接种的条件下,可以顺利启动琼脂反应器;在温度为25℃左右,琼脂反应器在进水NO3--N约25 mg/L、水力停留时间1.5 h时,能获得70%的硝酸盐氮去除率;曝气生物滤池在水力停留时间0.5 h、气水比2.8时,可控制最终出水的CODMn和NO2--N分别在5.0 mg/L和0.10 mg/L以下;琼脂反应器的脱氮效果与温度、进水NO3--N浓度及水力停留时间等有关。研究指出,琼脂反应器与曝气生物滤池构成的组合系统能较好地脱除水源水中的硝酸盐并且能控制最终出水水质,不会导致二次污染,从而获得合格的饮用水源水。     

接种物对厌氧同步脱硫反硝化特性的影响实验研究

分别以厌氧污泥、脱氮硫杆菌菌悬液和厌氧污泥并添加脱氮硫杆菌菌悬液为接种物,以硫化物和硝酸盐为进水基质,考察不同接种物条件下,各反应器的硫化物氧化特性、反硝化特性、生化反应机理及微生物特性。结果表明,在无菌条件下,硫化物不能被硝酸盐化学氧化。接种脱氮硫杆菌菌悬液的2#反应器的硫氧化速率为1.98 g S/(m3.h),停留24 h硫化物的去除率高达97%,脱硫能力最强,该接种条件下以硝酸盐氧化硫化物为主反应,优势菌为杆菌,进水的NO3--N/S应控制在0.4以下,可以实现高效生物脱硫。接种厌氧污泥的1#和3#反应器的脱氮效果比2#反应器好,停留时间为24 h时,硝酸盐的平均去除率为96%。单独接种厌氧污泥的1#反应器的硫氧化速率为1.78 g S/(m3.h),其优势菌为球菌,该接种条件下以硝酸盐氧化硫化物和硝酸盐氧化单质硫为主反应,进水的NO3--N/S应控制在0.8左右。以厌氧污泥联合脱氮硫杆菌为接种物时,硫氧化速率为1.71 g S/(m3.h),反应器以硝酸盐氧化硫化物、硝酸盐氧化单质硫以及异养反硝化为主反应,驯化后优势菌为球形、卵圆形和短杆状,应控制进水NO3--N/S为1.2,可以实现同步脱硫反硝化,该工艺既可以用于含硫废水的处理,也可以用于C/N低的硝酸盐废水的处理。     

电极-生物复合反应器处理城市污水的初步研究

微生物固定在电极表面，电解水产氢与氧所营造的微环境在一定条件下对生物硝化／反硝化及吸／放磷产生了促进作用，使电极-生物复合反应器在脱除有机污染物的同时强化了生物的脱氮及除磷效果。本试验采用了2套结构与尺寸完全相同的单槽内循环反应器，1套通电，1套不通电，在不同电流强度下比较了2套反应器对污染物的去除效果。反应器中以石墨为阳极，活性炭纤维为阴极，电极-生物复合反应器的总氮去除率可比未通电流的反应器高出30％左右，总磷去除率增加11．5％，而氨氮、COD的去除率都维持在100％和95％左右。试验表明，电流的引入在一定条件下能明显强化生物反应器脱氮除磷效果。     

厌氧流化床微生物燃料电池同步除碳脱氮产电性能影响因素

研究了厌氧流化床微生物燃料电池(AFB-MFC)除碳脱氮产电性能的影响因素。结果表明:(1)AFB-MFC对NH4+-N的去除不起作用。电压下降主要是由于进水有机基质浓度下降造成。(2)不添加NO3--N时,在满足AFB-MFC脱氮所需的电子供体条件下增加进水COD/TN有利于AFB-MFC产电。(3)3种无机氮共存下,AFB-MFC在进水有机碳与无机氮质量比(C/N)不低于1.37时,对COD、NO2--N和NO3--N具有理想的去除效果。AFB-MFB在一定进水C/N范围内(1.37～2.50),能得到稳定的输出电压及功率密度。(4)固定进水C/N时,AFB-MFC在高碳氮负荷下仍能得到较理想的NO2--N、NO3--N、COD去除效果,AFB-MFC对NH4+-N去除效果不明显;增加碳氮负荷,AFB-MFC输出电压及功率密度没有明显的改变。(5)有机基质浓度不变下,AFB-MFC中充足的电子供体可保证较高的NO3--N、COD去除率。AFB-MFC输出电压及功率密度随着时间延长而先增加至稳定值后下降。     

厌氧氨氧化耦合部分反硝化处理低浓度氨氮废水

通过接种厌氧氨氧化菌(Candidatus Brocadia)与部分反硝化菌(Thauera)形成厌氧氨氧化与部分反硝化耦合处理模拟城镇污水中的氨氮(NH_4~+-N)与硝氮(NO3--N),考察不同NO3--N/NH_4~+-N比对耦合系统脱氮性能的影响及最佳NO3--N/NH_4~+-N比下耦合系统的稳定性和脱氮的途径。结果表明:在COD/NO3--N为2.5、NH_4~+-N浓度为20~40 mg·L~(-1)的条件下,NO3--N/NH_4~+-N比在0.8~1.6的范围内均可实现部分反硝化与厌氧氨氧化协同脱氮,且当NO3--N/NH_4~+-N比为1.2时,耦合效果最佳,对应的NH_4~+-N、NO3--N及总氮(TN)去除率分别为92.85%、99.68%和96.42%;厌氧氨氧化菌在耦合系统中的活性稳定在(4.62±0.44)mg·(g·h)-1(以VSS计),且与反硝化菌存在协同竞争关系,进水NO3--N的84.3%由厌氧氨氧化途径去除,15.7%由异养反硝化途径去除。     

一株施氏假单胞菌Pseudomonas stutzeri DN-LWX19的脱氮性能

从缺氧生物滤池筛选纯化得到一株具有高效反硝化能力的异养菌DN-LWX19,通过形态观察、生理生化特性及16S rDNA同源性分析,确定该菌株为施氏假单胞菌(Pseudomonas stutzeri).脱氮性能研究结果表明,菌株DN-LWX19在NO3--N初始浓度为120.43 mg/L的试管培养基中,60 h对NO3--N去除率达90％,NO2--N积累浓度仅0.05 mg/L.以添加适量乙酸钠的实际污水处理二级出水为液体培养基,研究DN-LWX19在初始NO3--N浓度约为30.00 mg/L时的脱氮效果,当碳氮比(COD/NO3--N)为5∶1时,菌株DN-LWX19在32 h对NO3--N去除率为100％,但是有NO2--N的积累(7.00 mg/L),且至72 h无明显变化;当碳氮比为9∶1时,菌株DN-LWX19在32h对NO3--N的去除率为100％,且无NO2-N的积累.     

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.     

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.     

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.