广西城镇污泥掺烧利用组分特性的分析

对广西城镇污水处理厂污泥进行元素分析、组分分析、工业分析和热重分析,探讨污泥掺烧应用特性,为广西的污泥资源化利用提供数据。结果表明,污泥的元素组成与煤差别较大,如污泥中的氮元素含量为4.627%,高于煤的1.628%;污泥焚烧灰含有高达15%的Si O2;污泥的挥发分为34.6377%比煤的25.089%略高;污泥的焚烧可分为3个阶段,分别为水分析出阶段(室温~160℃)、挥发分析出燃烧阶段(160~500℃)、固定碳及剩余可燃物燃烧阶段(510~950℃),升温速率升高,挥发分析出阶段提前了约50℃,粒径对析出温度影响不大,但粒径小更利于干污泥燃烧。因此,广西污泥是一种低热值,燃烧剧烈的燃料,可以用于掺烧,焚烧灰分具有较高的建材价值。     

含油污泥与玉米秸秆共热解协同特性

利用热重-傅里叶变换红外分析仪(TG-FTIR)对含油污泥与玉米秸秆共热解特性进行了研究,分析了各温度段的协同效应。TG分析表明,共热解主要呈现3个阶段:挥发分的析出(210～520℃)、碳酸盐的分解(600～780℃)、长链难分解重质油的热裂解和半焦的气化(900～1100℃),且在不同热解阶段呈现出不同的协同效应。热解动力学分析表明,含油污泥与玉米秸秆共热解后,第1阶段的活化能有所增高,而第2、3阶段的活化能大幅降低。FTIR分析表明,第1、2阶段,共热解与单一物料热解的产物种类基本一致,而在第3阶段,共热解使含油污泥热解产物甲基化合物发生分解和转化。含油污泥与玉米秸秆共热解可促进CO_2、CO、CH_4和C=O化合物的析出,其中添加玉米秸秆质量分数为10%时,对CO_2、CO和CH_4析出的促进作用最强,添加30%时则对C=O化合物的析出更为有利。     

污泥热干化和燃烧特性试验研究

分别在桨叶式干化机和热重仪上进行污泥干化和燃烧试验,研究了污泥干化特性和污染物排放特性,并对污泥的燃烧特性进行分析。结果表明,污泥干化过程分为黏稠区、粘滞区和颗粒区3个阶段。干化过程排放的污染气体有氨气、氯化氢、氟化氢、氰化氢、甲烷和挥发性有机酸等,其中氨气为主要污染气体。经冷凝吸收和活性炭吸附处理后,各种污染气体浓度均显著降低,其中氨气去除率最高,达97.04%。污泥干化冷凝液的BOD5和COD质量浓度分别为4 040、8 510mg/L,氨氮的质量浓度为1 025mg/L,pH为9.84,属于高浓度有机废水。污泥的燃烧过程可以分为3个失重阶段:水分析出阶段(50～150℃),挥发分燃烧阶段(150～450℃),固定碳燃烧阶段(450～650℃)。分别用Kissinger法和Ozawa法计算挥发分燃烧阶段和固定碳燃烧阶段的活化能和动力学方程,挥发分燃烧阶段的活化能低于固定碳燃烧阶段,表明挥发分燃烧阶段污泥更易燃烧。污泥的燃烧过程在650℃时基本完成,因此实际工程应用中,设计干化污泥的焚烧温度在750℃比较合理。     

粉煤灰替代石灰进行污泥深度脱水的中试研究

采用板框压滤机在中试规模下,以粉煤灰替代工业石灰,对污泥进行调质脱水实验研究,从而考察粉煤灰替代石灰进行污泥调质脱水的可行性。结果表明:粉煤灰投加后可降低污泥p H,降低其二次污染危害,但污泥进料量却降低14.3%~15.2%,脱水能力下降;针对不同有机质含量的污泥,粉煤灰的替代性并不相同,对于低有机质含量污泥,采用粉煤灰替代工业石灰具有一定可行性,且随着粉煤灰投加量的加大,污泥热值逐步上升,而对于高有机质含量污泥,粉煤灰并不适用于其深度脱水过程。     

工业废水污泥的热解及升温速率对热解的影响

利用热重分析法对印染、中药和废水处理厂3种典型工业废水污泥进行了热解动力学实验研究。结果表明,工业污泥是一种高挥发分、低固定碳和低热值的劣质燃料。经过消化处理的污泥灰分含量较高,挥发分含量变小。热解过程中有3个失重速率较高的阶段,以挥发分的析出为主。升温速率对热解的最终失重率有重要影响。升温速率增加,热解更剧烈,但最终失重率的变化趋势与污泥种类有关;为使热解效果更好,不同种类的污泥应选择不同的升温速率。不同种类的污泥具有不同的热解特性,印染污泥挥发分析出阶段有2次热解。中药污泥活化能最小,印染污泥挥发分第2次热解的活化能比第1次大幅增加。     

污水污泥流化床空气气化焦油的燃烧特性

利用热重分析法,研究了气化温度(650、750和850℃)和污泥性质对污泥流化床气化焦油燃烧特性的影响变化规律。结果表明:6种污泥气化焦油的燃烧过程均分为轻质有机物挥发和燃烧、重质有机物分解和燃烧以及微量残炭燃烧3个阶段;其中第一阶段失重率均明显高于第二阶段,且第一阶段和第二阶段的失重率随气化温度的升高而分别呈现为升高和降低的变化趋势。来自于活性污泥法工艺未消化污泥气化焦油在第一阶段的失重率高于消化污泥的,而A2/O工艺未消化污泥气化焦油在第一阶段的失重率则低于消化污泥的。6种气化焦油的机理函数不完全相同,但反应级数均在1~2.5之间,且第一阶段的表观活化能均低于30 k J·mol-1。污泥流化床空气气化焦油的着火点和表观活化能均比其固定床空气气化焦油的低。     

污泥水煤浆的基础特性研究

通过与纯水煤浆的对比实验，分析了污泥添加量对水煤浆流变性、稳定性及燃烧等基础特性的影响。结果表明，在污泥添加比例为5％～10％，分散剂用量为0．6％～1．2％，稳定剂用量为0．1％的情况下，可以得到流变性和稳定性良好的污泥水煤浆。随着水煤浆中污泥添加比例的提高，着火温度T1降低，燃尽温度提前，燃烧特性变好。管式炉中燃烧实验表明，试样中硫析出率随温度的升高而增大，而污泥水煤浆比纯水煤浆具有更好的固硫效果。     

城市污泥与煤混合热解特性及动力学分析

为了污泥与煤混合热解的实验研究及工程化应用提供初步的数据及理论支持,利用热重分析仪讨论了污泥与煤混合热解的主要影响因素(加热速率、热解终温及混合比例)以及动力学参数.结果表明:加热速率对污泥热解影响较小;混合物热解终温与煤的热解终温基本一致;煤在污泥(干基)中的添加比例小于50％有利于挥发分的产出;通过热解特性及动力学参数分析,得出混合物比单一物料更易分解,且两者存在一定的协同效应;建立了污泥与煤不同混合比例在有机质主要热解区间内的经验动力学方程,经具体混合比例验证,经验动力学方程推导出的动力学参数及TG曲线与实际实验结果吻合较好.     

生活污泥与煤混烧及热解特性

采用热重分析法,对生活污泥与煤以1∶1质量比混合的试样进行燃烧及热解实验研究,重点分析了升温速率对其热解及燃烧特性的影响,为煤泥混烧及热解技术的工业化应用提供理论支持。结果表明:煤泥混合样燃烧失重分为4个阶段,混燃过程中污泥与煤共同影响着混合试样的燃烧特性,随着升温速率从15℃·min~(-1)增加到50℃·min~(-1),其可燃性指数C增幅达60%和综合燃烧特性指数S提高了4倍多,燃烧性能得到明显提高;煤泥混合样的热解失重分为2个阶段,各阶段热解的挥发份最大析出速率(dw/dt)_(max)及挥发分析出特性指数D均随升温速率的升高而大幅增大,且试样总的挥发综合释放指数D从0.081 7×10~(-8)K~(-3)·min~(-2)增大到5.868×10~(-8)K~(-3)·min~(-2),可见升温速率越高,煤泥混合物的热解性能越好。     

板材类生物质燃烧及动力学特性热重研究

采用非等温升温法研究了4种板材类生物质在空气气氛下的燃烧特性和动力学特性。通过对TG、DTG等曲线的分析,发现4种板材燃烧过程均可分成3个阶段,即水分蒸发阶段、挥发份析出(或燃烧)阶段和固定碳燃烧阶段。综合燃烧特性:松木集成材>纤维密度板>夹芯胶合板>刨花板。4种板材均具有良好的燃烧特性。4种生物质燃烧均存在1个吸热峰和2个放热峰,分别与挥发分析出峰、挥发分燃烧、固定碳燃烧对应。采用Fridman法和Fridman-Carroll法分别对4种板材的动力学参数进行了计算,2种方法得出的结果符合较好。分析得出:由于生物质燃烧与环境换热、挥发分析出吸热、固定碳燃烧放热等因素作用,4种生物质的表观活化能高温区均低于低温区。动力学计算结果表明:松木集成材平均表观活化能最低,燃烧反应能较容易进行。     

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.     

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.     

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.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.