PCL-SND系统的脱氮效果

以处理水产养殖水体中的含氮化合物为目的,采用气提反应器,建立以聚己内酯(polycaprolactone,PCL)为碳源和生物膜载体的同时硝化反硝化(simultaneous nitrification and denitrification,SND)系统(PCL-SND),研究其启动过程及脱氮效果以及水力停留时间(hydraulic retention time,HRT)对PCL-SND系统脱氮效果的影响。结果表明,在PCL填充率为10%,HRT为24 h,进水氨氮(NH+4-N)浓度为10 mg/L,硝态氮(NO-3-N)浓度为50 mg/L的条件下,系统运行45 d达到稳定状态,NH+4-N和TN的去除率分别为(76.55±0.98)%和(56.85±2.21)%。HRT对PCL-SND系统脱氮效果的研究表明,一定范围内,TN去除率随着HRT的减小而下降,出水NO-3-N浓度随着HRT的减小而升高,当HRT8 h,NH+4-N去除率基本稳定(85%~89%),HRT为24 h时,脱氮效果最好,TN和NH+4-N去除率分别为(68.56±1.64)%和(87.75±2.78)%,出水NO-3-N浓度(15.72±1.46)mg/L。p H和总碱度均随HRT的减小而下降,生物量却随HRT的减小而增大。     

水力停留时间对反应沉淀一体化反应器中半亚硝化反应的影响

由于反应沉淀一体化反应器的HRT与SRT不同,因此HRT是否会影响反应器中氮的存在状态,亚硝态氮积累是否能实现尚无明确结论。针对以上问题,研究不同水力停留时间对反应沉淀一体化反应器中半亚硝化反应的影响,研究结果表明：反应器运行虽然运行过程中无污泥流失,但仍可实现亚硝酸盐的积累,出水亚硝态氮和氨氮的浓度比例受水力停留时间的影响。HRT为24 h时,亚硝酸盐积累率可达到70%,但出水氨氮接近于0,很难满足ANAMMOX 的进水要求;HRT为16 h和12 h时,亚硝酸盐积累率均可超过80%,出水氨氮和亚硝态氮的比例分别达到1.39：1和1.46：1,可为后续ANAMMOX反应提供良好进水条件。水力停留时间对污泥亚硝化潜力的影响为12 h>16 h>24 h,对硝化潜力的影响为24 h>16 h>12 h。不同水力停留时间下氨氧化速率和亚硝酸盐氧化速率均为24 h>16 h>12 h。     

水力停留时间对反应沉淀一体化反应器中半亚硝化反应的影响

由于反应沉淀一体化反应器的HRT与SRT不同,因此HRT是否会影响反应器中氮的存在状态,亚硝态氮积累是否能实现尚无明确结论。针对以上问题,研究不同水力停留时间对反应沉淀一体化反应器中半亚硝化反应的影响,研究结果表明：反应器运行虽然运行过程中无污泥流失,但仍可实现亚硝酸盐的积累,出水亚硝态氮和氨氮的浓度比例受水力停留时间的影响。HRT为24h时,亚硝酸盐积累率可达到70％,但出水氨氮接近于0,很难满足ANAMMOX的进水要求;HRT为16h和12h时,亚硝酸盐积累率均可超过80％,出水氨氮和亚硝态氮的比例分别达到1．39：1和1．46：1,可为后续ANAMMOX反应提供良好进水条件。水力停留时间对污泥亚硝化潜力的影响为12h〉16h〉24h,对硝化潜力的影响为24h〉16h〉12h。不同水力停留时间下氨氧化速率和亚硝酸盐氧化速率均为24h〉16h〉12h。     

低温下聚氨酯水凝胶包埋硝化菌去除氨氮

采用聚氨酯水凝胶为固定化载体制备了包埋硝化菌颗粒,并在上流式内循环反应器内以人工配制的模拟氨氮废水对包埋硝化菌颗粒进行驯化。在驯化完成后实验考察了温度变化和水力停留时间(HRT)对低温下聚氨酯水凝胶包埋硝化菌颗粒去除氨氮的影响以及出水中亚硝态氮、硝态氮的累积情况。结果表明,在进水氨氮浓度为40 mg/L,HRT为4h,水温从22℃降低到10℃时,包埋硝化菌颗粒对氨氮的去除率从97%下降到48%,调整10℃运行时的HRT,氨氮去除率可达到75%。将进水氨氮浓度降低至15 mg/L,当HRT为4 h,温度在7~13℃范围内变动时,氨氮去除率稳定在80%左右。在整个运行过程中,保持DO充足,没有出现亚硝酸盐积累的现象。     

固定化微生物深度降解垃圾渗滤液氨氮

采用固定化微生物深度处理垃圾渗滤液,研究水力停留时间(HRT)、溶解氧(DO)和进水pH对系统脱氮效果的影响。通过对厌氧出水和好氧出水的脱氮效果比较,探讨固定化微生物构筑物的合理位置。结果表明:固定化微生物处理厌氧出水时最佳HRT为72 h最佳DO为5 mg·L~(-1),最佳进水pH为7.5±8.5;处理好氧出水时最佳HRT为84 h最佳DO为5 mg·L~(-1),最佳进水pH为7.5±8.5;处理厌氧出水和好氧出水时氨氮平均去除率分别达到63.8%和92.6%將固定化微生物构筑物单元设置在好氧处理之后更合理,可以充分发挥固定化微生物处理渗滤液脱氮方面的独特优势,切实解决渗滤液高效脱氮的问题。     

生物膜反应器中低氨氮浓度废水的亚硝化

在连续流生物膜反应器中通过控制DO、pH和HRT,对低氨氮浓度废水进行了亚硝化的实验研究。结果表明,在进水氨氮浓度为35～45 mg/L,温度为34℃的情况下,当DO=1.4～1.5 mg/L,pH=8.3,HRT=6 h时,氨氮的去除率与亚硝态氮的积累率均可达到80%左右,实现了较好的氨氮降解及稳定的亚硝态氮的积累。     

低温季大型表流湿地对微污染水体脱氮效果及优化运行

低温季表流湿地脱氮效果下降是业内公认的难题,长期以来备受人们的关注,但针对大型表流湿地处理微污染水体的相应研究开展较少。综述了表流湿地脱氮机理及低温季限制因素,同时以盐龙湖工程的表流湿地单元为实例,分析了其在低温季对微污染水体中各形态氮素的净化效果,从优化湿地运行角度出发开展研究。结果表明,在低温季表流湿地进水的TN平均值为1.16~3.35 mg/L条件下,TN、NH3-N、硝态氮、Org-N的平均去除率为13%、35%、15%、-14%;显著影响表流湿地出水TN浓度的因素为湿地运行面积、进水负荷、温度以及进水浓度(p0.05),影响程度为TN进水浓度(正相关)湿地运行面积(负相关)进水负荷(负相关)温度(负相关)。显著影响表流湿地NH3-N出水浓度的因素为温度与进水浓度(p0.05),影响程度为进水浓度(正相关)温度(负相关);当HRT从0.5 d延长到0.5~1 d时,TN、NH3-N的平均去除率分别由6%、26%提升到17%与41%。     

模拟垂直潜流人工湿地中植物种类和植物多样性对脱氮效果的影响

在模拟垂直潜流人工湿地中选种了水烛和菩提子两种常见湿地植物,以氨氮为湿地唯一氮源,通过植物单种和混种研究了植物种类和植物多样性对湿地脱氮效果的影响。结果表明,菩提子单种时,出水氮浓度均明显低于水烛单种。菩提子单种时,出水硝态氮、氨氮、总无机氮(TIN)质量浓度分别为72.34、13.80、86.14mg/L;水烛单种时,出水硝态氮、氨氮、TIN质量浓度分别为235.41、32.12、267.53mg/L。水烛与菩提子混种时,出水比菩提子或水烛单种具有更低的硝态氮和TIN,硝态氮和TIN质量浓度分别为55.60、80.50mg/L。因此,相比水烛,菩提子更有利于湿地脱氮;加强植物多样性可提高湿地的脱氮效果。湿地的脱氮效果与植物生物量具有显著相关性。     

不同DO下亚硝态氮氧化菌硝化系统N 2O减量化研究

采用序批式活性污泥反应器(SBR),在富集亚硝态氮氧化菌(NOB)的基础上,考察了DO对连续进水模式下硝化过程中N_2O减量化的影响。结果表明,在污泥氨氧化菌(AOB)和NOB的比耗氧速率(SOUR)分别为(2.36±0.31)、(7.62±0.43)mg/(L·h)条件下,不外加碳源进行小试实验,氨氮均小于1.0mg/L,亚硝态氮均小于0.5mg/L。DO由0.2mg/L增至3.0mg/L过程中,随着DO增加,积累的硝态氮浓度逐渐上升,而累计产生的N_2O浓度先上升后下降。DO为0.2mg/L时,积累的硝态氮和累计产生的N_2O浓度最低,可以实现N_2O的最大减量化。在进水连续投加氨氮的方式下,氨氮氧化速率不是引起N_2O生成的关键步骤,碳源缺乏的情况下NOB硝化系统中低DO可以有效控制N_2O的释放。     

不同水力停留时间条件下PCL为碳源去除水产养殖水体硝酸盐的效率及微生物群落分析

以可生物降解聚合为碳源的固相反硝化可以避免水产养殖用水硝酸盐处理过程中碳源反复添加、碳源不足或过量等问题。水力停留时间(hydraulic retention time,HRT)是生物反应器运行管理的主要参数之一,用固定膜反应器固相反硝化的方法研究了HRT对以聚己内酯(polycaprolactone,PCL)为碳源的反应器去除循环水养殖系统硝酸氮(浓度为170~197 mg·L~(-1))的效率的影响。研究结果表明不同水力停留时间对硝酸盐去除效率差异显著。在HRT为6 h和8 h时,硝酸盐速率分别为(0.55±0.32)g·(L·d)~(-1)和(1.05±0.33)g·(L·d)~(-1),且出水亚硝氮浓度和氨氮浓度均明显低于进水浓度;在HRT为4 h和2 h时,进出水硝酸盐浓度差异不明显。电子扫描显微镜观察显示PCL表面生物膜主要为杆状菌,应用傅里叶红外扫描观察发现使用前后PCL的化学结构没有发生明显改变。应用高通量方法测定的微生物群落结构表明,62%的细菌为Proteobacteria(62%),在鉴定出的细菌中,食酸菌属(Acidovorax),固氮螺菌属(Azospira),丛毛单胞菌属(Comamonas),代尔夫特菌属(Diaphorobacter),懒小杆属(Ignavibacterium),弗拉特氏菌属(Frateuria)可以同时降解PCL和进行反硝化。     

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.