低碳氮比对生物膜-电极反应器反硝化的影响

以乙酸钠作为碳源,给阴阳极外加2V的直流电压,考察了不同低C/N对连续运行的生物膜-电极反应器反硝化的影响。结果表明,当C/N从1.5∶1减少到0.8∶1时,生物膜-电极反应器NO-3-N去除率从99.5%下降至64.1%,出水NO-3-N的浓度从0.27mg/L增加到17.96mg/L,出水NO-2-N的浓度从0.24mg/L增加到2.6mg/L,出水NH+4-N浓度从4.93mg/L下降至3.35mg/L。当C/N为1.5∶1时,生物膜-电极反应器的自养反硝化率仅为8.0%,当C/N降至1∶1时,自养反硝化率增加至30.4%,然而,当C/N从1∶1进一步降低至0.8∶1时,自养反硝化率却从30.4%下降至21.8%。各C/N条件下,生物膜-电极反应器出水的SCOD浓度均高于对照生物膜反应器。生物膜-电极反应器的自养反硝化率与其出水pH呈正相关。     

反硝化生物滤池用于再生水脱氮效能及动力学研究

采用反硝化生物滤池处理城市污水厂二级出水,研究了反硝化生物滤池脱氮效能及其影响因素,构建了反硝化生物滤池脱氮动力学模型。结果表明,反硝化生物滤池启动7d后出水水质稳定,对NO-3-N的去除率达到90%以上,NO-2-N积累现象消失;当外加乙酸钠作碳源并使C/N≥4.7时,对NO-3-N的去除率达到90%以上,出水NO-3-N浓度在1.0mg/L以下;反硝化生物滤池具有较高的处理负荷,当HRT≥5 min时,对NO-3-N的去除率能达到90%以上;在实验水质条件下,滤池反硝化反应遵循一级反应动力学,且反应速率常数与流速成正比。     

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。     

可生物降解塑料与沸石载体体系对硝酸盐氮污染地下水的生物修复研究

生物反硝化是修复地下水硝酸盐氮污染的一种有效途径。为进一步确定异养反硝化碳源与载体投加量的配比,取用污水处理厂活性污泥为微生物来源,以可生物降解塑料为新型固相碳源,沸石为微生物载体,设计了9组固相碳源与载体不同配比的柱实验,旨在遴选出可生物降解塑料和沸石的最优配比。同时考察在最优配比时,不同进水硝酸盐氮浓度下的硝酸盐氮去除率、填料降解率、生物膜附着量、生物膜附着效率、反硝化效率等反应特性。结果表明,可生物降解塑料∶沸石(质量比)=2∶1为最优配比。在最优配比下,进水硝酸盐氮质量浓度为40~100mg/L时,异养反硝化对硝酸盐氮具有很好的去除效果(最终去除率均在99%以上),且能够保持较高的反硝化效率,同时载体负载微生物的性能稳定。     

生物沸石滤池处理富营养化水体的挂膜实验

采用上向流生物沸石滤池处理富营养化水体,考察了挂膜阶段(前30 d)滤池对浊度、COD和TP等的去除效果,重点研究了系统中各形态氮素(NH4+-N、NO2--N、NO3--N和TN)的变化情况。结果表明,对于富营养化水体,生物沸石滤池对浊度、COD和TP的去除率分别约为80%、30%和24%;出水NH4+-N始终保持在0.5 mg/L以下,去除率在90%以上;NO2--N出现峰值(4.98 mg/L,第9 d),第13 d后即一直低于进水值;实验后期出水NO3--N与进水NH4+-N变化趋势基本一致,表明硝化生物膜已成熟,原位再生可行;生物沸石床内可能存在同步硝化反硝化现象。出水NO2-N浓度低于进水可作为生物沸石挂膜成功的一个标志。     

以玉米芯为外加碳源的SBBR脱氮特性

针对低碳氮比生活污水总氮去除效果不佳的问题,以玉米芯作为SBBR生物载体和外加碳源,开展同步硝化反硝化脱氮特性研究。主要考察了碳源投加比及曝气时间对脱氮效果的影响。在最佳碳源投加比为1∶80、最适曝气时间为5.5 h时,出水COD、TN、NH_3-N分别为48.95、6.25和1.01 mg/L,满足城镇污水厂一级A排放标准。研究表明,采用玉米芯为外加碳源,可实现固体碳源释碳与反硝化需碳的平衡,有效增强低碳氮比污水的脱氮效果,同时能够保证出水COD满足排放标准。     

湿地植物作为低C?N比生活污水反硝化碳源的研究

以风车草、香根草、再力花、芦荻、美人蕉5种湿地植物作为低C/N比生活污水的反硝化碳源材料。静态碳源释放实验中,5种湿地植物释碳能力为风车草再力花芦荻香根草美人蕉,风车草COD释放量最高,可达(129.2±6.2)mg/(g·L),其TN、TP的释放量相对较低。静态反硝化脱氮实验中,风车草和再力花脱氮效果最好,反硝化出水中硝态氮质量浓度均降低至3mg/L左右,硝态氮去除率均达88%左右,出水COD均在100mg/L左右,COD去除率均达到84%左右。在低C/N比生活污水反硝化脱氮中试实验中,以风车草为反硝化碳源,出水中TN、COD去除率可分别达到73%、75%左右,说明风车草是一种良好的低C/N比生活污水深度处理的反硝化碳源材料。     

高氨氮污泥脱水液短程硝化反硝化的启动及稳定

采用A/O-CSTR工艺处理高氨氮污泥脱水液。进水氨氮浓度浓度约为375 mg/L，C/N比小于1.0，反硝化碳源明显不足。A/O反应器完成短程硝化反应，CSTR定期投加初沉污泥作为碳源进行反硝化。两者联合达到总氮去除的目的。实验研究短程硝化反应的启动过程，以及CSTR出水回流对短程硝化和系统脱氮效果的影响。实验结果表明系统具有良好的硝化反硝化效果。A/O反应器亚硝酸盐积累率迅速提高并稳定在90%以上。CSTR有效利用初沉污泥实现了稳定的反硝化。出水回流有利于提高总氮去除率，在回流比为200%时，系统平均总氮去除率达到85%以上。     

低C/N比水产养殖废水生物脱氮实验研究

随着短程硝化-反硝化理论研究的发展,在低C/N比条件下,实现污水的生物脱氮处理已成为可能。为此,设计了水产养殖用水的三级生物膜短程硝化-反硝化处理工艺,并对该工艺在去除模拟水产养殖废水主要污染物的作用进行了初步研究。研究结果表明,在进水pH值7.5~8.5,温度为28~32℃,溶解氧为0.5~1 mg/L,游离氨浓度为5~10 mg/L的条件下,模拟废水的COD、NH4+-N和TN的平均去除率分别达到94.4%、91.6%和70.1%;并且低C/N比对出水氨氮NH4+-N的去除率影响不大,NO2--N的平均浓度控制在5.2 mg/L以下,低于鱼类的耐受浓度。表明该短程硝化-反硝化工艺设计,可用于低C/N比水产养殖废水主要污染物的生物处理,尤其是可消除NO2--N对水产养殖的潜在威胁,基本达到养鱼回用标准。     

碱度指示MBR中同步硝化反硝化的研究

在连续的操作环境下,通过改变在膜生物反应器(MBR)中的C/N和曝气量,研究碱度对同步硝化反硝化脱氮效果的指示作用。结果发现,在反硝化完全的情况下,出水碱度(330~440 mg/L)在硝化过程中较高并与出水TN表现出好的线性关系(Alk=3.22[N]+333.08,R2=0.85);在硝化完全的情况下,出水碱度(60~280 mg/L)在反硝化过程中较低并与出水TN也有很好的线性关系(Alk=-4.93[N]+317.86,R2=0.89)。实际消耗的碱度可以作为另一个指示因子(ΔAlkexper),实际消耗的碱度随出水的NH4+-N浓度升高而降低(ΔAlkexper=-3.85[N]+149.11,R2=0.88,出水NO3--N4.5 mg/L);实际消耗的碱度随出水的NO3--N浓度升高而升高(ΔAlkexper=3.68[N]+161.11,R2=0.88,出水NH4+-N5.5 mg/L)。虽然pH的变化有一定的规律,但是对SND脱氮效果指示不灵敏。     

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.     

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.     

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.     

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.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.     

Biochemical interaction of six op delayed neurotoxicants with several neurotargets

Abstract

Five organophosphorous insecticides: Leptophos, EPN, Cyano‐fenphos, trichloronate and salithion proved to cause irreversible ataxia not only to chicken but also to mice and sheep. TOCP was included as a reference. Cyanofenphos blocked the catecholamine B‐receptor binding activity with ³H‐norepinephrine at a level similar to that of the specific inhibitor propranolol in the mouse heart preparation. In the lamb heart preparation, the B‐receptor was more sensitive to Leptophos, salithion and TOCP than to propranolol. The six compounds and their oxons were screened for their in‐vitro inhibition to monamine oxidase (MAO), acetyl cholinesterase (AChE) and neurotoxic esterase (NTE) in the brain of either mouse, lamb or chicken. It is believed that their AChE inhibition stands for their acute toxicity, while NTE inhibition is responsible for their paralytic ataxia.