Factors Influencing Anaerobic Biodegradation of Biodiesel Industry Wastewater

Economic and environmental stimuli for biodiesel production have also increased production of glycerol, a byproduct present in biodiesel industry wastewater (BIW). The objective of the present study was to analyze which factors influenced glycerol biodegradation in anaerobic sequencing batch reactors (AnSBR) in the attempt to optimize chemical oxygen demand (COD) removal efficiency. Six factors were analyzed: pH, temperature, mixing speed, influent COD, inoculum mass, and reaction time. The results indicated that mixing speed, temperature, mass of inoculum, and reaction time had direct influence on COD removal efficiency in BIW. The reactor used in the experiments operated with efficiencies and applied loads above those mentioned in the literature. The mathematical model generated in this study can be used for estimating efficiency, process control and scale up of AnSBR.     

Microbial Sulfate Reduction and Biogeochemistry of Arsenic and Chromium Oxyanions in Anaerobic Bioreactors

A pilot-scale anaerobic bioreactor with high levels of microbial sulfate reduction, known to be capable of removing cationic metals from a metal- and acid-contaminated waste stream, was utilized to determine if the system would be effective in removing metals in the form of oxyanions such as arsenate and chromate. The system removed 90 % to >99 % of the arsenic and between 86 % and 94 % of the chromium from a waste stream containing 5 mg/L of each. Cadmium, copper, iron, lead, and zinc also were removed. An equilibrium geochemistry computer modeling code, MINTEQAK, modified from MINTEQA2, was used for the chemical modeling of processes in the bioreactor. Experimental evidence on the chemical and biological reduction of arsenic and chromium and fluorescent diffraction analysis of precipitates support the following hypotheses: the primary removal process for chromium was the reduction of Cr(VI) to Cr(III) by sulfides, followed by precipitation of chromium hydroxide [Cr(OH)_3(s)]; removal of arsenic was by direct microbial enzymatic reduction of As(V) to As(III) followed by precipitation of arsenic sulfides (As₂S₃ or AsS). Experimental evidence and modeling with MINTEQAK confirmed that 90 % to 95 % of the removal of arsenic and chromium occurred in the first quarter volume of the bioreactor. Additional removal of arsenic and chromium occurred in the remaining volume of the bioreactor. The use of a sulfate reduction-based anaerobic treatment system was effective for metal-laden wastewater with elevated concentrations of arsenic and chromium.     

Enhanced Biodegradation of Naphthalene and Anthracene by Modified Vermiculite Mixed with Soil

Hydrophobic modified vermiculite mixed with soil was investigated in biodegradation experiments of naphthalene and anthracene. The experiments had been carried out on mixtures of soil and vermiculite at a proportion of 2%, 10%, and 15% and also in the absence of clay used for control. Biodegradation of the pollutants was followed by the decline of naphthalene and anthracene concentration, measured by CG. Compound mineralization was also proved by the evolution of CO₂. The results showed that in the mixture with a higher proportion of vermiculite biodegradation is enhanced compared to that performed in the absence of vermiculite. In general, when vermiculite proportions are increased, the rate of degradation increases, which may account for the bioavailability of compounds. Bioavailability is an important factor for the degradation of compounds with low solubility. Comparison of biodegradation rates shows that naphthalene is degraded faster than anthracene. The chemical structure could be responsible for this observation. However, although we did not identify the microorganism that was in the soil, we can conclude that vermiculite could be an alternative for the bioavailability of such compounds. Vermiculite in the modified form could also be very useful as a barrier to retain organic pollutants in accidental spills.     

水体中硝基苯厌氧降解微生物的筛选及其降解特性研究

以硝基苯为碳源,采用间歇式曝气方式,经90d驯化培养,从处理硝基苯废水的生物活性污泥中分离得到13株高效降解菌,在厌氧环境条件分离纯化,筛选得到降解能力最强的MY4菌,并研究了其对不同浓度硝基苯的降解特性。结果表明,经16SrRNA鉴定,MY4菌属于兼性葡萄球菌属（Staphylococcus sp）,其在104～107CFU·mL^-1范围内对硝基苯的去除率没有显著差异,降解率均为65%,硝基苯的降解速率在3～5d期间达到最大。高浓度的硝基苯对微生物的降解过程存在抑制作用,随着浓度的增高,其降解半衰期明显延长。GC-MS分析表明,硝基苯经MY4菌株降解后的主要产物为苯胺。     

Benzene Biodegradation under Anaerobic Conditions Coupled with Metal Oxides Reduction

Anaerobic benzene biodegradation was performed in batch experiments using Rhine River sediment as inoculum and amorphous Mn(IV) or Fe(III) as independent final electron acceptors. Benzene (4.5 μmol) was degraded in 80 and 710 days in batch experiments under Mn(IV) and Fe(III) reducing conditions, respectively. Highest benzene degradation rate, 0.07 μmol/day, was obtained under Mn (IV) reducing conditions, with soluble Mn(II) and CO₂ recoveries of 71.5% and 93% regarding to the stoichiometric values, respectively. Likewise, benzene biodegradation was performed in a continuous column coupled to the reduction of Mn(IV). Efficiency of benzene biodegradation was up to 97% under steady state operation in a sediment column operated continuously for more than 160 days. The carbon dioxide and Mn(II) recoveries were 88% and 77%, respectively, of the theoretical ratio according to the stoichiometry for benzene biodegradation.     

Anaerobic Biodegradation of Pyrene by Paracoccus denitrificans Under Various Nitrate/Nitrite-Reducing Conditions

The recovery of Tween 80 from a liquid residue, obtained after washing of a contaminated soil with p-Cresol, was studied by selective adsorption of p-Cresol with activated carbons. A modified expression of the Langmuir equation was succesfully used to predict the adsorption isotherms of p-Cresol in the absence and presence of different surfactant concentrations. The presence of surfactant seems to modify the adsorption equilibrium, but it does not produce any significant influence on the adsorption kinetic of p-Cresol. A mathematical model was developed to predict the optimum activated carbon dosage demanded to reduce the p-Cresol concentration as a function of the surfactant concentration, also obtaining the corresponding surfactant loss. The regenerated solution was favorably used as washing solution in a new contaminated soil. These results indicate that this technique can be adequate to recover the surfactant solution, with a relatively minimal loss, for a subsequent application.     

Effects of Nitrogen and Phosphorus Supply on Hexadecane Biodegradation in Soil Systems

The biodegradation of hexadecane (C as hexadecane-C) was assessed under 34 different external nitrogen (N supplied as NO3-N) and phosphorus (P supplied as PO4-3-P) supply conditions in order to determine how different nutrient formulations affected nutrient limitation conditions during degradation. CO2 production yields indicated that shifts in N and P supply levels resulted in variable biodegradation responses due to shifts in the limiting-nutrient (e.g., from N to P). For example, the estimated maximum fractional CO2 yield ratio was 0.24 (mg CO2-C produced mg-1 hexadecane-C) for P-limited nutrient formulations (P:hexadecane-C<0.01), whereas the yield ratio was more than two times greater when the system was not P- limited. Similar effects were observed for N-limited (N:hexadecane- C<0.15) versus non-N-limited formulations. The relative bioavailability of natural soil-N and soil-P also was examined. In the soil studied, background soil-N was 96.3% organic-N and was found to be largely nonbioavailable. In contrast, high CO2 yields were observed even when no external P was supplied. An iterative mathematical procedure indicated that the Olsen soil-P subfraction (inorganic soil-P plus soluble organic soil- P) best approximated bioavailable soil-P for this soil. Our results indicate that both N and P additions affect biodegradation yields, but that stoichiometrically inappropriate nutrient mixes produce suboptimal CO2 yields. We also found that the bioavailable fractions of soil-N and soil-P should be incorporated into estimating the most suitable nutrient formulations for a given contamination scenario.     

湿地生物地球化学研究概述

湿地有其独特的生物地球化学循环,其间许多化学迁移和转化过程不为其它生态系统所共享。湿地土壤在淹水时形成强还原区,但在水—土界面上常有一氧化薄层。发生于还原环境中的C,N,P,S,Fe,Mn的转化都影响着物质对生态系统的有效性;一些化学转化还会导致毒性环境,许多化学转化由微生物种群来调节。化学物质经降水、地表径流、地下水和潮汐等水文途径被输送至湿地中,降水途径占优势的湿地一般养分较贫乏,经另外3个途径输入湿地的化学物质的浓度变化较大,并非所有的湿地都是养分的汇,而且其季节之间、年际之间的模型也不一致。尽管对毗邻的生态系统的直接影响难以定量化,湿地通过有机物质的输出常与毗邻生态系统进行化学耦合。湿地与陆生、水生生态系统相类似,因为它们都可能是富营养或贫营养系统;当然它们之间也有一些差异,特别是在沉积物贮存养分以及植被在不同养分循环中的功能方面差异较大。     

外源碳氮输入对元阳梯田土壤有机氮厌氧矿化的影响

采用室内培养法研究了元阳梯田3个海拔梯度(高海拔为1626~1672 m、中海拔为1532~1537 m和低海拔为1445~1459 m)表层(0~30 cm)土壤和同一海拔3个土壤层次(0~30 cm、30~60 cm和60~90 cm)氮素在厌氧条件下的矿化特征。结果表明:4种矿化处理(对照、加碳、加氮和加碳氮)20天的培养,净矿化量均随海拔高度的降低而降低,随土层深度的增加而降低。矿化速率随培养时间呈现出下降的趋势,后期矿化量变幅缓慢。四种处理净矿化量与土壤有机碳(TOC)、全氮(TN)、溶解性有机碳氮(DOC和DON)、微生物量碳(MBC)、易氧化碳(ROC)及轻组碳氮(LFC和LFN)均呈显著性正相关(P0.05)。20天的培养期内的净矿化量总体表现为:对照和加氮处理大于加碳和加碳氮处理。表明有机碳的投入降低了净矿化,可减少氮的损失,元阳梯田土壤中的碳可能对土壤中有限氮素资源具有良好的保蓄作用。     

Optimisation of Key Abiotic Factors of PAH (Naphthalene, Phenanthrene and Anthracene) Biodegradation Process by a Bacterial Consortium

The aim of this work was to determine the optimum values for the biodegradation process of six abiotic factors considered very influential in this process. The optimisation of a polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and anthracene) biodegradation process was carried out with a degrading bacterial consortium C2PL05. The optimised factors were the molar ratio of carbon/nitrogen/phosphorus (C/N/P), the nitrogen source, the iron source, the iron concentration, the pH and the carbon source. Each factor was optimised applying three different treatments during 168 h, analysing cell density by spectrophotometric absorbance at 600 nm and PAH depletion by HPLC. To determine the optimum values of the factors, an analysis of variance was performed using the cell density increments and biotic degradation constants, calculated for each treatment. The most effective values of each factor were: a C/N/P molar ratio of 100:21:16, NaNO₃ as nitrogen source, Fe₂(SO₄)₃ as iron source using a concentration of 0.1 mmol l^?1, a pH of 7.0 and a mixture of glucose and PAHs as carbon source. Therefore, high concentrations of nutrients and soluble forms of nitrogen and iron at neutral pH favour the biodegradation. Also, the addition of glucose to PAHs as carbon source increased the number of total microorganism and enhanced PAH biodegradation due to the augmentation of PAH degrader microorganisms. It is also important to underline that the statistical treatment of data and the combined study of the increments of the cell density and the biotic biodegradation constant have facilitated the accurate interpretation of the optimisation results. For an optimum bioremediation process, it is very important to perform these previous bioassays to decrease the process development time and, therefore, the costs.     

湿地磷的生物地球化学特性

综述了湿地磷的生物地球化学特性，包括湿地土壤中磷的存在形态与磷的固定，湿地淹水对磷固定的影响，持久性淹水土壤中磷的行为，淹水和干旱转换条件下磷的反应，湿地在水体磷去除过程中的作用等。     

Composting Wastes Contaminated with Naphthalene

Recent data show composting as an alternative for treatment of PAHs contaminated wastes. Nevertheless, the presence of highly volatile compounds like naphthalene might compromise the interest of this treatment and thus its careful evaluation is justified. A bench scale composting system was built to evaluate the importance of volatilization in the transformation of naphthalene by composting. Naphthalene concentration was measured in solid, aqueous and gas phases by HPLC and GC. Preliminary results have shown that the presence of microorganisms able to degrade naphthalene reduces naphthalene loss by volatilization.     

Manganese Biogeochemistry in a Central Czech Republic Catchment

Mn biogeochemistry was studied from 1994 to 2003 in a small forested catchment in the central Czech Republic using the watershed mass balance approach together with measurements of internal stores and fluxes. Mn inputs in bulk deposition were relatively constant during a period of sharply decreasing acidic deposition, suggesting that the Mn source was terrestrial, and not from fossil fuel combustion. Mn inputs in bulk deposition and Mn supplied by weathering each averaged 13 mg m^?2 year^?1 (26 mg m^?2 year^?1 total input), whereas Mn export in streamwater and groundwater averaged 43 mg m^?2 year^?1. Thus an additional Mn source is needed to account for 17 mg m^?2 year^?1. Internal fluxes and pools of Mn were significantly greater than annual inputs and outputs. Throughfall Mn flux was 70 mg m^?2 year^?1, litterfall Mn flux was 103 mg m^?2 year^?1, and Mn net uptake by vegetation was 62 mg m^?2 year^?1. Large pools of labile or potentially labile Mn were present in biomass and surficial soil horizons. Small leakages from these large pools likely supply the additional Mn needed to close the watershed mass balance. This leakage may reflect an adjustment of the ecosystem to recent changes in atmospheric acidity.     

农业土壤中汞的生物地球化学行为及其生态效应

综述了国内外近年来农业土壤中汞的生物地球化学行为,包括了土壤环境中汞的来源,汞的形态和生物有效性,汞在农业生态系统中的迁移和转化途径,影响汞对植物有效性的主要因子。同时讨论了汞对植物、动物生长发育的影响,特别强调了土壤中汞污染对食物中汞积累和分配的影响及通过食物链途径给人类健康带来的危害。最后提出了汞污染土壤的各种修复措施,展望了今后研究的方向。     

Anaerobic Incubation without Shaking over a Prolonged Period as a Method to Determine Mineralizable Nitrogen in Rice Soils

Fertilization rates of nitrogen (N) in rice crop are based on crop needs and the capacity of the soil to supply N, which is determined by several methods. This study evaluated a method of anaerobic incubation without shaking for extended periods of time. Three rice soils of the Inceptisol, Alfisol, and Vertisol orders were fertilized with N rates of 0, 80, and 160 kg ha^?1 and incubated for 0, 7, 14, 21, and 28 d at 20 and 40 °C. The methodology also used short-term anaerobic incubation and constant shaking for 7 d at 40 °C. Field experiments were conducted with rice in the same soils with equal N rates, and extracted plant N was compared with mineralized N. Results indicated that the methodology without shaking is comparable to the constant shaking procedure for short-term incubations. However, incubations without shaking for longer periods of time had the greatest relation to crop extracted N.     

Biodegradation of beta-cyfluthrin by fungi

Five fungal species, namely, Trichoderma viride strain 5-2, T. viride strain 2211, Aspergillus niger, A. terricola, and Phanerochaete chrysoporium were screened for degradation study of beta-cyfluthrin. Each fungal species was allowed to grow in Czapek dox medium containing beta-cyfluthrin (5 mg/mL) as the major carbon source of the medium. The highest degradation of beta-cyfluthrin was observed by T. viride 5-2 (T(1/2) = 7.07 days), followed by T.viride 2211 (T(1/2) = 10.66 days). The degradation of beta-cyfluthrin followed first-order kinetics with a fast degradation rate during first 7 days of growth of the fungi. In the case of T. viride strain 5-2, five degradation products were isolated after 20 days of growth of the fungi, out of which three products were identified as alpha-cyano-4-fluorobenzyl-3- (2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate, alpha-cyano-4-fluoro-3-phenoxy benzyl alcohol, and 3(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanoic acid.     

15th International Conference on the Biogeochemistry of Trace Elements Successfully Held

<正>With Pedosphere being one of the sponsors, the15th International Conference on the Biogeochemistry of Trace Elements (ICOBTE), organized by Nanjing Agricultural University, in cooperation with the Institute of Soil Science, Chinese Academy of Sciences and Nanjing University, has been successfully held in May     

Natural Sunlight Induced Photooxidation of Naphthalene in Aqueous Solution

There is surprisingly little data on the photooxidation of polycyclic aromatic hydrocarbons (PAHs) under environmentally relevant lighting conditions. The aqueous photooxidation reactions of naphthalene (the simplest and most water soluble PAH) were investigated using natural sunlight as a light source.Six of the major reaction products were identified, including 1-naphthol, coumarin, and two hydroxyquinones. The reactionproducts were consistent with initial [2,2] or [2,4] photocycloaddition reactions, with subsequent oxidations and/or rearrangements. The oxidation reactions in aqueous phase favoredproducts different from those observed in atmospheric oxidation reactions. However, similar photoproducts were observed withtitanium catalysts or in the presence of hydrogen peroxide. Theproducts from aqueous photooxidation were also similar to the products resulting from naphthalene metabolism. The observedphotooxidation products were generated by mechanisms that areexpected to occur with other PAHs as well, and thus naphthaleneoxidation provides a model for possible photoreactions of largerPAHs.     

采用厌氧分步固体反应器系统进行蔬菜废弃物厌氧分解

最近获得专利的厌氧分步固体反应系统(美国专利号6342378B1)是一种新型的用于将固体废弃物转化为沼气以获取生物能源的新技术。此技术已被用以转化多种固体废弃物的科学研究,其中包括作物秸秆、动物粪便、食品废弃物和城市固体废弃物。研究结果证明,此技术不仅先进可行,而且操作简单。根据此技术,一种大型的用于将废弃物转化为能源的厌氧分步固体反映系统已经在美国开发出来。该文主要介绍此技术用于大蒜废弃物转化的研究结果