滤层曝气对炭砂双层滤池去除氨氮的影响

通过现场中试试验,考察了不同气水比和曝气深度下滤层曝气对炭砂生物滤池氨氮去除效果的影响。试验结果表明滤池对氨氮去除量随着气水比和曝气深度的增加呈现出先增加后不变的趋势,炭砂双层滤池对NH3-N的去除限为2．8～3．0mg／L。在滤池某一深度进行曝气,当气水比小于0．1时,增加气水比,增大的是滤池0～0．5m滤段滤料对氨氮的去除;当气水比为0．1～0．25时,增加气水比,增加的是0．5～0．9m滤段滤料对氨氮的去除。充足的气水比条件下,在0．4m深度以上曝气,提高的是0～0．5m滤段的氨氮去除效果,在0．4～0．8m深度曝气,提高的是0．5～0．9m的氨氮去除效果,0．9m滤段以下滤料对氨氮基本没有去除作用。为保证出水浊度,建议在滤池0．6m深度对滤池进行曝气。     

生物接触氧化法去除微污染水源水中的氨氮

采用生物接触氧化法对北京某水库的微污染水源水进行了除氨效果研究。结果表明,生物接触氧化法具有较好的除氨效果,生物接触氧化原水氨氮的质量浓度在不大于0.234mg/L时,氨氮的月平均去除率为30.8%~72.9%,进水氨氮的质量浓度人工增加至0.126~2.080mg/L时,氨氮去除率最高可达97.4%,平均去除率为71.2%。同时探讨了水温及进水氨氮的质量浓度对氨氮去除效果的影响。     

垃圾渗滤液中总氮检测的适用方法探讨

采用紫外分光光度法及离子色谱法检测垃圾渗滤液中的总氮,针对不同的检测结果,分析两种方法的准确性,并对导致方法不准确的原因进行探讨。结果表明,离子色谱法所测值高于氨氮值的6.7%,其标准曲线在0.05~10.00 mg/L呈现良好的线性,方法检出限为0.018 mg/L,相对标准偏差介于0.84%~4.05%,加标回收率介于95.1%~98.4%,精密度和准确度满足要求,适用于垃圾渗滤液中总氮的测定;紫外分光光度法的标准曲线和精密度虽满足检测要求,但总氮的测定值低于氨氮值的16.0%;导致检测结果偏低的主要原因是消解过程中产生的细微悬浮颗粒对紫外光有散射作用,可通过超滤膜的过滤减弱这一影响。     

给水管网水中氯胺消毒的氨氮释放规律

研究了对不同氯氨比条件下氯胺释放氨氮的规律,考察了pH、有机物浓度、亚硝酸盐浓度和Fe2＋对氯胺释放氨氮规律的影响。结果表明随着氯氨比的增加氨氮释放量降低,Cl∶N＝3∶1和Cl∶N＝5∶1的氯胺释放氨氮的量分别为0．91和0．35 mg/L;pH对氯胺释放氨氮有一定影响,氨氮浓度随着pH升高而降低;有机物含量和亚硝酸盐浓度对氯胺释放氨氮有显著影响,随着有机物和亚硝酸盐含量的增加,氯胺释放的氨氮浓度增加;管网中的 Fe2＋也会加快氯胺释放氨氮的速度。     

配煤含氮量与硫铵产量关系的研究

使用Minitab软件研究了配煤含氮量与硫铵产量之间的定量关系。研究表明,含氮量为0.8%～1.4%时,配煤含氮量与硫铵产量之间有明显的线性关系。含氮量改变0.1%,硫铵收率改变约0.01%。     

Foliar urea fertilization of cereals: A review

It has been suggested that there are several potential benefits of providing nitrogen to cereals via the foliage as urea solution. These include: reduced nitrogen losses through denitrification and leaching compared with nitrogen fertilizer applications to the soil; the ability to provide nitrogen when root activity is impaired e.g., in saline or dry conditions, and uptake late in the season to increase grain nitrogen concentration. Factors that influence the degree of foliar absorption in field conditions have not, however, been clearly defined and losses to the atmosphere and soil can occur. Foliar urea applications may also hinder crop productivity although the explanations for this vary, and include desiccation of leaf cells, aqueous ammonia and urea toxicity, biuret contamination and the disruption of carbohydrate metabolism. It has not yet been determined which one, or combinations, of these mechanisms are most important in field situations. When damage has not been severe, foliar urea applications have increased grain yield, particularly when applied before flag leaf emergence and when nitrogen availability is limiting. Increases in grain nitrogen content are often larger when applications of nitrogen fertilizers to the soil are reduced, and when the urea solution is sprayed either at anthesis or during the following two weeks. It is during this period that foliar urea sprays can be of greater benefit than soil applications with regard to nitrogen utilization by the crop. Increases in wheat grain nitrogen concentration following urea application can improve breadmaking quality. Responses in loaf quality may, however, be variable particularly when increases in grain nitrogen content have been large, and/or when the nitrogen: sulphur ratio in the grain is increased. These circumstances have lead to alterations in the proportions of the different protein fractions which influence breadmaking potential.To exploit the full potential benefits of foliar urea application to cereals, more needs to be known about the mechanisms, and thus how to prevent losses of nitrogen from the foliage, and to reduce the phytotoxic influences of sprays. More information is also required to exploit the reported effects that urea may have on limiting the development of cereal diseases.     

Desintering Process in the Gas-Pressure Sintering of Silicon Nitride

A unique desintering phenomenon has been observed in gas-pressure sintering of silicon nitrides with additives of yttria and alumina. The desintering phenomenon occurred, simultaneous with weight increase, only when a boron nitride crucible was used in combination with the application of high nitrogen pressure (5 MPa). When the nitrogen pressure was low (0.5 MPa), or when the boron nitride crucible was replaced by a graphite crucible, this desintering phenomenon was not observed. These results could be rationalized by the chemical dissolution of nitrogen into the oxynitride melts and the resultant evolution of carbon monoxide. This indicates that the high nitrogen overpressure employed in gas-pressure sintering of silicon nitride ceramics is not always beneficial.     

底泥中氮的释放与溶解氧量的关系

调研分析基础上,结合贾鲁河(郑州段)污染的实际情况,通过自制的原始柱状底泥模拟试验装置,研究了溶解氧量对底泥中氮的释放转化规律。结果表明:溶解氧是影响底泥中氮转化的主要因素,给氧条件下可以促进硝化作用的进行,氨氮的去除转化较彻底;当水样中溶解氧量为8.5~11.4 mg/L时,氨氮的去除率最高,最早发生硝化反应。     

Role of Anion Vacancies in Nitrogen-Stabilized Zirconia

Introduction of nitrogen into zirconia creates oxygen vacancies in the anion sublattice as required by charge neutrality when N³⁻ replaces for O²⁻ in the structure, being similar to those obtained by lower valency cation substitution for zirconium. There is no essential structural difference between the cation-related vacancy and the anion-related vacancy, and their effects on the stabilization of zirconia are additive. The zirconia structure can, when formed in the Zi─Y─O─N system, tolerate a total of 6% of vacancies in the anion lattice without deviating from the original fluorite structure; above this limit, ZrN precipitates. Therefore, both partially and fully stabilized zirconia can dissolve a certain amount of nitrogen when these phases react with either atmospheric nitrogen or a solid nitride at high temperatures.     

Development of nitrogen fertilizer recommendations for arable crops in the Netherlands in relation to nitrate leaching

In the Netherlands, current nitrogen fertilizer recommendations for arable crops are based on the amount of soil mineral nitrogen in early spring. The larger the amount of soil mineral nitrogen, the lower the recommended application rate of fertilizer nitrogen. A more refined method is to draw up a balance sheet in which the nitrogen requirement of the crop is given on the one side and the contributions of fertilizer nitrogen, soil mineral nitrogen, and the amount of nitrogen mineralized during the growing period on the other. The most refined method of nitrogen fertilizer recommendation is the use of a simulation model that predicts the daily crop nitrogen requirement and nitrogen supply to the crop from various pools during the growing period. A simulation model thus adds the time element to nitrogen fertilizer recommendations. Moreover, in contrast with the other two methods, a simulation model allows identification of environmental side-effects of nitrogen fertilizer application.The current Dutch nitrogen fertilizer recommendations aim at predicting the economically optimum application rate of fertilizer nitrogen. From the environmental point of view it is interesting to know how much soil mineral nitrogen has accumulated in the soil at harvest, because this nitrogen is a potential loss to the environment through nitrate leaching during the subsequent winter period. If the economically optimum application rate of fertilizer nitrogen is applied to arable crops, it is unlikely that soil mineral nitrogen accumulates, except in the case of potatoes. Model calculations have shown that accumulation of soil mineral nitrogen after potatoes can be prevented when the recommended nitrogen application rate is reduced by 25%. In that case tuber yield is reduced by only 2%.     

Protein digestibility and energy in diets based on rice and beans in human adults

Four studies were carried out for the purpose of measuring the digestibility of diets based on rice and beans (Phaseolus vulgaris), and in order to quantify the effect of their supplementation with animal protein (milk) and energy (oil), on the energy and protein digestibility of such diets in human adults. Diets were offered so that they supplied 46, 72, and 103 mg N/kg/day. When the basal diet--where rice provided 60% of the protein and beans 40%--was administered at a level of 102.5 mg of nitrogen/kg/day and 49.5 Kcal/kg/day of gross energy, an apparent and true nitrogen, energy and metabolizable energy digestibility of 59.1, 70.8, 93.8 and 92.5%, respectively, were observed. When substituting 10% of the vegetable protein by milk protein in the same diet, the same indicators revealed a digestibility of 65.3, 76.8, 93.5 and 92.1%, respectively. The information indicates that supplementation with animal protein improves nitrogen absorption at any of the energy levels studied. In contrast, caloric supplementation does not have any positive effect on nitrogen or energy absorption. It was also found that nitrogen apparent digestibility increases significantly when the N level in the diet is raised, and stabilizes when intake exceeds 100 mg nitrogen/kg/day. It is therefore proposed that for digestibility studies in diets where animal protein is utilized at a nitrogen level of around 120 mg/kg/day, true digestibility remains constant, no matter what nitrogen level is used in the diet.     

Interaction of ammonium and nitrate nutrition with potassium in wheat

A greenhouse experiment with wheat in 3L pots filled with a sandy loam soil in a factorial design was conducted to determine the effect of potassium on nitrogen utilization. Nitrogen was applied in three NH₄-N/NO₃-N ratios, 0/100, 25/75 and 50/50, at three levels: 0.75, 1.50 and 3.00gN/pot, and potassium was applied at three levels: 0, 0.5 and 1.0gK/pot. The higher levels of nitrate nitrogen with or without potassium reduced dry matter yields drastically, while the same levels of a NH₄-N/NO₃-N mixture of 50/50 with applied potassium reduced yields only slightly. Highest grain yield and total yield were obtained with a 25/75 mixture of ammonium/nitrate nitrogen with added potassium. Potassium addition to soil increased the utilization of nitrogen fertilizers, particularly when the ratio of ammonium to nitrate was increased. The highest uptake of reduced nitrogen was at the highest level of the ammonium to nitrate nitrogen ratio (50/50) when potassium was applied. Tillering was enhanced by an increased ammonium ratio in the nitrogen mixture, and by potassium.     

温度对序批式生物反应器工艺同步硝化反硝化的影响

为了考察不同温度下碳氮质量比w(C/N)和污泥龄(SRT)对同步硝化反硝化(SND)的影响,研究采用序批式生物反应器(SBR)对模拟废水进行了长期连续实验.结果表明:在pH值为7.5-8的条件下,温度为(5±1)℃,当w(C/N)为8、污泥龄为20 d时,总氮反应速率为1.25 ms/(L·h),COD去除率达到60%...     

紫外分光光度法测定水中总氮的改进消解方法

采用碱性过硫酸钾消解紫外分光光度法测定水中的总氮时,分别用电热恒温干燥箱和压力蒸汽灭菌器消解试样,对测定得到的总氮标准曲线和实际水样中总氮的含量进行了对比.结果表明,与压力蒸汽灭菌器消解方法相比,电热恒温干燥箱消解法操作简便、温度容易控制,节约了大量蒸馏水,且测定结果准确.此方法能够替代传统的水样预处理方法,在满足试验...     

高温乙二醇在不同水和氮气含量下爆炸极限的测定

爆炸极限不是固定不变的,它随温度、压力、含氧量、氮气含量等因素的变化而变化。利用自制爆炸容器,在高温下(260℃),改变氮气和水蒸气含量,测定乙二醇的爆炸极限,通过分析得出随着氮气和水蒸气含量的增加,乙二醇的爆炸极限不断缩小,达到一定值时,该体系不再爆炸,而进入安全区域。而水比氮气具有更加好的压缩乙二醇爆炸极限的作用。     

改性膨润土对氨氮废水吸附性能的研究

用内蒙膨润土及其碱改性膨润土进行模拟氨氮废水的脱氮实验研究。结果表明,在氨氮溶液初始浓度为300 mg/L,pH值为3.0～7.0时,相对于天然膨润土,碱改性膨润土对氨氮的吸附量有了很大提高,其吸附等温线符合Freundlich和Langmuir方程,且对氨氮的吸附动力学符合准一级和准二级吸附动力学模型,说明化学吸附和物理吸附共同起作用;在应用于畜禽废水处理中,碱改性膨润土对氨氮去除率达到91.0%。     

介孔材料低温氮气吸脱附的孔道网络模型

介孔结构的表征和分析对于介孔材料的开发至关重要,其中低温氮气吸脱附法是最常用的介孔表征方法之一。然而,目前氮气吸脱附法采用的分析模型仍基于平行孔假设,无法描述脱附过程堵孔现象,以及获取孔道连通性等重要孔结构信息。本文建立了低温氮气吸脱附的孔道网络模型,用于分析介孔结构对氮气等温吸脱附行为的影响。通过对比氧化铝材料的氮气吸脱附实验数据和模拟结果,证实了建立的孔道网络模型能很好地描述介孔材料中低温氮气吸脱附行为。模拟结果表明平均孔径较小时,毛细凝聚分压低,液氮堵孔效应显著,氮气吸脱附曲线回滞环的范围和面积较大;孔径分布较宽时,小孔和大孔数量均较多,毛细凝聚和堵孔效应显著,回滞环面积较大;孔道连通性不会影响吸附过程,但会通过改变堵孔效应显著影响脱附过程,连通性越差,堵孔效应越强。证实了堵孔效应对氮气脱附过程影响显著,因而氮气吸脱附法需要考虑堵孔效应,建立的孔道网络模型也可为介孔结构分析提供合理的模型工具。     

焦炉煤气循环干熄焦及焦炭脱硫

研究了焦炉煤气代替氮气作为循环换热介质的干熄焦工艺,该工艺在冷却焦炭的同时实现了焦炭脱硫. 通过物料和热量平衡计算表明,干熄焦过程循环焦炉煤气比循环氮气气料比显著降低;焦炉煤气在熄焦炉入口补充气体的比例越高,循环气量越小,干熄焦系统的动力消耗越小. 焦炭加氢脱硫实验结果表明,干熄焦过程循环焦炉煤气能显著降低焦炭中的硫含量.     

改性凹凸棒石和沸石对氨氮废水吸附性能的研究

采用焙烧、钠化、酸化和碱化4种改性方法对天然凹凸棒石和沸石进行改性,其中碱化改性对氨氮吸附能力提高最大,研究了碱化样品的结构及对氨氮废水的吸附性能。结果表明,碱改性品在氨氮溶液初始浓度300 mg/L,pH值2.5~8.0时,对氨氮的吸附量较高;对氨氮的吸附等温线符合Freund lich和Langmu ir方程式。同时,对氨氮的吸附动力学符合准二级吸附动力学模型,并以化学吸附为主。用于畜禽废水处理中,对氨氮去除率最高达到87.6%。     

硝化工艺及原料的预处理对硝化棉含氮量及其分布均匀性的影响

采用硝化棉(NC)含氮量及其分布均匀性测试仪,考察了硝化系数、精制棉的膨润预处理和超声预处理三因素对硝化棉含氮量及氮量分布均匀性的影响规律.结果表明,NC的含氮量随硝化系数的增大而增大.当硝化系数分别为40、50和80时,NC含氮量分布值Dε较小,当硝化系数为20或100时,Dε值均显著增大;采用硫脲和尿素水溶液预处理...