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881.
Anaerobic ammonium oxidation (ANAMMOX) technology has potential technical superiority and economical efficiency for the nitrogen removal from landfill leachate, which contains high-strength ammonium nitrogen (NH4 -N) and refractory organics. To complete the ANAMMOX process, a preceding partial nitritation step to produce the appropriate ratio of nitrite/ammonium is a key stage. The objective of this study was to determine the optimal conditions to acquire constant partial nitritation for landfill leachate treatment, and a bench scale fixed bed bio-film reactor was used in this study to investigate the effects of the running factors on the partial nitritation. The results showed that both the dissolved oxygen (DO) concentration and the ammonium volumetric loading rate (Nv) had effects on the partial nitritation. In the controlling conditions with a temperature of 30±1℃, Nv of 0.2-1.0 kg NH4 -N/(m3d), and DO concentration of 0.8-2.3 mg/L, the steady partial nitritation was achieved as follows: more than 94% partial nitritation efficiency (nitrite as the main product), 60%-74% NH4 -N removal efficiency, and NO2--N/NH4 -N ratio (concentration ratio) of 1.0-1.4 in the effluent. The impact of temperature was related to iVv at certain DO concentration, and the temperature range of 25-30癈 was suitable for treating high strength ammonium leachate. Ammonium-oxidizing bacteria could be acclimated to higher FA (free ammonium) in the range of 122-224 mg/L. According to the denaturing gradient gel electrophoresis analysis result of the bio-film in the reactor, there were 25 kinds of 16S rRNA gene fragments, which indicated that abundant microbial communities existed in the bio-film, although high concentrations of ammonium and FA may inhibit the growth of the nitrite-oxidizing bacteria and other microorganisms in the reactor. 相似文献
882.
CAI Peng HUANG Qiao-yun LU Yan-du CHEN Wen-li JIANG Dai-hu LIANG Wei 《环境科学学报(英文版)》2007,19(11):1326-1329
Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments. 相似文献
883.
LIANG Xin-qiang CHEN Ying-xu LI Hu TIAN Guang-ming ZHANG Zhi-jian NI Wu-zhong HE Miao-miao 《环境科学学报(英文版)》2007,19(12):1474-1481
A field experiment located in Taihu Lake Basin of China was conducted,by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen(N)export in a typical rice field through"zero-drainage water management"combined with sound irrigation,rainfall forecasting and field drying,N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations,and subsequently tended to retum to the background level.Before the first field drying,total particulate nitrogen(TPN)was the predominant N form in floodwater of plots with no N input,dissolved inorganic nitrogen(DIN)on plots that received urea only,and dissolved organic nitrogen(DON)on plots treated with the mixture of urea and manure.Thereafter TPN became the major form.No N export was found from the rice field,but total nitrogen(TN)of 15.8 kg/hm~2 was remained,mainly due to soil N sorption.The results recommended the zero-drainage water management for full-scale areas for minimizing N export. 相似文献
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885.
埋地管道腐蚀剩余寿命预测概率模型 总被引:6,自引:0,他引:6
为考察腐蚀参数的不确定性对埋地管道失效和剩余寿命的影响,建立以Shell—92确定性模型为基础的管道腐蚀剩余寿命预测概率模型。采用Monte-Carlo方法计算管道剩余寿命及其累积分布函数,并进行参数敏感性分析,详细研讨影响埋地管道腐蚀剩余寿命的主要参数及其随服役时间的变化规律。计算结果表明,提出的管道腐蚀剩余寿命预测模型能有效预测实际中受多因素影响的管道失效和剩余寿命问题。 相似文献
886.
基于改进熵权的灰色关联模型在湿地水质综合评价中的应用 总被引:13,自引:1,他引:12
湿地是自然界生物多样性较为丰富的生态系统,具有很大的生态功能及生态学价值,湿地水质评价需要综合考虑各指标的属性.介绍了基于改进熵权的灰色关联模型在湿地水质综合评价中的应用.以黑龙江省扎龙国家级自然保护区湿地调查采样数据为例,通过构建灰色关联决策矩阵,同时采用改进熵值法确定权重,再由计算各样本的灰色关联度来确定其所属级别,进而对保护区水质采样点的水质进行综合评价.基于改进熵权的灰色关联度模型,为湿地生态系统水质综合评价提供了新的思路. 相似文献
887.
存在化学有害因素的小型企业职业危害定性评价研究 总被引:1,自引:1,他引:0
小型企业数量多、雇工人数总量大,分散在全国各地,行业分布广,由于其用于控制职业危害的资源和技术都非常有限,这对企业自身的职业危害控制和政府的职业卫生管理来说都是一大难题.本文在参考国外职业危害分级管理方法的基础上,为存在化学危害因素的小型企业建立了一个简便、实用的职业危害定性评价模型.该模型综合考虑了化学有害物质的危害性和接触可能性,并结合具体的实例进行分析,验证了其适用性和可靠性.该方法也适用于管理不够规范、缺乏监测资料和数据的作业场所职业危害评价. 相似文献
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890.
Chen JA Luo J Qiu Z Xu C Huang Y Jin YH Saito N Yoshida T Ozawa K Cao J Shu W 《Chemosphere》2008,70(9):1545-1551
The Three Gorge Reservoir (TGR) is the largest reservoir in China and its water quality is an important health concern, we have determined the concentrations of PCDDs/PCDFs and PCBs in the water samples collected at three seasons: August 2004, January 2005 and August 2005. The results showed that the average WHO-TEQ of total dioxins-like compounds (PCDDs/PCDFs+PCBs) was 0.06558 pg l(-1), ranged from 0.0008 to 0.32439 pg l(-1), which are much lower than other reported water sources. The main dioxins (PCDDs/PCDFs) are hepta- and octa-chlorinated dibenzo-p-dioxins (CDDs) and chlorinated dibenzofurans (CDFs). Since the levels of dioxins may change after the last water-store stage, the present study provides important data to compare the water quality in the TGR in the future. 相似文献