异波折板高效水解酸化废水的处理技术

提出了异波折板高效水解酸化废水处理技术.通过水力学措施实现水解酸化系统内湍流涡旋以加速传质,并改善系统内pH值条件以增强微生物活性.试验结果表明,对浓度范围在450～900mg/L之间的溶解性COD的去除率为40%±4%.     

中国城市污水处理厂资源配置效率的比较

采用平均生产函数模型、边界生产函数以及数据包络分析(DEA)模型3种方法,对中国81个污水处理厂的样本观测数据,从不同角度进行了比较研究,分别得出上述3种模型对产出弹性、技术效率和规模经济性等主要指标的模拟结果.研究发现,资本对我国城市污水处理厂的产出弹性最大(0.507),其次是运营电耗(0.415),再次为劳动力;我国污水厂普遍处于规模报酬率递增阶段,样本总体的规模报酬率为1.11;根据DEA的分析结果,列出了81个样本污水厂的效率排序清单,这将有助于制定行业绩效标准.     

不同流态生物膜反应器对微囊藻毒素的降解特性

以富营养化源水为处理对象,考察了三阶、单阶气水顺流、单阶气水逆流生物膜反应器对微囊藻毒素的去除特性.三阶生物膜反应器比单阶反应器更接近于推流反应器,对藻毒素的去除效率高于单阶反应器,且效果稳定.在试验水质条件下,水力停留时间(HRT)为2h时,三阶反应器可有效去除85.9%的胞外微囊藻毒素与84.0%的总微囊藻毒素,对胞外微囊藻毒素-LR、RR与总微囊藻毒素-LR、RR的去除率分别为86.7%、81.7%与71.5%、80.5%.三阶生物膜工艺可用于富营养化源水的预处理.     

耕地流转农户行为影响因素的实证分析——基于江西省1396户农户耕地流转行为现状的调研

论文利用江西省42个县(区)74个行政村1396户农户的抽样调查数据,通过建立耕地流转行为与各自变量的Logistic回归计量模型,从家庭特征因素、家庭经济因素和资源禀赋因素三方面分析了农户耕地流出和流入行为的影响因素。研究表明:外出打工对耕地流出影响最大,是农户耕地流出的最大驱动力;而经济收入与耕地流转是互为因果的关系,耕地流入户的经济收入存在明显低于流出户的经济收入的趋势;地形特征对耕地流出行为有明显影响,地形越平坦,越容易流出,同样耕地越破碎,越不易被流入户接受。     

水流模拟断面中硝基苯的迁移转化规律

采用实验室模拟装置研究了4,10和20 ℃条件下,封闭、开放状态和不同环境因素影响下硝基苯污染水团流经模拟断面前后, 硝基苯在上覆水与沉积物中的迁移转化规律. 结果表明:封闭、开放状态模拟断面上覆水和沉积物中硝基苯迁移分配受温度变化影响显著;开放状态下,上覆水、沉积物中硝基苯变化量均低于封闭状态. 挥发不但影响硝基苯在沉积物-上覆水间的迁移分配,而且能促进沉积物中硝基苯的解吸;光照对模拟断面硝基苯迁移转化无影响. 对于相同的沉积物和上覆水,影响模拟断面系统中硝基苯迁移、分配的因素依次为温度、挥发和光照. 分析实验结果和材料推测,硝基苯在该实验条件下不存在降解转化.      

The Time Invariance Principle,the absence of ecological chaos,and a fundamental pitfall of discrete modeling

This paper is to show that most discrete models used for population dynamics in ecology are inherently pathological that their predications cannot be independently verified by experiments because they violate a fundamental principle of physics. The result is used to tackle an on-going controversy regarding ecological chaos. Another implication of the result is that all dynamical systems must be modeled by differential equations. As a result it suggests that researches based on discrete modeling must be closely scrutinized and the teaching of calculus and differential equations must be emphasized for students of biology.     

一株高效产氢突变体RF-9的筛选与产氢特性

以从连续流搅拌槽式反应器(CSTR)内的活性污泥中分离出的厌氧产氢菌Ethanologenens sp.ZGX4为出发菌株,经过紫外线和亚硝酸复合诱变,从大量的突变体中筛选出一株稳定的高效产氢菌株RF-9.磷酸盐浓度在120mmol/L、温度37℃、初始pH6.0、葡萄糖浓度10g/L培养条件下,RF-9的单位体积产氢量和氢气产率为139.7mmol/L和2.52mol H2/mol葡萄糖,分别是对照的1.50倍和1.43倍.在发酵时间为15h、pH4.1、细胞干重0.722g/L时,RF-9获得其最大产氢速率345mLH₂/(h·L),是对照ZGX4的1.41倍.RF-9的主要液相末端产物为乙醇和乙酸,为典型的乙醇发酵细菌,与对照相似.     

黄河河口地区生态供水效益分析

流域生态需水是指流域生态系统为维持一定程度的生态系统健康所需要一定质量的水量,以保证流域生态系统结构和生态功能等为目标,实现流域生态系统健康。流域生态需水量的研究对于社会经济的可持续发展具有重要的战略意义。论文针对南水北调西线一期工程的供水规划,在提出配水效益计算方法的基础上,针对不同的配水量,计算了黄河河口地区的生态需水量、生态效益以及供水对减少断流所带来的生态效益,并进行了方案比较分析。主要结论是:当来水量分别为55×10⁸、122.8×10⁸或240×10⁸m³时,产生的湿地综合生态效益则为34.85×10⁸、47.18×10⁸或54.72×10⁸元。     

移动床生物膜反应器内气液传质性能研究

采用移动床生物膜反应器,利用清水进行了在不同悬浮填料体积含率和曝气强度时反应器内气液传质性能研究。结果表明,随着曝气强度增加,传质系数增大,但曝气强度过大,并不利于移动床操作;当填料体积含率大于40%时,氧传质系数出现最大值后逐渐减小。在填料体积含率为30%~50%、曝气强度为4.5~7 m3/(h.m)时,传质效果良好,氧转移效率较高。     

Effect of scale on freely propagating flames in aluminum dust clouds

The majority of experimental tests done on combustible dusts are performed in constant volume vessels that have limited or no optical access. Over the years, McGill University has been developing alternative experimental techniques based on direct observation of dust flames, yielding reliable fundamental parameters such as flame burning velocity, temperature and structure. The present work describes two new experimental set-ups allowing direct observation of isobaric and freely propagating dust flames at two sufficiently different scales to test the influence of scale on dust flame phenomena. In the laboratory-scale experiments, a few grams of aluminum powder are dispersed in transparent, 30 cm diameter latex balloons that allow for full visualization of the spherical flame propagation. In the field experiments, about 1 kg of aluminum powder is dispersed by a short pulse of air, forming a conical dust cloud with a total volume of about 5 m³. High-speed digital imaging is used to record the particle dispersal and flame propagation in both configurations. In the small-scale laboratory tests, the measured flame speed is found to be about 2.0 ± 0.2 m/s in fuel-rich aluminium clouds. The burning velocity, calculated by dividing the measured flame speed by the expansion factor deduced from thermodynamic equilibrium calculations, correlates well with the previously measured burning velocity of about 22–24 cm/s from Bunsen dust flames. Flame speeds observed in field experiments with large-scale clouds, however, are found to be much higher, in the range of 12 ± 2 m/s. Estimations are presented that show that the presumably greater role of radiative heat transfer in larger-scale aluminium flames is insufficient to explain the six-fold increase in flame speed. The role of residual large-eddy turbulence, as well as the frozen-turbulence effect leading to large-scale dust concentration fluctuations that cause flame folding, are discussed as two possible sources for the greater flame speed.