System for quasi‐continuous simultaneous measurement of oxygen diffusion rate and redox potential in soil

Oxygen diffusion rate (ODR) and redox potential (E_H) are quantitative indices representing oxygen availability and redox status in soils, which is valuable information for better understanding causes and effects of soil aeration. Because these indices are spatially and temporally highly variable, continuous measurements and adequate numbers of repetitions are essential for accurate in situ monitoring. Here, we present a new, fully automated recording system for in situ measurements where ODR and E_H are measured at the same platinum electrode. The conflict between electrode polarization for ODR and the resulting biased E_H readings is solved by reducing the polarization time and introducing a recovery interval between two consecutive measurement cycles. The shorter polarization time ensures accurate E_H readings. It also results in moderately overestimated ODR readings, but this can be corrected before data analysis. The recovery interval restricts temporal resolution of the E_H‐ODR data pairs to 8 h. We illustrate the use of the system with measurements in a field experiment in Zürich, Switzerland. ODR curves at different depths ran roughly parallel to the corresponding curves of O₂ concentration in soil air but ODR was much more sensitive to precipitation. Low ODR was a necessary but not a sufficient condition for declining E_H. E_H ran parallel to O₂ concentration in soil air rather than to ODR. The fully automated system allows for time series of replicate measurements in multifactorial field studies with reasonable labor requirements. It may be particularly suitable for studies examining the effects of soil tillage, compaction, and irrigation, where structure‐related soil properties such as porosity, gas permeability, and soil aeration play a dominant role.     

Performance evaluation of venturi aeration system

The venturi aeration is an effective practice to increase the dissolved oxygen accessibility in the water bodies. This study aims to optimize the various geometrical parameters of the venturi aeration system. A non-dimensional technique was applied to find the optimum performance of various geometric parameters i.e. throat lengths (t_l), number of air holes (N), and converging and diverging angles (α and β). These experiments have been carried out using 1124 L capacity of tank having dimensions of 105 cm long, 105 cm wide and 102 cm deep. The experiments were conducted at a constant flow velocity of water (1.096 m/s) with varying throat length (t_l = 20–100 mm keeping 20 mm as interval between two consecutive length), number of air holes (N = 1–17 at an equal hole to hole distance of 5 mm between them), and converging and diverging angles (α and β = 10°, 15°, 20° and 25°). Multiple non-linear regression equations were also developed from the linear relation with the dependent variable (Non-dimensional form of standard aeration efficiency, NDSAE) and independent variables (t_l and N). With the geometrically optimized venturi aerator the optimum performance was found for t_l =100 mm, N = 17, and α and β = 15°. The maximum value of standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE) obtained was 0.0216 kgO₂/h and 0.611 kgO₂/kWh respectively. From the non-dimensional study, it was found that the NDSAE is the function Reynolds number (Re) and Froude number (Fr). The simulation equations were developed on the basis of Re and Fr for NDSAE, and subjected to 7.378 × 10⁻⁶ < Re < 3.689 × 10^-5 and 0.163 < Fr < 0.817, respectively.     

Discussion of the Application and Foreground of Falling Water Aeration with the Process of Sewage Treatment

The engineering design of sewage treatment plant for the Chongqing city, P. R. China is analyzed in this paper. Considering the situation of China and other projects, the characteristics of falling water reactor for the environment protection project and economy of investment is introduced ; the application and foreground of falling water aeration in the process of sewage treatment is discussed, such as Oxidation - ditch, SBR, and so on. The conclusion indicated that the falling water aeration can be designed and used as an independent aeration, and, it is an upgraded technology of sewage treatment which is adaptive for city water environment control in middle and small towns in China. The falling water aeration may reduce running cost of the sewage treatment plant, is adaptive for foothill and the mountainous areas, and reduces project investment and environments damage.     

Bubbleless Aerated Membrane Bioreactor for Ramie Degumming Wastewater Treatment

Through introducing the principle of bubbleless aerated membrane bioreactor, the traditional membrane bioreactor was improved. It could be obtained that the removal efficiency of COD and NH3 - N in bubbleless aerated membrane bioreactor increased 4% and 2% than that in traditional membrane bioreactor, respectively. Adopting bubbleless aeration as reflushing air which not only increased DO in the MBR, but also advanced the oxygen utilization, and the energy consumption decreased as well.     

基于充油流量与曝气程度的拖拉机动力换向性能研究

围绕拖拉机动力换向离合器充油流量易受温度、回位弹簧刚度和预紧力等因素影响,液压油在加注及工作过程中易受空气污染,导致液压油空气含量增加的工程应用问题,探究了不同充油流量及曝气程度对动力换向性能的影响。以换向时间、冲击度、滑摩功和磨损量为评价指标对换向性能进行了评估,以期提高拖拉机动力换向品质、工作效率和传动系使用寿命。以东方红LF2204型拖拉机TX4A传动系为研究对象,建立了考虑充油流量和曝气程度的动力换向过程数学模型,基于ADAMS、Matlab/Simulink和AMESim平台分别建立了换向离合器机械模型、控制模型和液压模型,对拖拉机Ⅰ挡作业时前进挡切换为倒退挡的工况进行了仿真分析与台架试验验证。仿真结果表明：当液压油曝气程度为0.1%,充油流量分别为16、14 L/min时,与20 L/min流量相比,换向时间分别增长20%和43%,变速器最小输出转矩分别下降26%和52%,滑摩功分别上升33%和78%,最大冲击度分别下降11%和18%,最大磨损量分别上升24%和44%。当充油流量为20 L/min,曝气程度分别为1%和5%时,与0.1%曝气程度相比,换向时间分别增长26%和...     

发酵鸡粪养鱼试验

用充氧动态发酵机加工鸡粪，并将这种发酵鸡粪添加到饲料中，进行池塘和网箱养鱼试验，均取得良好效果。     

纯氧充气对大菱鲆生长及水质指标的影响

主要研究了纯氧增氧技术对大菱鲆的生长及养殖水体中几项重要水质因子的影响。本实验中,实验池中的溶氧最低能维持在8.96±0.16mg/L,最高时可达到12.2±0.71mg/L。经过282d的培养,大菱鲆体重由30.43±0.42g达到1103.73±19.00g,日增重率平均为1.24±0.14%,整个实验期间大菱鲆均处于快速生长状态。至实验结束时,养殖密度最终达到33.99±0.59kg/m3。养殖水体中,pH变化范围在7.62～8.03之间,平均pH为7.76±0.05。COD变化范围在0.75～1.85mg/L,平均COD为1.04±0.16mg/L。亚硝酸盐浓度1.27～7.23μg/L之间,平均浓度在3.23±0.21μg/L。氨氮浓度一般维持在0.07～0.28mg/L,平均浓度为0.14±0.02mg/L。硝酸盐浓度在0.39～0.69mg/L之间,平均浓度为0.51±0.02mg/L。COD、pH、亚硝酸盐浓度很低,均在渔业水质标准所规定的范围以内。     

渭北旱塬果园土壤干燥化生态修复方式效应研究

【目的】探讨不同生态修复方式对渭北旱塬果园土壤水分和果树光合特性的影响。【方法】2012-05-12,以地处渭北旱塬的陕西陇县梁甫村10年生红富士苹果园为研究对象,设置秸秆覆盖、起垄覆膜、微孔梯度深层集水、秸秆覆盖+起垄覆膜、秸秆覆盖+微孔梯度深层集水、起垄覆膜+微孔梯度深层集水、起垄覆膜+微孔梯度深层集水+秸秆覆盖7个处理,以裸地为对照(CK),于7-11月每月30号采集果园0~2m土层土样测定土壤含水量,8-9月每月30号测定果树叶片光合特性。【结果】各处理0~2m土层土壤平均含水量均高于对照,其中以起垄覆膜+微孔梯度深层集水+秸秆覆盖处理的效果最好,其0~1m土层土壤含水量比对照提高9.83%,1~2m土层土壤含水量比对照提高7.91%,其次是秸秆覆盖+微孔梯度深层集水处理,其0~1和1~2m土层土壤含水量分别比对照增加8.55%和7.40%;不同生态修复方式均能明显提高苹果树的净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),且均以起垄覆膜+微孔梯度深层集水+秸秆覆盖处理最高,其Pn、Tr、Gs分别比对照提高了18.46%,0.90%和52.94%。各生态修复处理的Pn均与对照差异达极显著水平(P0.01),而在Tr和Gs中,除起垄覆膜+微孔梯度深层集水+秸秆覆盖和秸秆覆盖+微孔梯度深层集水处理与对照差异达显著水平(P0.05)外,其他处理均与对照差异不显著。Pn、Tr、Gs与土壤含水量呈正相关线性关系。【结论】微孔梯度深层集水方式与地表覆盖方式相结合能够大幅度提高土壤水分含量,影响果树光合特性,其中以起垄覆膜+微孔梯度深层集水+秸秆覆盖方式效果最好,可作为改善果园土壤干燥化的方法加以利用。     

复式潜流湿地净化生活污水的试验研究

研究了新型复式潜流人工湿地对生活污水的净化效果。在不同水力负荷、季节、曝气方式等条件下经过小试试验,分析了该湿地对污染物净化效果的影响。结果表明,该系统出水水质稳定,达到《城镇污水处理厂污染物排放标准》(GB 18918-2002)的一级A标准。在水力负荷184 mm·d^-1条件下COD、NH₃-N去除率最大分别可达87.2%、68.9%。冬季低温条件下对各类污染物去除率仍大于20%。正交试验分析得知,最佳运行条件是气温28.6℃、水力负荷0.184 m³·m^-2·d^-1、水力停留时间2.4 d。对比试验表明,采用预曝气方式对湿地净化效果明显优于厌氧处理。