Evaluation of SWAT sub-daily runoff estimation at small agricultural watershed in Korea

A study was undertaken for the prediction of runoff flow from 0.8 ha field-sized agricultural watershed in South Korea using Soil and Water Assessment Tool (SWAT) sub-daily. The SWAT model with sub-daily configuration predicted flow from the watershed within the range of acceptable accuracy. The SWAT sub-daily simulations were carried out for a total of 18 rainfall events, 9 each for calibration and validation. Overall trend and extent of matching simulated flow for the rainfall events in 2007-2008 with measured data during the calibration process were coefficient of determination (R²) value of 0.88 and Nash and Sutcliffe Efficiency (E_NS) value of 0.88. For validation, R² and E_NS values were 0.9 and 0.84, respectively. Whereas R² and E_NS values for simulation results using daily rainfall data were 0.79 and -0.01, respectively, that were observed to be out of acceptable limits for the model simulation. The importance of higher time resolution (hourly) precipitation records for flow simulation were evaluated by comparing R² and E_NS with 15 min, 2 h, 6 h and 12 h precipitation data, which resulted in lower statistics with increases in time resolution of precipitation data. The SWAT sub-daily sensitivity analysis was performed with the consideration of hydraulic parameter and was found as in the rank order of CN2 (curve number), ESCO (soil evaporation compensation factor), GW_DELAY (ground water delay time), ALPHA_BF ( base flow alpha factor), GWQMN ( a threshold minimum depth of water in the shallow aquifer required for return flow to occur) , REVAPMN (minimum depth of water in shallow aquifer for re-evaporation to occur) , LAT_TIME (lateral flow travel time) respectively. These sensitive parameters were evaluated at 10% higher and lower values of the parameters, corresponding to 70.5% higher and 23.2% lower in simulated flow out from the SWAT model. From the results obtained in this study, hourly precipitation record for SWAT sub-daily with Green-Ampt infiltration method was proven to be efficient for runoff estimation at field sized watershed with higher accuracies that could be efficiently used to develop site-specific Best Management Practices (BMPs) considering rainfall intensity, rather than simply using daily rainfall data.     

Enhancement of sludge gravitational thickening with weak ultrasound

Gravitational thickening is the prevailing method to reduce sludge volume but the process is slow and usually requires addition of polyelectrolyte(s). This paper investigated the potential benefits of sonication on enhancing the sludge gravitational thickening with very low energy dose, so called “weak ultrasound”. Results showed that weak sonication significantly changed the sludge settlability and the main mechanism was release of the loosely bounded extracellular polymeric substances. The changes in sludge behaviors by sonication were strongly influenced by power density and sonication duration. Lower sound frequency was slightly better than higher frequency. Weak sonication (<680 kJ·kg^-1 DS) improved the sludge gravitational thickening while high ultrasonic energy deteriorated the process. Considering both the sludge thickening efficiency and energy consumption, the optimum conditions were 0.15 W·mL^-1, 7 s, and 25 kHz. Under such conditions, the energy dose was only 155 kJ·kg^-1 DS, much lower than literature reports, and the sludge settling time was shortened from 24 h to 12?h. Weak sonication could substitute expensive polyelectrolyte coagulant for sludge thickening. Combination of weak sonication and polyelectrolyte could further reduce the settling time to 6 h. The final water content of the thickened sludge was not changed after sonication or polyelectrolyte addition.     

基于模糊神经网络的A2/O工艺出水氨氮在线预测模型

采用厌氧/缺氧/好氧污水处理系统(A2/O)对人工合成污水进行处理,并利用人工神经网络(ANN)模型和自适应模糊人工神经网络(ANFIS)模型对A2/O处理污水的过程进行仿真模拟.在MATLAB环境下,选取可在线监测的水力停留时间(HRT)、进水pH值(pH)、好氧池溶解氧(DO)和混合液回流比(r)作为输入参量,系统出水氨氮浓度(NH4+eff)为输出量,建立在线预测模型.结合自适应模糊C均值聚类算法,确定ANFIS模型的模糊规则数及最优运行参数,对实验数据进行仿真预测.结果表明,与ANN模型相比,ANFIS模型的仿真输出值与实际值的拟合程度更高,相对误差在6.45%之内,平均绝对百分比误差(MAPE)为2.8%,均方根误差(RMSE)为0.1209,相关系数(R)达0.9956.模型训练过程中所得到的三维曲面图,可直观的反映各因素与出水氨氮浓度之间的非线性函数关系,为A2/O系统的高效稳定运行提供指导.     

耐高浓度苯酚菌株的筛选及其降解特性研究

通过液体富集培养,平板培养分离法从焦化废水的污泥中分离出1株可耐受2 000 mg/L苯酚的菌株,经16S rDNA序列分析,鉴定为施氏假单胞菌(Pseudomonas stutzeri).该菌能以苯酚为唯一碳源和能源生长.通过摇瓶试验和高效液相色谱( HPLC)分析法可知,在pH=7.5,温度为30℃的条件下,苯酚质量浓度在50～400 mg/L时,该菌细胞生长和对苯酚的降解转换快速同步进行.当苯酚质量浓度在800～900 mg/L,菌细胞依次出现快速生长、延缓生长、次快速生长3个生长时期,在前两时期内苯酚降解率低于5％,在次快速生长期内苯酚降解率从低于5％快速增加到100％.气相色谱-质谱联用仪(Gc-MS)测定结果表明,该菌可将苯酚转化成4-羟基-2-氧代戊酸、邻苯二酚、对苯二酚、3,4-二羟基苯甲酸和对羟基苯甲酸等中间产物.     

浅析管道输油中水击的危害及对策

分析了水击产生的原因及危害,介绍了防止水击的有关自动化控制技术.     

三峡库区复杂地形下的降雨时空分布特点分析

根据三峡水库坝区周边10个气象站1992~2002年逐日降雨资料,先用比值法将短期考察资料延长,再通过对比、回归等方法,客观分析降雨量、降雨日数、暴雨量、暴雨日数等指标随时间（年内、年际）和地形（高度、坡向）的变化,其特点如下：三峡坝区冬干、夏雨、秋雨明显,近年降雨增多;与武汉市相比,有降雨日多但降雨量、暴雨日及大暴雨日少的特点;降雨量、降雨日数、暴雨量、暴雨日数等多随高度上升而递增;由于受南北边山地阻挡和峡谷的影响,长江以南降雨大于长江以北;水体抑制库周降雨,且夜间比白天明显,强降雨过程比弱降雨过程明显。三峡地区降雨周边山地多于谷底,蓄水后差异将更明显,使地质灾害容易发生,应引起高度重视。     

Tourism effects on the environment and economic sustainability of sub-Saharan Africa

This paper integrates tourism, economic growth, and environmental issues in a multivariate format. Unlike recent research on this topic, a panel data of selected sample nations of sub-Saharan Africa is adopted by using cointegration and panel regression models. The current research discovers both long-run equilibrium and short-run dynamics between economic growth, tourism, energy use, and carbon emissions in sub-Saharan Africa. Furthermore, tourism and energy use show a highly significant direct impact on economic growth. In addition, tourism, energy use, and economic growth yield a highly significant positive effect on carbon emissions. Dissecting the region into oil producers and non-oil producers further suggests that the economic growth of sub-Saharan Africa has been accomplished by strong growth in tourism and energy use. However, there is highly significant evidence that in oil producing countries, CO₂ emissions are directly affected by energy use and economic growth and not by tourism. For non-oil producing countries, tourism and energy use but not economic growth incur a highly significant positive impact on carbon emissions.     

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.     

强腐蚀地区高性能抗腐蚀混凝土自拌质量控制

针对强腐蚀土壤地区钢筋混凝土结构的耐久性问题,对施工中的各个质量环节进行分析,提出质量控制措施。通过加强填料顺序控制、混凝土搅拌时间控制、温度控制、运输时间控制及浇筑等全过程质量控制,确保自拌高性能抗腐蚀混凝土制备各项质量指标可控、在控。应用结果表明:自拌高性能抗腐蚀混凝土的质量控制,为强腐蚀地区电力工程施工质量提供了可靠保证。     

反机场跑道润滑技术研究

反机场跑道润滑是一种新概念非致命性武器技术.本文以硬脂酸、甲基硅油及其他添加剂在常压下合成了一种新型硅油脂,并将其与几种常用润滑剂进行润滑摩擦系数的实验对比.通过摩擦学实验得到了0～72 h内其摩擦系数的变化曲线,并从分子结构角度对实验结果进行理论分析.结果表明,在对混凝土-橡胶轮胎摩擦副的润滑中,自制硅油脂可以使其摩擦系数保持在制动困难状态(μ≤0.35),并且可以维持较长时间(t≥72 h).综合各因素,它在机场跑道润滑过程中具有明显的优势,具有军事应用前景.