响应面法分析Fenton氧化处理采油废水的过程

采用Fenton氧化对采油废水进行研究,选取双氧水与二价铁离子的摩尔比、初始pH值和反应时间为自变量,以废水的COD去除率为响应值,通过Box-Behnken设计方法进行实验设计,进行了3因素3水平共15个实验点的实验。使用响应面分析法对实验结果进行模拟及分析,建立了响应值与3个自变量的二次多项式方程模型。Fenton氧化的优化工艺条件:n(H2O2):n(Fe2+)=0.8,pH=3.0以及反应时间60 min。在该优化条件下,废水的COD去除率可达72.8%,经实验验证,实际值与模型预测值拟合性好,偏差仅为0.5%。实验结果证实了该模型分析采油废水处理运行参数的准确性。优化工艺后的处理水质COD值完全满足油田废水达标排放的要求。通过总离子色谱图和质谱检索分析原油中的成分变化情况,证实Fenton方法对原油组分的降解效果。     

城市旅游区暴雨径流污染过程中的不透水面效应

选取武汉市动物园4种典型的不透水面暴雨径流污染特征进行了系统的研究,以期为旅游区面源污染危害评价和治理提供基本的依据.结果表明,动物园4种不透水面初期径流污染物浓度很高,COD最大值达1140 mg/L,下垫面类型及地表累积污染物是影响径流水质的主要因素.通过无量纲累积曲线的分析,表明旅游区不透水面径流初期冲刷严重,该曲线还为面源治理提供了重要的工程参数.     

响应曲面法优化复合絮凝剂的制备工艺

为了提高染料废水中COD和色度的去除效果,采用响应曲面法对聚硅酸类新型复合絮凝剂的制备工艺进行了优化实验研究。在单因素实验基础上采用Box-Behnken Design(BBD)实验设计方法,设计出了影响染料废水处理效果的3因素3水平共15组实验,其中n(Fe+Al):n(Si)的摩尔比为4～6,n(B+Mg):n(Si)的摩尔比为0.3～0.7,熟化时间为1～3 d。根据15组实验结果,以COD去除率和色度去除率为响应值分别建立了二次多项式响应曲面模型。模型优化结果显示,在n(Fe+Al):n(Si)摩尔比为5∶1,n(B+Mg):n(Si)为0.5∶1,熟化时间为2 d的条件下,制备得到的新型复合絮凝剂聚硅酸铝铁硼镁具有最佳的絮凝处理性能和脱色效果,能有效去除染料废水中的COD和色度,其中出水色度接近于0,COD的去除率达到87.65%,模型验证实验进一步验证了本文所建立的响应曲面法在复合絮凝剂制备工艺优化中的有效性。     

膜生物反应器在污水处理中的应用现状及展望

综述了膜生物反应器（MBR）的研究进展，介绍了其分类及特点、处理机理与MBR运行的影响因素以及膜污染的控制等，并概括了MBR的发展及展望。MBR是近来发展较迅速的一种污水治理设备，具有占地少、能耗低等优点，但也存在一定的缺点，其中膜污染是影响其推广应用的主要因素，目前国内外学者一般都以膜污染作为切入点进行研究，通过改变料液性质、优化操作参数、提高膜清洗效率等方法得以防治膜污染。     

剩余污泥发酵液对黏性膨胀污泥特性的影响

为了解决剩余污泥碱性发酵液作为低碳氮比生活污水外加碳源时引发的黏性污泥膨胀问题,采用序批式反应器(SBR),以剩余污泥碱性发酵液为进水碳源,对黏性膨胀污泥的沉降性能及其影响因素之间的相关性进行了系统研究。结果表明：当进水COD值为300~350 mg·L⁻¹时,随着运行时间的推移,污泥容积指数(SVI)逐渐升高,最终达到540 mL·g⁻¹,此时发生污泥黏性膨胀现象;黏性膨胀污泥表面负电荷由0.62 mV累积到29.49 mV,相对疏水性(RH)从44%下降至19%,污泥容积指数(SVI)与Zeta电位、相对疏水性(RH)呈负相关(R²分别为0.837 71和0.678 54),与污泥粒径不相关;胞外聚合物总量从31 mg·g⁻¹提高至39 mg·g⁻¹,但LB-EPS/TB-EPS的比例从0.92增加至2.92;与TB-EPS相比较,LB-EPS与污泥容积指数(SVI)、Zeta电位、相对疏水性(RH)具有显著相关性(R²分别为0.892 88、0.885 29和0.776 68)。以上结果揭示了以发酵液为碳源引发的黏性膨胀污泥特性的变化规律,可为实际工程中以发酵液为碳源的黏性污泥膨胀问题提供借鉴。     

氧化铁改性砂联合生物预处理对氨氮的吸附特性

对含氨氮(NH3-N)的微污染原水,采用自制氧化铁改性石英砂(iron oxide coated sand,IOCS)滤料强化过滤与生物预处理技术联合,进行强化处理与吸附效果研究.结果表明,采用强化挂膜法,生物预处理反应器的生物膜成熟期约为7 d,其对氨氮的去除率为60%~70%,但反应器中存在亚硝酸盐氮积累的现象.IOCS与生物预处理技术联合,对NH3-N的平均去除率为84.67%,出水NH3-N浓度均低于0.5 mg/L,NO2--N含量趋于0;而普通石英砂(RQS)在同等条件下,对氨氮的去除效果不稳定,平均去除率为74.31%,出水NH3-N平均浓度未达标,对NO2--N平均去除率仅有33.29%.在4 m/h滤速工况下,与生物预处理技术联合,IOCS和RQS对NH3-N最高去除率分别为94.3%和82.72%.IOCS与RQS的表面形态结构存在明显差异:前者的表面结构更加复杂多孔,比表面积大,有利于生物牢固附着;后者表面较光滑,比表面积小,挂膜后生物易脱落.     

PREDICTING MEASUREMENT ERROR OF AREAL MEAN PRECIPITATION DURING EXTREME EVENTS1

ABSTRACT: The areal mean precipitation (AMP) over a catchment is normally calculated using point measurements at rainfall gages. Error in AMP estimates occurs when an insufficient number of gages are used to sample precipitation which is highly variable in space. AMP error is investigated using historic, severe rainfalls with a set of hypothetical catchments and raingage networks. The potential magnitude of error is estimated for typical gage network densities and arrangements. Possible sources of error are evaluated, and a method is proposed for predicting the magnitude of error using data that are commonly available for severe, historic rainfall.     

COMPUTATION OF UNSTEADY FLOWS IN THE ALABAMA RIVER1

ABSTRACT: An application is described of the branch-network flow model, BRANCH, to the upper Alabama River system in central Alabama. The model is used to simulate one-dimensional unsteady flows and water surface elevations in approximately 60 river miles of the Alabama River system. Preliminary calibration was made using 72 hours of observed data. Simulated discharges are about 10 percent lower than observed discharges at higher discharge rates and computed flows lag observed flows by about 30 minutes.     

COMPARISON OF PROCESS‐BASED AND ARTIFICIAL NEURAL NETWORK APPROACHES FOR STREAMFLOW MODELING IN AN AGRICULTURAL WATERSHED1

ABSTRACT: The performance of the Soil and Water Assessment Tool (SWAT) and artificial neural network (ANN) models in simulating hydrologic response was assessed in an agricultural watershed in southeastern Pennsylvania. All of the performance evaluation measures including Nash‐Sutcliffe coefficient of efficiency (E) and coefficient of determination (R²) suggest that the ANN monthly predictions were closer to the observed flows than the monthly predictions from the SWAT model. More specifically, monthly streamflow E and R² were 0.54 and 0.57, respectively, for the SWAT model calibration period, and 0.71 and 0.75, respectively, for the ANN model training period. For the validation period, these values were ?0.17 and 0.34 for the SWAT and 0.43 and 0.45 for the ANN model. SWAT model performance was affected by snowmelt events during winter months and by the model's inability to adequately simulate base flows. Even though this and other studies using ANN models suggest that these models provide a viable alternative approach for hydrologic and water quality modeling, ANN models in their current form are not spatially distributed watershed modeling systems. However, considering the promising performance of the simple ANN model, this study suggests that the ANN approach warrants further development to explicitly address the spatial distribution of hydrologic/water quality processes within watersheds.     

ASSESSMENT OF POSSIBLE IMPACTS OF CLIMATE CHANGE IN AN URBAN CATCHMENT1

ABSTRACT: Stationarity of rainfall statistical parameters is a fundamental assumption in hydraulic infrastructure design that may not be valid in an era of changing climate. This study develops a framework for examining the potential impacts of future increases in short duration rainfall intensity on urban infrastructure and natural ecosystems of small watersheds and demonstrates this approach for the Mission/Wagg Creek watershed in British Columbia, Canada. Nonstationarities in rainfall records are first analyzed with linear regression analysis, and the detected trends are extrapolated to build potential future rainfall scenarios. The Storm Water Management Model (SWMM) is used to analyze the effects of increased rainfall intensity on design peak flows and to assess future drainage infrastructure capacity according to the derived scenarios. While the framework provided herein may be modified for cases in which more complex distributions for rainfall intensity are needed and more sophisticated stormwater management models are available, linear regressions and SWMM are commonly used in practice and are applicable for the Mission/Wagg Creek watershed. Potential future impacts on stream health are assessed using methods based on equivalent total impervious area. In terms of impacts on the drainage infrastructure, the results of this study indicate that increases in short duration rainfall intensity may be expected in the future but that they would not create severe impacts in the Mission/Wagg Creek system. The equivalent levels of imperviousness, however, suggest that the impacts on stream health could be far more damaging.