Modeling of a sequencing batch reactor treating municipal wastewater using multi-layer perceptron and radial basis function artificial neural networks

A sequencing batch reactor was modeled using multi-layer perceptron and radial basis function artificial neural networks (MLPANN and RBFANN). Then, the effects of influent concentration (IC), filling time (FT), reaction time (RT), aeration intensity (AI), SRT and MLVSS concentration were examined on the effluent concentrations of TSS, TP, COD and NH₄⁺-N. The results showed that the optimal removal efficiencies would be obtained at FT of 1 h, RT of 6 h, aeration intensity of 0.88 m³/min and SRT of 30 days. In addition, COD and TSS removal efficiencies decreased and TP and NH₄⁺-N removal efficiencies did not change significantly with increases of influent concentration. The TSS, TP, COD and NH₄⁺-N removal efficiencies were 86%, 79%, 94% and 93%, respectively. The training procedures of all contaminants were highly collaborated for both RBFANN and MLPANN models. The results of training and testing data sets showed an almost perfect match between the experimental and the simulated effluent of TSS, TP, COD and NH₄⁺-N. The results indicated that with low experimental values of input data to train ANNs the MLPANN models compared to RBFANN models are more precise due to their higher coefficient of determination (R²) and lower root mean squared errors (RMSE) values.     

岩溶地下河污染物运移模型对比研究

两区模型（TRM）和暂时存储模型（TSM）为两种常用的岩溶地下河（管道）污染物运移模型,为了更好表征岩溶地下河污染物运移过程,开展模型对比研究.采用两种模型拟合室内管道示踪实验穿透曲线,从概念模型框架、模型优缺点、参数校正过程和物理意义、参数敏感性等方面对比分析两种模型的异同.结果表明,OTIS软件提供TSM的数值解,而CXTFIT软件提供TRM的解析解,但两者均能通过下游不同位置的穿透曲线分段表征地下河不同阶段的污染物运移过程.两种模型的物理意义相近,均可近似描述岩溶地下河中溶质的暂时性存储现象,较好地拟合溶质运移曲线.采用TSM可校正得到暂时存储区的横截面积,但采用TRM只能获得非流动区所占的比例.两种模型中弥散系数和传质/交换系数的敏感度较低,并且弥散系数的变化对穿透曲线拖尾无显著影响.研究结果为岩溶地下河污染物运移模型的选取与应用提供了依据.     

Body fluid analog chlorination: Application to the determination of disinfection byproduct formation kinetics in swimming pool water

Disinfection by-products(DBPs) are formed in swimming pools by the reactions of bather inputs with the disinfectant.Although a wide range of molecules has been identified within DBPs,only few kinetic rates have been reported.This study investigates the kinetics of chlorine consumption,chloroform formation and dichloroacetonitrile formation caused by human releases.Since the flux and main components of human inputs have been determined and formalized through Body Fluid Analogs(BFAs),it is possible to model the DBPs formation kinetics by studying a limited number of precursor molecules.For each parameter the individual contributions of BFA components have been quantified and kinetic rates have been determined,based on reaction mechanisms proposed in the literature.With a molar consumption of 4 mol Cl_2/mol,urea is confirmed as the major chlorine consumer in the BFA because of its high concentration in human releases.The higher reactivity of ammonia is however highlighted.Citric acid is responsible for most of the chloroform produced during BFA chlorination.Chloroform formation is relatively slow with a limiting rate constant determined at 5.50 × 10~(-3) L/mol/sec.L-histidine is the only precursor for dichloroacetonitrile in the BFA.This DBP is rapidly formed and its degradation by hydrolysis and by reaction with hypochlorite shortens its lifetime in the basin.Reaction rates of dichloroacetonitrile formation by L-histidine chlorination have been established based on the latest chlorination mechanisms proposed.Moreover,this study shows that the reactivity toward chlorine differs whether L-histidine is isolated or mixed with BFA components.     

A Spatial Model to Estimate Habitat Fragmentation and Its Consequences on Long-Term Persistence of Animal Populations

The increasing use of the landscape by humans has led to important diminutions of natural surfaces. The remaining patches of wild habitat are small and isolated from each other among a matrix of inhospitable land-uses. This habitat fragmentation, by disabling population movements and stopping their spread to new habitats, is a major threat to the survival of numerous plant and animal species. We developed a general model, adaptable for specific species, capable of identifying suitable habitat patches within fragmented landscapes and investigating the capacity of populations to move between these patches. This approach combines GIS analysis of a landscape, with spatial dynamic modeling. Suitable habitat is identified using a threshold area to perimeter ratio. Potential movement pathways of species between habitat patches are modeled using a cellular automaton. Habitat connectivity is estimated by overlaying habitat patches with movement pathways. The maximum potential population is calculated within and between connected habitat patches and potential risk of inbreeding within meta-populations is considered. The model was tested on a sample map and applied to scenario maps of predicted land-use change in the Peoria Tri-county region (IL). It (1) showed area of natural area alone was insufficient to estimate the consequences on animal populations; (2) underscored the necessity to use approaches investigating the effect of land-use change spatially through the landscape and the importance of considering species-specific life history characteristics; and (3) highlighted the model's potential utility as an indicator of species likelihood to be affected negatively by land-use scenarios and therefore requiring detailed investigation.     

垃圾转运站污水回用处理工艺设计

垃圾转运站污水回用处理采用了膜 -生物反应器处理工艺 ,它具有高效、稳定、工艺流程简单、设备占地面积小和投资少等优点 ,且处理后出水可用于自身站内所需 ,即冲车、喷洒道路、冲厕、绿化、冲刷车间地面等多种用途 ,实现了污水处理后再利用的目的。     

热带海洋环境中BHC和DDT的行为特征研究Ⅰ.中国珠江口区旱季BHC和DDT的含量与分布

本文于1994年11月用气相色谱法研究了旱季珠江口区环境中BHC和DDT的含量与分布。结果表明，表层海水BHC含量为0.187μg/L，DDT为0.080μｇ/L；底层海水BHC为0.117μｇ／L，DDT为0.506μｇ／L。沉积物BHC为11.15×10－9（干），DDT为33.46×10－9（干）。海水中的盐度、DO、C     

上海地区高空气流长距离输送轨迹及其与酸雨的关系

分析了影响上海地区的高空气流输送轨迹。不同月份影响上海的高空气流来向不一。轨迹输送路径与天气系统的变化密切有关,且与上海地区出现的酸雨有关。研究表明,上海地区的酸雨,除与局地污染有关外,还与远处输送的外来污染有关。这些外来污染影响,主要来自上海西南向的北部湾和两广等地。也有部分来自东北——东方向的南朝鲜和日本西部地区。     

铜山口铜(钼)矿床成矿流体水-岩反应数值模拟

铜山口铜(钼)矿床位于湖北省大冶市境内,是一典型的矽卡岩-斑岩复合型矿床。通过对其流体包裹体的系统研究,确定了成矿阶段成矿流体的成分及温压条件,并结合矿床学研究,将成矿过程分解为两个平行的成矿阶段,即矽卡岩型矿化阶段和斑岩型矿化阶段。根据Johson和Reed等人建立的水 岩反应模型,对本矿床成矿流体与围岩反应并析出金属沉淀的过程进行了数值模拟计算,其结果与实际地质情况吻合较好。     

Impact of triazophos insecticide on paddy soil environment

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