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.     

基于复杂系统建模的水管理政策研究进展

基于Agent的建模方法（ABSS）通过自下而上的方式，考察系统中主体的不同状态和行为特征、主体与环境的作用、主体之间的作用，来表征系统的宏观特征，是进行复杂社会环境系统分析和政策研究的重要手段，在水资源、水环境管理系统中得到了有效的应用。本文在大量文献调研的基础上，讨论了ABSS建模方法的基本原理、主要特征、系统构成、分类方法和开发工具等特征，总结了其供水系统发展、水资源分配和流域水资源管理、农业土地和水资源利用、居民用水行为、农业污染控制及人类活动的水环境影响等方面的应用，分析了其在研究内容、研究方法、研究结果等方面的发展趋势，讨论了利用该方法研究我国水资源管理和水污染控制政策的必要性和重要性。     

EFFECTS OF ADJACENT AGRICULTURAL ACTIVITIES AND WATERSHED CHARACTERISTICS ON STREAM MACROINVERTEBRATE COMMUNITIES1

Benthic macroinvertebrate communities in streams adjacent to cornfields, streams where cows had unrestricted access, and reference locations without agriculture were compared to examine the effects of local land use and land use/land cover in the watershed. At each local site, macroinvertebrates and a variety of habitat parameters were measured upstream, adjacent, downstream, and farther downstream of the local land use. A geographic information system (GIS) was used to calculate drainage basin area, land use/land cover percentages in each basin, and the distance from sample sites to the stream source. Three‐way analysis of covariance (ANCOVA) tests with date, site type, and sampling location as main effects were used to explore differences in macroinvertebrate metrics using median substrate size, percent hay/pasture area, and stream depth as covariates. The covariates significantly improved model fit and showed that multiple contributing factors influence community composition. Local impacts were greatest at sites where cows had access, probably because of sedimentation and embeddedness in the substrate. Differences between the upstream and the adjacent and downstream locations were not as great as expected, perhaps because upstream recolonization was reduced by agricultural impacts or because of differences in the intensity or proximity of agriculture to riparian areas in the watershed. The results underscore the importance of both local and watershed factors in controlling stream community composition.     

中国主要电子废物产生量估算

在分析了电子废物类型及其可能造成的主要环境问题的基础上。根据电子电器产品的销量、社会保有量以及产品寿命期等因子建立模型对我国2000-2010年间的电脑、电视机、冰箱、洗衣机、空调等5大类电子电器产品的年度废弃量进行估算。结果显示到2003年电脑年度废弃量达到447万台，总体呈增长趋势；电视机、冰箱的废弃量在2003年分别达到4229万台和976万台；洗衣机年度废弃量有一定波动。大约在2005年达到一个高峰，废弃量为1521万台；空调废弃量相对于其他家电较少，但一直处于稳步增长期。并在此基础估算了我国2003年主要电子废物中的可回收资源含量。量大而且增长较快的电子废物的处置和资源再生化将是我国电子废物管理面临的一个难题。     

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.     

Preparation of solar-enhanced AlZnO@carbon nano-substrates for remediation of textile wastewaters

Photoactive aluminum doped ZnO(AlZnO) was synthesized by sol-gel method.After that,AlZnO photocatalyst was deposited on five carbon-based materials(CBMs) using ultrasonic route followed by solid-state mixing using ball mill.The CBMs used were poly aniline(PANI),carbon nitride(CN),carbon nanotubes(CNT),graphene(G),and carbon nanofibers(CNF).The crystal phases,elemental compositions,morphological,and optical properties of the AlZnO@CBMs composites were investigated.Experimental results revealed that two of AlZnO@CBMs composites exhibited superior bleaching efficiency(100% removal) and photocatalytic stability(three cycles) for 50 μmol/L Methylene Blue(MB) contaminated water after 60 min irradiation in visible light at pH 6.5,0.7% H_2O_2,and 5 g/L inorganic salts.Under optimum conditions,AlZnO@CBMs nanocomposites were employed for the treatment of mixed dyestuffs composed of MB,Methyl Orange(MO),Astrazone Blue FRR(BB 69),and Rhodamine B(RhB) dyes under dark,ultraviolet,visible,and direct sunlight.For mixed dyestuffs,the AlZnO@G achieved the highest dye sorption capacity(60.91 μmol dye stuffs/g) with kinetic rate 8.22 × 10~(-3) min~(-1) in 90 min via multi-layer physisorption(Freundlich isotherm) on graphene sheet.In additions,AlZnO@CN offered the highest photo-kinetic rate(K_(photo)) of～54.1 × 10~(-3) min~(-1)(93.8% after 60 min) under direct sunlight.Furthermore,the selective radical trapping experiment confirmed that the holes and oxidative superoxide radicals are crucial on dyes photodegradation pathway.Owing to their superior performance,AlZnO@G and AlZnO@CN nanocomposites can offer an effective in-situ solar-assisted adsorption/photocatalytic remediation of textile wastewater effluents.     

我国能源资源税改革对城乡居民的收入分配效应——基于CGE模型的分析

通过构建包含7个城镇居民组和5个农村居民组的多收入阶层CGE模型,并将劳动力要素分为农业劳动力、技术工人和生产工人3类,在低税率、实际税率和高税率三种情景下模拟了煤炭、石油和天然气资源税改革单独实施和同时实施对城镇和农村居民的收入分配效应,并对税收补偿措施的效果进行分析.结果表明：单独实施煤炭资源税或天然气资源税改革对城镇居民组收入差距有正向的缩小作用,有利于收入分配公平,但对农村居民组收入差距起到负向的扩大作用,不利于收入分配公平;单独实施石油资源税改革则同时缩小了城镇和居民组的收入差距,有利于收入分配公平;同时实施三类能源资源税改革的收入分配效应与税率组合方式有关;将能源资源税收入以补贴的方式返还给农村居民可以缩小其收入差距,有利于收入分配公平.     

未来气候变化对武夷山自然保护区毛竹异戊二烯排放速率的影响

采用全球气候模式Nor ESM1-M产生的RCP2.6、RCP4.5、RCP6.0和RCP8.5气候变化情景数据和植物异戊二烯排放计算模型,模拟分析了未来气候变化对武夷山自然保护区毛竹(Phyllostachys pubescens)异戊二烯排放速率的影响.结果显示,气候变化下武夷山自然保护区气温上升,年降水量和辐射强度波动较大,呈增加或下降趋势.毛竹异戊二烯平均日排放速率在未来气候变化情景下比基准情景下高约30μg·g~(-1)·d~(-1),在RCP8.5情景下比基准情景下高约48μg·g~(-1)·d~(-1);毛竹异戊二烯日排放速率在未来气候变化情景与基准情景下的差异在1~90 d和301~365 d较小,在91~300 d差异较大;相比基准情景,未来气候变化情景下毛竹异戊二烯日排放速率在1~190 d(平均增加15%以上)和271~365 d(平均增加20%)增幅较大,在191~270 d增幅较小,在RCP8.5情景下增幅最大(平均增加17%).另外,毛竹异戊二烯年排放速率在未来气候变化情景下比基准情景下约高10000μg·g~(-1)·a~(-1)以上,在RCP8.5情景下比基准情景下约高13%.研究表明,未来气候变化将使毛竹异戊二烯排放速率增加.     

Effects of Na+ on Cu/SAPO-34 for ammonia selective catalytic reduction

Copper-exchanged chabazite (Cu/CHA) catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na⁺ ions on Cu/SAPO-34 for ammonia selective catalytic reduction (NH₃-SCR) are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na⁺ ion-exchanges with H⁺ and Cu^2 + of Cu/SAPO-34. The exchange of H⁺ is easier than that of isolated Cu^2 +. The exchanged Cu^2 + ions aggregate and form “CuAl₂O₄-like” species. The NH₃-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu^2 + and acid sites is responsible for the activity loss.