Reduced graphene oxide-nano zero value iron (rGO-nZVI) micro-electrolysis accelerating Cr(VI) removal in aquifer

Nanoscale zero-valent iron (nZVI) assembled on graphene oxide (GO) (rGO-nZVI) composites were synthesized by reduction of GO and ferrous ions with potassium borohydride, for use in Cr(VI) removal from aqueous solution. The results showed that the two-dimensional structure of GO could provide a skeleton support for Fe⁰, thus overcoming the bottleneck of aggregation for nZVI. Also, rGO-nZVI would form a ferric-carbon micro-electrolysis system in Cr(VI)-contaminated aquifers, enhancing and accelerating electron transfer, exhibiting high rate and capacity for Cr(VI) removal. The optimum dosage of the applied rGO-nZVI was linearly correlated with the initial Cr(VI) concentration. Characterization of rGO-nZVI before and after reaction with Cr(VI) revealed the process of Cr(VI) removal: rGO-nZVI firstly transferred electrons from Fe⁰ cores via their Fe(II)/Fe(III) shells to the GO sheet; there, negatively charged Cr(VI) received electrons and changed into positively charged Cr(III), which was adsorbed by the negatively charged GO sheet, avoiding the capping and passivating of nZVI. rGO-nZVI formed a good electrically conductive network, and thus had long-term electron releasing properties, which was important for groundwater remediation.     

洪水等级的划分方法

分析了洪水要素的多样性和洪水的复杂性，提出了利用洪水重现期划分洪水安全度等级和利用标准面积洪峰流量划分洪峰标准等级的两种方法，并对1998年长江流域的洪水等级进行了简要分析。     

电晕法处理挥发性有机化合物技术研究现状

本文介绍了挥发性有机物(VOCs)的特点及危害，综述了各种处理技术的基本原理、优势及存在的问题，并进行对比。重点介绍了电晕放电技术的原理以及研究现状，强调其相对于其他技术所独有的优越性，针对其存在的问题，预期了研究工作未来的发展方向。     

IMPLICATIONS OF CLIMATIC VARIABILITY FOR REGULATORY LOW FLOWS IN THE SOUTH PLATTE RIVER BASIN,COLORADO1

ABSTRACT: The maximum concentration of a regulated substance that is allowed in a wastewater effluent usually is determined from the amount of dilution provided by the receiving water. Dilution flow is estimated from historical data by application of statistical criteria that define low flow conditions for regulatory purposes. Such use of historical data implies that the past is a good indicator of future conditions, at least for the duration of a discharge permit. Short records, however, introduce great uncertainty in the estimation of low flows because they are unlikely to capture events with recurrence frequencies of multiple years (e.g., ENSO events or droughts). We conducted an analysis of daily flows at several gages with long records in the South Platte River basin of Colorado. Low flows were calculated for successive time blocks of data (3‐, 5‐, 10‐, and 20‐years), and these were compared with low flows calculated for the entire period of record (> 70 years). In unregulated streams, time blocks of three or five years produce estimates of low flows that are highly variable and consistently greater than estimates derived from a longer period of record. Estimates of low flow from 10‐year blocks, although more stable, differ from the long term estimates by as much as a factor of two because of climate variation. In addition, the hydrographs of most streams in Colorado have been influenced by dams, diversions, or water transfers. These alterations to the natural flow regime shorten the record that is useful for analysis, but also tend to increase the calculated low flows. The presence of an upward trend in low flows caused by water use represents an unanticipated risk because it fails to incorporate societal response to severe drought conditions. Thus, climate variability poses a significant risk for water quality both directly, because it may not be represented adequately in the short periods of the hydrologic record that are typically used in permits, and indirectly, through its potential to cause altered use of water during time of scarcity.     

中国排污权交易制度的实现条件研究

排污权交易目前在中国非常受重视,但其中也存在一些问题,主要是企业和政府尚没有处理好经济发展和环境保护的关系,也存在着制度设置不合理的问题。今后应重视排污权交易中的内部和外部条件的建设。内部条件主要有排污总量的确定和排污许可证的发放,外部条件主要包括政府加强环境执法力度和提供有效的排污信息。     

河流及污水处理厂全氟化合物排放估算

为了解全氟化合物（PFCs）的环境排放强度,利用通量计算的方法,综合国内现有PFCs监测数据,对我国部分主要流域的河流水体和部分主要城市的污水处理厂PFCs排放通量进行了估算研究.环渤海北部沿海区域主要河流水体中全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）排放总通量分别为122 kg/a和216 kg/a,其中大辽河和大凌河分别为该区域PFOS和PFOA排放的主要河流.珠江和长江是中国PFOS排放的主要河流,PFOS排放通量分别为4.47×10³ kg/a和807 kg/a.长江和黄浦江为中国PFOA排放的主要河流,PFOA排放通量分别为3.92×10⁴ kg/a和1.60×10⁴ kg/a.天津市和北京市污水处理厂人均PFOS排放量分别为291 μg·（a·人）^-1和221 μg·（a·人）^-1,远低于瑞士和美国污水处理厂的人均PFOS排放量.城市污泥PFCs排放量较高区域多集中在PFCs相关生产厂家集中省份的工业较发达城市.研究结果可为进一步进行污染源识别以及控制和减少PFCs污染和排放提供科学依据.     

基于流域尺度的农业非点源污染物空间排放特征与总量控制研究

农业非点源污染是导致流域水质恶化的重要原因之一.依据农业污染源主要污染物空间排放特征和排放强度分析,划分农业非点源污染空间管理分区,并研究设计分区污染物总量控制方案,是提高农业非点源污染控制成效的重要途径之一.以湖北省四湖流域为研究案例区,系统开展了流域尺度的农业非点源污染空间排放特征识别与总量控制研究.结果表明,四湖流域水环境COD、总氮、总磷、氨氮负荷主要来自于农业非点源污染,4类非点源污染物分别占到流域污染物排放总量的67.6％、 82.2％、 84.7％和50.9％.对四湖流域非点源污染物空间排放特征分析结果表明,水产和畜禽养殖业发达的洪湖、监利、潜江、沙洋地区是流域非点源污染物的主要贡献源区.根据污染物在流域空间上的排放特征和源强评价结果,将四湖流域划分为3个农业非点源污染管理分区,即长湖上游水产和畜禽养殖污染重点控制区、四湖干渠农村非点源污染综合控制区和洪湖水产养殖污染重点控制区,针对不同管理分区分别提出了污染控制措施.基于水质改善和水体纳污能力综合考虑,设计了针对3个非点源污染管理分区的总量控制方案,分阶段实现监测断面全指标达标和满足水体纳污能力要求.主要污染物中,COD主要削减区域为四湖干渠区和洪湖区,分别占到流域COD削减量的43％和42％;氨氮主要削减区域为四湖干渠区,占到氨氮总削减量的66％;总氮主要削减区域为四湖干渠区和洪湖区,分别占到流域总氮削减量的42％和31％;总磷主要削减区域为四湖干渠区,占到流域总磷削减量的53％.     

介质阻挡放电产生臭氧的特性研究

臭氧由于具有强氧化性,在众多领域已经得到了广泛的应用。本文通过试验研究了介质阻挡放电产生臭氧的特性。结果表明:外加电压增大时,臭氧浓度和产速都不断增大,臭氧产率则是先增长,达到最大值后又开始略微下降;气体流速增大时,臭氧浓度不断减小,而臭氧产速和产率都是先增长,达到最大值后又开始下降;电源频率在5.0～9.9kHz范围内改变时,臭氧浓度、产速和产率变化不明显;当电介质厚度不变时,在0.3～0.5mm范围内改变间隙厚度,小间隙厚度优势不明显。     

SBR改良工艺处理北京市城乡结合部污水的研究

通过采用SBR改良工艺处理城乡结合部生活污水的试验,根据城乡结合部污水的特点,采用SBR改良工艺,研究工艺的处理效果、水量波动和排水位置对处理效果的影响。结果表明,SBR改良工艺对城乡结合部污水有良好的处理效果;SBR改良工艺耐冲击负荷能力大,在连续2倍进水量的情况下,仍有良好的处理效果;降低排水位置对出水SS有一定的影响,但SBR工艺的污泥沉降效果好。     

Dechlorination of chlorophenols by zero valent iron impregnated silica

Laboratory studies were conducted to find out the efficacy of uniquely prepared zero valent iron impregnated silica in transforming xenobiotic chlorophenols namely 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. Continuous mode column experiments were performed to investigate the transformation of chlorophenols by varying pH, column height, flow rate and initial chlorophenol concentration. Reusability study of the zero valent iron impregnated silica was studied as well as the morphological changes and the chemical composition of the catalyst medium were also investigated. Dechlorination kinetic studies were conducted and the order of dechlorination of chlorophenols was found to be 2,4,6-trichlorophenol > 2,4-dichlorophenol > 4-chlorophenol. The optimum pH, column height and flow rate were found to be 7, 20 cm and 0.75 L/hr respectively for all chlorophenols in the reaction duration of 4 hr. Intermediates formed during dechlorination study were identified by gas chromatography-mass spectroscopy analysis. This method was applied to real pulp and paper wastewater and was found satisfactory.