污水处理厂不同工艺的污泥脱水效能分析及其影响因素研究

污泥脱水是污泥减量的主要手段,直接影响到后续污泥处理处置.本研究以北京某大型污水处理厂A2/O工艺和A2/O-MBR工艺污泥脱水为对象,基于2013年全年的运行数据,分析不同工艺的污泥脱水效果、絮凝剂投配率、污泥脱水电耗和污泥脱水成本,并通过冗余分析(RDA)研究了不同污水处理工艺污泥脱水性能的影响因素.结果表明,污泥脱水性能和絮凝剂投配率均呈现季节性变化特征,冬季污泥较难脱水,絮凝剂消耗大.A2/O-MBR工艺的脱水污泥含水率年均值为(81.92±1.64)%,A2/O工艺为(82.56±1.35)%,污泥脱水絮凝剂消耗(以DS计,下同)分别为(8.70±7.25)kg·t-1和(7.42±2.96)kg·t-1,电耗(以DS计,下同)分别为331.82 k W·h·t-1和121.57 k W·h·t-1.A2/O-MBR工艺的污泥脱水絮凝剂成本(以DS计,下同)为204.76元·t-1,用电成本为231.61元·t-1;A2/O工艺的污泥脱水絮凝剂成本为175.00元·t-1,用电成本为84.86元·t-1.RDA分析表明,水温等季节性因素引起污泥有机质变化是影响污泥脱水性能的关键因素之一,此外,污泥龄也与污泥脱水性能有一定相关性.     

纳米Fe3O4/CeO2-H2O2非均相类Fenton体系对3,4-二氯三氟甲苯的降解

以浸渍法制备的新型纳米Fe3O4/Ce O2为催化剂,3,4-二氯三氟甲苯(3,4-DCBTE)为目标污染物,在Fe3O4/Ce O2-H2O2非均相类Fenton体系中对目标污染物的降解进行研究,考察催化剂的催化效果和温度、p H、H2O2投加量等因素对催化剂催化效果的影响.结果表明,以纳米Fe3O4/Ce O2作为催化剂的非均相类Fenton体系对3,4-二氯三氟甲苯的处理效果极佳;随着温度的升高,纳米Fe3O4/Ce O2的催化效果不断提高;在偏酸性环境中,p H越低催化效果越好,p H=2时反应去除效率可达96.67%;随着H2O2投加量的增加,3,4-二氯三氟甲苯的降解效率先提高后降低,投加量为15 mg·L-1时去除效果最好可达99.47%;随着催化剂投加量的增加,同样出现了处理效果先升高后降低的现象,投加量为0.5 g·L-1时催化效果最好可达99.64%.在以纳米Fe3O4/Ce O2为催化剂的非均相类Fenton体系中,3,4-二氯三氟甲苯的降解符合一级反应动力学,反应所需活化能较低只需30.26 k J·mol-1.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin promotes migration ability of primary cultured rat astrocytes via aryl hydrocarbon receptor

Emerging evidence showed that 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) could induce expression of certain reactivation-associated genes in astrocytes, however, the consequent cellular effects and molecular mechanisms are still unclear. During the process of astrocyte reactivation, migration is a critical cellular event. In the present study, we employed wound-healing assay and Transwell® motility assay to explore the effects of TCDD on cell migration in primary cultured rat cortical astrocytes. We found that upon TCDD treatments at relative low concentrations (10^? 10 and/or 10^? 9?mol/L), the ability of primary astrocytes to migrate horizontally and vertically was promoted. In line with this cellular effect, the mRNA expression of two pro-migratory genes, including cell division cycle 42 (CDC42) and matrix metalloproteinase 2 (MMP2) was induced by TCDD treatment. Dioxin exerts its toxic effects mainly through aryl hydrocarbon receptor (AhR) pathway. So the role of AhR pathway in the pro-migratory effects of TCDD was examined using an AhR antagonist, CH223191. We found that application of CH223191 significantly reversed the pro-migratory effects of TCDD. Interestingly, the basal ability of horizontal migration as well as basal levels of CDC42 and MMP2 expression were dramatically reduced suggesting a possible physiological role of AhR in maintaining the endogenous migration ability of the primary astrocytes. These findings support the notion that dioxin promotes astrocyte reactivation at molecular and cellular levels.     

Enzyme-electrolytic degradation of dichloromethane: Efficiency, kinetics and mechanism

Enzymatic electrolysis cell(EEC) has advantages over microbial electrolysis cell(MEC) due to the needless of microbe inoculation and high-efficiency of enzymatic reaction. In this study, an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane(CH_2Cl_2) was utilized as a model pollutant. The results indicate that the degradation efficiency of CH_2Cl_2 after 2 hr reaction in the EEC was almost100%, which was significantly higher than that with enzyme(51.1%) or current(19.0%). The current induced the continuous regeneration of reduced glutathione(GSH), thus CH_2Cl_2 was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination, and successively formed monochloromethane(CH_3Cl) and methane(CH_4). The kinetic result shows that with a current of 15 mA, the maximum specific degradation rate of CH_2Cl_2(3.77 × 10~(-3) hr~(-1)) was increased by 5.7 times. The optimum condition for CH_2Cl_2 dechlorination was also obtained with pH, current and temperature of 7.0, 15 mA and 35°C,respectively. Importantly, this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC, providing a possible treatment technology for halogenated organic pollutants.     

Effect of air masses motion on the rapid change of aerosols in marine atmosphere

The impact of air masses motion on marine aerosol properties was investigated using an on-board single particle mass spectrometer(SPAMS) deployed for the determination of single particle size resolved chemical composition over Southeast China Sea. Two aerosol blooms(E1 and E2) were observed during the cruise. High average particle number count occurred in E1(7320), followed by E2(5850), which was more than 100–150 times of the average particle number count during normal periods. Particles were classified as four major sources, including continental source, shipping source, marine source, and transport source based on the mass spectral similarity. Transport source was identified as those particles with high particle number count occurred only during aerosol bloom period. Three sub-types of EC-Ca, OC-Ca, and Al-rich were classified as transport source.EC-Ca was the dominant particles of the transport source, accounting for more than 70%of the total particles in aerosol bloom events. A uni-modal size distribution in the size range of 0.1–2.0 μm was observed during normal period, while a bimodal distribution with a tiny mode(0.3 μm) and a coarse mode between 0.4 and 0.6 μm was present during aerosol bloom. The variation of aerosol source is consistent with air masses back trajectories, for the reason that most of the long-range air trajectories are from the ocean,while short air trajectories originate in the continental regions, which means that air masses have a significant impact on the aerosol physical–chemical properties along their tracks.     

轮作方式对冬水田温室气体排放的影响

以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内的冬水田(RF)、水稻-油菜轮作(RR)和水稻-儿菜轮作(RV)农田为研究对象,采用静态箱-气相色谱法对农田的温室气体的排放通量进行了为期一年的原位观测,其中采用静态暗箱技术观测CH4和N2O,静态明箱技术观测CO2.结果表明,不同轮作方式下CH4的年排放总量[以CH4计,kg·hm-2]RF(422.87±27.1) RR(132.05±23.11) RV(50.91±3.83),其中RV与RR处理较RF处理CH4排放量有明显下降(P0.05);N2O的年排放总量[以N2O计,kg·hm-2]依次为RV(21.38±6.51) RR(20.02±5.23) RF(0.48±0.02),RV和RR处理N2O的排放总量均显著高于RF(P0.05);CO2的年净排放总量[以CO2计,t·hm-2]为RR(-55.43±5.04) RV(-29.1±3.00) RF(-14.08±1.81),RV和RR处理CO2的吸收量显著高于RF处理(P0.05).在100a时间尺度上,全年排放的CH4、N2O和CO2所引起综合GWP(以CO2计,t·hm-2)为RR(-46.43) RV(-22.01) RF(-2.11),表明冬水田转变为水旱轮作系统后能显著提升农田生态系统的增汇效果,相比于RV处理,RR处理增汇效果更好,即在西南地区水稻-油菜轮作农田在生态系统增汇上是一种最有效的轮作方式.     

北京市PM2.5时空分布特征及其与PM10关系的时空变异特征

PM_(2.5)时空分布特征及其与其它污染物的相关关系是PM_(2.5)时空统计分析的主要研究内容.然而,现有的方法直接从监测站点的角度对时空分布特征进行分析,难以有效地揭示PM_(2.5)浓度的聚集分布特征;同时,常用的地理加权回归在对PM_(2.5)与其它污染物间关系进行建模的过程中,缺乏同时考虑时间异质性与空间异质性,从而不能准确地描述依赖关系的时空变异特征.为此,首先借助于空间聚类分析技术,对北京市2014年PM_(2.5)浓度的聚集结构进行探测,在此基础上,通过聚集结构来分析PM_(2.5)季节性时空分布特征.然后,利用地理时空加权回归对北京市PM_(2.5)与PM_(10)季节平均浓度间关系进行建模,依据回归结果分析PM_(2.5)-PM_(10)间关系的时空变异特征.实验结果表明,春夏季节PM_(2.5)污染程度及空间变异程度均低于秋冬季节,各季节PM_(2.5)浓度均表现为北部浓度低、南部浓度高的空间分布特征;地理时空加权回归具有更好的拟合效果,由回归系数进一步可发现,春夏季PM_(2.5)-PM_(10)相关性低于秋冬季PM_(2.5)-PM_(10)相关性;各季节均表现为西北部PM_(2.5)-PM_(10)的相关性高于东南部PM_(2.5)-PM_(10)的相关性.     

舟山渔场有色溶解有机物(CDOM)的三维荧光-平行因子分析

利用三维荧光光谱(EEMs)-平行因子分析(PARAFAC)技术研究春季舟山渔场有色溶解有机物(CDOM)的荧光成分组成、分布特征及来源.PARAFAC模型解析出舟山渔场CDOM由2类5个荧光组分组成,即类腐殖质成分C1(330/420 nm)、C2[(290)365/440 nm]、C3[(260)370/490 nm]及类蛋白质成分C4(285/340 nm)、C5(270/310 nm).5种荧光组分的平面分布模式基本一致,在各层均呈现由近岸海域向远岸海域逐渐减小的趋势,但各层又略有差别.表层高值区出现在杭州湾口外北部海域、虾峙门航道口外海域,且杭州湾口外北部海域的荧光值要高于虾峙门航道口外海域;中层高值出现区域与表层相同,但杭州湾口外北部海域的荧光值要低于虾峙门航道口外海域;底层从近岸向远岸梯度减小,高值区出现在舟山本岛附近海域.各荧光组分的分布与盐度之间存在明显负相关关系,与叶绿素a的线性关系不明显.分析表明,春季舟山渔场CDOM表、中层主要受长江输入和舟山工农业等人为活动排放影响,而底层主要受舟山工农业等人为活动排放影响.从垂直分布模式上,CDOM在30°N断面上由中、表层水体向底层呈现逐渐减小的趋势,并在近岸和远岸海域都出现了高值区,且与盐度低值区、叶绿素a高值区相对应,反映该断面近岸区CDOM主要受长江输入影响,远岸区CDOM主要受生物活动影响;在30°N断面,CDOM分布模式与30.5°N断面基本类似,只是在近岸区域底层出现CDOM高值区,可能是由于潮汐、底层上升流等物理外力作用下,沉积物间隙水中高浓度的CDOM释放出来,使得靠近沉积物界面的底层水体中CDOM浓度升高.5种荧光组分中,C1、C3、C4之间相关性较强,与C2、C5相关性相对较弱,说明C1、C3、C4在来源上具有相似性与C2、C5有一定的差异性.春季舟山渔场CDOM腐殖化指数(HIX)的值较小,反映了春季舟山渔场CDOM的腐殖化程度较低,稳定性较差,在环境中存在时间较短;生物指数(BIX)在舟山外海出现高值区,近岸海域出现低值区,反映出在近岸海域人类活动的影响较大,而在外海生物活动的影响较为明显.     

氯化铁絮凝-直接过滤工艺对地下水中As(Ⅴ)的去除机制研究

为探明氯化铁(Fe Cl3)絮凝-直接过滤工艺对地下水中砷(As)的去除过程及机制,分别进行了批吸附实验、现场絮凝-直接过滤实验、扩展X射线精细结构光谱(EXAFS)及电荷分布多位络合(CD-MUSIC)模拟.采集的地下水样品As主要为五价[As(Ⅴ)],浓度为40μg·L-1.现场柱实验直接过滤工艺中Fe投加量为1.5 mg·L-1,出水As(Ⅴ)浓度均低于10μg·L-1,92 h内可提供64 984 L安全饮用水.固体废物毒性浸出实验表明泥饼浸出液中As浓度为3.4μg·L-1,远低于美国环保署限定值(5 mg·L-1).EXAFS和CD-MUSIC模拟表明Fe Cl3絮凝去除地下水中As(Ⅴ)存在两种机制:在p H 3~9.5范围内,As(Ⅴ)主要以双齿双核吸附在氢氧化铁上;p H9.5时,As(Ⅴ)主要与Ca2+和Mg2+形成沉淀而去除.     

ClO2消毒工艺对污水处理厂出水超级耐药基因的影响

为了研究二氧化氯（chlorine dioxide,ClO₂）消毒工艺对污水处理厂出水中超级耐药基因（super antibiotic resistance genes,SARGs）的去除效果,对污水处理厂出水消毒前后的水样进行了全年采集,并采用微孔滤膜正压过滤法及核酸吸附柱-洗脱法分别富集水中细菌和胞外核酸后,利用荧光定量PCR技术对其中的9种SARGs进行定量检测.结果表明,无论是胞内还是胞外核酸,均有NDM-1、MCR-1 和MEC-A被检测出;同时,ClO₂消毒后上述3种SARGs的胞内相对总浓度明显上升（P<0.05）,且ClO₂消毒对胞内SARGs相对浓度的影响与季节有关,其中春季、夏季和秋季均发生上升,且春季升高最为明显,达2倍,而冬季出水在消毒前后均未测出胞内SARGs;胞外SARGs则在ClO₂消毒前后没有明显浓度变化.因此,ClO₂消毒不能有效去除污水处理厂出水中胞内和胞外SARGs污染.