A comparison study of the start-up of a MnOx filter for catalytic oxidative removal of ammonium from groundwater and surface water

As an efficient method for ammonium (NH4+) removal, contact catalytic oxidation technology has drawn much attention recently, due to its good low temperature resistance and short start-up period. Two identical filters were employed to compare the process for ammonium removal during the start-up period for ammonium removal in groundwater (Filter-N) and surface water (Filter-S) treatment. Two types of source water (groundwater and surface water) were used as the feed waters for the filtration trials. Although the same initiating method was used, Filter-N exhibited much better ammonium removal performance than Filter-S. The differences in catalytic activity among these two filters were probed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and compositional analysis. XRD results indicated that different manganese oxide species were formed in Filter-N and Filter-S. Furthermore, the Mn3p XPS spectra taken on the surface of the filter films revealed that the average manganese valence of the inactive manganese oxide film collected from Filter-S (FS-MnOx) was higher than in the film collected from Filter-N (FN-MnOx). Mn(IV) was identified as the predominant oxidation state in FS-MnOx and Mn(III) was identified as the predominant oxidation state in FN-MnOx. The results of compositional analyses suggested that polyaluminum ferric chloride (PAFC) used during the surface water treatment was an important factor in the mineralogy and reactivity of MnOx. This study provides the theoretical basis for promoting the wide application of the technology and has great practical significance.     

西安市人为源一次PM2.5排放清单及减排潜力研究

颗粒物是影响西安市环境空气质量的主要因子.结合《西安统计年鉴2015》《2014年环境统计数据》和现场调查等确定了西安市各类PM_2.5排放源的活动水平数据,采用物料衡算法和排放因子法测算了西安市2014年大气中PM_2.5的年排放总量,并从行业和区域角度详细分析了PM_2.5的排放贡献率.在此基础上,以2014年为基准年,依据西安市地方政策和各行业最新排放标准,对PM_2.5的减排潜力进行了预测.结果表明:2014年西安市人为源一次PM_2.5排放总量为33 660.1 t,其中,固定燃烧源、工艺过程源、移动源、生物质燃烧源、扬尘源和餐饮源的贡献率分别为27.6%、23.5%、6.8%、10.7%、31.1%和0.3%.道路扬尘、窑炉和发电为西安市PM_2.5的重点排放行业,其PM_2.5排放量分别占排放总量的21.4%、20.3%和11.0%.各区县中,鄠邑区、灞桥区和未央区的PM_2.5排放量较高,其贡献率分别为15.7%、13.7%和12.7%;新城区PM_2.5排放量最小,为297.8 t/a.2014年西安市PM_2.5平均排放强度为2.07 t/km2,其中,碑林区排放强度（16.80 t/km2）最大,高陵区（0.48 t/km2）最小.按照《西安市2017年"铁腕治霾保卫蓝天"工作实施方案》等新政策的规定,预测在新的排放标准下西安市PM_2.5排放量将比2014年削减63.7%.研究显示,固定燃烧源、工艺过程源和生物质燃烧源有较大的减排潜力.      

硝化污泥胞外聚合物分层组分提取方法的比较

采用温和加热法、超声法、超声+振荡法和离心法4种方法提取硝化污泥松散结合型胞外聚合物(LB-EPS),及乙二胺四乙酸(EDTA)法、甲醛+NaOH法、甲醛+超声、阳离子树脂法(CER)和加热法提取硝化污泥紧密结合型胞外聚合物(TB-EPS),通过化学分析结合三维荧光(3DEEM)光谱对各提取方法进行比较.结果表明,LB-EPS和TB-EPS的最优提取方法分别为温和加热法和甲醛+Na OH法,TOC提取量分别为16.82、58.43 mg·g~(-1).三维荧光光谱显示温和加热法能有效提取LB-EPS中的类色氨酸和类腐殖酸;甲醛+NaOH法、CER和加热法提取的TBEPS中物质最为全面,主要包括类色氨酸、类腐殖酸和类酪氨酸.TB-EPS三维荧光浓度效应分析表明荧光峰位置与EPS浓度变化无关;类腐殖酸和类酪氨酸荧光峰强度随EPS浓度降低而减小,分别呈二项式和对数关系.     

Effects of fulvic acid and humic acid on aluminum speciation in drinking water

This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water. Factors including the concentration of residual chlorine and pH value had been concerned. Aluminum species investigated in the experiments included inorganic mononuclear, organic mononuclear, mononuclear, polymer, soluble, and suspended forms. It was found that the e ects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight. Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation; while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L (calculated as TOC). Aluminum species, in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid, were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton, and varied little with reaction time. Within pH range 6.5–7.5, soluble aluminum increased notably in water with organic matter. As the concentration of residual chlorine increased, the e ects of fulvic acid and humic acid became weak. The reactions between humic acid, fulvic acid with large molecular weight, and aluminum were considered to be a multi-dentate coordination process. With the consideration of aluminum bioavailability, reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5–7.5 were recommended during drinking water treatment.     

分层水库水深对扬水曝气原位控藻效果的影响

扬水曝气是分层水源水库原位藻类控制的有效技术.针对西安金盆水库扬水曝气水质改善工程典型设计工况,采用商业化Fluent软件模拟计算了不同水深条件下扬水曝气器的外围流场,分析了水深对扬水曝气控藻区域和效果的影响.结果表明,当扬水曝气器外围流场稳定时,进水口附近的顺时针环流和其他区域的逆时针环流共存,进水口顺时针环流范围和强度不受水深影响,水流速度沿扬水曝气器径向减小.当水深从50 m逐渐增加到110 m时,扬水曝气核心控藻区域的百分比从12.5%增大到30.6%,核心控藻区域半径从60 m增加到175 m,藻类完全混合的时间从16 d增加到30 d.当水深不浅于65 m时,藻类在补偿点以下的停留时间均大于48 h,且随水深的增加而延长.非核心控藻区域内的藻类随逆时针环流被动迁移至核心区域,最终悬浮并滞留在扬水曝气器底部附近.分层水库中扬水曝气器合理设计间距为水深的1.2~1.6倍.     

基于膜特征参数变化的蛋白质超滤过程膜污染研究

为进一步研究多种蛋白质体系超滤过程的膜污染机制,采用切割相对分子质量为50×103的聚醚砜(polyethersulfone,PES)超滤膜,对溶菌酶(lysozyme,LYS)、牛血清蛋白(bovine serum albumin,BSA)、LYS+BSA等3种不同蛋白质溶液的超滤过程进行了研究.运用接触角仪、场发射扫描电镜(field emission scanning electron microscope,FESEM)、原子力显微镜(atomic force microscope,AFM)测定了不同污染阶段膜特征参数的变化.结果表明,超滤膜通量变化明显呈现3个阶段:初期(约0~5min)衰减迅速、中期(约5~60 min)衰减缓慢、后期(约60~120 min)趋于稳定;整个超滤过程中,LYS污染膜的通量衰减幅度最大,LYS+BSA次之,BSA最小.膜特征参数变化表明:LYS对膜的初期污染主要以膜孔窄化为主,中期污染由膜孔堵塞和膜孔窄化共同控制;BSA初期膜污染以膜孔堵塞为主,中期污染以膜孔窄化为主;滤饼层过滤是BSA、LYS后期膜污染的主要机制.LYS+BSA二元混合溶液中的LYS对膜污染的产生起主导作用.     

一株芽胞杆菌和一株黄杆菌代谢芘的摄取方式解析

通过溶剂萃取、薄层色谱和紫外分光光度法研究了一株芽胞杆菌CN2和一株黄杆菌CN4在初始pH=6.00的条件下对芘的降解过程.研究表明:芘降解液的pH值随降解时间向中性波动变化;用牛肉膏蛋白胨培养出的CN2菌体表面具有亲水性,CN4菌体表面具有疏水性,CN2表面疏水性在芘的降解过程中随时间有变大的趋势,CN4表面疏水性在芘的降解过程中随时间有变小的趋势;从芘降解的整个过程看,大部分时间CN2的降解比CN4的快,CN4菌体捕获的芘量比CN2要大,尤其在接种刚开始的一段时期较为明显;细胞表面、细胞壁中、细胞内部均有芘富集迹象,其中细胞表面富集的芘最多.根据试验结果推测,在菌株对芘的降解过程中吸附和降解同时发生;菌体对芘首先通过表面吸附或其它方式结合,随后溶人细胞壁中,跨过细胞膜进入细胞内被降解;这个传质过程很可能不是连续的,而是由细菌控制的主动的间歇的动态过程.     

城市地表水中肠道病原微生物与粪便污染指示菌的关系研究

本研究选择肠道病毒、伤寒沙门氏菌、志贺氏菌、大肠埃希氏菌作为城市水体中典型的肠道病原微生物,分别建立起相应的实时荧光定量PCR检测方法.对水源水、景观娱乐用水以及城市河流样品进行长期监测,考察典型肠道病原微生物的分布特征和变化规律.肠道病毒在各地表水体中都有检出,浓度大都在103copy·L-1以下.大肠埃希氏菌的含量在保护良好的水体和接纳城市污水的水体中有明显差别,而伤寒沙门氏菌和志贺氏菌通常出现在受粪便污染较重的水体中.统计学的分析结果显示各种水体中的肠道病原微生物检出浓度均符合对数正态分布规律.粪便污染指示菌与肠道病毒之间不存在显著的相关性,但却能在一定程度上反映典型肠道病原菌的存在情况.在大肠菌群或粪大肠菌群浓度为104CFU·L-1以上的样品中,伤寒沙门氏菌、志贺氏菌具有较高的阳性率.     

城市污水管网中不同生化作用的基质流向

为研究城市污水管网中有机污染物在生物代谢反应过程中的利用机制,通过运行以实际管网沉积物为底物和以人工配置沉积物为底物的不同模拟条件下的污水管网中试系统,对比分析了管网中污水与沉积物之间COD、甲烷、硝态氮和硫酸根的迁移转化特性.结果表明,污水在模拟管网中流动一周期内,污水中COD的总变化量为170.58 mg·L~(-1),其中,由沉积作用导致COD的变化量为101.53 mg·L~(-1),由生化作用导致COD的变化量为69.05 mg·L~(-1).同时,在微生物的代谢作用下,管网甲烷产量为7.39 mg·L~(-1);污水中硝态氮减少量为0.33 mg·L~(-1);硫酸根减少量为21.35 mg·L~(-1),依据公式推算,在污水管网运行过程中,发酵产甲烷过程消耗的COD为32.51 mg·L~(-1);反硝化作用消耗的COD为8.04 mg·L~(-1);硫酸盐还原菌还原硫酸盐消耗的COD为6.41 mg·L~(-1).由此可知,沉积作用导致的COD变化量占COD总变化量的65.38%;生化作用导致的COD变化量占COD总变化量的34.62%,而发酵产甲烷、反硝化作用和硫酸盐还原菌还原硫酸盐这三项生化代谢作用消耗的COD共占生化作用降解COD的68.01%,该结果表明,沉积作用是污水管网中有机污染物去除的主要方式,而发酵产甲烷、反硝化作用和硫酸盐还原菌还原硫酸根是管网中生化作用去除有机污染物的重要过程.     

浅层平铺炭质吸附剂治理多氯联苯污染底泥的有效性评价研究

以颗粒活性炭和粉末活性炭为修复剂,并对其表面性质进行了表征.同时,应用三维荧光光谱、半透膜被动采样装置(SPMDs)和低密度聚乙烯膜(LDPEs)被动采样3种方法评价其治理多氯联苯污染底泥的效果.三维荧光实验结果表明,到第3个月,底泥修复开始显现了比较明显的效果,溶解性污染物明显减少.SPMDs试验结果显示,颗粒活性炭和粉末活性炭修复的底泥在修复后的第5个月,其目标污染物PCB40被摄取量的减少率分别达到88%和70%,LDPEs相应结果达到了91%和83%.试验表明,炭质吸附剂浅层平铺修复污染底泥效果显著,且颗粒炭比粉末炭修复效果更好.