Factors effecting aluminum speciation in drinking water be laboratory research

Effects of aluminum on water distribution system and human health mainly attribute to its speciation in drinking water. Laboratory experiments were performed to investigate factors that may influence aluminum speciation in water supply system. The concentration of soluble aluminum and its transformation among other aluminum species were mainly controlled by kinetics processes of related reactions. Total aluminum concentration had a notable effect on the concentrations of mononuclear and soluble aluminum in the first 4 day; while, when the reaction time was above 4 day, its effect became weak. At pH above 7.50, both fluoride and orthophosphate had little effect on aluminum speciation; while, when the solution pH was below 7.50, the concentrations of mononuclear and soluble aluminum were proportional to the concentration of fluoride and inversely proportional to the concentration of orthophosphate. Both mononuclear and polynuclear silicic acids could complex with mononuclear aluminum by forming soluble aluminosilicates. In addition, the adding sequence of orthophosphate and aluminum into drinking water would also affect the distribution of aluminum species in the first 4 day. In order to minimize aluminum bioavailability in drinking water, it was suggested that orthophosphate should be added prior to coagulant process, and that the concentrations of fluoride and silicic acids be controlled below 2.0 and 25 mg/L, respectively, prior to the treatment. The solution pH in coagulation and filtration processes should be controlled in the range of 6.50-7.50.     

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.     

Transfer and transport of aluminum in filtration unit

Aluminum salt coagulants were used prevalently in various water works.In this article,the effects of filtration on residual aluminum concentration and species distribution were researched by determining the concentration of diiferent aluminum species before and after single layer filter,double layer filter,and membrane filtration units.In the research,size exclusion chromatography(SEC)was used to separate colloidal and soluble aluminum,ion exchange chromatography(IEC)was used to separate organic and inorganic aluminum, and inductivity coupled plasma-atomic emission spectrometry(ICP-AES)was used to determine the aluminum concentration.The results showed that the rapid filtration process had the ability of removing residual aluminum from coagulant effluent water,and that double layer filtration was more effective in residual aluminum removal than single layer filtration,while nano filtration was more effective than micro filtration.It was found that when the residual aluminum concentration was below 1mg/L in sediment effluent,the residual aluminum concentration in treated water was above 0.2 mg/L.The direct rapid filtration process mainly removed the suspended aluminum.The removal of soluble and colloidal aluminum was always less than 10% and the natural small particles that adsorbed the amount of soluble or small particles aluminum on their surface were difficult to be removed in this process.Micro filtration and nano filtration were good technologies for removing aluminum;the residual aluminum concentration in the effluent was less than 0.05 mg/L.     

基于化学反应动力学的饮用水铝形态分布模型研究

目前饮用水中的总铝超标现象十分严重,其危害与铝的存在形态密切相关.本研究利用三层前反馈式的人工神经网络技术,建立了基于化学反应动力学的铝形态预测模型.结果表明,无机单核铝和溶解铝的浓度变化速率与反应时间及水温、pH、总铝、氟离子、磷酸根和硅酸根等水质参数密切相关,二者的反应级数均为三级.通过人工神经网络可有效地进行饮用水中无机单核铝和溶解铝反应动力学参数的预测;反应速率常数k和初始浓度项1/c02的计算值和模型预测值的相关系数R均大于0.999.由M市管网水铝形态的预测结果可知:当总铝浓度0.05mg·L-1时,模型对无机单核铝浓度的预测误差较大;而当总铝浓度0.05mg·L-1时,模型有较好的预测能力,无机单核铝和溶解铝的相对预测误差分别为±15%和±10%.     

水温和pH对饮用水中铝形态分布的影响

铝对输配水系统及人体健康的影响主要与其存在形态有关.本研究采用硫酸铝模拟配水考察了水温和pH对溶液中铝形态分布的影响情况.考察的主要铝形态包括单核铝、溶解铝、悬浮铝和多核铝;采用的形态分析方法为荧光分光光度法.结果表明:当pH=6.5时,悬浮铝为饮用水中铝的主要存在形态,在总铝中的质量分数为62.2%;而当pH>7.0时,单核铝为主要形态,且随反应时间的增加变化不大.各水质条件下的多核铝浓度均较低,且随反应时间的变化也不大.水温对铝形态的影响与pH是一致的,由pOH可将二者统一起来.通过调节pOH可以实现饮用水中铝形态的控制,这将对输配水系统的运行管理及铝毒性控制提供理论依据.     

Spatial variations of aluminum species in drinking water supplies in Xi’an studied applying geographic information system

This article aimed to investigate the variation of aluminum species and the effects of coagulant type and water quality on aluminum speciation in drinking water.Statistical analysis showed that the concentration of total aluminum(AlT) of drinking water in Xi'an ranged from 0.051 to 0.417 mg/L and the concentration of AlT in about 24.7% studied samples was higher than the currently recommended value(0.2 mg/L).The areas fed by surface water plants had a larger portion(39.4%) of samples over the recommended value.In drinking water treated by alum coagulant,the average concentration of monomeric aluminum(Ala) was higher than that in water treated by poly aluminum chlorine(PACl) and poly aluminum ferric chloride(PAFC).The average concentrations of polynuclear aluminum(Alb) and colloidal/suspended aluminum(Alc) in the drinking water treated by alum were lower than those in water treated by PACl and PAFC.There was a notable decrease in AlT along with the delivery pipeline away from the plants,with an average decline of about 36 μg/(L·km).Besides coagulant type,water quality also could afflect aluminum speciation.In drinking water without orthophosphate,the concentrations of Ala and AlT were positively correlated with pH;while,in drinking water with orthophosphate,the concentrations of Ala and AlT were negatively correlated with pH.The addition of orthophosphate salts in the drinking water treatment process would be an effective method for aluminum control in pH range 6.5-8.2.     

混凝沉淀过程中铝系混凝剂的形态转化规律

研究了模拟配水中硫酸铝和氯化铝2种传统铝凝聚剂和2种聚合氯化铝(PAC)絮凝剂在混凝过程中的形态转化规律以及原水浊度和溶解性有机碳(DOC)对残余铝形态分布的影响.结果表明,在低浊体系中,投加铝系混凝剂是导致出水余铝升高的主要原因;但在高浊体系中,铝系混凝剂,尤其是聚合铝具有一定的除铝功能;混凝沉淀过程中传统铝凝聚剂的残余铝总量明显高于聚合铝混凝剂的残余铝总量;聚合铝混凝剂的残余铝全部为悬浮态铝,传统铝混凝剂的残余铝中还存在着胶体态铝和溶解态铝.原水浊度和DOC浓度增加,会提高残余铝中胶体态铝和溶解态铝的含量.     

高岭土吸附态铜对鲤鱼鱼鳃的生物有效性

为了验证高岭土颗粒吸附态铜对鲤鱼鳃部的生物有效性并从形态的角度对其可能的机理进行说明,本研究在保持水相溶解态铜浓度不变、高岭土颗粒吸附态铜浓度递增的条件下进行了暴露实验,并利用MINTEQA2化学平衡计算软件分析了鱼鳃微环境中铜的形态分布特征.暴露实验的结果表明鲤鱼鳃样的铜吸收率随颗粒态铜浓度的递增而增加; 形态分析的结果表明颗粒吸附态铜在鱼鳃微环境中会发生一定程度的离解,从而转化为可被鱼鳃直接吸收的形态.     

Al的海洋生物地球化学研究

比较系统地介绍了国内外Al的海洋生物地球化学研究进展，内容包括Al在海洋中的来源及输送通量，不同海区的分布特点，水体中的溶解态Al的赋存形式及其迁移转化规律等，简要介绍了我国在这一研究领域所取得的成果及存在的不足，并对今后的发展方向进行展望。     

酸雨对茶树中铝的形态分布及生态化学影响

建立茶树中铝的化学形态分析方法,探讨铝在茶树老叶、芽叶及培植土等一系列化学行为及与其它元素的关系,就酸雨对茶树中铝形态的影响进行了模拟实验,结果为茶树在我国西南酸雨地区的种植和生态协调提供信息.     

聚硅酸对不同形态铝沉积行为的影响

针对给水管网中残余铝沉积和再溶解现象可能引起的水质问题,研究了聚硅酸对不同水解聚合形态铝沉积、再溶解的影响,并以石英微晶天平为表征手段,初步探讨了聚硅酸对不同形态铝沉积、再溶解过程影响的机理.结果表明,聚硅酸能显著改变不同水解聚合形态铝的沉积、再溶解行为.聚硅酸可与3种水解聚合形态的铝迅速结合而生成可沉积产物,但产物性质不同.以单体形态为主的Al_0与聚硅酸的反应产物性质较稳定,部分以溶解态存在,部分以非溶解态(可沉积态)存在;尽管铝的两种聚合形态Al_(13)和Al_(30)与聚硅酸反应也生成了部分可沉积产物,但随着时间的推移,这些产物又逐渐向溶解态转化.铝硅比对Al_0体系中铝的沉积溶解行为影响较小,而对Al_(13)和Al_(30)影响较大,且在0.2∶20(以Al和SiO_2计的质量比)时,沉积态铝的溶解速率最快.     

铝盐混凝剂的混凝效果与残留铝含量和组分之间的关系研究

研究了氯化铝、硫酸铝、聚合氯化铝(poly-aluminum chloride, PAC)3种铝盐混凝剂在腐殖酸-高岭土模拟水样中的应用,以比较3种混凝剂在该水样中的混凝效果与残留铝含量和组分之间的关系.结果表明, 3种铝盐混凝剂在试验选取的投加量下对浊度和UV254的去除率最高可达90%左右,PAC能在较高的投加量下达到较好的混凝效果;较高投加量下PAC混凝沉淀出水中残留总铝含量为0.9 mg/L左右,余铝率为-3.0%左右,均明显低于传统的铝盐混凝剂;3种混凝剂混凝处理腐殖酸-高岭土模拟水样时,残留铝均大部分以溶解性总铝的形式存在,且溶解性有机铝在总溶解性铝中所占比例较大;PAC在腐殖酸-高岭土混凝沉淀出水中残留总铝的含量下降最快,且能够有效降低出水中毒性较大的溶解性铝的含量,其混凝沉淀出水中残留总溶解性铝含量为0.6 mg/L左右.     

川东平行岭谷区典型岩溶含水系统中NO3-的存储和运移

为了研究NO3-在岩溶含水系统中的存储和运移规律,对降雨条件下重庆川东平行岭谷区青木关地下河系统的水化学动态进行在线监测和高密度采样测试,结合NO3-的月动态变化,并利用主成分分析方法.结果表明,降雨期间地下河中的NO3-与全Fe、全Mn、Al3+是两组不同来源的元素,在含水系统中表现出不同的地球化学行为.NO3-从地表输入后随土壤水下渗存储于岩溶非饱和带的裂隙、孔隙和溶隙等含水介质中,而全Fe、全Mn、Al3+则是地表受雨水侵蚀的土壤随地表径流通过落水洞、竖井等通道,以集中流的形式灌入地下河造成的.进而将NO3-在岩溶含水系统中的运移过程分为输入存储、快速输出和再输入存储这3个理想的阶段.在外部条件大致相同的情况下,非饱和带的岩溶发育程度是影响降雨期间地下河中NO3-浓度变化的关键因素.降雨条件下存储于非饱和带的NO3-很容易被释放出来,破坏地下水生态环境,严重威胁着当地群众的健康安全.需要加强岩溶生态系统管理工作,改善土地利用方式,科学施肥,有效控制地下水营养成分的地表输入.     

滇池内湖滨带沉积物中重金属形态分析

采用BCR3步分级提取法测定了滇池内湖滨带沉积物中4种重金属(Pb、Cd、Cu和Zn)不同形态的含量,初步评估了这4种重金属的生物有效性.结果表明,Cd和Zn主要以可提取态存在(即弱酸溶解态、可还原态和可氧化态),而Pb和Cu均以残渣态为主要存在形式.通过计算可提取态含量所占总量百分量大小,可知各金属的生物有效性大小排序为:Zn(53.06%)>Cd(50.84%)>Cu(34.62%)> Pb(28.65%).沉积物中总有机碳(TOC)与各金属不同形态间的相关性分析表明,可氧化态重金属与有机碳结合的趋势远大于弱酸溶解态和可还原态.表层沉积物中可提取态重金属的空间分布特征明显表现为草海>外海,除Cu外,大部分样点的可提取态Pb、Cd和Zn含量均随采样深度增加而减少.     

从铝形态转化角度分析AlCl3的混凝性能

应用Ferron逐时络合比色法,从铝形态转化角度对AlCl₃混凝性能进行了研究. 结果表明,AlCl₃的混凝性能与其发生二次水解反应后水解产物形态中的Al_b所占比例成正比,而影响AlCl₃水解产物中Al_b所占比例的主要因素是体系中的pH. 混凝过程中的水系组成及浓度和AlCl₃投加量的不同均会引起体系pH变化,从而影响AlCl₃水解产物中Al_b所占比例,最终影响AlCl₃的混凝效果.AlCl₃在混凝过程中所表现出的水解程度大、产生H+多的特征,使其在高碱度体系和高浓度有机酸体系的污水处理中效率更高.      

大宝山矿区污染水体中重金属的形态分布及迁移转化

对受广东大宝山矿区矿山废水排放污染的横石河水体中的过滤水、悬浮物和沉积物中重金属的污染分布特征及其迁移转化进行了系统地研究.结果表明:该水体的环境污染是以Cu,Zn,Cd和Pb则为主的多金属复合污染,综合污染指数(PI)为2.23～18.11,重金属Cu,Zn,Cd和Pb的溶解态质量浓度分别达13.82,50.83,0.103和2.91 mg/L;Cu,Zn,Cd和Pb的溶解态、悬浮态及总量沿河流断面呈相似的空间分布规律,而As则略有不同,但都是沿水流方向逐渐降低的;由于受低pH的影响,水体中As主要以细微颗粒物悬浮态为迁移载体,而Cu,Zn,Cd和Pb则以水溶态为主要迁移方式; 沉积物中5种重金属元素都以残渣态为主要存在形态,Cd和Pb的可交换态及Cu和Zn的有机态含量很高,说明这4种元素对环境都有一定的潜在威胁性.      

干法烟气脱硫副产物中汞的形态分布

通过分析干法烟气脱硫副产物中不同形态汞的含量,研究干法脱硫灰中汞的环境稳定性. 利用逐级化学提取法,分析了锅炉底灰、锅炉飞灰、脱硫塔底灰和除尘器灰中水溶态、酸溶态、过氧化氢溶态及王水溶残渣态汞的含量,研究了不同形态汞含量的变化规律. 结果表明,锅炉底灰、锅炉飞灰、脱硫塔底灰和除尘器灰中w（总汞）分别为0.23,0.36,0.46和1.22 mg/kg,且随着脱硫除尘时间的延长w（总汞）呈增加的趋势,其中,以氯化物、硝酸盐和硫酸盐存在的水溶态汞变化明显,除尘器灰中w（水溶态汞）高达0.72 mg/kg. 分析认为,干法烟气脱硫灰吸附的大部分汞蒸气转化为可溶性的氯化物、硝酸盐和硫酸盐等,另外还有少量汞以单质状态存在.      

沉积物中氧化物结合态镉对芦苇的生物有效性研究：氧化物种类、结合形式、老化的影响

沉积物中重金属的生物有效性在很大程度上取决于其赋存形态.选用沉积物中2种典型氢氧化物矿物:氢氧化铁和氢氧化铝,以水培法和矿物结合态Cd为培养介质,以芦苇为受试植物,研究环境中吸附和共沉淀态Cd生物有效性差别,并探究老化过程对生物有效性的影响.经过13 d的培养,发现2种结合形式的Cd均可被芦苇富集,不同处理体系中富集强度不同,根中富集量为9.1~37.8 mg.kg-1;地上部分富集量为0~10.0 mg.kg-1.其中,结合在Fe0.5Al0.5(OH)3矿物上的Cd的生物有效性最大,其次是Fe(OH)3和老化的Fe0.5Al0.5(OH)3,富集量最少的是老化的Fe(OH)3的处理.采用2种低分子量有机酸对Cd进行解吸实验,Cd的解吸规律与芦苇对Cd的富集规律一致.因此,共沉淀处理降低了Cd的富集,矿物的理化性质决定了含铝矿物对Cd的结合较差,老化作用抑制了吸附态Cd的富集,有机酸解吸实验也验证了不同形态Cd生物有效性的差异.     

Effects of advanced oxidation pretreatment on residual aluminum control in high humic acid water purification

Due to the formation of disinfection by-products and high concentrations of Al residue in drinking water purification, humic substances are a major component of organic matter in natural waters and have therefore received a great deal of attention in recent years. We investigated the effects of advanced oxidation pretreatment methods usually applied for removing dissolved organic matters on residual Al control. Results showed that the presence of humic acid increased residual Al concentration notably. With 15 mg/L of humic acid in raw water, the concentrations of soluble aluminum and total aluminum in the treated water were close to the quantity of Al addition. After increasing coagulant dosage from 12 to 120 mg/L, the total-Al in the treated water was controlled to below 0.2 mg/L. Purification systems with ozonation, chlorination, or potassium permanganate oxidation pretreatment units had little effects on residual Al control; while UV radiation decreased Al concentration notably. Combined with ozonation, the effects of UV radiation were enhanced. Optimal dosages were 0.5 mg O3/mg C and 3 hr for raw water with 15 mg/L of humic acid. Under UV light radiation, the combined forces or bonds that existed among humic acid molecules were destroyed; adsorption sites increased positively with radiation time, which promoted adsorption of humic acid onto polymeric aluminum and Al(OH)3(s). This work provides a new solution for humic acid coagulation and residual Al control for raw water with humic acid purification.     

固态聚合氯化铝的27Al NMR研究

聚合氯化铝(PAC)是一种水处理混凝剂,可为液态(PAC-L),也可浓缩成固体(PAC-S)、PAC-L在水中稀释时铝的形态的变化已用~(27)Al核磁共振法(NMR)进行了研究。本工作试图用~(27)Al NMR法对PAC-S及其在水中溶解稀释物中铝的形态进行研究,以探讨固化对PAC及其在水中铝的形态的影响。