Effects of water quality on the coagulation performances of humic acids irradiated with UV light

The presence of humic acid in drinking water treatment has received significant attention in recent years because of its adverse effects on the removal of many pollutants in coagulation. In this paper, the effects of water quality including pH, turbidity, alkalinity, and hardness on the removal of humic acid were investigated in a UV light hybridized coagulation process. Our results suggested that UV light radiation could effectively improve the removal rate of humic acid in coagulation under both neutral and basic conditions, and the variations of the selected water quality parameters had little adverse effect on the function of UV light. After UV light radiation, the removal rate of the nitro-humic acid (NHA) increased from 20% to 60% in coagulation, and increased further to 75% and 85% for the raw waters with 10.0 NTU kaolin and 100 mg·L^-1 hardness, respectively. In addition to NHA, the removal rates of the humic acid extracted from peat coal (PHA) and the humic acid provided by Japan metals and chemicals company (JHA) in coagulation were also improved, both in the range of 80%–90% after undergoing UV light radiation. By changing the radiation location from prior to coagulation to the flocculation process, similar experimental results were obtained. The formation of positive charged sites after UV light radiation was considered to be the primary factor that led to an enhanced removal of the humic acid in coagulation.     

Effects of humic acid and surfactants on the aggregation kinetics of manganese dioxide colloids

The aggregation of common manganese dioxide (MnO₂) colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered (e.g. water treatment) and natural aquatic environments. Nevertheless, little is known about the aggregation kinetics of MnO₂ colloids and the effect of humic acid (HA) and surfactants on these. In this study, the early stage aggregation kinetics of MnO₂ nanoparticles in NaNO₃ and Ca(NO₃)₂ solutions in the presence of HA and surfactants (i.e., sodium dodecyl sulfate (SDS), and polyvinylpyrrolidone (PVP)) were modeled through time-resolved dynamic light scattering. In the presence of HA, MnO₂ colloids were significantly stabilized with a critical coagulation concentration (CCC) of ~300 mmol·L^-1 NaNO₃ and 4 mmol·L^-1 Ca(NO₃)₂. Electrophoretic mobility (EPM) measurements confirmed that steric hindrance may be primarily responsible for increasing colloidal stability in the presence of HA. Moreover, the molecular and/or chemical properties of HA might impact its stabilizing efficiency. In the case of PVP, only a slight increase of aggregation kinetics was observed, due to steric reactions originating from adsorbed layers of PVP on the MnO₂ surface. Consequently, higher CCC values were obtained in the presence of PVP. However, there was a negligible reduction in MnO₂ colloidal stability in the presence of 20 mg·L^-1SDS.     

Applying chemical sedimentation process in drinking water treatment plant to address the emergent arsenic spills in water sources

Arsenic (As) spills occurred more frequently and sometimes polluted water sources in recent years in China. It is as urgent need to develop emergency treatment technologies to address the arsenic threat for large-scale water treatment plants. In response, we developed a chemical sedimentation technology to remove arsenic contaminants for water treatment plants. Bench-scale experiments were conducted to investigate the efficiency of arsenic removal and the influencing factors of the chemical sedimentation treatment process. The influencing factors included the choice and dosage of coagulants, the valence of arsenic and pH value of solution. The As(V) contaminants can be almost completely removed by ferric or alum coagulants. The As(III) contaminants are more recalcitrant to chemical sedimentation, 75% for ferric coagulant and 40% for alum coagulant. The quantitative results of arsenic removal load by different ferric or alum coagulants were presented to help determine the parameters for arsenic treatment technology. The dominant mechanism for arsenic removal is static combination, or adsorption of negative arsenic species onto positive ferric hydroxide or alum hydroxide flocs. The efficiency of this treatment technology has also been demonstrated by a real production test in one water treatment plant with arsenic-rich source water and one emergency response. This technology was verified to be quick to set-up, easy to operate and highly efficient even for high concentration of arsenic.     

Treatment,residual chlorine and season as factors affecting variability of trihalomethanes in small drinking water systems

Seasonal variability in source water can lead to challenges for drinking water providers related to operational optimization and process control in treatment facilities. The objective of this study is to investigate seasonal variability of water quality in municipal small water systems (<3000 residents) supplied by surface waters. Residual chlorine and trihalomethanes (THM) were measured over seven years (2003–2009). Comparisons are made within each system over time, as well as between systems according to the type of their treatment technologies. THM concentrations are generally higher in the summer and autumn. The seasonal variability was generally more pronounced in systems using chlorination plus additional treatment. Chloroform, total THM (TTHM) and residual chlorine concentrations were generally lower in systems using chlorination plus additional treatment. Conversely, brominated THM concentrations were higher in systems using additional treatment. Residual chlorine was highest in the winter and lowest in the spring and summer. Seasonal variations were most pronounced for residual chlorine in systems with additional treatment. There was generally poor correlation between THM concentrations and concentrations of residual chlorine. Further study with these data will be beneficial in finding determinants and indicators for both quantity and variability of disinfection byproducts and other water quality parameters.     

黄铁矿对水体中腐殖酸的吸附特性

选择富里酸(fulvic acid,FA)和胡敏酸(humilic acid,HA)作为吸附对象,通过铁矿物吸附筛选实验,以黄铁矿(pyrite)为吸附剂研究其对水体中两种典型腐殖酸(humic acid)的吸附特性.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X-射线光电子能谱(XPS)、红外光谱(IR)、纳米粒度及电位(Zeta)分析仪和比表面仪(BET)对黄铁矿进行组成及结构表征.考察了腐殖酸溶液p H、离子强度和温度等条件对黄铁矿吸附的影响.结果表明,黄铁矿是层状结构,吸附腐殖酸后,在黄铁矿表面形成了大小均匀的分子簇,且黄铁矿晶粒尺寸减小了约10 nm;黄铁矿对FA、HA的最大吸附量分别为11.8 mg·g-1和13.1 mg·g-1.随着p H增加,黄铁矿对腐殖酸的吸附量均表现为先增大后减小;离子强度(NaCl)对吸附的影响较小;随着温度升高,其吸附量不断增大.两种腐殖酸吸附数据与Langmuir吸附模型拟合良好且其吸附动力学规律均符合二级动力学模型,热力学研究表明,黄铁矿吸附两种腐殖酸均属于自发进行的吸热反应.     

酸性紫色土腐殖酸对毒死蜱的水解和吸附作用

土壤组分与农药的环境化学行为之间存在着密切的关系。腐殖酸是土壤有机质的重要成分,由于其复杂的结构和所含的多种功能基团,对各种污染物具有强烈的吸持作用,从而对农药的环境行为产生重要影响。采用平衡振荡法研究酸性紫色土腐殖酸对毒死蜱水解的影响和毒死蜱在酸性紫色土腐殖酸上吸附的影响因素。结果表明,酸性紫色土腐殖酸可促进毒死蜱水解,腐殖酸质量浓度从0mg·L-1增大到360mg·L-1时,毒死蜱的水解速率常数k增大了2倍。毒死蜱在腐殖酸上的吸附行为均可用Linear方程和Freundlich方程来描述,拟合效果均达到显著水平;试验条件下温度为15℃时的吸附量最大,随着试验温度的升高吸附量呈现出先降低后增大的趋势;pH减小,吸附能力增大;离子强度对吸附影响不明显;腐殖酸添加量增大,单位质量腐殖酸的吸附量减小。     

环丙氨嗪在Aldrich胡敏酸中吸附-解吸特征的研究

采用批平衡法,研究了不同温度下环丙氨嗪在Aldrich胡敏酸中的吸附与解吸特征。结果表明：环丙氨嗪吸附和解吸过程都包含极快速、快速和缓慢阶段。伪二级动力学方程能较好地描述不同温度下环丙氨嗪的吸附动力学特性,表明吸附速率决定于胡敏酸表面吸附位点的可用度,而不是溶液中环丙氨嗪的浓度。环丙氨嗪在极快速吸附阶段的吸附速率随温度的升高而增大,但平衡时的吸附量却随温度的增加而降低。吸附等温线和解吸曲线符合Langmuir方程和Freundlich方程。环丙氨嗪在胡敏酸上的解吸速率小于吸附速率,表明存在滞后效应。吸附焓变、熵变和自由能都为负值,表明环丙氨嗪在胡敏酸上的吸附是一个自发、熵减小的放热过程。-Go〈40 kJ.mol^-1表明环丙氨嗪在胡敏酸表面以物理吸附为主。     

Comparative genotoxicity of water processed by three drinking water treatment plants with different water treatment procedures

• Genotoxicity of substances is unknown in the water after treatment processes. • Genotoxicity decreased by activated carbon treatment but increased by chlorination. • Halogenated hydrocarbons and aromatic compounds contribute to genotoxicity. • Genotoxicity was assessed by umu test; acute and chronic toxicity by ECOSAR. • Inconsistent results confirmed that genotoxicity cannot be assessed by ECOSAR. Advanced water treatment is commonly used to remove micropollutants such as pesticides, endocrine disrupting chemicals, and disinfection byproducts in modern drinking water treatment plants. However, little attention has been paid to the changes in the genotoxicity of substances remaining in the water following the different water treatment processes. In this study, samples were collected from three drinking water treatment plants with different treatment processes. The treated water from each process was analyzed and compared for genotoxicity and the formation of organic compounds. The genotoxicity was evaluated by an umu test, and the acute and chronic toxicity was analyzed through Ecological Structure- Activity Relationship (ECOSAR). The results of the umu test indicated that biological activated carbon reduced the genotoxicity by 38%, 77%, and 46% in the three drinking water treatment plants, respectively, while chlorination increased the genotoxicity. Gas chromatograph-mass spectrometry analysis revealed that halogenated hydrocarbons and aromatic compounds were major contributors to genotoxicity. The results of ECOSAR were not consistent with those of the umu test. Therefore, we conclude that genotoxicity cannot be determined using ECOSAR .     

Abiotic association of phthalic acid esters with humic acid of a sludge landfill

The abiotic association between phthalic acid esters (PAEs) and humic substances (HS) in sludge landfill plays an important role in the fate and stability of PAEs. An equilibrium dialysis combined with ¹⁴C-labeling was used to study the abiotic association of two abundant PAEs (diethyl phthalate and di-n-butyl phthalate) with humic acid (HA) isolated from a sludge landfill with different stabilization times and different molecular weights. Elemental analysis and Fourier Transform Infrared Spectrophotometer (FTIR) suggested that high K _A value of HA was related to the high aromatic content and large molecular weight of HA. The results indicated that the association strength of PAEs with HA depended on both the properties of the PAEs and the characteristics of HA. The K _A values of the association were strongly dependent on solution pH, and decreased dramatically as the pH was increased from 3.0 to 9.0. The results suggested that nonspecific hydrophobic interaction between PAEs and HA was the main contributor to the association of the PAEs with HA. The interactive hydrogen-bonds between the HA and the PAEs molecules may also be involved in the association.     

水体环境中天然有机质腐殖酸研究进展

腐殖酸作为一种资源广泛存在于自然界中,它是影响环境生态平衡的重要因素,也是潜在的、可大力开发和综合利用的有机资源。腐殖酸类物质具有多种活性官能团,具有酸性、亲水性、界面活性、阳离子交换能力、络合作用及吸附分散能力。腐殖酸概念、理论出现了重大突破,已从传统腐殖酸重点或仅研究腐殖酸自身发生中的物质流动、能量转化规律,同时着眼研究腐殖酸与土壤、水体和生物多界面的环境过程和机理。文章主要以水环境为例,天然有机质研究历史、化学结构,对环境污染物效应和去除技术等几个方面的研究进展进行了简要的总结;对现代腐殖酸的研究趋势进行了展望。     

Seasonal and treatment-process variations in invertebrates in drinking water treatment plants

• Seasonal and treatment-process variations in invertebrates in a DWTP were analyzed. • The propagation and leakage of invertebrates in BAC filter were the most serious. • Invertebrates can survive and reproduce in chlorine disinfected clear water tanks. • Proportions of endogenous invertebrates increased along the treatment process. Problems associated with excessive propagation and leakage of invertebrates in drinking water have received increasing attention in recent years. We performed a monthly survey of invertebrate abundance and taxa in the effluent of each treatment stage in a drinking water treatment plant between May 2015 and April 2016 and analyzed seasonal and treatment-process variations in invertebrates. The results showed that invertebrate abundances in raw water, effluent of the biological activated carbon (BAC) filter, and finished water significantly correlated with water temperature, whereas no correlation was observed between water temperature and invertebrate abundance in the effluents of the sedimentation tank and sand filter. The dominant taxa in the effluent of each treatment stage were rotifers, nematodes, and crustaceans. The sedimentation tank could efficiently remove invertebrates with an annual average removal rate of 92%. The propagation and leakage of invertebrates occurred in the sand and BAC filters but more seriously in the latter. The average reproduction rate in the BAC filter was 268.8% with rotifers as the taxon that leaked the most. Invertebrate survival and reproduction were also observed in the chlorine-disinfected clean water reservoir with an average reproduction rate of 41.9%. Owing to differences in chlorine resistance, the reproduction ability of the dominant taxa was in the order nematodes>crustaceans>rotifers. The proportion of endogenous invertebrates gradually increased along the treatment process. The average proportion of endogenous invertebrates in the finished water was higher than 79.0%. Our findings suggested that waterworks should pay more attention to endogenous invertebrate growth.     

Electrochemical oxidation of humic acid at the antimony- and nickel-doped tin oxide electrode

This work investigated the degradation of humic acid （HA） in aqueous solution by electrochemical oxidation with Antimony- and Nickel-doped Tin oxide electrode （Ni-Sb-SnO2/Ti electrode） as the anode. Initial concentrations of HA ranged from 3 to 9 mg-L 1. Under such a concentration scope, the degradation of HA was a mass transfer controlled process. Degradation rate increased with the increase of HA initial concentration. Test on the effect of tert-butanol revealed that · OH played an important role in the oxidation of HA. The absence of cation Ca2＋ was beneficial to HA degradation, which suggested that both indirect and direct electrolyze happened during the whole electrochemical oxidation process. Alkaly （pH = 12） and neutral （pH = 7） conditions were benefical to HA degradation.     

广州市饮用水中挥发性有机物的研究

饮用水中的挥发性有机化合物（VOCs）来源于水源水受到的环境污染或是在净化消毒工艺处理工程中反应产生的副产物,可对人体健康造成极大的危害。改革开放以来,广州人口和经济得到突飞猛进的发展,也带来了包括饮用水安全在内的诸多严重的社会和环境问题。虽然饮用水中VOCs的研究已经得到越来越多的重视,但是目前对广州市饮用水中挥发性有机物的研究还鲜有报道。本文在广州市中心城区选取15个不同位置的采样点进行了自来水水样采集,并利用吹扫-捕集-气相色谱-质谱（GC-MS）联用系统分析技术测定水中 VOCs 的种类和三卤甲烷的质量浓度。结果表明,广州市中心城区的自来水中VOCs有20种,以三卤甲烷（THMs）和芳香烃类为主,占了所检出的物质总量的78%以上。THMs中四种化合物（氯仿、一溴二氯甲烷、二溴一氯甲烷、溴仿）的检出率达100%,总三卤甲烷的平均质量浓度为46.46μg· L-1,最大值为53.31μg· L-1,最小值39.91μg· L-1。根据2006版国家饮用水标准,四种三卤甲烷质量浓度均低于标准限值,符合标准要求。对市面上一般的瓶装水的研究发现,瓶装水中三卤甲烷的质量浓度非常低,总三卤甲烷平均质量浓度仅为1.47μg·L-1,约是自来水中质量浓度的1/30。为了解温度及煮沸对自来水中 THMs 质量浓度的影响,本研究设计了实验进行探究。结果发现加热至沸腾过程中,THMs质量浓度随温度升高而升高,而沸腾后THMs骤降,煮沸5 min可降低水中约95%的THMs,接近瓶装水中THMs质量浓度。     

Bactericidal effects of adsorbent on Escherichia coli for use in disinfection of drinking water

A synergistic action of silver (Ag) and groundnut husk carbon was shown, which markedly enhanced inactivation of Escherichia coli. The purpose of this study was to assess the feasibility of using a silver-impregnated groundnut husk carbon adsorbent (AdSG) for drinking water disinfection and evaluate % disinfection of E. coli. The results showed that contact of bacterial cells with AdSG resulted in a transfer of Ag ion to the cell, as evidenced by bactericidal activity. It is also possible that Ag produced generation of reactive oxygen species in the cell that led to bactericidal activity of the adsorbent. Data indicated that AdSG was effective as a bactericidal agent and may prove to be economically beneficial in drinking water disinfection.     

A red water occurrence in drinking water distribution systems caused by changes in water source in Beijing,China: mechanism analysis and control measures

A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control measures were investigated. The results indicated that a significant increase in sulphate concentration as a result of the new water source was the cause of the red water phenomenon. The mechanism of iron release was found that the high-concentration sulphate in the new water source disrupted the stable shell of scale on the inner pipe and led to the release of iron compounds. Experiments showed that the iron release rate in the new source water within pipe section was over 11-fold higher than that occurring within the local source water. The recovery of tap water quality lasted several months despite ameliora- tive measures being implemented, including adding phosphate, reducing the overall proportion of the new water source, elevating the pH and alkalinity, and utilizing free chlorine as a disinfectant instead of chloramine. Adding phosphate was more effective and more practical than the other measures. The iron release rate was decreased after the addition of 1.5 mg. L-1 orthophosphate- P, tripolyphosphate-P and hexametaphosphate-P by 68%, 83% and 87%, respectively. Elevating the pH and alkalinity also reduced the iron release rate by 50%. However, the iron release rate did not decreased after replacing chloramine by 0.5-0.8 mg. L-1 of free chlorine as disinfectant.     

Removal of Cu（ll） ions from aqueous solution by activated carbon impregnated with humic acid

Humic acid （HA） was impregnated onto powdered activated carbon to improve its Cu（II） adsorption capability. The optimum pH value for Cu（II） removal was 6. The maximum adsorption capacity of HAimpregnated activated carbon was up to 5.98mg.g-1, which is five times the capacity of virgin activated carbon. The adsorption processes were rapid and accompanied by changes in pH. In using a linear method, it was determined that the equilibrium experimental data were better represented by the Langmuir isotherm than by the Freundlich isotherm. Surface charges and surface functional groups were studied through zeta potential and FTIR measurements to explain the mechanism behind the humicacid modification that enhanced the Cu（II） adsorption capacity of activated carbon.     

The role of soil humic and fulvic acid in the sorption of endosulfan (alpha and beta)

The sorption behaviour of alpha- and beta-endosulfan in soil organic matter was investigated using standard soil humic acid (HA) and soil fulvic acid (FA) with a modified solubility enhancement method and a dialysis bag technique. For HA, all the experiments were conducted at an ionic strength of 0.001 mol/L, in both the presence and absence of calcium and at an ionic strength of 0.01 mol/L. For FA, the experiments were conducted at two ionic strengths: 0.001 mol/L (with calcium) and 0.01 mol/L. This study is the first to describe the striking differences in the sorption behaviours of the two stereoisomers of endosulfan in HA and in FA. The sorption coefficients of alpha-endosulfan in HA and FA were significantly higher than those of beta-endosulfan. Beta-endosulfan has comparable sorption coefficients (1.5–5.4 L/g) in HA and in FA. Ionic strength and the presence of calcium have no significant effect on the sorption of beta-endosulfan in HA. However, calcium can significantly (p=0.01) enhance the solubility of alpha-endosulfan in HA. Changes in ionic strength by one order of magnitude also affect the solubility of alpha-endosulfan in HA. The sorption coefficients of alpha-endosulfan in HA (10–36 L/g) were greater than those in FA (9–14 L/g). The chirality of the alpha-isomer was hypothesised to be the primary reason behind its higher sorption in soil organic matter relative to the beta-isomer. In the presence of dissolved HA and FA found in natural soil environments, solubility of endosulfan can be increased by five times than the aqueous solubility of endosulfan without HA and FA.     

中国饮水型砷中毒区的水化学环境与砷中毒关系

中国各饮水型砷中毒区的水化学特点受沉积环境和气候因素所控制,砷中毒的流行和发病程度与其地下水的水化学环境、水中砷的形态和价态有密切联系。在实地考察监测和对台湾、新疆、内蒙古、山西、吉林饮水型砷中毒病区环境和地下水水化学特征总结的基础上,系统分析了饮水水源中总As、As(III)、甲基胂、腐植酸与砷中毒的关系,揭示了不同病区病情差异的原因。研究表明,除台湾外,各砷中毒区均分布在干旱半干旱区;各病区多分布在沉积盆地中心或平原内相对低洼的地带,饮用的地下水均取自中新生代地层;砷中毒病情不仅与总砷含量有明显的剂量-效应关系,还与As(III)和甲基胂的浓度直接相关。台湾、内蒙古和山西病区地下水为富含有机质的复杂还原环境,水中不仅As(III)含量高,且检出有机物、腐植酸和甲基胂,新疆和吉林病区地下水为以无机砷中As(V)为主的氧化环境,吉林病区未检测出甲基胂,这是新疆与吉林病区患病率较低的主要原因。研究成果可为区域防病改水、砷中毒的预报提供重要技术支撑。     

Adsorption of humic acid from aqueous solution on bilayer hexadecyltrimethyl ammonium bromide-modified zeolite

Surfactant-modified natural zeolites (SMNZ) with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide (HTAB) onto the surface of a natural zeolite. The adsorption behavior of humic acid (HA) on SMNZ was investigated. Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite. HA removal efficiency by SMNZ increased with HTAB loading. Coexisting Ca²⁺ in solution favored HA adsorption onto SMNZ. Adsorption capacity decreased with an increasing solution pH. For typical SMNZ with bilayer HTAB coverage, HA adsorption process is well described by a pseudo-second-order kinetic model. The experimental isotherm data fitted well with the Langmuir model. Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^-1, respectively. E2/E3 (absorbance at 250 nm to that at 365 nm) and E4/E6 (absorbance at 465 nm to that at 665 nm) ratios of the residual HA in solution were lower than that of the original HA solution. This indicates that the HA fractions with high polar functional groups, low molecular weight (MW), and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage. Results show that HTAB-modified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.     

An exploratory study of chemical elements in drinking water and non-Hodgkin's lymphoma

Nanomaterials are widely used in the field of engineering and in modern society. Although the unique characteristics of nanoparticles also enable them to provide environmental solutions to reduce the formation and emissions of pollutants, adverse effects on human health may occur from the exposure to nanomaterials during the manufacturing processes and when nanomaterials are released and they contaminate the environment. It is essential to understand the factors affecting the accumulation, aggregation, deposition, translocation, and distribution of nanomaterials (natural or engineered) in the ecosystem. This study presents an extensive review of the environmental effects of nanomaterials, including classification, adverse impacts on human health and the environment, transport pathways, monitoring methods, and the current regulations regarding nanomaterials. The review indicates that the diversity of nanoparticles and their properties make the identification and characterization of nanomaterials a difficult task, and an improvement in sensitivity and selectivity of analytical methods for detecting nanoparticles in the environment is required. Besides, few regulations have been established for the management of nanoparticles released into the environment. In order to expedite the environmental management of nanomaterials, this study proposes a risk assessment framework based on the findings in the review as a practice alternative for the environmental assessment and effective management of nanomaterials. Development of practical innovative risk-based management measures may help us to find answers to the concerns such as safety of engineering and applying nanomaterials and effective control of nanoparticle contamination in the environment.