Phylogenetic analysis and arsenate reduction e ect of the arsenic-reducing bacteria enriched from contaminated soils at an abandoned smelter site

Microbial reduction of As(V) (i.e., arsenate) plays an important role in arsenic (As) mobilization in aqueous environment. In this study, we investigated As(Ⅴ) reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site. It was found that As(Ⅴ) was completely reduced to As(Ⅲ) (i.e., arsenite) in 21 h. After 3-d incubation, a yellow solid was precipitated and the concentration of As(Ⅲ) decreased sharply. After 150 h incubation, ca. 65% of soluble arsenic was removed from the solution. The analysis of the precipitate by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) revealed that the main component was crystalline arsenic sulfide (ASS). Microbial mediated reduction and mobilization of adsorbed As(Ⅴ) on ferric hydroxide was also examined. In the microcosm slurry experiment, ca. 53% of the adsorbed As(V) was reduced to As(Ⅲ) by the bacteria, which resulted in an appreciable release of arsenic into aqueous phase. The released arsenic was present predominantly as As(Ⅲ). The microbial diversity was analyzed by 16S rDNA-dependent molecular phylogeny. A near-full-length 16S rDNA gene clone library was constructed. The 197 clones were analyzed using RFLP (restriction fragment length polymorphism) and 72 OTUs were obtained, which contributed 51% of the content for total clone number in six OTUs. Six bacterial clones in these six OTUs were selected for sequencing and the sequenced clones were found to belong to the group Caloramator, Clostridium, and Bacillus.     

Isolation, identification and arsenic-resistance of Acidithiobacillus ferrooxidans HX3 producing schwertmannite

Schwertmannite, a ubiquitous mineral present in iron oxyhydroxides formed in iron- and sulfate-rich acid media, favors incorporation of some toxic anions in its structure. We reported an iron-oxidizing bacterial strain HX3 from a municipal sludge that facilitates the formation of pure schwertmannite in cultures. Ferrous iron oxidation by the isolated strain HX3 was optimum at an initial pH of 2.0-3.3 and temperature of 28-35°C. Pure schwertmannite was found through bacterial oxidation of ferrous iron at an initial pH 2.8and temperature 28°C. Following 16 S rDNA gene sequence analysis the bacterial strain HX3 was identified as Acidithiobacillus ferrooxidans. The arsenic-resistance A. ferrooxidans HX3 showed the potential of environmental application in arsenic removal from the As（Ⅲ）- and iron-rich acid sulfate waters directly by As（Ⅲ） adsorption or the formation of schwertmannite in the environment.     

Preparation and evaluation of Zr-β-FeOOH for efficient arsenic removal

A Zr-β-FeOOH adsorbent for both As(V) and As(III) removal was prepared by a chemical co-precipitation method.Compared with β-FeOOH,the addition of Zr enhanced the adsorption capacities for As(V) and As(III),especially As(III).The maximum adsorption capacities for As(III) and As(V) were 120 and 60mg/g respectively at pH 7.0,much higher than for many reported adsorbents.The adsorption data accorded with Freundlich isotherms.At neutral pH,for As(V),adsorption equilibrium was approached after 3 hr,while for As(III),adsorption equilibrium was approached after 5 hr.Kinetic data fitted well to the pseudo second-order reaction model.As(V) elimination was favored at acidic pH,whereas the adsorption of As(III) by Zr-β-FeOOH was found to be effective over a wide pH range of 4-10.Competitive anions hindered the adsorption according to the sequence:phosphate > silicate > bicarbonate > sulfate > nitrate,while Ca2+ and Mg2+ increased the removal of As(III) and As(V) slightly.The high adsorption capability and good performance in other aspects make Zr-β-FeOOH a potentially attractive adsorbent for the removal of both As(III) and As(V) from water.     

Phylogenetic analysis and arsenate reduction effect of the arsenic-reducing bacteria enriched from contaminated soils at an abandoned smelter site

Microbial reduction of As(V)(i.e.,arsenate)plays an important role in arsenic(As)mobilization in aqueous environment.In this study,we investigated As(V)reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site.It was found that As(V)was completely reduced to As(III)(i.e.,arsenite)in 21 h.After 3-d incubation,a yellow solid was precipitated and the concentration of As(III)decreased sharply.After 150 h incubation,ca.65%of soluble arsenic was removed fro...     

城市污水处理厂污泥对水中硫化物的吸附特性

为研究城市污水厂污泥对水中硫化物的吸附特性,从3座城市污水处理厂采集回流污泥,考察了硫化物浓度、温度、pH值和其他离子对污泥吸附硫化物的影响.结果表明,污水厂回流污泥对硫化物的吸附等温线可以用Langmuir方程很好地描述,其最大硫化物吸附量为15~27mg/g-干污泥.在温度为5~35℃条件下,吸附量随温度上升而增加,表明该吸附为吸热过程.pH值在2~7范围内,pH值对污泥吸附硫化物的影响不大,当pH值低于2时,污泥对硫化物的吸附量随pH降低显著减小.硫化物可能以离子形式被污泥吸附,该过程为化学吸附过程.水中存在0~25mg/L Cl-或0~12mg/L SO2- 4不影响污泥对硫化物的吸附量.     

Arsenic and chromate removal from water by iron chips-Effects of anions

The purpose of this study is to estimate the removal efficiency of As and Cr (VI) by one kind of industrial waste — iron chips, as well as to estimate the effects of typical inorganic anions (sulfate, phosphate, and nitrate), and typical organic anions (citrate, oxalate, and humate) on As or Cr (VI) removal. The results showed that 98% of As (V) and 92% of As (III) could be removed from aqueous phase by the iron chips within 60 min. Compared with As species, Cr (VI) was removed much more rapidly and efficiently with 97% of Cr (VI) being removed within 25 min. The removal efficiency for arsenic was in the order: As (III) (sulfate), As (III) (nitrate) or As (III), As (III) (humate), As (III) (oxalate), As (III) (citrate), As (III) (phosphate), and for chromate was in the order: Cr (VI) (sulfate), Cr (VI) (phosphate) or Cr (VI) (nitrate) or Cr (VI) (oxalate), Cr (VI), Cr (VI) (citrate), Cr (VI) (humate). In all the treatments, pH level increased with time except for As (III), the removal of which was either without anions or in the presence of humate or nitrate.     

磁性吸附材料CuFe2O4吸附砷的性能

根据Cu(Ⅱ)和Fe(Ⅲ)都对砷有较强的亲和性,制备了同时含有Cu(Ⅱ)和Fe(Ⅲ)的、可用磁分离方法进行分离回收的磁性吸附材料CuFe₂O₄,并对其进行了表征及吸附砷的性能研究.结果表明,该吸附剂对砷的吸附能力与溶液pH有关,在弱酸性及中性条件下,吸附砷的能力最强,而对As(V)的吸附能力比对As(Ⅲ)更强些,在平衡浓度为10μg/L时,其吸附容量可达10mg/g左右,可以很容易地将水中浓度为1～20mg/L的As(V)降到10μg/L以下.实验考察了几种无机阴离子对吸附砷的影响,表明较高浓度(砷浓度的20倍)的硫酸盐对As(Ⅲ)和As(V)的吸附均有一定影响,盐酸盐及磷酸盐则影响不明显;负载的As(V)可较容易地用0.1mol/L NaOH洗脱下来,使吸附剂再生,而As(Ⅲ)则难以洗脱,这与2种价态砷的吸附机理不同有关.     

Bacterial reduction and release of adsorbed arsenate on Fe(Ⅲ)-, Al- and coprecipitated Fe(Ⅲ)/Al-hydroxides

Mobilization of arsenic under anaerobic conditions is of great concern in arsenic contaminated soils and sediments. Bacterial reduction of As(V) and Fe(Ⅲ) influences the cycling and partitioning of arsenic between solid and aqueous phase. We investigated the impact of bacterially mediated reductions of Fe(Ⅲ)/Al hydroxides-bound arsenic(V) and iron(Ⅲ) oxides on arsenic release. Our results suggested that As(V) reduction occurred prior to Fe(Ⅲ) reduction, and Fe(Ⅲ) reduction did not enhance the release of arsenic. Instead, Fe(Ⅲ) hydroxides retained their dissolved concentrations during the experimental process, even though the new iron mineral-magnetite formed. In contrast, the release of reduced As(Ⅲ) was promoted greatly when aluminum hydroxides was incorporated. Thus, the substitution of aluminum hydroxides may be responsible for the release of arsenic in the contaminated soils and sediments, since aluminum substitution of Fe(Ⅲ) hydroxides universally occurs under natural conditions.     

Arsenic biotransformation in industrial wastewater treatment residue: Effect of co-existing Shewanella sp. ANA-3 and MR-1

Shewanella sp. ANA-3 with the respiratory arsenate reductase (ArrAB) and MR-1 with ferric reduction ability always coexist in the presence of high arsenic (As)-containing waste residue. However, their synergistic impacts on As transformation and mobility remain unclear. To identify which bacterium, ANA-3 or MR-1, dominates As mobility in the coexisting environment, we explored the As biotransformation in the industrial waste residue in the presence of Shewanella sp. ANA-3 and MR-1. The incubation results show that As(III) was the main soluble species, and strain ANA-3 dominated As mobilization. The impact of ANA-3 was weakened by MR-1, probably due to the survival competition between these two bacteria. The results of micro X-ray fluorescence and X-ray photoelectron spectroscopy analyses further reveal the pathway for ANA-3 to enhance As mobility. Strain ANA-3 almost reduced 100% surface-bound Fe(III), and consequently led to As(V) release. The dissolved As(V) was then reduced to As(III) by ANA-3. The results of this study help to understand the fate of arsenic in the subsurface and highlight the importance of the safe disposal of high As-containing industrial waste.     

缺氧条件下土壤砷的形态转化与环境行为研究

采集张士污灌区0～100 cm深的土壤并在实验室里负载低浓度的砷,采用不加硫和加硫对比研究了厌氧条件下土著微生物对土壤中砷的形态转化、环境行为影响及其机制.结果表明,在不外加硫酸盐条件下厌氧培养8 d后,微生物还原作用造成砷的大量还原和释放,释放的砷70%以上是以As(Ⅲ)形式存在,尤其20～40 cm深度土壤砷的释放量明显高于其它层土壤,As(Ⅲ)和As(T)分别达到892.8μg.L-1和1 240.6μg.L-1.与非生物对照相比每层土中盐酸可提取的砷总量都大大降低,且盐酸提取的As(T)几乎全部转化为As(Ⅲ).伴随砷的释放,铁发生还原和释放,溶解态的亚铁基本都在40 mg.L-1以上,不同土层固相中亚铁离子的量都在9.0～13.4 g.kg-1范围内,固相盐酸可提取态总铁中亚铁离子所占的比例基本都在50%以上,说明微生物还原作用造成固相中铁氧化物发生还原性溶解和矿物结构转化.当体系中添加10 mmol.L-1的硫酸盐时,每层土的生物培养体系中铁的释放几乎完全被抑制,砷和铁浓度也减少了50%.与不加硫生物培养体系相比,固相中盐酸可提取的砷量减少了50%,一部分砷被转化为稳定的硫化物As2S3而固定.可见在硫酸盐不足条件下微生物还原作用可造成砷被还原、活化和释放,而补充土壤中硫酸盐的量可促使微生物还原/活化的砷转化成更加稳定的形态,稳定的硫化物矿物As2S3是土壤微生物固定砷的重要途径.     

Biogeochemical reductive release of soil embedded arsenate around a crater area (Guandu) in northern Taiwan using X-ray absorption near-edge spectroscopy

This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure (XANES) and atomic absorption spectrometry.Total arsenic (As) concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite (As(III)) and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.     

Use of microbes for cost reduction of metal removal from metals and mining industry waste streams

Acid-rock drainage (ARD) – also known as acid-mine drainage (AMD) – results from the exposure of sulfide minerals, particularly pyritic and pyrrhotitic minerals, to atmospheric oxygen and water. AMD directly impacts tens of thousands of kilometers of streams, lakes and estuaries throughout the world. The impacted water bodies tend to have elevated concentrations of metals in the water column or sediments, and are also stressed by significant inputs of hydrogen ions.There are several conventional treatment technologies available. The most common is chemical precipitation using lime or other basic substances. These systems produce large volumes of wet sludge that often require drying facilities to concentrate the metal hydroxide sludge. Wetland treatment systems have also been used for several decades to treat AMD. Recent developments and improvements have resulted in construction of bioreactors that have a smaller footprint, and treat the metals and acidity more effectively.Many studies have demonstrated that the primary removal mechanisms for the metals are sulphate-reducing bacteria (SRB). These microbes facilitate the conversion of sulphate to sulphide. The sulphides react with metals to precipitate them as metal sulfides, many of which are stable in the anaerobic conditions of the treatment system.Plants have been shown to remove metals by uptake or oxidative precipitation near the roots. Plants seem to account for only a small percentage of the metal removal capacity of the wetland treatment systems. Adsorption of metals to the organic substrates of the treatment systems can result in metal removal, but adsorption capacity is saturated in short periods of time.High oxygen, low pH waters often enter the treatment systems. The SRB are obligate anaerobes which prefer conditions between pH 5 and 8. Thus, the input water characteristics could impact the efficiency and life expectancy of the treatment systems. The most important characteristic of input waters seems to be pH. Low oxygen of the influent waters did not enhance treatment capabilities. Low pH waters do reduce the capacity of the treatment systems to treat metals effectively.Oxyanions such as chromate and arsenate can be removed using the wetland treatment system (passive bioreactor) technology. Arsenic is removed as an arsenic sulfide compound and chromate is reduced to Cr(III) and precipitated as a hydroxide.The passive bioreactor – wetland treatment system – offers a less expensive alternative to the conventional chemical precipitation technologies. There still are problems of system hydraulics and useful life to be addressed.     

微生物电解系统生物阴极的硫酸盐还原特性研究

针对传统硫酸盐生物还原方法中供氢体系能耗大和氢气利用率低的特点,构建双极室微生物电解系统(microbial electrolysis system,MES),研究了微生物利用阴极作为电子供体去除废水中硫酸盐及电子利用的特性.外加电压为0.8 V时,MES生物阴极在36 h内SO2-4平均去除量为109.8 mg·L-1,平均还原速率可达73.2 mg·(L·d)-1.运行时MES的最高电流密度为50~60 A·m-3,电子回收率为(43.3±10.7)%,约90%的电子被用于还原SO2-4.微生物利用MES阴极产生的H2作为电子供体还原SO2-4,主要还原产物为溶解态的S2-和气态的H2S,还原过程主要发生在前12 h.对MES施加不同外加电压的实验显示,外加电压为0.8 V时的SO2-4去除率和电荷量都比0.4 V时高;但0.4 V情形下MES的电子回收率可达到70%,且周期结束时阴极H2低于检出限,推测微生物可以直接利用阴极的电子从而提高了能量效率.实验结果最终表明,微生物可利用MES的阴极进行代谢去除废水中的SO2-4,阳极微生物产生电子降低了系统能耗,这为含硫酸盐废水的高效低耗处理提供了新的研究思路.     

络合吸收脱除NO体系中FeⅢ(EDTA)的生物还原

利用驯化得到的微生物还原Fe^Ⅲ(EDTA)的研究结果表明,葡萄糖比乙醇和甲醇更适合于作为该体系的碳源;由于硝酸盐在反应过程中对Fe^Ⅲ(EDTA)的微生物还原形成抑制,选择铵盐为微生物生长的氮源;反应最适pH值范围为6~7;温度在30℃~40℃范围之间变化,Fe^Ⅲ(EDTA)还原率相差不大,温度大于40℃以后,还原率随温度升高而下降.碳源量和菌体接种量满足还原反应需要即可,过量碳源或菌体接种量对还原率没有明显的促进作用.在实验考察的浓度范围内,FeⅢ(EDTA)的生物还原符合1级反应动力学,最大反应速率γ_max=1.3 mmol·(L·h)^-1,半饱和速率常数k_m=53.5 mmol·L^-1.     

化纤厂PTA废水处理污泥生物减量效果及影响因子

通过小试试验研究PTA废水处理污泥生物减量效果及影响因子,结果表明,一次性进料、设备温度60℃、菌剂占污泥干基比例4%,可实现污泥含水率、干物质和毒性物质（钴）分别减少79%、22%和9%的最佳减量效果.基于污泥生物减量过程中多参数、三维荧光和微生物属水平变化并结合相关和主成分分析,探明了影响PTA污泥生物减量的关键因子分别为温度、电导率、胡富比、碳氮比、溶解性有机碳和8种微生物菌属（即为Gemmatimonas、Pelotomaculum、Azohydromonas、Pseudomonas、Paeniglutamicibacter、Weissella、Nitrospira、Novosphingobium）.研究结果可为化纤厂PTA污泥生物减量提供科学依据.     

硫酸盐在厌氧生物过程中的行为 Ⅱ.硫酸盐还原行为及对体系抑制作用机理

采用半连续实验方法,研究了中温厌氧条件下硫酸盐的还原行为及产生抑制作用的机理.实验结果表明,SO_4~(2-)在厌氧体系中被硫酸盐还原菌(SRB)全部或部分还原为硫化物,其还原率与SO_4~(2-)累积加入浓度有关.还原产物的形态与体系中pH值有关,较高的pH值(7.6—8.4)使体系中H_3S含量下降.SO_4~(2-)对厌氧体系的抑制与SO_4~(2-)还原过程中SRB与产甲烷菌(MRB)的底物竞争及还原产物的毒性相关.前者受COD/SO_4~(2-)比值的影响,比值大于7,对厌氧体系只产生轻度抑制作用.而后者与沼气中H_2S含量有直接关系,沼气中H_3S含量小于40mg/L时,基本不产生抑制作用.     

Characteristics and model studies for fluoride and arsenic adsorption on goethite

Fluoride and arsenic are major anionic elements of concern in drinking water treatment. The effects of contact time, pH, surface loading and ionic strength on adsorption of fluoride and As(V) were investigated using batch methods. Adsorption of fluoride and As(V) onto goethite obeyed a pseudo second-order rate law. Through experimental data and adsorption kinetic analysis, the affinity of As(V) onto goethite was stronger than fluoride. Fluoride and As(V) uptake by goethite all decreased with pH increasing at the same surface loading; however, ionic strength had slight influence on their adsorption. A surface sites-species model was used to quantify the adsorption of fluoride and As(V) onto goethite as function of pH and surface loading. This model can satisfactorily predict their adsorption characteristics with several adsorption constants.     

Shewanella oneidensis MR-1对不同价态砷的生物转化与甲基化

在实验室纯培养条件下,通过分别向培养基中投加As(Ⅲ)和As(Ⅴ),探讨Shewanella oneidensis MR-1对不同价态砷的生物转化与甲基化作用.结果表明,S.oneidensis MR-1介导下不同价态砷的生物转化与微生物对砷的耐受和代谢特性有着密切联系,在投加As(Ⅲ)时,由于细胞自身的解毒作用会产生少量的As(Ⅴ),同时在酶的作用下As(Ⅲ)与甲基供体结合生成甲基砷;而在投加As(Ⅴ)时,遵循Challenge机制,先产生一甲基砷后生成二甲基砷.此外,弱酸性环境比碱性更有利于甲基砷的产生;温度30℃时甲基砷的产生量较高,过低或过高的培养温度砷甲基化率下降.     

Anaerobic oxidation of arsenite by bioreduced nontronite

The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay minerals are commonly found in soils and sediments, which are an important host for arsenic. However, limited information is known about the redox reactions between arsenic and structural Fe in clay minerals. In this study, the redox reactions between As(III)/As(V) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments. No oxidation of As(III) was observed by the native Fe(III)-NAu-2. Interestingly, anaerobic oxidation of As(III) to As(V) occurred after Fe(III)-NAu-2 was bioreduced. Furthermore, anaerobic oxidization of As(III) by bioreduced NAu-2 was significantly promoted by increasing Fe(III)-NAu-2 reduction extent and initial As(III) concentrations. Bioreduction of Fe(III)-NAu-2 generated reactive Fe(III)-O-Fe(II) moieties at clay mineral edge sites. Anaerobic oxidation of As(III) was attributed to the strong oxidation activity of the structural Fe(III) within the Fe(III)-O-Fe(II) moieties. Our results provide a potential explanation for the presence of As(V) in the anaerobic subsurface environment. Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.     

Removal of arsenate and arsenite from aqueous solution by waste cast iron

The removal of As(III) and As(V) from aqueous solution was investigated using waste cast iron, which is a byproduct of the iron casting process in foundries. Two types of waste cast iron were used in the experiment: grind precipitate dust (GPD) and cast iron shot (CIS). The X-ray diffraction analysis indicated the presence of Fe0 on GPD and CIS. Batch experiments were performed under different concentrations of As(III) and As(V) and at various initial pH levels. Results showed that waste cast iron was effective in the removal of arsenic. The adsorption isotherm study indicated that the Langmuir isotherm was better than the Freundlich isotherm at describing the experimental result. In the adsorption of both As(III) and As(V), the adsorption capacity of GPD was greater than CIS, mainly due to the fact that GPD had higher surface area and weight percent of Fe than CIS. Results also indicated the removal of As(III) and As(V) by GPD and CIS was influenced by the initial solution pH, generally decreasing with increasing pH from 3.0 to 10.5. In addition, both GPD and CIS were more effective at the removal of As(III) than As(V) under given experimental conditions. This study demonstrates that waste cast iron has potential as a reactive material to treat wastewater and groundwater containing arsenic.