Limitations of heavy metal removal from waste water by means of algae

It has been suggested by several authors that heavy metals might be removed from aqueous systems by phytoplanktonic algae, whose high capacity for accumulating dissolved metals has previously been described. This paper shows—by comparing results obtained on accumulation factors and growth rates in different models—that metal removal by means of algae is not feasible in practice. It was found that under optimum conditions in a static system the reduction of a given initial metal concentration by 50% requires approx. 14 days, while in a dynamic model a retention time of approx. 19 days is needed to achieve the same reduction. Finally, measurements of nitrogenase activity inhibition caused by various concentrations of mercury and cadmium demonstrate that nitrogen-fixing blue-green algae can be used for biological sewage treatment only at very low heavy metal concentrations in the medium.     

Estimation of heavy metal transformations in municipal solid waste

The behaviour of heavy metals bound to municipal solid waste (MSW) and exposed to 2 decades of anaerobic waste stabilization processes have been estimated. Heavy metal solid forms in a waste degradation residue have been compared with a reconstructed waste similar to that initially disposed of in 1973. The initial waste was composed of a mixture of shredded MSW (95% dry wt.) and anaerobic sewage sludge (5% dry wt.). A sequential chemical extraction method has been used to fractionate the heavy metals into five categories of available and reactive solid forms. The results imply that these forms can be ascribed to approximately 30% of the total content of the heavy metals in the degraded waste and the portion of heavy metals bound to oxidizable solid forms seems to be higher in the degraded than the fresh MSW. The bulk of the remaining heavy metals are assumed to be less available and bound into resistant lattice structures, such as metal and polymer items. A comparison between fractionation patterns of the waste in this study and of a few sediments collected from different environments imply similarities between the fresh MSW and an oxic sediment from one site and the sewage sludge and anoxic sediments from another site. Fractionation patterns of the degraded waste are found to be quite similar to those of the anoxic sediments, except for Pb, Ni and Cd which are more similar to fresh MSW.     

废弃混凝土中重金属浸出性研究

以我国现有废弃混凝土为原料,研究废弃混凝土中重金属含量,采用模拟德国水槽试验法,以不同粒径、不同pH值、不同重金属元素(Cd、Cr、Cu、Ni、Pb、Z)为影响因素,研究废弃混凝土中重金属离子的浸出性,结果表明,废弃混凝土中不同重金属含量不同,以Zn含量最高,Cr含量最低;粒径在1mm以上时随着粒径增加重金属浸出性减小...     

垃圾填埋场覆盖层现场试验及特性评价(英文)

填埋场覆盖系统由不同的土层组成,它们具有不同的性质和功能。覆盖层直接与大气和植被接触,因此土的含水率随季节和天气条件不断变化。冬天,土的饱和度增加。夏天,土的含水率减少,同时土中吸力增加。如果土中吸力达到某个极限值,将出现干缩裂缝。这时,粘土阻隔层的密封功能将受到损害。为了研究粘土覆盖系统的长期性状,我们进行了两个大规模现场试验。本文介绍第一批现场试验结果,包括水流量、土中吸力和温度的变化规律。重点介绍保护层(营养层)厚度对覆盖系统水平衡的影响。     

重金属污染废水微生物处理机制及其研究进展

从微生物对重金属离子的转化机制、吸附机制、絮凝机制等方面阐述了微生物法去除废水中重金属离子的基本原理,并对其研究进展及未来的主要研究方向进行了综述,指出微生物法具有良好的生态效益和应用前景。     

Long-term fate of organics in waste deposits and its effect on metal release.

The long-term chemical evolution in waste deposits and the release of toxic metals was investigated. The degradation of organic matter and hence the potential efflux of heavy metals in a long-term perspective was studied by defining some scenarios for waste deposits containing organic compounds, different longevity and functions of covers and different water and air intrusion rates. The scenarios were based on various transport processes as well as different landfill constructions. The rates of influx of oxygen into both saturated and partially saturated landfills have been estimated. Each scenario takes the form of a mathematical model. The starting point for all the studied cases is the humic phase, i.e. the phase after the methane production has stopped. Based on the different cases studied, it appeared that landfills where the waste is below the water table could have advantages over the other cases. Recognizing that this option is not accepted in most countries we, nevertheless, suggested it should be reevaluated. The main conclusion is that the degradation of humic matter and hence the release of toxic metals can be substantially decreased if potential build-up of hydraulic gradients are avoided and if the landfill is located below the water surface. A conceivable alternative construction would be to place it in a depression--either natural or artificial--and to construct it so that under normal conditions it would always be water-saturated.     

铅锌尾矿重金属释放影响因素的探讨

铅锌尾矿废渣若不经过处理,会通过风蚀、径流对环境造成重金属污染,对尾矿废渣污染的研究一直是大家关注的方向。多年来,pH被证实是影响重金属释放的重要因素。本文通过实验,研究了浸提方法、pH和盐度对铅锌尾矿废渣重金属元素释放的影响。结果表明,Pb、Zn、Cd、As在pH值呈酸性和碱性时浸出率都较高,Cu、Ni则在pH值为碱性时浸出率更高,盐度对Pb的释放影响效果更为明显。     

Leaching heavy metal from deposits of heavy metals with bacteria oxidizing elemental sulphur

Experiments were carried out on bacterial leaching heavy metals from aerobically stabilize excessive activated silt of Bortnichi Aeration Station of Kiev when adding elementary sulphur as a stimulant of the activity of acidophilic thiobacilli. It has been shown that a decrease of silt pH in the course of the process is a decisive factor of efficiency of leaching heavy metals.     

水泥窑协同处置固体废弃物水泥熟料重金属含量和水泥可浸出重金属含量检测及防控研究

通过水泥窑协同处置固废物水泥熟料及水泥重金属含量风险预警监测,从检测数据分析了熟料及水泥可浸出重金属超标的根本原因,并提出相应的预防和控制措施。     

Hybrid flotation--membrane filtration process for the removal of heavy metal ions from wastewater

A promising process for the removal of heavy metal ions from aqueous solutions involves bonding the metals firstly to a special bonding agent and then separating the loaded bonding agents from the wastewater stream by separation processes. For the separation stage, a new hybrid process of flotation and membrane separation has been developed in this work by integrating specially designed submerged microfiltration modules directly into a flotation reactor. This made it possible to combine the advantages of both flotation and membrane separation while overcoming the limitations. The feasibility of this hybrid process was proven using powdered synthetic zeolites as bonding agents. Stable fluxes of up to 80l m(-2)h(-1) were achieved with the ceramic flat-sheet multi-channel membranes applied at low transmembrane pressure (<100 mbar). The process was applied in lab-scale to treat wastewater from the electronics industry. All toxic metals in question, namely copper, nickel and zinc, were reduced from initial concentrations of 474, 3.3 and 167mg x l(-1), respectively, to below 0.05 mg x l(-1), consistently meeting the discharge limits.     

Evaluation of heavy metal removal from aqueous solution onto scolecite

Scolecite is a zeolite associated to basalts of the Parana Continental Igneous Province (PCIP South America). The potential of scolecite as a new material for heavy metal removal (Pb2+ Cu2+, Zn2+, Ni2+, Co2+ and Cd2+) from aqueous solutions is evaluated. The experiments were carried out by immersion of 0.5 g of sample in solutions containing the metal ions, and kept under constant agitation for 24h, at ambient temperature. The meq of cations retained per mass of scolecite was evaluated as a function of: initial concentration (5-60 mg L(-1)), pH (4-6), liquid/solid ratio (200, 1000 and 2000) and particle size. The results indicated a great affinity of scolecite for Cu2+ with a retention value of 130 microeq g(-1) at pH 6, Ci = 30 mg L(-1) and liquid/solid ratio of 200. In the same conditions, the maximum retention measured for the other ions were 64 microeq g(-1) (Zn2+), 56 microeq g(-1) (Pb2+), 31 microeq g(-1) (Ni2+), 7.8 microeq g(-1) (Co2+) and 3.2 microeq g(-1) (Cd2+). These values increase substantially when the L/S ratio is increased. The affinity of copper and lead for scolecite is discussed based on their free ionic forms (i.e., their hydrated bivalent ions) and their hydrolysis products. The remaining ions are retained as free ions.     

A preliminary model for predicting heavy metal contaminant loading from an urban catchment

The toxicity of heavy metals to biota in urban catchments has been regarded as a very important non-point source pollution issue. Numerous studies on heavy metal pollution in urban receiving waters have found that metal transport by surface runoff is closely correlated to the partitioning of the metal forms between dissolved and particulate phases, where sediment plays an important role in the transport process. Sediment cycling on urban streets, metal binding form, and rainfall character in the catchment area are considered to be the key factors for metal transport. A preliminary model is developed based on these considerations. Starting from classical build-up and wash-off processes for the suspended sediment (SS) on the urban impervious surface, the model links the transport of suspended sediment to the transport of metal species. Monitoring data from a small highway catchment were used in the model development. A total of 47 rain events over 1 year were monitored intensively at short time intervals (5-10 min) for hydrological data, rainfall intensity, and stormwater quality. In developing the model, lead was used for the metal load prediction, as it has been a common fuel additive for urban transportation. Agreement between model results and monitoring data indicates that the model can be used in predicting metal load from impervious urban areas, such as streets and roadways, on a long-term basis.     

Mechanisms of metal adsorption from aqueous solutions by waste tyre rubber

The mechanisms of adsorption of cadmium(II), mercury(II) and lead(II) on to shredded rubber from old automobile types have been studied and it is shown that at least two distinct processes can be involved depending upon the metal being adsorbed. Mercury and cadmium uptake are accompanied by displacement of zinc and therefore probably involve an ion exchange type mechanism. Lead adsorption, in contrast, involves no zinc displacement and is not competitive with cadium or mercury uptake, suggesting that a completely separate mechanism and site of binding are used by lead(II).     

某选矿厂尾矿库稳定性分析与评价

通过现场勘查和室内试验充分调查了甘肃天水某尾矿库工程地质特性,定性分析了该尾矿库稳定性。然后采用Geostudio软件模拟并利用瑞典圆弧法计算分析了两种工况条件下的稳定性。     

Implications of nutrient release from iron metal for microbial regrowth in water distribution systems

Control of microbial regrowth in iron pipes is a major challenge for water utilities. This work examines the inter-relationship between iron corrosion and bacterial regrowth, with a special focus on the potential of iron pipe to serve as a source of phosphorus. Under some circumstances, corroding iron and steel may serve as a source for all macronutrients necessary for bacterial regrowth including fixed carbon, fixed nitrogen and phosphorus. Conceptual models and experimental data illustrate that levels of phosphorus released from corroding iron are significant relative to that necessary to sustain high levels of biofilm bacteria. Consequently, it may not be possible to control regrowth on iron surfaces by limiting phosphorus in the bulk water.     

A simplified equilibrium model for sorption of heavy metal ions from aqueous solutions on chitosan

The amounts of sorption of Cu2 , Ni2+, and Zn2+ from water on cross-linked chitosan were measured. Experiments were performed as a function of initial pH (2-5), total metal concentration (0.77-17 mol/m3), and metal concentration ratio (0.25-4) at 25 degrees C in single- and binary-metal systems. The sorption was so highly pH dependent that the isotherm could not be described by one specific equation. A simplified equilibrium model was thus proposed considering competitive sorption of proton and metal ions. The number of active sites on chitosan bound with one metal ion was adjustable and model parameters could be graphically determined. Given initial metal concentrations and solution pH, the proposed model could predict the amounts of sorption of proton and metals as well as the equilibrium pH. In general, application of the model parameters calculated in single-metal systems to the prediction of sorption in binary-metal systems was not satisfactory due to a remarkable effect of competitive sorption.     

Ionic liquids for extraction of metals and metal containing compounds from communal and industrial waste water

In a fundamental study the potential of ionic liquids based on quaternary ammonium- and phosphonium cations and thiol-, thioether-, hydroxyl-, carboxylate- and thiocyanate-functionalized anions has been assessed for future application in advanced sewage treatment. The elimination of the metal(oid)s Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Pt, Sn, Zn and the cancerostatic platinum compounds cisplatin and carboplatin was screened using a liquid phase micro-extraction set-up. The analytical tool-set consisted of ICP-SFMS and LC-ICP-MS for quantification of metal(oid)s and cancerostatic platinum compounds, respectively. The purity of the ILs was assessed for the investigated metal(oid)s on the base of present EU environmental quality standards and was found to be sufficient for the intended use. In model solutions at environmental relevant concentrations extraction efficiencies ≥95% could be obtained for Ag, Cu, Hg and Pt with both phosphonium- and ammonium-based ILs bearing sulphur functionality in the form of thiosalicylate and 2-(methylthiobenzoate) anions, as well as with tricaprylmethylammonium thiocyanate within an extraction time of 120 min. All other metals were extracted to a lower extent (7-79%). In the case of cancerostatic platinum compounds a phosphonium-based IL bearing thiosalicylate functionality showed high extraction efficiency for monoaquacisplatin.For the first time, liquid phase micro extraction with ionic liquids was applied to industrial and communal waste water samples. The concentration of all investigated metal(oid)s could be significantly reduced. The degree of elimination varied with the initial concentration of metals, pH and the amount of suspended particulate matter.     

冶炼企业降尘中铊等重金属的监测研究分析

选取湖南某地铅锌冶炼企业进行大气降尘中重金属监测研究分析,通过优化集尘缸内径、采样间隔时间等采样条件,监测降尘中的重金属镉、锌、铅、铊含量,计算土壤中一年内重金属新增质量比,反映涉重冶炼企业环境空气中的铊及其他重金属污染情况。结果表明,内径30cm的集尘缸降尘收集效率高于内径15cm;夏季采样间隔时间7d、冬季采样间隔时间15～30d能较客观反映企业废气中降尘量及重金属含量;试验地区大气降尘中铊的含量为208mg/kg,超出背景值340倍,其他重金属含量均值超过湖南区域背景值,大气降尘作用导致土壤中重金属铊超标的累积时间约需4年,镉超标的累积时间可能为30年以上。     

Influence of saliva medium on freeing heavy metal ion from fixed dentures

In dental-prosthetic practice, various kinds of fixed dentures, crowns and bridges, have very often been used in order to replace natural teeth and to respond to all health and esthetic needs. This study investigated the effect of saliva medium on migration of ions of heavy metals from fixed dentures that were fixed with various cements. Also, the influence of saliva medium on natural human teeth was observed. Potentiometric stripping analysis was used in order to determine the content of toxic heavy metals in the examined samples. The study confirmed that synthetic saliva had no significant influence on heavy metal ion migration from the natural teeth, whereas slight migration of some observed toxic heavy metal ions from the fixed dentures was present. This, however, indicates that these contents, although very low, must be taken seriously, because the above mentioned metals have cumulative effect which after some period of time may lead to functional disorders of some organs, and even to some very serious diseases.     

Clay mineral and heavy metal distributions in the lower estuary of Huelva and adjacent Atlantic shelf,SW Spain

The Huelva estuary, on the south-western Spanish Atlantic coast, is an environment strongly polluted by acid mine drainage and industrial effluents. Clay mineralogy, heavy metal and particle-size distribution in estuarine and adjacent shelf sediments have been analyzed in order to identify the sources and transport pathways of the contaminated sediments. The estuarine sediments consist of detrital terrigenous minerals (illite, kaolinite, quartz, feldspars, dolomite and heavy minerals) derived from river catchments and coastal erosion, with biogenic components (calcite and aragonite) and minor authigenic minerals (pyrite and possibly gypsum). Mineral distribution pattern in the estuary-shelf system is controlled by grain-size sediment, physico-chemical conditions of waters and hydrodynamic factors. Important proportions of fine-grained sediments highly enriched in sulphide-associated heavy metals are supplied by the Tinto-Odiel river system. Most of these sediments are trapped when river waters reach the estuary because of flocculation processes during estuarine mixing, thus the estuary acts as a storage basin for metallic pollutants. In terms of public health, this estuary is well above recommended safety guidelines for most metals. Although the shelf sediments show metal concentration levels close to background values, eventually, a metallic plume emerges from the estuary to ocean, and consequently elevated metal concentrations can be locally detected on the inner shelf.