Bioleaching of heavy metals from wastewater sludge by ferrous iron oxidizing bacteria

Experiments on bacterial leaching of heavy metals from aerobically stabilized surplus activated sludge at the Bortnichi aeration plant in Kiev have been conducted with addition of FeSO₄ ? 7H₂O as a stimulant of iron-oxidizing bacteria. The mechanism of heavy metal leaching involving the ferrous iron oxidation by bacteria with subsequent formation of Fe(OH)₃ was confirmed. This process is accompanied by the reduction of pH level of wastewater sludge that results in leaching of heavy metals.     

Partitioning variation of heavy metals in contaminated river sediment via bioleaching: effect of sulfur added to total solids ratio

The aim of this study was to determine the effect of the ratio of sulfur added to total sediment solids (SA/TS) on the remobilization of heavy metals from contaminated river sediment by indigenous sulfur-oxidizing bacteria. Also, the difference in metal binding fractions before and after bioleaching was explored.It was found that sediment pH decreased at a significantly faster rate at higher SA/TS ratios (0.413 and 0.199) than at lower ones. Sulfate concentrations increased at a faster rate at these higher SA/TS ratios. At the lower SA/TS ratios, more acid must be produced and therefore it took more time for sulfur-oxidizing bacteria to lower the sediment pH. Remobilization efficiency of total extractable Pb and Cr was significantly higher at higher SA/TS ratios. After bioleaching, Mn-oxides became a stronger binding pool, and the percentage of Pb and Zn bound to Mn-oxides and Cr and Cu bound to organic matter increased with the decrease of SA/TS. Different heavy metals showed different binding behavior at the various SA/TS ratios.     

Bioleaching of heavy metals from sludge after biological treatment of municipal effluent

The article has compared the efficiency of removing heavy metals from the sludge after biological treatment of municipal wastewaters in the course of biological leaching involving heterotrophic and chemotrophic microorganisms and chemical leaching. The article also showed advantages of the bioleaching of metals under conditions of acidogenic heterotrophic metabolism. The efficiency of the leaching of heavy metals from the sludge varies 80% (Zn) to 15% (Cr) and corresponds to the following series: Zn > Mn > Cu > Ni > Cd > Pb > Cr.     

Mobilization of heavy metals from Le An River sediment

The release of sediment-bound heavy metals can have a significant influence on river water quality. Generally speaking, variations of pH and oxygen are among the most important chemical factors that affect the mobility of sediment-bound metals. Recent research has indicated that sulfide, measured as acid-volatile sulfide (AVS), is an important partitioning component of heavy metals. We determined the metal release potential of sediments from the Le An River which receives drainage from a major copper mining operation. We found that the in-situ Cu, Pb, Zn, Cd and As concentrations of the Le An River sediments below the mine are much higher than are the global background values, but that Ni was not elevated. There is potential for mobilization of bound metals to the overlying water, the order of metal release ratio in terms of pH dependencies is Zn > Cu > Cd approximately Pb. Sulfide is not a major binding component for metals in Le An River sediment. It is more likely that the iron and manganese oxides are the most important metal binding components in the sediments of the Le An River.     

Distribution of heavy metals in the sediment of an unpolluted estuarine environment

The distribution of cadmium, cobalt, copper, lead, manganese, mercury, nickel and zinc in the sediments of Urr Water, an estuary relatively free of industrial and sewage pollution, has been investigated.The aim of this study was to provide baseline information for comparison with similar geochemical areas which are subject to pollution.     

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.     

Bioleaching of metals from sewage sludge: Microorganisms and growth kinetics

Microbial leaching is one of the advantageous methods of removing heavy metals from sewage sludge, however, the microbiological aspects of this technology have not been studied. This study presents the characterization of the naturally occurring microorganisms, responsible for the metal leaching activity, in 21 different sewage sludges. The results obtained indicate that the bioleaching of metals is carried out by successive growth of less-acidophilic and acidophilic thiobacilli. Several species of less-acidophilic thiobacilli participate in the sludge acidification, but Thiobacillus thioparus is the most important species. In contrast, Thiobacillus thiooxidans seems to be the only species involved in the acidophilic group of thiobacilli. The growth kinetics of the two groups of thiobaciili was followed in five different sewage sludges. After 5 days of incubation in shake flasks, the pH of the sludge was decreased to about 2.0 and this pH decrease solubilized the toxic metals (Cd: 83–90%; Cr: 19–41%; Cu: 69–92%; Mn: 88–99%; Ni: 77–88%; Pb: 10–54%; Zn: 88–97%). The maximum specific growth rate (μ_max) for the less-acidophilic thiobacilli varied between 0.079 and 0.104 h⁻¹ and that for the acidophilic thiobacilli varied between 0.067 and 0.079 h⁻¹.     

Effect of temperature on removal of heavy metals from contaminated river sediments via bioleaching

The aim of this study was to determine the effect of temperature on the solubilization of heavy metals from contaminated river sediment by sulfur oxidizing bacteria taken from Ell-Ren River sediment. Of three temperatures tested (25 degrees C, 37 degrees C and 55 degrees C), pH decrease was greatest at 37 degrees C, indicating that, after acclimation, bacterial oxidizing activity is greatest at this temperature. At 55 degrees C, pH change was similar to that which occurred with no inoculum added. The increase in sulfates and high pH at 55 degrees C indicate that the indirect mechanism was not initiated at this temperature. Solubilization efficiency of total extractable Ni, Zn, Cu and Cr was high (>90%) at 37 degrees C, whilst that of Pb was only 60.4%. Except for Pb, the optimal temperature for solubilization of total extractable heavy metal was 37 degrees C. The order of average solubilization efficiency of total extractable heavy metals was Ni, Zn, Cu>Cr>Co, Pb. The solubilization efficiency of Pb and Co was markedly less than that of other heavy metals. Transfer of heavy metals between binding fractions was most apparent at 55 degrees C before and after bioleaching.     

Spatial distribution of arsenic and heavy metals in willow roots from a contaminated floodplain soil measured by X-ray fluorescence spectroscopy

Under changing redox conditions some plants create plaques at their root surface, which may affect the mobility and uptake of As and heavy metals but it is unknown to what extent this also holds true for willows in contaminated floodplain soils. Therefore, willow roots were sampled from a phytoremediation trial in the contaminated floodplain of the river Elbe (Germany), cryofixed, freeze-dried, and cross sections were mapped for the distribution of As, Ca, Cu, Fe, K, Mn, Ni, S and Zn by synchrotron based X-ray fluorescence spectroscopy. The elements Ca, Cu, Ni, S and Zn were concentrated in the aerenchymatic tissue, and not associated with Fe and Mn. Mixed Fe-Mn plaques covered the surface of the willow roots and As was accumulated in these plaques. The observed association pattern between As and Fe was explained by the different sorption/desorption properties of As(III) and As(V). The Cu and Zn intensities were not associated with the intensity of Fe in the plaque, which seems to be a willow-specific difference compared to other wetland plants. These results suggested that willows are especially suited to stabilize low-phytoextractable elements like Cu and As in their roots and rhizosphere. Thus, short rotation coppicing of willows may be a practical approach to mitigate the adverse effects of floodplain soil contamination.     

Chelate-assisted phytoextraction of heavy metals in a soil contaminated with a pyritic sludge

The occurrence of many polluted areas as that affected by the accident of the Aznalcóllar pyrite mine has promoted phytoremediation as a technology able to reduce the risk of heavy metal contamination at low cost. White lupin plant has been considered a good candidate for phytoremediation. We studied the capacity of several complexing agents to improve the ability of white lupin for heavy metal phytoremediation in soils with multi-elemental pollution from acid pyritic sludge. Solution-soil interaction was studied and pot experiments with sludge-affected soil were carried out to this end. The interaction experiments indicated that EDTA and NTA were more efficient than malate and citrate in solubilizing metals (Fe, Mn, Cu, Zn, Cd), with minimum differences between EDTA and NTA. The pot trial showed that NTA was able to mobilize toxic elements from sludge-polluted soil and hence increasing their concentrations in plant (Mn, Cu, Zn, As, Cd). However, the NTA treatment promoted an increase of toxic elements concentrations, especially for As, Cd, Pb, in the lixiviates exceeding the maximum permissible levels, so a careful management of chelate is necessary.     

The uptake of heavy metals by epiphytic bacteria on Alisma plantago-aquatica

Bacterial epiphytes on the surface of the fresh-water plant Alisma plantago-aquatica collected from a polluted river were found to be a major factor in contributing to the total metal concentrations of the plant. The removal of epiphytes from the leaf surface resulted in significant reductions in the concentrations of Cr (reduced by 15–50%), Cu (30–35%), Fe, Pb, and Zn (10–50%). While numbers of epiphytes and concentrations of heavy metals increased in samples collected from polluted water compared with from unpolluted water, the fraction of metals held by the epiphytes appeared to remain similar for all samples.     

Bioremoval of arsenic species from contaminated waters by sulphate-reducing bacteria

A mixed culture of sulphate-reducing bacteria was used to study the bioremoval of arsenic species (As(III) or As(V)) from groundwater. During growth of a mixed SRB culture adapted to 0.1 mg/L arsenic species through repeated sub-culturing, 1 mg/L of either As(III) or As(V) was reduced to 0.3 and 0.13 mg/L respectively. Sorption experiments on the precipitate produced by batch cultured sulphate-reducing bacteria (SRB-PP) indicated a removal of about 77 and 55% of As(V) and As(III) respectively under the following conditions: pH 6.9; biomass (2 g/L); 24 h contact time; initial arsenic concentration, 1 mg/L of either species. These results were compared with synthetic iron sulphide as adsorbent. The adsorption data were fitted to Langmuir and Freundlich isotherms. Energy dispersive X-ray analysis showed the SRB-PP contained elements such as sulphur, iron, calcium and phosphorus. Biosorption studies indicated that SRB cell pellets removed about 6.6% of the As(III) and 10.5% of the As(V) from water containing an initial concentration of 1 mg/L of either arsenic species after 24 h contact.     

Removal of heavy metals from aqueous solutions by hydrogels

The results of the removal of Cu (II) and Fe (III) heavy metals from individual, mixed solutions and natural water by means of hydrogels sorption are provided. Copolymer acrylic hydrogels and agar-agar were used. It was found that sorption of heavy metals occurs synchronously with the hydrogels swelling. The efficiency of heavy metals removal (up to 99% for individual solutions with the 2 mM concentration, and up to 95% for natural water) and strength of its retention are maximum for copolymers of acrylamide and acrylic acid.     

Disposal of heavy metal‐contaminated sediment from Ulsan Bay,South Korea: treatment processes and legal framework

The effectiveness of two different management schemes to dispose of heavy metal‐contaminated sediments from Ulsan Bay, South Korea, soil washing and solidification/stabilization, were evaluated through a series of analyses. NaOH proved to be an effective washing reagent for As, extracting 75% of the As in sediment samples. EDTA was found to significantly enhance the extraction of Cu, Pb and Zn. However, complete removal of any metals was not achieved even after application of 100 mM concentrations of washing reagents. Therefore, a solidification/stabilization technique was applied to dredged sediment samples using ordinary Portland cement (1–40%) and fly ash (～20%). Solidified sediments did not release meaningful amount of the metals via leaching tests. Our results suggest that solidification/stabilization is a better option for effective disposal of heavy metal‐contaminated sediments than soil washing. A legal framework for the treatment of hazardous wastes and contaminated soils in Korea is discussed.     

Simulation analysis of the concentration process of trace heavy metals by aquatic organisms from the viewpoint of nutrition ecology

This paper describes the importance of a food chain to estimate the concentration of heavy metals from the viewpoint of nutrition ecology.The experiments were performed to investigate the effects of the following experimental conditions on the uptake of heavy metals by a predator, using ¹³⁷Cs as a tracer; ration size per day, feeding interval and the change in weight of the predator fish. Top minnows (Oryzias latipes) were used as preys and Golden astro (Astronotus ocellatus) as predators. The preys were raised without feeding in an aquarium and the predators were fed top minnows.The set of results showed that (1) the concentration of a metal in predator fish increased with the ration size, (2) the feeding interval had no effect on the uptake of the metal by fish under the experimental conditions performed, and (3) the concentration in the growing fish was suppressed increasing in value with the increase of its weight. They suggest the importance of generalization of the experimental food conditions when the study on the concentration process of heavy metals through a food chain is performed. The paper also deals with the compartment model applied to the concentration process of the metal by a fish. The theoretical results depicted well the experimental ones.     

The vertical distribution of some heavy metals in three recent sediment cores from the Western Nigerian continental shelf

Results of trace metal analyses of three shallow sediment cores from the Nigerian continental shelf show homogeneities with respect to the vertical distributions of Pb, Ni, Cr and Cu. However, surface enrichment of heavy metals which results from human activities particularly, from Lagos city, is recognised in the uppermost few centimeters in core 12 nearest to the entrance of Lagos harbour. Sediments below this surface enrichment zone, and in the entire lengths of the other two cores which are situated farther east of Lagos port, show heavy metal contents that are more or less constant in vertical distribution with depth.     

Solubility of metals in an anoxic sediment during prolonged aeration

This work was conducted to study the evolution of the solubility of selected metals during the aeration of an anoxic sediment. Batch experiments were carried out for 76 days with a metal-polluted dredged sediment. The pH, Eh and concentration of Al, Cu, Fe, Hg, Pb and Zn were periodically recorded. Results showed that during the early stages of aeration, the solubility of metals increased rapidly but was then followed by fast re-adsorption. As a consequence, after 14 days most of the metals excepted Cu and Zn were present at low or undetectable concentrations in solution. Re-adsorption of Zn was observed to be much slower during the first two weeks, whereas solubilisation of Cu increased gradually during months after land disposal. According to speciation calculations, Cu solubilisation was in part due to complexation in solution by carbonates. In the case of Hg, although complexation by dissolved organic matter (DOM) could be expected, re-adsorption was the dominant process. However, more knowledge about the behaviour of the DOM present in anoxic sediments is needed in order to make more quantitative statements about the mobility of heavy metals contained in dredged material.     

Removal of heavy metals from waters by means of natural zeolites

The natural zeolite clinoptilolite can be used as an ion exchanger for the removal of ammonium ions from drinking waters. These waters may also contain small amounts of heavy metals. The retention possibilities of these cations by the zeolite are presented.

The study of the selectivity of the Na-exchanged clinoptilolite in presence of ammonium ions has been achieved by plotting the exchange isotherms relative to the various cations. This leads to the following order of decreasing efficiency of the zeolite.     

Uptake of organic xenobiotics by benthic invertebrates from sediment contaminated by the pulp and paper industry

Uptake of pulp and paper mill-derived pollutants by benthic invertebrates from sediment in Southern Lake Saimaa, eastern Finland, was studied. Two groups of benthic invertebrates (Diptera and Oligochaeta) were analyzed for their concentrations of resin acids (RAs), chlorophenolics (CPs) and beta-sitosterol. The samples were collected 1 and 3km downstream from the mill. In laboratory experiments Chironomus plumosus (a dipteran) and Lumbriculus variegatus (oligochaete) were exposed for 14d to sediments collected from the same locations. The concentrations of RAs, CPs and beta-sitosterol were higher in the areas downstream from the mill than those in the upstream reference area in both the feral and laboratory-exposed animals. Examination of the possible conjugation of contaminants revealed hydrolyzable fractions of RAs in Diptera, C. plumosus and L. variegatus. The results indicate both the bioavailability uptake of contaminants and uptake by benthic fauna when exposed to pulp and paper mill-contaminated sediment.     

Selective heavy metals removal from waters by amorphous zirconium phosphate: behavior and mechanism

Selective removal of heavy metals from water has been of considerable concern for several decades. In the present study, the amorphous zirconium phosphate (ZrP) was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron micrography (SEM), thermogravimetric analysis (TGA) as well as pH-titration experiments. Uptake of heavy metals including lead, cadmium, and zinc onto ZrP was studied by using a polystyrene sulfonic-acid exchanger D-001 as a reference sorbent and Ca(2+) as a competing cation due to its ubiquity in natural or industrial waters. The results indicated that the uptake of heavy metals onto ZrP is essentially an ion-exchange process and dependent upon solution pH. In comparison with D-001, ZrP exhibited more favorable sorption of heavy metals particularly in terms of high selectivity, as indicated by the distribution coefficients of ZrP even several orders higher than D-001 towards heavy metals when calcium ion coexisted at a high level in solution. The Fourier transform-infrared (FT-IR) spectroscopic investigation indicated that the uptake of calcium, cadmium, and zinc ions onto ZrP is only driven by the electrostatic interaction, while that of lead ion is possibly dependent upon the inner-sphere complex formation with ZrP. XPS results further elucidated that ZrP displays different sorption affinity towards heavy metals in the same order as selectivity sequence of Pb(2+)>Zn(2+) approximately Cd(2+)>Ca(2+), which can be explained by hard and soft acids and bases (HASB) theory. Moreover, uptake of heavy metals onto ZrP approached to equilibrium quickly and the used ZrP could be readily regenerated for reuse by the dilute HCl solution. Thus, all the results suggest that amorphous ZrP has excellent potential as a sorption material for water treatment.