Bioleaching of Heavy Metals from Textile Sludge by Indigenous Sulfur-and-Iron-Oxidizing Microorganisms Using Elemental Sulfur and Ferrous Sulfate as Energy Sources: A Comparative Study

The present study was undertaken to investigate the potential of enriched indigenous sulfur-and-iron-oxidizing microorganisms in the bioleaching of Cu, Ni, Zn and Fe from textile sludges by using elemental sulfur and ferrous sulfate (FS), respectively, as an energy source under batch conditions. The experiments were performed with three different textile sludges (S1, S2 and S3) at initial neutral pH of the sludges procured from different parts of the country i.e., UP, Haryana and Punjab. The three sludges used were not only procured from different parts of the country but also differ in physiochemical characteristics. The extent of heavy metals solubilization in each sludge was found to be different using sulfur- and iron-oxidizing microorganisms. The results of the study indicate that sulfur-oxidizing microorganisms were found more efficient in the bioleaching process, irrespective of any sludge. The use of sulfur-oxidizing microorganisms led to higher solubilization of heavy metals and after 7 days of bioleaching about 84–96% Cu, 64–78% Ni, 81–92% Zn and 74–88% Fe were removed compared to 62–73% Cu, 62–66% Ni, 74–78% Zn and 70–78% Fe using iron-oxidizing microorganisms. This study had shown the feasibility of applying the bioleaching process to textile sludge contaminated with heavy metals. The results of the present study indicate that the bioleached sludge would be safer for land application.     

Phytoextraction of heavy metals from municipal sewage sludge by Rosa multiflora and Sida hermaphrodita

The aim of the study was to evaluate the efficacy of the multiflora rose var. “Jatar” (Rosa multiflora Thunb. ex Murray) and the Virginia fanpetals (Sida hermaphrodita Rusby) to phytoextract heavy metals from municipal sewage sludge. The 6-year field experiment involved four levels of fertilization with sewage sludge at doses of 0, 10, 20, 40, and 60 Mg DM (Dry Mass) sludge ha^?1. The increasing doses of sewage sludge were found to significantly increase the yield of multiflora rose and Virginia fanpetals biomass. They also significantly increased the content of heavy metals in these plants. The highest uptake of heavy metals by the multiflora rose and Virginia fanpetals crops was recorded at the fertilization dose of 60 Mg DM ? ha^?1. Our investigations show that the Virginia fanpetals was more efficient in the phytoextraction of Cr, Ni, Cu, Zn, and Cd from the sewage sludge than the multiflora rose, due to the greater yields and higher heavy metal uptake by the former plant. In turn, the multiflora rose phytoextracted greater amounts of Pb from the sewage sludge. The analyses indicate that the Virginia fanpetals can be used for phytoremediation (phytoextraction) of heavy metals contained in sewage sludge.     

Bioleaching of heavy metals from mine tailings by indigenous sulfur-oxidizing bacteria: effects of substrate concentration

The aim of this study was to determine the effect of substrate concentration (elemental sulfur) on remobilization of heavy metals from mine tailings by indigenous sulfur-oxidizing bacteria. Also, the variation in the binding forms of heavy metals before and after bioleaching was explored. This work showed the laboratory results of bioleaching experiments on Pb-Zn-Cu mine tailings. The results showed that 97.54% Zn, 97.12% Cu, and 44.34% Pb could be removed from mine tailings by the bioleaching experiment after 13 days at 2% w/v substrate concentration. The results also indicated that substrate concentration 2% was found to be best to bacterial activity and metal solubilization of the five substrate concentration tested (0.5%, 1%, 2%, 3%, and 5%) under the chosen experimental conditions. The bioleaching had a significant impact on changes in partitioning of heavy metals.     

Effects of different sewage sludge applications on heavy metal accumulation,growth and yield of spinach (Spinacia oleracea L.)

In this study, we present the response of spinach to different amendment rates of sewage sludge (0, 10, 20, 30, 40 and 50 g kg^?1) in a greenhouse pot experiment, where plant growth, biomass and heavy metal uptake were measured. The results showed that sewage sludge application increased soil electric conductivity (EC), organic matter, chromium and zinc concentrations and decreased soil pH. All heavy metal concentrations of the sewage sludge were below the permissible limits for land application of sewage sludge recommended by the Council of the European Communities. Biomass and all growth parameters (except the shoot/root ratio) of spinach showed a positive response to sewage sludge applications up to 40 g kg^?1 compared to the control soil. Increasing the sewage sludge amendment rate caused an increase in all heavy metal concentrations (except lead) in spinach root and shoot. However, all heavy metal concentrations (except chromium and iron) were in the normal range and did not reach the phytotoxic levels. The spinach was characterized by a bioaccumulation factor <1.0 for all heavy metals. The translocation factor (TF) varied among the heavy metals as well as among the sewage sludge amendment rates. Spinach translocation mechanisms clearly restricted heavy metal transport to the edible parts (shoot) because the TFs for all heavy metals (except zinc) were <1.0. In conclusion, sewage sludge used in the present study can be considered for use as a fertilizer in spinach production systems in Saudi Arabia, and the results can serve as a management method for sewage sludge.     

异养微生物在金属生物淋滤技术中的应用

生物淋滤技术主要应用于低品位矿石金属选矿、煤气脱硫、废弃物中金属回收和污染介质中金属离子毒性的去除等方面。作为生物淋滤技术中的主体微生物之一,异养微生物可通过其产生的酸性代谢物还原、酸化及络合,提取或者溶解非硫化矿、固体废弃物、污水污泥及土壤中的金属,有助于解决目前的资源短缺问题,还可对污染环境治理提供技术支持,具有重要的理论意义和实践价值。应用于异养微生物淋滤技术中的常见微生物包括细菌(以假单胞菌为主)和真菌(以曲霉菌和青霉菌应用最为广泛)。淋滤过程涉及酸解、络合、还原及碱化等。目前,异养微生物淋滤技术主要应用于生物冶金、固体废弃物处理、污水处理和污染土壤修复等。本文分析了异养微生物金属淋滤过程中的问题,并提出了未来研究的发展方向。     

Metal Removal from Contaminated Soils Through Bioleaching with Oxidizing Bacteria and Rhamnolipid Biosurfactants

The use of surfactants as a method for solubilization and removal of heavy metal contamination from soil has been reported before. Biosurfactants produced by some microorganisms are able to modify the surface of various metals and aggregate on interphases favoring the metal separation process from contaminated environments. We evaluated the feasibility of enhancing the removal of metal ions from mineral waste/contaminated soils using alternate cycles of treatment with rhamnolipid biosurfactants and bioleaching with a mixed bacterial culture of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans. Bioleaching alone removed 50% Zn and 19% Fe. When rhamnolipids were used at low concentration (0.4 mg/mL), 11% Fe and 25% Zn were removed, while at 1 mg/mL 19% Fe and 52% Zn removal were achieved. When using a cyclic treatment combining bioleaching and biosurfactants, metal removal reached up to 36% for Fe and 63% to 70% for Zn.     

Simultaneous sewage sludge digestion and metal leaching — effect of temperature

The effect of temperature on the simultaneous sewage sludge digestion and metal leaching process was studied in laboratory bioreactors of 20 l working volume. The results thus obtained showed that the process can be employed efficiently for metal solubilization, elimination of indicator microorganisms and sewage sludge stabilization at temperatures between 10°C and 30°C. Rates of pH reduction, sulfur oxidation, growth of thiobacilli, elimination of indicator microorganisms and solids degradation were found to decrease with temperature. Low metal solubilization efficiency was observed at 10°C; however, metals were solubilized to below the recommended level. The solubilization of organic matter and nutritive elements (N, P and K) was not significantly affected by the variation in temperature. The fertilizer value of sludge after leaching and digestion did not change significantly and remained the same irrespective of temperature. *** DIRECT SUPPORT *** AG903078 00005     

Evaluation of the Biotechnological Potential of Pure and Mixture of Indigenous Iron-Oxidizing Bacteria to Dissolve Trace Metals from Cu Bearing Ore

Abstract

This study aimed to investigate the ability of pure and consortia of indigenous iron-oxidizing bacteria to enhance the dissolution of trace metals from Cu and Zn-bearing ore. Three bacterial strains Acidithiobacillus ferrooxidans strain WG101, Leptospirillum ferriphilum strain WG102, Leptospirillum ferrooxidans strain WG103 isolated from Baiyin copper mine, China were used in this study. The biotechnological potential of these indigenous isolates was evaluated both in pure and in consortia to extract cobalt, chromium, and lead from the copper and zinc bearing ore. The sulfur and iron-oxidizing bacterial isolate Acidithiobacillus ferrooxidans strain WG101 exhibited efficient dissolution compared to sole iron-oxidizing Leptospirillum ferriphilum strain WG102, and Leptospirillum ferrooxidans strain WG103. Initial medium pH, pulp density, and temperature were studied as influential parameters in bioleaching carried out by bacterial consortia. The achieved optimum conditions were; initial pH of 1.5, 10% of pulp density, and temperature 30?°C with 68.7?±?3.9% cobalt, 56.6?±?3.9% chromium, and 36?±?3.7% lead recovery. Analytical study of oxidation-reduction potential and pH fluctuation were observed during this whole process that shows the metal dissolution efficiency of bacterial consortia. Alterations in spectral bands of processed residues were reported through FTIR analysis compared with control ore sample. Mössbauer spectroscopy analysis showed the influence of bacterial consortia on iron speciation in bioleached samples. The findings confirm that the indigenous acidophilic iron-oxidizing bacterial strains are highly effective in the dissolution of trace elements present in ore samples. This study not only supports the notion that indigenous bacterial strains are highly effectual in metal dissolution but provides the basic vital conditions to upscale the bioleaching technique for metals dissolution.     

生物沥滤污泥土地利用适用性分析

研究了污泥生物沥滤对重金属(Cu、Pb和Zn)形态、营养物质和SO42-存在形式的影响,分析生物沥滤污泥土地利用的适用性。结果表明:生物沥滤后,污泥上清液中重金属通过固液分离而去除,污泥中Cu、Pb和Zn的去除率分别为84.1%、34.8%和80.0%,残存于污泥中的重金属含量大幅降低,且生物有效性低,提高了污泥土地利用的安全性。污泥经生物沥滤后氮、磷和钾的流失分别为38.2%、52.1%和42.8%,但仍能保持较好的肥效。采用X-射线衍射光谱分析发现,残留于污泥中的SO24-主要与Ca2 相结合,较为稳定,生物沥滤后的污泥施用于土地后对环境影响较小。     

Sewage sludge bioleaching by indigenous sulfur-oxidizing bacteria: effects of ratio of substrate dosage to solid content

The aim of this work was to study the effect of ratio of substrate dosage to solid content (Sd/SC) on sewage sludge bioleaching. The inocula--indigenous sulfur-oxidizing bacteria were enriched and cultured from the fresh activated sludge to a wastewater treatment plant. The results showed that Sd/SC significantly influenced the sludge bioleaching process. With increase in Sd/SC the sludge bioleaching was enhanced, which was represented by the acceleration of sludge acidification, oxidizing environment formation, and substrate (sulfur) utilization. Higher Sd/SC was more efficient to solubilize the heavy metals and total phosphorus (TP) than lower Sd/SC, while total nitrogen (TN) release was not influenced by Sd/SC. Zinc and copper were efficiently bioleached because of sludge acidification and sludge oxidation, but lead was bioleached with a low efficiency because of the formation of low soluble PbSO(4) precipitates. After bioleaching the biotoxicity of sewage sludge greatly reduced.     

Tolerance to copper and zinc of Acidithiobacillus thiooxidans isolated from sewage sludge

The effect of copper and zinc ions on sulphur oxidation by Acidithiobacillus thiooxidans, strain SFR01, isolated from anaerobic sewage sludge was assessed, resulting in tolerance levels up to 20 and 200 mmol l^–1 for copper and zinc, respectively. The tolerance levels obtained were higher than the concentration of copper and zinc usually found in the collected sewage sludge. The tolerance levels obtained indicate no constraints for sludge bioleaching of those metals due to their toxicities to the indigenous A. thiooxidans.     

Optimization and/or acclimatization of activated sludge process under heavy metals stress

The present study aimed to overcome the toxicity of the heavy metals load, discharged with the industrial effluents into Alexandria sewerage network, on the activated sludge treatment system through effective acclimation for organic matter and heavy metals removal. Optimization and/or acclimatization of the activated sludge process in the presence of Cu, Cd, Co and Cr contaminating mixed domestic-industrial wastewater was investigated. Acclimatization process was performed through abrupt and stepwise addition of tested metals using sequencing batch reactors treatment approach and evaluated as microbial oxygen uptake rate (OUR), dehydrogenase activity (DHA), organic matter (COD) and heavy metals removal. Abrupt addition of metals adversely affected sludge bioactivity leading to decline in the removal efficiency of the targeted contaminants and loss of floc structure. Metals IC₅₀ confirmed that copper possessed the highest toxicity towards the OUR, DHA activity and COD removal with orders Cu > Cd > Cr > Co; Cu > Cd > Co = Cr and Cu > Cd > Cr > Co, respectively. The highest metal removal was recorded for Cd followed by Co, Cu and finally Cr, most of which was retained in the dissolved influent. However, controlled stepwise application of the tested metals exhibited high sensitivity of DHA and OUR activities only at the highest metal concentrations although enhanced at the lowest concentrations while COD removal was not significantly affected. In conclusion, this approach resulted in adaptation of the system where sludge microbes acquired and developed natural resistance to such metals leading to remarkable enhancement of both organic matter and heavy metals removal.     

Solubilization profiles of metal ions from bioleaching of sewage sludge as a function of pH

Two patterns of solubilization of metal ions resulting from bioleaching of sewage sludge by sulphur-oxidizing Thiobacillus spp. were established as a function of pH. Chromium and copper ions required a pH of 2–3 to initiate their solubilization, whereas nickel and zinc ions had their solubilization initiated at pH 6–6.5. The patterns obtained were independent of the sludge solids concentrations investigated (10, 17, 25, 32.5 and 40 g l^–1).     

Thermophilic microorganisms in biomining

Biomining is an applied biotechnology for mineral processing and metal extraction from ores and concentrates. This alternative technology for recovering metals involves the hydrometallurgical processes known as bioleaching and biooxidation where the metal is directly solubilized or released from the matrix for further solubilization, respectively. Several commercial applications of biomining can be found around the world to recover mainly copper and gold but also other metals; most of them are operating at temperatures below 40–50 °C using mesophilic and moderate thermophilic microorganisms. Although biomining offers an economically viable and cleaner option, its share of the world´s production of metals has not grown as much as it was expected, mainly considering that due to environmental restrictions in many countries smelting and roasting technologies are being eliminated. The slow rate of biomining processes is for sure the main reason of their poor implementation. In this scenario the use of thermophiles could be advantageous because higher operational temperature would increase the rate of the process and in addition it would eliminate the energy input for cooling the system (bioleaching reactions are exothermic causing a serious temperature increase in bioreactors and inside heaps that adversely affects most of the mesophilic microorganisms) and it would decrease the passivation of mineral surfaces. In the last few years many thermophilic bacteria and archaea have been isolated, characterized, and even used for extracting metals. This paper reviews the current status of biomining using thermophiles, describes the main characteristics of thermophilic biominers and discusses the future for this biotechnology.     

Biotransformation of Heavy Metals from Soil in Synthetic Medium Enriched with Glucose and Shewanella sp. HN-41 at Various pH

The biotransformation of heavy metals from contaminated soil was examined using a facultative anaerobic bacterium Shewanella sp. HN-41. The experiments were carried out to assess the influence of glucose at various pH on the transformation of heavy metals from soil thorough solubilization. A preliminary study on the transformation of heavy metals from soil was first performed using a defined medium supplemented with glucose at 10, 20, and 30 mM to select the effective concentration. Among the three concentrations examined, glucose at 30 mM leached a highest level of metal ions. Therefore, 30 mM glucose was used as the representative carbon source for the subsequent experiments in a defined medium at various pH (5, 6, 7, 8, and 9). The organism HN-41 was not influenced by pH ranging from acidic to neutral and was able to metabolize all the metal elements from contaminated soil. The level of Fe, Cr, As, Mn, Pb, and Al solubilization ranged from 3 to 7664 mg kg^?1 at various initial pH. The rate of metal solubilization was found to be low at neutral pH compared with acidic and alkaline. These results are expected to assist in the development of heavy metal transformation processes for the decontamination of heavy metal-contaminated soil.     

Effects of Municipal Sewage Sludge Doses on the Chlorophyll Contents and Heavy Metal Concentration of Sugar Beet (Beta vulgaris var. saccharifera)

The present study was conducted to assess the suitability of sewage sludge amendment (SSA) in soil for Beta vulgaris var. saccharifera (sugar beet) by evaluating the heavy metal accumulation and physiological responses of plants grown at a 10%, 25%, and 50% sewage sludge amendment rate. The sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently increasing accumulation in plant parts. Cd, Pb, Ni, and Cu concentrations in roots were significantly higher in plants grown at 25% as compared to 50% SSA; however, Cr and Zn concentration was higher at 50% than 25% SSA. The concentrations of heavy metal showed a trend of Zn > Ni > Cu > Cr > Pb > Cd in roots and Zn > Cu > Ni > Cr > Pb > Cd in leaves. The only instance in which the chlorophyll content did not increase after the sewage sludge treatments was 50%. There were approximately 1.12-fold differences between the control and 50% sewage sludge application for chlorophyll content. The sewage sludge amendment led to a significant increase in Pb, Cr, Cd, Cu, Zn, and Ni concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency (US EPA). The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake and the leaf and root concentrations of Ni, Zn, Cd, Cu, Cr, Pb, and Zn in plants as compared to those grown on unamended soil. More accumulation occurred in roots and leaves than in shoots for most of the heavy metals. The concentrations of Cd, Cr, and Pb were more than the permissible limits of national standards in the edible portion of sugar beet grown on different sewage sludge amendment ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet may not be a good option due to risk of contamination of Cr, Pb, and Cd.     

构树的污泥适应性及养分和重金属吸收累积特征

构树是我国重要速生经济树种,具有适应性强、生物量大和重金属富集能力强等优点,而污泥中含有大量养分和重金属,在污泥中种植构树有望同时实现污泥生态修复和构树资源生产。本研究通过盆栽试验,分析在对照(赤红壤)、50%污泥(污泥、赤红壤混合基质,重量比各50%)和100%污泥基质中构树生长及不同部位(根、茎、叶)养分和重金属吸收累积特征,并通过主成分分析和隶属度函数对吸收累积能力进行综合评价。结果表明: 构树在50%和100%污泥中均可正常生长且株高、生物量显著高于对照,在100%污泥中长势最好,质量指数(1.02)分别是对照和50%污泥处理的4.3和2.4倍。50%和100%污泥处理构树各部位N含量和茎P含量显著高于对照,100%污泥处理构树茎、叶K含量显著低于对照。构树对Cu、Zn、Pb、Cd、Ni的吸收部位以根为主,根系重金属含量与污泥比例呈正相关,叶Pb、Cd含量符合《饲料卫生标准》(GB 13078—2017)。构树对Cd的吸收累积效果好于其他重金属元素。与对照相比,50%和100%污泥处理构树根部Zn、Pb、Cd滞留率显著提高(57.8%~85.8%),100%污泥处理构树根部Cu、Ni滞留率显著提高(67.5%和74.8%)。污泥处理全株养分和重金属累积量均显著大于对照,其中100%污泥处理显著大于50%污泥处理。与50%污泥处理相比,100%污泥处理构树各部位及全株养分和重金属累积量大幅提高。不同处理下构树污泥适应性和元素吸收累积的综合评价得分为100%污泥(0.848)>50%污泥(0.344)>对照(0.080)。构树对污泥具有良好的适应性,在纯污泥中能够正常生长并具有较强的吸收累积养分和重金属能力,可在修复污泥的同时进行构树资源生产。     

Diversity of Arbuscular Mycorrhizal Fungus Populations in Heavy-Metal-Contaminated Soils

High concentrations of heavy metals have been shown to adversely affect the size, diversity, and activity of microbial populations in soil. The aim of this work was to determine how the diversity of arbuscular mycorrhizal (AM) fungi is affected by the addition of sewage-amended sludge containing heavy metals in a long-term experiment. Due to the reduced number of indigenous AM fungal (AMF) propagules in the experimental soils, several host plants with different life cycles were used to multiply indigenous fungi. Six AMF ecotypes were found in the experimental soils, showing consistent differences with regard to their tolerance to the presence of heavy metals. AMF ecotypes ranged from very sensitive to the presence of metals to relatively tolerant to high rates of heavy metals in soil. Total AMF spore numbers decreased with increasing amounts of heavy metals in the soil. However, species richness and diversity as measured by the Shannon-Wiener index increased in soils receiving intermediate rates of sludge contamination but decreased in soils receiving the highest rate of heavy-metal-contaminated sludge. Relative densities of most AMF species were also significantly influenced by soil treatments. Host plant species exerted a selective influence on AMF population size and diversity. We conclude based on the results of this study that size and diversity of AMF populations were modified in metal-polluted soils, even in those with metal concentrations that were below the upper limits accepted by the European Union for agricultural soils.     

An “ex situ” microbial process for the removal of heavy metals from polluted soil: A case study of Ada rice field,Adani, Enugu State,Nigeria

An “ex situ” microbial method for the removal of heavy metals from soil is described. Elemental sulfur was added to generate the lixiviant in shaker flask experiments in which soil sampled from a polluted agricultural field was treated. The biotic oxidation of sulfur to sulfuric acid resulted in significant drop in pH of the bioleaching liquor from 6.94 to 1.8 after 50 days. In batches operated at very low (10 g/kg) sulfur concentrations, pH changed from 6.94 to 5.45. The 50 g/kg soil sulfur concentration was found to be most beneficial to the solubilization process because more than 95% of metals such as zinc (Zn), cadmium (Cd), and nickel (Ni) were recovered while approximately 67% of manganese (Mn) got solubilized. The least concentration of dissolved metals was lead (Pb) – (25%) and chromium (Cr) – (10%). Sulfate accumulation rose to 47% in samples spiked with 50 g/kg soil of sulfur. At lower sulfur concentrations, the sulfates generated were higher than the amount of sulfur added. The microbial process compared well to the abiotic process involving extraneous addition of sulfuric acid except that very high concentrations of acid had to be used. The treatment of the bioleaching wastewater promoted precipitation of the dissolved metals into insoluble hydroxides making discharge of the effluent into the environment safe. The leached soil recovered sufficiently for agricultural use after quick lime and animal manure was used to improve, stabilize, and restore its physical, chemical, and biological conditions.     

Comparative study of six different sludges by sequential speciation of heavy metals

The presence of heavy metals in the sludges produced in wastewater treatment plants restricts their use for agricultural purposes. This study looks at different types of sludge (aerobic, anaerobic, unstabilised, sludge from a waste stabilisation pond, sludge from an extended aeration plant and heat treated sludge) and compares the distribution of heavy metals with the treatment that they have undergone. In addition, the total quantity of metals (Cd, Cr, Cu, Ca, K, Fe, Mg, Ni, Na, Pb and Zn) and some agronomic parameters necessary for characterising a sludge as suitable for use as amendment were determined. The BCR method for heavy metal speciation was followed. Principal component analysis (PCA) was applied in order to obtain more information about metal speciation in the sewage sludges. It was confirmed that the concentration of heavy metals did not exceed the limits set out by European legislation and that the stabilisation treatment undergone by the sludges strongly influenced the heavy metal distribution and the phases to which they were associated. The waste stabilisation pond sludge, which has undergone a higher degree of mineralisation than the others, shows a lower metal bioavailability index since practically all the heavy metals in it are associated to the oxidisable and residual fraction. On the other hand the unstabilised sludge, which, along with that exposed to extended aeration, contains the highest accumulations of heavy metals in the most easily assimilable fractions.