Removal and recovery of metal cyanides using a combination of biosorption and biodegradation processes

Cladosporium cladosporioides biomass was a highly efficient biosorbent of copper cyanide and nickel cyanide from aqueous solutions. A 32–38 fold concentration of initial 0.5 mM metal cyanides could be achieved when biosorption process was carried out under standardised conditions. Residual, unrecoverable metal cyanide could be completely biodegraded in 5–6 h. The solution treated with the combined biosorption-biodegradation process was fit for discharge in the environment.     

Anaerobic biodegradation of cyanide under methanogenic conditions

Upflow, anaerobic, fixed-bed, activated charcoal biotreatment columns capable of operating at free cyanide concentrations of greater than 100 mg liter-1 with a hydraulic retention time of less than 48 h were developed. Methanogenesis was maintained under a variety of feed medium conditions which included ethanol, phenol, or methanol as the primary reduced carbon source. Under optimal conditions, greater than 70% of the inflow free cyanide was removed in the first 30% of the column height. Strongly complexed cyanides were resistant to removal. Ammonia was the nitrogen end product of cyanide transformation. In cell material removed from the charcoal columns, [14C]bicarbonate was the major carbon end product of [14C]cyanide transformation.     

Anaerobic biodegradation of cyanide under methanogenic conditions.

Upflow, anaerobic, fixed-bed, activated charcoal biotreatment columns capable of operating at free cyanide concentrations of greater than 100 mg liter-1 with a hydraulic retention time of less than 48 h were developed. Methanogenesis was maintained under a variety of feed medium conditions which included ethanol, phenol, or methanol as the primary reduced carbon source. Under optimal conditions, greater than 70% of the inflow free cyanide was removed in the first 30% of the column height. Strongly complexed cyanides were resistant to removal. Ammonia was the nitrogen end product of cyanide transformation. In cell material removed from the charcoal columns, [14C]bicarbonate was the major carbon end product of [14C]cyanide transformation.     

Stability of Prussian Blue in Soils of a Former Manufactured Gas Plant Site

Soil contamination with iron-cyanide complexes is a common problem at former manufactured gas plant (MGP) sites. Dissolution of the cyanide, from Prussian Blue (ferric ferrocyanide), creates an environmental hazard, whereas the risk of groundwater contamination depends on the stability of dissolved iron–cyanide complexes. Lack of a standard leaching method to determine the water-soluble (plant-available) cyanide fraction generates potential limitations for implementing remediation strategies like phytoremediation. Applicability of neutral solution extraction to determine the water-soluble cyanide fraction and the stability of Prussian Blue in surface and near-surface soils of an MGP site in Cottbus, undersaturated and unsaturated water conditions, was studied in column leaching and batch extraction experiments. MGP soils used in the long-term tests varied according to the pH (5.0–7.7) and the total cyanide content (40–1718 mg kg^?1). Column leaching, after four months of percolation, still yielded effluent concentrations exceeding the German drinking water limit (> 50 μg L^?1) and the solubility of Prussian Blue reported in the literature (< 1 mg L^?1) from both alkaline and acidic soils. Long-term (1344 h) extraction of MGP soils with distilled water was sufficient to dissolve 97% of the total cyanide from the slightly alkaline soils and up to 78% from the acidic soils. Both experiments revealed that dissolution of ferric ferrocyanide under circum-neutral pH and oxic water conditions is a function of time, where the released amount is dependent on the soil pH and total cyanide content. Unexpectedly high and continuous solubility of Prussian Blue, both in acidic and slightly alkaline MGP soils, implies the need to introduce an additional cyanide fraction (“readily soluble fraction”) to improve and specify cyanide leaching methods. Long-term extraction of cyanide-contaminated soil in neutral solution seems to be a promising approach to evaluate the potential hazard of groundwater pollution at the MGP sites.     

The role of salicylate and biosurfactant in inducing phenanthrene degradation in batch soil slurries

The majority of polycyclic aromatic hydrocarbons (PAHs) sorb strongly to soil organic matter posing a complex barrier to biodegradation. Biosurfactants can increase soil-sorbed PAHs desorption, solubilisation, and dissolution into the aqueous phase, which increases the bioavailability of PAHs for microbial metabolism. In this study, biosurfactants, carbon sources, and metabolic pathway inducers were tested as stimulators of microorganism degradation. Phenanthrene served as a model PAH and Pseudomonas putida ATCC 17484 was used as the phenanthrene degrading microorganism for the liquid solutions and soil used in this investigation. Bench-scale trials demonstrated that the addition of rhamnolipid biosurfactant increases the apparent aqueous solubility of phenanthrene, and overall degradation by at least 20% when combined with salicylate or glucose in liquid solution, when compared to solutions that contained salicylate or glucose with no biosurfactant. However, salicylate addition, with no biosurfactant addition, increased the total degradation of phenanthrene 30% more than liquid systems with only biosurfactant addition. In soil slurries, small amounts of biosurfactant (0.25 g/L) showed a significant increase in total removal when only biosurfactant was added. In soil slurries containing salicylate, the effects of biosurfactant additions were negligible as there was greater than 90% removal, regardless of the biosurfactant concentration. The results of experiments performed in this study provide further evidence that an in situ enhancement strategy for phenanthrene degradation could focus on providing additional carbon substrates to induce metabolic pathway catabolic enzyme production, if degradation pathway intermediates are known.     

Nutrient-enhanced survival of and phenanthrene mineralization by alginate-encapsulated and freePseudomonas sp. UG14Lr cells in creosote-contaminated soil slurries

The effects of nutrient amendment and alginate encapsulation on survival of and phenanthrene mineralization by the bioluminescentPseudomonas sp. UG14Lr in creosote-contaminated soil slurries were examined. UG14Lr was inoculated into creosote-contaminated soil slurries either as a free cell suspension or encapsulated in alginate beads prepared with montmorillonite clay and skim milk. Additional treatments were free-cell-inoculated slurries amended with sterile alginate beads, free-cell-inoculated and uninoculated slurries amended with skim milk only, and uninoculated, unamended slurries. Mineralization was determined by measuring¹⁴CO₂ released from radiolabelled phenanthrene. Survival was measured by selective plating and bioluminescence. Inclusion of skim milk was found to enhance both survival of and phenanthrene mineralization by free and encapsulated UG14Lr cells.     

Radiation-induced polymerization in dilute aqueous solutions of cyanides

It has been found that the addition polymerization of cyanides (HCN and NH₄CN) takes place in dilute, O₂-free irradiated aqueous solutions, in addition to the abundant formation of various smaller molecules. A polymer with a molecular mass of 16,000 amu was found. Its abundance increases with initial cyanide concentration and absorbed dose and can be up to 31% of the total amount of radiolytic products. HPLC data also indicate the presence of two more products at 22,000 amu and 10,000 amu, which are less abundant by one order of magnitude. The same molecular masses appear throughout the examined range of cyanide concentration (0.001–0.2 mol dm^–3) and absorbed dose (2–200 kGy). They remain also at large doses (up to 1250 kGy) after a complete destruction of cyanide.     

The current and future applications of microorganism in the bioremediation of cyanide contamination

Inorganic cyanide and nitrile compounds are distributed widely in the environment, chiefly as a result of anthropogenic activity but also through cyanide synthesis by a range of organisms including higher plants, fungi and bacteria. The major source of cyanide in soil and water is through the discharge of effluents containing a variety of inorganic cyanide and nitriles. Here the fate of cyanide compounds in soil and water is reviewed, identifying those factors that affect their persistence and which determine whether they are amenable to biological degradation. The exploitation of cyanides by a variety of taxa, as a mechanism to avoid predation or to inhibit competitors has led to the evolution in many organisms of enzymes that catalyse degradation of a range of cyanide compounds. Microorganisms expressing pathways involved in cyanide degradation are briefly reviewed and the current applications of bacteria and fungi in the biodegradation of cyanide contamination in the field are discussed. Finally, recent advances that offer an insight into the potential of microbial systems for the bioremediation of cyanide compounds under a range of environmental conditions are identified, and the future potential of these technologies for the treatment of cyanide pollution is discussed.     

Unpredicted impacts of insect endosymbionts on interactions between soil organisms,plants and aphids

Ecologically significant symbiotic associations are frequently studied in isolation, but such studies of two-way interactions cannot always predict the responses of organisms in a community setting. To explore this issue, we adopt a community approach to examine the role of plant–microbial and insect–microbial symbioses in modulating a plant–herbivore interaction. Potato plants were grown under glass in controlled conditions and subjected to feeding from the potato aphid Macrosiphum euphorbiae. By comparing plant growth in sterile, uncultivated and cultivated soils and the performance of M. euphorbiae clones with and without the facultative endosymbiont Hamiltonella defensa, we provide evidence for complex indirect interactions between insect– and plant–microbial systems. Plant biomass responded positively to the live soil treatments, on average increasing by 15% relative to sterile soil, while aphid feeding produced shifts (increases in stem biomass and reductions in stolon biomass) in plant resource allocation irrespective of soil treatment. Aphid fecundity also responded to soil treatment with aphids on sterile soil exhibiting higher fecundities than those in the uncultivated treatment. The relative allocation of biomass to roots was reduced in the presence of aphids harbouring H. defensa compared with plants inoculated with H. defensa-free aphids and aphid-free control plants. This study provides evidence for the potential of plant and insect symbionts to shift the dynamics of plant–herbivore interactions.     

Plasmid transfer between strains of Pseudomonas putida, and their survival, within a pilot scale percolating-filter sewage treatment system

Abstract: The effect of Pseudomonas aeruginosa UG2 biosurfactants or UG2 inocula on phenanthrene mineralization in uninoculated nonsterile soil slurries and slurries inoculated with the phenanthrene-mineralizing Pseudomonas sp. UG14r was investigated. In sandy loam and silt loam slurries amended with phenanthrene, inoculation with UG14r alone or in co-culture with UG2Lr reduced the lag period before onset of phenanthrene mineralization by 1 week. The total amount mineralized after 5 weeks was lower or not significantly different from the uninoculated control slurries. Inoculation with P. aeruginosa UG2Lr alone did not improve phenanthrene mineralization. In creosote-contaminated soil slurries, no lag period in phenanthrene mineralization was observed in any treatment. After 4 weeks, the greatest extent of mineralization was observed in creosote-contaminated soil slurries inoculated with the UG14r-UG2Lr co-culture and UG14r alone. In sandy loam and silt loam soil slurries inoculated with Pseudomonas sp. UG14r, addition of UG2 rhamnolipid biosurfactants (100 to 400 mg rhamnose equivalents (RE) · l⁻¹ slurry) inhibited phenanthrene mineralization by 10 to 15%. Mineralization was also inhibited in uninoculated sandy loam slurries. In creosote-contaminated soil slurries inoculated with Pseudomonas sp. UG14r, biosurfactants at 250 mg RE · l⁻¹ slurry enhanced mineralization whereas 400 mg RE · l⁻¹ had no effect, compared to unamended slurries. In uninoculated creosote-contaminated soil slurries, UG2 biosurfactants at 250 and 400 mg RE · l⁻¹ slurry enhanced mineralization, compared to unamended slurries.     

Examination of Thermophilic Methane-Producing Digesters by Analysis of Bacterial Lipids

Thermophilic methane-producing digesters were examined by the analysis of lipids to determine the microbial biomass, community structure, and nutritional status of the microbes within the digesters. The digesters received a daily feedstock of cattle feed and Bermuda grass, with some digesters receiving additional supplements of propionate, butyrate, or nitrate. Microbial biomass, measured as total extractable lipid phosphate, was decreased in slurries from digesters receiving continuous addition of the fermentation intermediates propionate or butyrate as compared with slurries from control digesters receiving the feedstock alone. In slurries from digesters that received continuous addition of nitrate, the microbial biomass was higher than in the slurries from control digesters. The control digesters had ca. 2.5 × 10¹¹ bacteria per g (dry weight) as determined from total extractable lipid phosphate. Shifts in microbial community structure were observed by analysis of ester-linked phospholipid fatty acids. Statistical analysis of the patterns of phospholipid fatty acids indicated that the digesters receiving different supplements could be distinguished from the control digester and from each other. Poly-β-hydroxybutyric acid, an indicator of metabolic stress, was detected in slurries from all the digesters. Slurries from the nitrate-amended digester had the highest concentration of poly-β-hydroxybutyric acid, whereas slurries from the propionate-amended digester had the lowest concentration. These chemical analyses offer a quantitative means to correlate shifts in microbial biomass, community structure, and nutritional status in complex fermentation systems to the production of a specific end product.     

氰化物污染的植物修复可行性研究

氰化物是目前世界范围内最常使用的提取黄金和白银等贵重金属的沥滤剂,其对自然生态环境的污染和破坏以及对人畜和其它生物的毒性作用是众所周知的.本试验用一自行设计的生物反应器来观察黄豆(Glycine max(L)Merr.)和玉米(Zea mays L.)对氰化物污染土壤的原位修复的可能性.室温条件下(23.0～26.0℃),低浓度的氰化物污染液对(≤45.5 CN mg·L^-1)二种测试植物的生长没有产生任何毒性作用;而在高浓度的氰化物试验组(≥91.0 CNmg·L^-1),二种测试植物的生长都出现了明显的滞长现象(生长率下降大于10%),但没有观察到其它毒性反应.同时二种测试植物的叶片细胞用来测定植物细胞线粒体中的氰丙氨酸合成酶(β-cyanoalanine synthase)转化氰化物的潜力.实验是在一封闭的玻璃器皿(100mL)中进行的(100mL的氰化钾溶液中加入1.5g(鲜重)植物的叶片,氰化钾溶液的浓度大约1.0 CNmg·L^-1).在为期28 h的时间内,水溶液中超过90%的氰化物被植物的叶片去除;黄豆和玉米的的叶片细胞对氰化物去除率分别测定为4.43mg CN·kg^-1(鲜重)·h^-1和3.42mg CN·kg^-1(鲜重)·h^-1.本实验结果表明,植物对氰化物污染的土壤原位修复方法是一种可行的和有效的选择.     

Removal of metal cyanides from aqueous solutions by suspended and immobilized cells of Rhizopus oryzae (MTCC 2541)

This paper presents a study on biodegradation and simultaneous adsorption and biodegradation (SAB) of zinc and iron cyanides by Rhizopus oryzae (MTCC 2541), with a brief process review. Granular activated carbon was used for the immobilization of Rhizopus oryzae (MTCC 2541) for the SAB study. pH and temperature were optimized at an initial cyanide concentration of 100 mg/L for biodegradation and SAB. The microbes adapted to grow at maximum cyanide concentration were harvested and their ability to degrade cyanide was measured in both biodegradation and SAB. The removal efficiency of the SAB process was found to be better as compared to the biodegradation process. In the case of biodegradation, removal was found up to a maximum cyanide concentration of 250 mg CN^?/L for zinc cyanide and 200 mg CN^?/L for iron cyanide, whereas in the case of SAB, about 50% removal of cyanide at 400 mg CN^?/L zinc cyanide and 300 mg CN^–/L iron cyanide was possible. It was found that the SAB process is more effective than biodegradation.     

Use of Fenton's Reagent for the Degradation of TCE in Aqueous Systems and Soil Slurries

Fenton's reaction is comprised of hydrogen peroxide (H₂O₂) catalyzed by iron, producing the hydroxyl radical (·OH), a strong oxidant. ·OH in turn may react with H₂O₂ and iron and is capable of destroying a wide range of organic contaminants. In this laboratory study, Fenton's reaction was observed in aqueous and soil slurry systems using trichloroethylene (TCE) as the target contaminant, with the goal of maximizing TCE degradation while minimizing H₂O₂ degradation. Fenton's reaction triggers a complex matrix of reactions involving ·OH, H₂O₂, iron, TCE, and soil organics. In soil slurries with a high fraction of organic carbon (f_OC), iron tends to sorb to soil organics and/or particles. In aqueous systems the optimal ratio of H₂O₂:Fe²⁺:TCE to degrade TCE in a timely fashion, minimize costs, and minimize H₂O₂ degradation is 300?mg/L: 25?mg/L: 60?mg/L (19:1:1 molar ratio), while soil slurries with a f_OC up to approximately 1% and a soil:water ratio of 1:5 (weight ratio) require about ten times the amount of H₂O₂, the optimal ratio being 3000?mg/L: 5?mg/L: 60?mg/L (190:0.2:1 molar ratio). TCE degradation rates were observed to decrease in soil slurries with higher f_OC because of competition by soil organic matter, which appears to act as a sink for ·OH. H₂O₂ degradation rates tended to increase in soil slurries with higher f_OC, most likely due to increased demand for ·OH by soil organics, increased available iron and other oxidation processes.     

Effect of HRT on the biological pre-denitrification process for the simultaneous removal of toxic pollutants from cokes wastewater

A lab-scale serial anoxic-aerobic reactor for the pre-denitrification process was continuously operated to efficiently and economically treat actual cokes wastewater containing various pollutants, such as phenol, ammonia, thiocyanate and cyanide compounds. The biodegradation efficiencies of the pollutants were examined by changing hydraulic retention time (HRT) as a main operating variable. The long-term operation of the pre-denitrification process reactor showed that approximately 100% phenol, approximately 100% free cyanide, approximately 100% SCN(-), 97% ammonia, 85% COD, 84% TOC (total organic carbon) and 83% TN (total nitrogen) were removed at HRT above 11.9h. Removal efficiency of total cyanides significantly decreased with a decrease in the HRT. Free cyanide and some of total cyanides were removed in anoxic reactor, whereas thiocyanate was removed in aerobic reactor. Phenol was completely removed under successive anoxic and aerobic conditions. Although actual cokes wastewater contained high concentrations of various toxic pollutants, the pre-denitrification process showed stable and successful performances in both nitrification and denitrification reactions.     

Complex formation between the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and valinomycin in the presence of potassium

Spectroscopic evidence is presented which indicates that the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and the peptide antibiotic valinomycin form a complex in the presence of potassium. Complex formation has been observed both in aqueous and nonaqueous media. Several techniques have been used to indicate the existence of a complex in aqueous solution. In the presence of valinomycin and K+, the absorption spectrum of FCCP is significantly perturbed, and there is also a large induced circular dichroism signal. In addition, the previously characterized complex which forms between valinomycin, K+, and the fluorescent probe 8-anilino-1-naphthalene-sulfonate (ANS) in aqueous solution is apparently disrupted by the addition of FCCP. The result is an effective quenching of the fluorescence due to the bound probe as it is displaced from the valinomycin.K+ by the uncoupler. In a nonpolar solvent, the absorption spectrum of FCCP is also perturbed by valinomycin in the presence of K+, again indicating the formation of a complex. These data point to the importance of considering the role of valinomycin.K+.uncoupler complex in interpreting physiological or ion transport data in which these substances have been used together.     

Biotreatment of hydrocarbons from petroleum tank bottom sludges in soil slurries

Summary Biotreatment of oil wastes in aqueous slurries prepared with sandy loam soil and inoculated with selected soil cultures was evaluated. After 90 days, oil removal was 47%. Removal of each hydrocarbon class was 84% for saturates, 20% for aromatics, and 44% for asphaltenes. Resins increased by 68%. The use of a soil with a lower level of fine particles or minor organic matter content, or reinoculation with fresh culture did not improve oil elimination. Residual oil recovered from slurries was biotreated. Oil removal was 22%. Slurry-phase biotreatment showed less variability and faster oil removal than solid-phase biotreatment.     

Free Cyanide Sorption on Freshwater Sediment and Model Components

The sorption of free cyanide (HCN) on mineral components of sediment, activated carbon, and a freshwater sediment was studied via batch experiments in synthetic freshwater at pH 6.4–7.6. It was found that free cyanide did not sorb to any significant extent on sediment mineral components, but did sorb strongly to activated carbon and moderately to a freshwater sediment. Results of experiments with 100 and 150 μ g/L free cyanide spike amounts resulted in no observed sorption to kaolin clay, Ottawa sand, or alumina in the synthetic freshwater. Extensive removal of free cyanide from the aqueous phase was observed in the partitioning experiments with the powdered activated carbon. Results with whole sediment indicated up to 46% removal of free cyanide from the aqueous phase in experiments with 20 and 50 μ g/L free cyanide. The organic-carbon-normalized distribution coefficient K_oc (= C_s/C_wf_oc) for free cyanide sorption on the activated carbon (f_oc = 1.0), 4.2 L/g_s, was similar to the K_oc value for free cyanide sorption on the freshwater sediment (f_oc = 0.0031), approximately 12.9 L/g_s. The results indicate that free cyanide can sorb to sediments with organic carbon content under freshwater conditions, primarily through interaction of HCN with organic carbon in the sediment.     

Bioaugmentation of cyanide-degrading microorganisms in a full-scale cokes wastewater treatment facility

To enhance biological removal efficiency of total cyanides, bioaugmentation was applied to a full-scale cokes wastewaters treatment process. After a laboratorial-scale cultivation (up to 1.2 m(3)) of a cyanide-degrading yeast (Cryptococcus humicolus) and unidentified cyanide-degrading microorganisms, the microbial consortium was inoculated into a fluidized-bed type process (1280 m(3)), and then enriched for two months with a huge supply of glucose, KCN and other nutrients. Target wastewater was effluent of a biological pre-denitrification process for treating cokes wastewater, and contained about 14 mg/L of total cyanides in the form of ferric cyanide. This may be a first or rare report on the full-scale bioaugmentation of specialized-microorganisms. However, continuous operation of the full-scale cyanides-degrading bioprocess showed poor removal efficiency than expected owing to poor settling performance of microbial flocs, slow biodegradation rate of ferric cyanide and lack of organic carbon sources within the wastewater. Therefore, there is a need for further studies on how to solve these operating problems in full-scale bioaugmentation approach.     

黑河中游荒漠绿洲区土地利用的土壤养分效应

土地利用影响地表覆被状况和生态过程,关系到土壤肥力与土壤碳库功能"源-汇"关系的改变。黑河中游甘州区和临泽县是我国西北干旱区典型的荒漠绿洲区,以土壤表层(0-20 cm)养分变化为对象,利用2011-2012年甘州区和临泽县的土壤野外调查数据和该区全国第二次土壤普查数据,对两时期土壤表层养分(土壤有机质、全氮、全磷、全钾及pH值)的变化特征进行比较研究。结果表明:研究区土壤有机质、全磷含量分别降低了3.54%和12.5%;而全氮、全钾和pH值分别增加了74.4%、98.2%和4.9%。全国第二次土壤普查时期,荒漠、耕地与草地三者在各土壤养分上没有显著差异,但林地在土壤有机质、全氮、全钾上显著高于前三者。2011-2012年,耕地土壤的全磷、全氮与其它土地利用存在显著差异。土地利用的保持和改变对土壤养分变化有着重要影响,耕地的长期耕作使得土壤有机质含量降低4.94%,全氮增加86.93%,全磷减少5.02%,土壤碱性增强;荒漠植被的自然演替使土壤有机质含量增加66.21%,全氮增加71.70%,全磷含量减少37.33%,土壤碱性变弱。所以,耕地扩张及其长期耕作活动将导致地力退化并有盐碱化风险,而荒漠等自然生态系统保护有利于土壤肥力的改善和土壤固碳功能的发挥。