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Biodegradation of cyanide containing effluents by Scenedesmus oblipus
Abstract
Biological degradation of cyanide has been shown a viable and robust process for degrading cyanide in mining process wastewaters. Several algal cultures can effectively degrade cyanide as carbon and/or nitrogen source for their growth. In this study, cyanide effluent degradation by Scenedesmus obliquus was examined. Gold mill effluents containing WAD cyanide concentration of 77.9mg/L was fed to batch unit to examine the ability of S. obliquus for degrading cyanide. Cyanide was reduced down to 6mg/L in 77h. Microbial growth and metal uptake of Zn, Fe and Cu was examined during cyanide degradation. The cells well adapted to high pH and the effluent contained cyanide and the metals. It is important that Zn level reduced down 50%, of the starting concentration. pH was kept at 10.3 to prevent loss of cyanide as HCN, due its volatile nature. The bio treatment process was considered to be successful in degrading cyanide in the mine process water.
... Physico-chemical treatments present some A C C E P T E D M A N U S C R I P T disadvantages including generation of harmful by-products, high operational costs, and difficulty of maintenance [3,11,12]. On the other hand, biological treatments are efficient, economical, and environmentally friendly [1,2,4,[12][13][14][15][16]. ...
... hydrolytic, oxidative, reductive, or substitution/transfer) [15,22] use CNas a nitrogen source [2,3,12,17], with the presence of an additional carbon source (e. g. glucose, fructose, sodium acetate, or whey) for their growth [10,12,14,[18][19][20][21]. Nonetheless, our research group has demonstrated the feasibility of a microbial consortium (containing Bacillus sp.) able to form a biofilm, which tolerates and biodegrades high concentrations of free cyanide ([CN − ] = 0.3g/L) as a sole carbon and nitrogen source [23]. ...
... and Chuamkaew[15] reported a 90% biological removal when [CN] i = 0.04g/L, Jumbo and Nieto[19] obtained a 85.63% biological removal when ...
In this study we modeled and simulated biofilm growth and free cyanide biological removal from gold mine wastewater using a bench-scale rotating biological contactor (RBC). Eight batch cultures were run in three independent compartments (1.7 L, each) of the RBC. The system worked under the following conditions: [CN-] = 0.3 g/L, pH = 10.5 ± 0.5, T = 20 ± 5 °C, ω = 5 rpm, and 40.5% of disc submersion. During each culture, biofilm thickness, biomass, and free cyanide concentration in the liquid were quantified. Subsequently, umax, KCN-, Y' x/CN-, qmax, b', Df, k, and JCN-, were determined using experimental data to later model and simulate the biofilm thickness and free cyanide biological removal with Wolfram Mathematica software. After the experiments, free cyanide biological removal was 96.33% after three days, and maximum biofilm thickness was 0.0292 cm in the 16th day. Moreover, biofilm growth and free cyanide consumption models adjusted to the experimental data with r2 = 0.90 and r2 = 0.99. Also, there was an equivalent error of 7.89 and 7.38 and a standard deviation of 10.89% and 10.17%, between the models and their experimental data, respectively. Finally, the proposed models will allow to improve reactor operation and its design.
... Commonly employed methods for cyanide gas elimination include absorption [9], adsorption [10], and combustion [11,12]. In this paper, we review currently implemented Commonly employed methods for cyanide gas elimination include absorption [9], adsorption [10], and combustion [11,12]. ...
... Commonly employed methods for cyanide gas elimination include absorption [9], adsorption [10], and combustion [11,12]. In this paper, we review currently implemented Commonly employed methods for cyanide gas elimination include absorption [9], adsorption [10], and combustion [11,12]. In this paper, we review currently implemented cyanide gas elimination methods. ...
Cyanide gas is highly toxic and volatile and is among the most typical toxic and harmful pollutants to human health and the environment found in industrial waste gas. In the military context, cyanide gas has been used as a systemic toxic agent. In this paper, we review cyanide gas elimination methods, focusing on adsorption and catalysis approaches. The research progress on materials capable of affecting cyanide gas adsorption and catalytic degradation is discussed in depth, and the advantages and disadvantages of various materials are summarized. Finally, suggestions are provided for future research directions with respect to cyanide gas elimination materials.
... On the other hand, Akinpelu et al. (2016) and Gurbuz et al. (2009) conducted studies on the biodegradation of cyanide complexed with metals; it should be noted that both worked under alkaline conditions (11 and 10 units, respectively) and at a temperature of 22-25 °C. Akinpelu et al. (2016) used a fungus (Fusarium oxysporum) and an initial cyanide concentration of 100 mg·L −1 , while the metals analyzed in this case were arsenic (7.1 mg·L −1 ), iron (4.5 mg·L −1 ), copper (8 mg·L −1 ), and lead and zinc (0.2 mg·L −1 ); the concentration of iron was lower than that used in the present study and that of copper higher; however, nickel was not studied. ...
... The results showed removals of 77% giving final cyanide concentrations of 13 mg·L −1 , which is higher than that obtained in the present study. In the study by Gurbuz et al. (2009), using the alga S. obliquus, no removal was obtained when cyanide (77 mg·L −1 ) was complexed with 0.65 mg·L −1 of copper (a slightly higher concentration than that used in the present study), while when working with an initial concentration of iron of 4 mg·L −1 , the removal was 63%. ...
Mexico is the top producer of silver and is on the eighth place from producing gold in the world. For instance, the hydrometallurgical extraction process produces wastewater (mining tailing) characterized by being composed with varying concentrations of cyanide and heavy metals. The purpose of this research was to study the biodegradation of cyanide contained in mining tailings by means of a bacterial consortium isolated from a tailings dam. For this purpose, three types of Eckendfelder reactors were used, one with suspended biomass (BS) and two moving bed biofilter reactors, one with biomass immobilized on Kaldnes (BK) supports, and the other on polyurethane cubes (BCP). Three experimental stages were worked; in each of them, the concentrations of total cyanide were varied. In the first one, it was 26 ± 2 mg·L⁻¹; in the second one 40 ± 4 mg·L⁻¹; and the third one 55 ± 4 mg·L⁻¹. During the whole operation, the pH and temperature were maintained at 9.5 units and 25 °C. After 141 days of operation, biodegradation of the total cyanide contained in the mining tailings was 69% (17 mg·L⁻¹) in the BS reactor, while in the BK reactor, it was 93% (3.9 mg·L⁻¹) and in the BCP reactor 95% (2.5 mg·L⁻¹). The predominant families in each of the reactors, as well as their respective relative abundances, were for the BS and for the BK of Cyclobacteriaceae (20.65% and 24.64%) and Rhizobiaceae (18.48% and 14.01%) and Halomonadaceae (46.97%) and Hyphomonadaceae (24.94%) in the BCP.
... In biosorption metal ions are bound on functional groups attached to the cell surface through ion exchange, chelation, complexation, and microprecipitation (Akar and Tunali, 2006;Zinicovscaia and Cepoi, 2016), while in bioaccumulation, the heavy metals are transported and translocated through the cell membrane into different tissues by the activeÀpassive transport system (Shaikh and Bhosle, 2011;Olguin and Sanchez-Galvan, 2012). Many living cells adopt a detoxification process to reduce the toxicity of different heavy metals, which is followed by precipitation of metals as phosphate, carbonate, or sulfide (Hamdy, 2000;Radway et al., 2001). Jaishankar et al. (2014) reported the causes of detoxification mechanisms as putative entrapment in extracellular polymeric substance, volatilization, and participation. ...
... However, Chen et al. (2012) reported a complete remediation of Cd 2 1 from aqueous solution through phycoremediation using S. obliquus. Gurbuz et al. (2009) reported 46% and 50% phycoremediation efficiency for Zn (Zinc) and Fe, respectively, from industrial effluents. Probably all living organisms require a little fraction of heavy metals, namely iron, copper, manganese, zinc, cobalt, nickel, etc. for their morphological growth and development (Park et al., 2006), however, these metals also become toxic to organisms beyond their maximum permissible limits. ...
Phycoremediation is algae-based remediation of contaminated soil, in which different kinds of algae are used with respect to the target pollutant to be removed . In addition to the reclamation of contaminated soil, algal biomass is also produced by the process called carbon sequestration; this biomass further could be used for the production of “green fuel”.
... Subsequently, and with the optimum values for pH, temperature and inoculum, the interference that exists in the biodegradation of cyanide when it is complexed with three different metals, either individually or in groups, when the biomass is suspended, was evaluated. The metals and their concentrations were chosen based on the tolerance of certain bacteria to these metals and on the characterization of mine tailings reported in the literature [62][63][64][65] and because they are characterized as forming strong complexes with cyanide [4,5]. The initial concentration of free cyanide was 30 mg·L −1 . ...
Mexico is characterized as a mining country since it is the world’s main silver producer. During its extraction, wastewater (mining tailings) is generated which contains cyanide and heavy metals. The purpose of this research was to determine whether a bacterial consortium isolated from a tailings dam can use cyanide as a source of nitrogen and carbon to carry out its biodegradation. The study determined the effects of three physicochemical factors (pH, temperature and inoculum concentration) and three metals (copper, iron and nickel) on cyanide biodegradation. The results showed that the highest cyanide removals were obtained when working with a pH of 9.5, a temperature of 25 °C and 15% v/v of inoculum (88%), while the optimum values for copper, iron and nickel were 0, 7.7 and 0.46 mg·L−1, respectively, showing that copper causes an inhibitory effect (cyanide biodegradation of 68%) on the bacteria and consequently on the biological degradation of cyanide and that iron can promote the biodegradation of the pollutant by 91%.
... In addition, cyanide degradation by Pseudomonas pseudoalcaligenes CECT5344 involves quinone oxidoreductase and an associated cyanide-insensitive electron transfer chain [7]. Some bacteria, fungi, and algal have been reported to be able to biodegrade cyanide, such as Klebsiella pneumoniae [8], Pseudomonas pseudoalcaligenes [9], Pseudomonas putida and Pseudomonas stutzeri [10], Bacillus pumilus [11], Serratia marcescens [12], Exiguobacterium acetylicum, and Bacillus marisflavi [13], Escherichia coli [14], and Scenedesmus obliquus [15]. Cyanide-degrading microbes use their unique enzymic systems and metabolic pathways to degrade cyanide [16]. ...
Microbial treatment of cyanide pollution is an effective, economical, and environmentally friendly method compared with physical or chemical approaches. A cyanide-degrading bacterium was isolated from electroplating sludge and identified as Aerococcus viridans (termed A. viridans T1) through an analysis of the biochemical reaction and 16 S rDNA gene sequence. A. viridans T1 showed a maximum resistance to 550 mg L−1 CN−. The effect of pH and temperature on cyanide degradation and bacterial growth was evaluated. The highest cyanide removal efficiency and bacterial growth occurred at pH 8 and pH7, respectively. The optimum temperature for cyanide degradation and bacterial growth was 34 ∘C. In addition, the carbon source and nitrogen source for cyanide degradation were optimized. The optimal carbon source and nitrogen source were glycerol and peptone, respectively. The cyanide degradation experiment indicated that A. viridans T1 was able to remove 84.1% of free cyanide at an initial concentration of 200 mg L−1 CN− within 72 h and 86.7% of free cyanide at an initial concentration of 150 mg L−1 CN− within 56 h. To improve the cyanide-degrading efficiency of A. viridans T1, eight process variables were further optimized using a response surface methodology. Three significant variables (soybean meal, corn flour, and L-cysteine) were identified using a Plackett–Burman design, and the variable levels were optimized using a central composite design. The optimal values of soybean meal, corn flour, and L-cysteine were 1.11%, 1.5%, and 1.2%, respectively. Under these optimal conditions, the confirmatory experiments showed that the actual degradation rate was 97.3%, which was similar to the predicted degradation rate of 98.87%. Its strong resistance to cyanide and cyanide-degrading activity may allow A. viridans T1 to be a candidate for the bioremediation of cyanide-contaminated environments.
... Pseudomonas spp. and Burkholderia cepacia are some of the identified microorganisms with this capability (Akcil et al., 2003;Gurbuz et al., 2009 ...
Nitrogen has traditionally been removed from wastewater by nitrification and denitrification processes, in which organic carbon has been used as an electron donor during denitrification. However, some wastewaters contain low concentrations of organic carbon, which may require external organic carbon supply, increasing treatment costs. As a result, processes such as partial nitrification/anammox (anaerobic ammonium oxidation) (PN/A), autotrophic denitrification, nitritation-denitritation and bioelectrochemical processes have been studied as possible alternatives, and are thus evaluated in this study based on process kinetics, applicability at large-scale and process configuration. Oxygen demand for nitritation-denitritation and PN/A is 25% and 60% lower than for nitrification/denitrification, respectively. In addition, PN/A process does not require organic carbon supply, while its supply for nitritation-denitritation is 40% less than for nitrification/denitrification. Both PN/A and nitritation-denitritation produce less sludge compared to nitrification/denitrification, which saves on sludge handling costs. Similarly, autotrophic denitrification generates less sludge compared to heterotrophic denitrification and could save on sludge handling costs. However, autotrophic denitrification driven by metallic ions, elemental sulfur (S) and its compounds could generate harmful chemicals. On the other hand, hydrogenotrophic denitrification can remove nitrogen completely without generation of harmful chemicals, but requires specialized equipment for generation and handling of hydrogen gas (H2), which complicates process configuration. Bioelectrochemical processes are limited by low kinetics and complicated process configuration. In sum, anammox-mediated processes represent the best alternative to nitrification/denitrification for nitrogen removal in low- and high-strength wastewaters.
... However, these processes are not always effective compared to biological treatment methods that can effectively remove a wide range of cyanide compounds [1]. Furthermore, biological methods are economical and reduce the toxicity and corrosiveness of the chemical oxidizers [13]. Therefore, the development of biological processes for the remediation of cyanide contaminated water and soil is of high importance in the context of gold mining. ...
... Apart from producing cyanides in carbohydrates, the metal finishing, gold ore preparation, plastic manufacture, and food processing sectors also create cyanides, which include radicals (CN-), such as hydrogen cyanide, and sodium cyanide, potassium cyanide, and thiocyanates (Gould et al. 2012). When compared to physical and chemical approaches for removing firmly bound cyanide substances from wastewater, biological processes, such as the use of microalgae, are less expensive, productive, and valuable (Gurbuz et al. 2009). The potential of various algal species to tolerate and/or use cyanide in wastewater differs widely. ...
Rapid increases in human populations and development has led to a significant exploitation of natural resources around the world. On the other hand, humans have come to terms with the consequences of their past mistakes and started to address current and future resource utilization challenges. Today’s primary challenge is figuring out and implementing eco-friendly, inexpensive, and innovative solutions for conservation issues such as environmental pollution, carbon neutrality, and manufacturing effluent/wastewater treatment, along with xenobiotic contamination of the natural ecosystem. One of the most promising approaches to reduce the environmental contamination load is the utilization of algae for bioremediation. Owing to their significant biosorption capacity to deactivate hazardous chemicals, macro-/microalgae are among the primary microorganisms that can be utilized for phytoremediation as a safe method for curtailing environmental pollution. In recent years, the use of algae to overcome environmental problems has advanced technologically, such as through synthetic biology and high-throughput phenomics, which is increasing the likelihood of attaining sustainability. As the research progresses, there is a promise for a greener future and the preservation of healthy ecosystems by using algae. They might act as a valuable tool in creating new products.
... Scenedesmus obliquus 92% Biodegradation of 3 mM cyanide concentration. [32] Agrobacterium tumefaciens SUTS 1 87.5% Biodegradation of 1, 2, and 6 mM cyanide concentration, [16] Rhodococcus UKMP-5M 94% Biodegradation of 12 mM cyanide concentration using immobilized cells. [33] Basidiomycota 100% Biodegradation of 4 mM cyanide concentration using 3 g fungal biomass. ...
Cyanide is a poisonous and dangerous chemical that binds to metals in metalloenzymes, especially cytochrome C oxidase and, thus, interferes with their functionalities. Different pathways and enzymes are involved during cyanide biodegradation, and cyanide hydratase is one of the enzymes that is involved in such a process. In this study, cyanide resistance and cyanide degradation were studied using 24 fungal strains in order to find the strain with the best capacity for cyanide bioremediation. To confirm the capacity of the tested strains, cyano-bioremediation and the presence of the gene that is responsible for the cyanide detoxification was assessed. From the tested organisms, Trichoderma harzianum (T. harzianum) had a significant capability to resist and degrade cyanide at a 15 mM concentration, where it achieved an efficiency of 75% in 7 days. The gene network analysis of enzymes that are involved in cyanide degradation revealed the involvement of cyanide hydratase, dipeptidase, carbon–nitrogen hydrolase-like protein, and ATP adenylyltransferase. This study revealed that T. harzianum was more efficient in degrading cyanide than the other tested fungal organisms, and molecular analysis confirmed the experimental observations.
... Subsequently, and with the optimum values for pH, temperature and inoculum, the interference that exists in the biodegradation of cyanide when it is complexed with three different metals, either individually or in groups, when the biomass is suspended, was evaluated. The metals and their concentrations were chosen based on the tolerance of certain bacteria to these metals and on the characterization of mine tailings reported in the literature [62][63][64][65] and because they are characterized as forming strong complexes with cyanide [4,5]. The initial concentration of free cyanide was 30 mg·L −1 . ...
... Oxygen from air cannot penetrate to the bottom of deep ponds (anaerobic ponds). In lagoons oxygen is provided by artificial aeration [50][51][52][53][54][55][56][57]. ...
Transport fuel is one of the major concerns ofthe energy market. This fuel mainly comes from the processing of crude petroleum oil. The transport fuel processing industries,such ascrude oil distillation plants, gas condensate fractionation plants, natural gas processing plants,etc.,are one of the most energy-and emission-intensive sectors in the world. On the other hand, the handling and transportation of petroleum products like gasoline, kerosene, diesel, naphtha, octane and sprite,etc. also produceenvironmental pollution. Thisstudy reviewed energy and waste management bytransport fuel processing industries in Bangladesh. Suchindustries are also known as petrochemical industries. Theymainly produce gaseous pollutantssuch as process gas, waste gas,etc. and liquid pollutants such as produced water, waste oil and grease,etc. Thegaseouspollutants are burnt in the flare system to save the environment. The liquid pollutants are more hazardous because of theirhigher salinityandcorrosivity and higher amounts of grease. Theliterature on waste water management techniques, pollution abatement techniquesand oil-water separator techniques is described.The waste water treatment techniquesused in the case study industriesare briefly discussed. Energy flows for both gaseous and liquid waste management are developed. Energy-savingand time frame measures which can be implemented arealso outlined. The study found that the rational use of energy and proper environmental management are essential for achieving the energy and environmental sustainability of transport fuel process industries.
... Cyanide: HCN and CNfree cyanide forms are considered to be the most toxic substances due to their high metabolic potential [99]. Cyanide usually gets into water through improper handling or failure during transportation [100]. Peterson & Cohen [101] have studied the effects of cyanide on brain mitochondrial cyto-chrome oxidase and respiratory activities in mice. ...
Presently water pollution is the one of the major threats faced by living things all over the world. The main cause of water pollution is its effect on the life of aquatic animals. Organic, inorganic, microbial and other pollutants often mix with water bodies mainly due to human activities. Because of the presence of pollutants in water, the amount of dissolved oxygen level can be decreased which in turn affect the survival of aquatic life. The pollutant water may enter the agriculture fields and damage the plants extensively. The methods, such as, coagulation, adsorption, foam floating, electrodialysis, capacitive deionization, etc. are presently employed to treat the waste water. Among these methods, heterogeneous photocatalytic degradation is considered to be a good method because of its low cost and environmental friendliness. In this review, the decontamination of different kinds of organic, inorganic and microbial contaminants in water with different photocatalysts process is presented.
... Arthrobacter sp., Zoogloearamigera, Acidovorax sp., Achromobacter sp., Janthinobacterium sp., Klebsiella sp., Bacillus pumillus, Burkhoderia cepacia, Alcaligenes sp., Serratia marcescen and Rhodococcus sp., among others, have been reported as cyanide degrading organisms [6,[12][13][14][15][16][17][18][19]. Besides bacteria, species of the archaeal genus Methanosarcina (under anaerobic conditions), some fungi like Fusarium solani and Trichoderma polysporum at pH 4 [20] and some algae like Scenedesmus obliquus [21] have been reported to degrade cyanide. ...
Cyanide is the basic component of many industrial processes, among which is gold processing, being very toxic or even lethal. Treatment, with the help of microorganisms, can be used effectively to reduce the load of harmful chemicals into the environment. The combination of microbiological methods and molecular tools allowed inferring the presence of a dominant population and the composition varied both in the places of origin and in the method used. The dominant phylogenetic affiliations of the bacteria were determined by sequencing the 16S rRNA gene. The isolates identified, as Bacillus and Enterococcus were capable to degrade 41.9 and 27.5 mg CN- L-1 respectively. This study provides information about the presence of a diverse bacterial community associated with residual effluents from cyanidation processes in Colombia and suggests that their presence could play a role in the biological degradation of cyanide compounds, offering an alternative for mining wastewater treatment.
... Cyanide solutions are employed in almost all precious metals (Au, Ag) extraction plants worldwide (Akcil, 2003;Brüger et al., 2018;Gurbuz et al., 2009). This usually results in the generation of large flowrates of discharges to be dumped in tailings ponds and rivers in rainy seasons. ...
The main purpose of this research has been to evaluate and optimize the application of hydrodynamic cavitation (HC), combined with hydrogen peroxide, as a promising process for the effective degradation of cyanide in aqueous effluents. The experimental work was carried out using cavitation equipment with a venturi device connected to a tubular circuit which allowed a closed-cycle flow to run for 120 min, in which the effect of control parameters as inlet pressure, H2O2:CN─ ratio, pH, and temperature have been evaluated for the treatment of solutions with initial cyanide concentration in range 100 to 550 mg L─1.
The results showed that in optimal conditions cyanide degradation using only HC reached 70% and, using solely H2O2 as oxidizing agent it reached 63%. Efficiency of the combined treatment process was evaluated on the basis of their synergetic effect as it turned out to be more effective showing a 99.9 % cyanide degradation in less than 120 min. The optimum set of conditions that produced the highest degradation rate and efficiency was: inlet pressure 4 bar; pH 9.5; and H2O2:CN─ ratio = 1.5:1. The process was also evaluated on the basis of cavitational yield and in terms of energy and chemical treatment costs. The results have demonstrated that the combined treatment technology of HC + H2O2 can be effectively used as a fast and highly efficient treatment of wastewater containing cyanide.
... Roughly 875 gold and silver extraction operations exist in the world, of which 460 (52% of the metallurgy industry) use cyanide in their extraction processes [6,7]. This use of cyanide is associated with hydrometallurgical processes [8]. ...
Given that mining is considered to be an essential activity for Mexico’s industrial development, cyanide has been increasingly used to recover precious metals such as gold and silver. Along with that arises the need to develop new technologies to treat the wastes (mining tailings). In addition to their high cyanide content, metal and other contaminants that are found in tailings also present a problem. As a result, conventional (physicochemical) strategies have been developed to reduce contamination from tailings, nonetheless, these have high operating costs and generate unwanted by-products. For this reason, studies have begun to focus on non-conventional strategies to treat free cyanide and cyanide complexes such as fungi, bacterial consortia, and pure bacteria. These are important because of the mechanisms involved in degrading or modifying contaminants at neutral to high pH levels, which convert contaminants into non-hazardous products. The ability of microorganisms to grow at an alkaline pH prevents HCN volatilization. These studies have been performed at the laboratory level using two types of microbial binding: suspended biomass and immobilized biomass. They have used both natural (granite rock, citrus peels, cellulose, gravel) and synthetic (stainless steel, geotextiles, alginate, plastics) packing material, as well as reactors with different types of flow, namely, batch and continuous.
... Similarly, carboxyl, hydroxyl, amino and carbonyl groups present on the surface of freshwater algae Anabaenaphaerica proved to have a major role in biosorption of Pb and Cd ions [219]. However, cyanide is degraded by several algal strains due to their ability to use it as a source of carbon and N for their growth [220]. ...
Environmental pollution is increasing day by day due to anthropogenic activities and different types of toxic contaminants such as heavy metals, chemicals, dyes, pesticides etc enter the environment from different sources such as municipal, industries and agricultural. Among wastewater treatment techniques, bioremediation is one of promising techniques, which utilize the inherent biological mechanism of plant and microorganism for the remediation of diverse pollutants. Microalgae have been applied to mitigate the toxic and recalcitrant pollutants in the effluents. Microalgae have the capacity to remove different types of contaminants through different methods such as biosorption, bioaccumulation and biodegradation. It has been observed that microalgae can remove the pollutants originated from the domestic effluents, agricultural runoffs, textile, leather, pharmaceutical and electroplating industries etc. Additionally, the microalgae have the ability to mitigate the carbon dioxide in their growth process and utilize the micronutrients in the effluents. This review paper critically analysed the application of microalgae for the remediation of diverse types of pollutants commonly present in the environment through different mechanisms.
... [3,22,38] Cyanobacteria strains employ several innate mechanisms to reduce the effects of CN À in their environment, [109] and subsequently use CN À as a nutrient to support growth. The main merits of utilizing microbes for GCT degradation are as follows: (i) microbes are economically and environmentally sustainable [105] and (ii) microbes can assimilate free CN À and other toxic contaminants (e.g. metals and metalloids) from GCTs. ...
The initial cyanide (CN-) concentration and amount of co-contaminants in GCTs can inhibit bacterial growth and reduce the CN--degrading ability of bacteria. Several microorganisms can biotransform a wide range of organic and inorganic industrial contaminants into nontoxic compounds. However, active enzymatic CN- metabolism processes are mostly constrained by the physical and chemical characteristics of GCTs. High concentrations of toxic metal co-contaminants, such as, Pb, and Cr, and factors, such as pH, temperature, and oxygen concentration create oxidative stress and limit the CN--degrading potential of cyanotrophic strains. The effects of such external and internal factors on the CN--degrading ability of bacteria hinder the selection of suitable microorganisms for CN- biodegradation. Therefore, understanding the effects of the physicochemical properties of GCTs on cyanobacteria strains can help identify suitable microbes and favorable environmental conditions to promote microbial growth and can also help design efficient CN- biodegradation processes. In this review, we present a detailed analysis of the physicochemical properties of GCTs and their effects on microbial CN- degradation.
... In general HCN is produced by the plant as a defense mechanism against herbs. Various algae like Cyanobacteria, Chlorella valgaris, Scenedesmus and Nostoc muscorum (Gurbuz et al. 2004(Gurbuz et al. , 2009) bacteria like Chromobacterium violaceum and certain Pseudomonas species (Fairbrother et al. 2009) and fungi like Actinomycetes and Tricholoma produce and metabolize cyanide. In bacteria normally HCN is produced during transition stage of growth and in fungus when fruiting bodies are formed or during damaged or stress condition as a mechanism to provide nitrogen and carbon source (Ezzi and Lynch 2005). ...
Industrial wastewater creates major environmental trouble if released without proper treatment. Large volumes of water contaminated with various industrial and anthropogenic activities can produce hazardous effects on the environment and the living organisms. Various industries discharge toxic materials, heavy metals, and anions into the environment that considerably enhanced the deterioration of environment, flora, and fauna, and significantly pose threats to the ecosystem. These noxious materials cause serious health issues, if they surpass the acceptable limit in water. There is a big challenge to remove toxic pollutants from water and wastewater. Some traditional methods such as coagulation, chemical precipitation, carbon adsorption, oxidation, ion exchange, evaporations, and membrane processes are found to be helpful in the treatment of wastewater. However, these methods are unlikable from both environmental and cost-effective viewpoints because these require utilizing chemical compounds, huge energy and also do not degrade the complete range of pollutants. Therefore, novel and more effective treatment methods of removing toxic compounds from water and wastewater needed to be develop. In this regard, the efforts have been made toward bioremoval applications and its efficiency for the removal of hazardous materials from water and wastewater by using microorganisms. Among all treatment methods introduced above, the biological treatment method is a proficient, inexpensive, simple, and environment friendly process for treating pollutants. Use of microbial technology in the treatment of pollutants gained a momentum of efficient degradation ability, simple technical operation, lower process time, low energy requirements, no secondary pollution, and long-term viability.
... Different methods have been applied to eliminate strongly attached cyanide radicals from wastewaters. However, the use of microalgae to remove cyanides is one of the most economical and efficient methods compared with the physical and chemical methods (Gurbuz et al., 2009). Capabilities of microalgae to consume cyanide compounds from the wastewaters vary from one algal species to the other. ...
Rapid urbanization and industrialization urged scientific communities to address several environmental concerns as the wastes from cities, towns, and industries are poured into the aquatic and terrestrial ecosystems without treatment. Aquatic ecosystems are more prone to these environmental hazards as ultimately almost all the pollutants gain entry into the natural water bodies. Although several physical, chemical, and biological methods have been proposed for the bioremediation of aquatic pollutants, all these methods have certain advantages as well as disadvantages. The conventional chemical methods used for the decontamination of wastewaters are either less effective or very expensive. Nowadays, the use of microalgae is being practised to treat the wastewaters safely. The exploited use of microalgae for the remediation of wastewaters is advantageous over other wastewater decontamination techniques due to their high surface to volume ratio, high removal capability toward toxic pollutants, higher biosorption capacity, adaptability to different environments, and cost-effectiveness. This chapter focuses on the sustainable utility of various microalgal species for the remediation of toxic metal ions, cyanides, hydrocarbons, pesticide residues, endocrinal disruptors, inorganic nutrients and reduction of BOD and COD from wastewaters.
... This may be due to accumulation of alpha-cypermethrin in nearby freshwater bodies after run-off from the rice field. It is reported that green algae have ability to bioaccumulate, immobilize, sequester and biotransform herbicides and other xenobiotic compounds in the environment (Gurbuz et al. 2009). It is reported that depending on the species microalgae may have different tolerances to pollutants such as pesticides (Vendrel et al. 2009). ...
The present study demonstrates that the environment play a vital role in the development of tolerance in the local algal isolates towardsalpha-cypermethrin. The isolates collected from rice fields (Scenedesmus ecornis NC-M9 and Tetradesmus dimorphus NC-K2) showed significantly higher tolerance than the isolates collected from freshwater bodies far from the rice fields. Also, significant reduction in Malondialdehyde (MDA) content was noticed in S. ecornis NC-M9 after fourth and seventh day exposure to alpha-cypermethrin compared to first day exposure. However, the Superoxide Dismutase (SOD) and Peroxidase (POD) contents of S. ecornis NC-M9 enhanced at 4th and 7th day exposure to alpha-cypermethrin compared to 1st day exposure. Further, biochemical studies of all isolates show that Graesiella emersonii NC-M1(the isolate from freshwater bodies near to rice field) possesses higher contents of Chlorophyll a (Chl a), carotenoid and lipid (5.59 ± 0.36 mg·L−1, 2.5 ± 0.024 mg·L−1 and 28 ± 2.5% Dry Cell Weight (DCW), respectively) compared to other. This variation in biochemical parameters present in different field areas as collected and tested could be further used as potential substrates for production of bioactive compounds which have many health and environmental benefits.
Graphical abstract
... Chen et al., (2008) recorded a complete removal of Cd 2+ from aqueous solution by S. obliquus. This microalgae also exhibited 50 and 46% removal for Zn and Fe from industrial wastewater (Gurbuz et al., 2009). The phycoremediation process contributes significantly in the removal of heavy metals and elements from wastewater, especially at low concentration (1-100 mg L -1 ) where chemical and physical methods such as chemical precipitation, electrolytic recovery, adsorption/ion exchange and solvent extraction are insufficient (Al-Gheethi et al., 2015). ...
Grey water from bath roomsare directly discharging into the drain or stream without any treatment in the rural area, due to the absence of a central treatment plant. These practices become unacceptable because its lead to water pollution and aggravate mosquito nuisance. The study aimed to investigate the potential of Botryococcus sp. cell to uptake of metal ions (Ca, Na, Mg, Feand Zn) from artificial grey water samples during the phycoremediation process. Botryococcussp. was inoculated into the phycoremediation flasks with 8 log10 cell mL-1 and incubated at room temperature for 3, 5, and 7 days. The highest uptake was 99.7% for Ca, 83% for Na, 96% for Mg, 64%for Fe and 98.8% for Zn ions. The specific uptake rate of Ca, Na, Mg, Fe and Zn ions have a significant relationship with initial concentration in the artificial grey water (R2= 0.93, 0.61, 0.92, 0.76 and 0.86 respectively). The kinetic coefficient of grey water parameters uptake by Botryococcussp. was determined as k=2.58 mg Ca 1 log 10 cell mL-1 d-1 and km=4.43 mg L-1 (R2=0.89), k=0.93 mg Na 1log 10 cell mL-1 d-1 and km=22.57 mg L-1 (R2=0.79), k=0.97 mg Mg 1 log10 cell mL-1 d-1 and km=1.56 mgL-1 (R2=0.98). k=0.39 mg Fe 1 log10 cell mL-1 d-1 and km=14.39 mg L-1 (R2=0.63) and k=0.21 mg Zn 1 log10cell mL-1 d-1 and km=1.3 mg L-1 (R2=0.77). Yield coefficient for Ca, Na, Mg, Fe and Zn ions removalby specific growth rate of Botryococcus sp. were 6.01, 10.35, 4.5, 0.57 and 0.54 respectively.
... Scenedesmus obliquus is suitable to produce biofuels, thanks to rapid cell growth, efficient CO 2 fixation, lipid accumulation, and the ability to grow in contaminated water (Gris et al. 2014). Scenedesmus obliquus can also uptake heavy metals (Gurbuz et al. 2009) and radionuclides such as 110m Ag, 137 Cs, 60 Co, 54 Mn (Adam and Garnier-Laplace 2003). Chlorella vulgaris is unicellular green microalgae and has asexual reproduction with doubling mass cell time about 19 hours (Daliry et al. 2017). ...
Radionuclides that have entered the environment through nuclear weapon tests, nuclear accidents or other human activities represent an ecological hazard. Many decontamination techniques are technically and financially demanding and often not environmentally beneficial. A suitable alternative is bioremediation techniques. One of them, phycoremediation utilizes the metabolic activity of microorganisms that degrade or eliminate contaminants from the environment. In our work, we focused on phycoremediation with microalgae Dunaliella salina and Chlorella vulgaris. An important parameter was the determination of the optimal pH values of the environment and subsequent monitoring of the radionuclide activity decline over time.
... Based on the investigations obtained from the literature, various plants such as Sorghum bicolor and Linum usitassimum var. omega-gold (6), Zea mays (7), various fungi such as Aspergillus niger (8), Cryptococcus humicolus (9), Fusarium lateritium (10,11), Fusarium oxysporum (12,13), Fusarium solani (14,15), Rhizopus arrhizus (16), Scenedesmus obliquus (17), Trichoderma sp. (18) and Trichoderma harzianum (19) were found as cyanide degrading species. ...
... Le cyanure est également biodégradé par différents types d'algues (e.g. Scenedesmus obliquus) en azote et carbone (Gurbuz et al., 2009). ...
En conditions hivernales rigoureuses, l'application des fondants routiers (principalement du chlorure de sodium - NaCl) permet d'assurer la sécurité des usagers de réseaux. Toutefois, son utilisation généralisée entraîne des risques de contamination des écosystèmes aquatiques et terrestres. En milieu routier, le Na+ et Cl- sont transportés par les eaux de ruissellement vers des ouvrages de traitement tels que les bassins de rétention-décantation. Or, ces bassins n'ont pas la capacité de traiter efficacement cet apport de fondants sous forme dissoute. L'objectif de cette thèse est d'étudier le transfert de ces fondants au sein du système routier et de déterminer leur rôle dans la libération des polluants en période hivernale. Les caractéristiques du bassin situé à Azerailles (Lorraine, France) sur une route nationale moyennement fréquentée ont été étudiées, ainsi que les conditions météorologiques, les salages, la composition des matières en suspension (MES) et la concentration en éléments traces métalliques (ETM). Les résultats ont permis de montrer que entre 50 et 90 % du Cl- ont été collectés par le bassin. Il joue un rôle de tampon qui permet une libération du Cl- dilué durant la période de ruissellement suivant la période de salage. La présence de NaCl dans les eaux a joué un rôle sur la diminution de la qualité des matières en suspension, en mettant en évidence la présence de polluants organiques en période de salage. Elle entraîne également une modification de la chimie des eaux et une augmentation des polluants métalliques (zinc).
... These organisms can synthesize and assimilate cyanide as a source of carbon and nitrogen. Bacteria that contain cyanide are Chromobacterium violaceum and Pseudomonas species [5,6]. Fungi like Trichoderma sp. and Actinobacteria sp. are used to produce and metabolize cyanide [7,8]. ...
Cyanide is one of the most poisonous substances in the environment, which may have originated from natural and anthro-pogenic sources. There are many enzymes produced by microorganisms which can degrade and utilize cyanide. The major byproducts of cyanide degradation are alanine, glutamic acid, alpha-amino-butyric acid, beta-cyanoalanine, pterin etc. These products have many pharmaceutical and medicinal applications. For the degradation of cyanide, microbes produce necessary cofactors which catalyze the degradation pathways. Pterin is one of the cofactors for cyanide degradation. There are many pathways involved for the degradation of cyanide, cyanate, and thiocyanate. Some of the microorganisms possess resistance to cyanide, since they have developed adaptive alternative pathways for the production of ATP by utilization of cyanide as carbon and nitrogen sources. In this review, we summarized different enzymes, their mechanisms, and corresponding pathways for the degradation of cyanide and production of pterins during cyanide degradation. We aim to enlighten different types of pterin, its classification, and biological significance through this literature review.
... The presence of a group of single-celled anaerobic cyanide degrading microorganisms in the chambers with the highest population perceived to be resident in the biofiltration chamber may account for this performance. Cyanide degradation by anaerobic and aerobic bacteria was also examined and reported by Gurbuz et al. (2004) and Gurbuz et al. (2009). The degrading effect of the treatment measures on hydrogen cyanide is presented in Table 2 and Table 3. ...
Local cassava agro-processing industries in Nigeria generate toxic organic effluent with negative environmental impact if disposed without adequate treatment. This study examines the performance of a lab-scale aerated sequencing batch reactor (SBR) in degrading cassava mill effluent using palm kernel (Elaeis guineensis) shell (PKS) as biofilter media. Wastewater samples were collected before and after flowing through each compartment at hydraulic retention times of 3, 5 and 7 hours. Continuous aeration and nature-based degradation of the effluent recorded overall removal efficiencies of 73.5% (Hydrogen cyanide), 70.59% (BOD), 69.18% (COD), 29.93% (Turbidity), 4.92% (Sodium), 25% (Magnesium) and 14.32% (Calcium) respectively. Effluent electrical conductivity (EC) slightly increased by 7.84%. The Sodium Adsorption Ratio (SAR) of the treated wastewater ranged from 6.9 to 7.3 while the final pH ranged from 4.5 to 4.6. The values of EC, BOD and COD were significantly different (P<0.05) along the treatment sequence, confirming the effectiveness of the chambers in reducing these pollutants. Despite achieving high removal efficiencies, the final values of most parameters still fall short of the local permissible limit signifying operational limitations and the need to optimize the system to reduce key contaminants to safe disposal limits.
Keywords: agro-processing, degradation, effluent, pollutants, sequencing batch reactor
(1) (PDF) Degrading cassava mill effluent using aerated sequencing batch reactor with palm kernel shell as medium. Available from: https://www.researchgate.net/publication/332128387_Degrading_cassava_mill_effluent_using_aerated_sequencing_batch_reactor_with_palm_kernel_shell_as_medium [accessed Apr 10 2019].
... The oxidative product of cyanide such as cyanate (OCN -) can be produced during treatment of cyanide-containing effluents. It has been estimated that the release of cyanide from industrial processes is above 14 million kg/year and these effluents contain a high concentration of cyanide (Gurbuz et al., 2009). ...
The study purified and investigated the physicochemical properties of rhodanese (a cyanide detoxifying enzyme) synthesized by Bacillus cereus. This was with a view to producing an industrially important enzyme. The bacterial strain was identified as B. cereus by sequencing of its 16SrRNA gene. B. cereus rhodanese was purified with a fold of 3.53, yield of 36.80% and specific activity of 25.30 µmol/min/mg protein. The molecular weight determined on SDS-PAGE was 33.800 kDa. The enzyme exhibited maximum activity at 9.0 pH and 50°C. The K m s of B. cereus rhodanese for sodium thiosulphate and potassium cyanide were 19.9 ± 1.05 and 31.4 ± 1.55 mM respectively, while V max were 6.19 ± 0.40 and 4.83 ± 0.93 RU/ml respectively. The substrate specificity study using different sulphur compounds showed that the enzyme prefers sodium thiosulphate. The enzyme showed stability at a temperature range of 40-50°C. At 10 mM concentration, metals such as (BaCl 2 , CaCl 2 , MnCl 2, and SnCl 2) had little influence on the enzyme activity while NaCl and HgCl 2 inhibited enzyme activity. The presence and biochemical properties of B. cereus rhodanese suggest its possible application in cyanide detoxification.
... Cyanide treatment by microorganism from wastewater is a proven and feasible alternative to chemical processes [3]. Cyanide degrading cyanobacteria can use cyanide as their carbon and/or nitrogen source and thereby, nutrient consumption will be lowered [1,4,5]. It is well-known that under stress condition algae produce more lipids which can effectively be used for preparation of biofuel [6]. ...
Mn 3 O 4 nanograins incorporated into reduced graphene oxide as a nanocomposite electrocatalyst have been synthesized via one-step, facile, and single-pot microwave-assisted hydrothermal technique. The nanocomposites were employed as cathode material of fuel cells for oxygen reduction reaction (ORR). The synthesized product was thoroughly studied by using important characterization, such as XRD for the structure analysis and FESEM and TEM analyses to assess the morphological structures of the material. Raman spectra were employed to study the GO, rGO bands and formation of Mn 3 O 4 @rGO nanocomposite. FTIR and UV–Vis spectroscopic analysis were used to verify the effective synthesis of the desired electrocatalyst. The Mn 3 O 4 @rGO-10% nanocomposite with 10 wt% of graphene oxide was used to alter the shiny surface of the working electrode and applied for ORR in O 2 purged 0.5 M KOH electrolyte solution. The Mn 3 O 4 @rGO-10% nanocomposite electrocatalyst exhibited outstanding performance with an improved current of − 0.738 mA/cm ² and shifted overpotential values of − 0.345 V when compared to other controlled electrodes, including the conventionally used Pt/C catalyst generally used for ORR activity. The tolerance of Mn 3 O 4 @rGO-10% nanocomposite was tested by injecting a higher concentration of methanol, i.e., 0.5 M, and found unsusceptible by methanol crossover. The stability test of the synthesized electrocatalyst after 3000 s was also considered, and it demonstrated excellent current retention of 98% compared to commercially available Pt/C electrocatalyst. The synthesized nanocomposite material could be regarded as an effective and Pt-free electrocatalyst for practical ORR that meets the requirement of low cost, facile fabrication, and adequate stability.
The main elements of mother earth, like air, water, and soil, are constantly being poisoned due to inadequate waste treatment and the lack of such technologies. Few chemicals such as cyanides and phenols are not environmentally benign, yet they can be spontaneously removed in nature unless their amount is overwhelming. Therefore, these compounds must be treated in the waste/wastewater at the point of discharge. However, many of the physical and chemical waste treatment technologies are expensive, require high maintenance, and are unsustainable because of the formation of other life-threatening chemical by-products. When released into the environment, cyanide and phenol often enter into the ecosystem and disturb all trophic levels. When these chemicals are allowed to degrade themselves in nature, the ecosystem breaks them down into nontoxic organic constituents. Many microbes like bacteria, algae, and fungi have been reported to detoxify these pollutants with their enzymatic action without any toxic by-products. This review highlights the fact that only a few genera and species of microorganisms have been exploited for this purpose. So far very few studies have been carried out on defining the role of uncultured microorganisms in the cyanide and phenol cycles in nature.
Artisanal and small-scale mining are informal activities used as a source of family income in many countries, mostly in developing regions. They also represent rudimentary practices that generate environmental and health impacts. In these activities, gold is the main mineral extracted commonly using cyanide leaching as the main technique in their production process, despite its environmental impacts. Biodegradation is an alternative technology that has shown advantages over other techniques; however, most microorganisms studied in cyanide biodegradation processes do not tolerate alkaline environments. Thus, the present study assessed the cyanide biodegradation potential under alkaline conditions of a native strain isolated from an artisanal gold mine. The methodology used consisted in the following steps: isolation of bacteria, identification of the isolated strain, adaptation to alkaline environments, and cyanide degradation tests. The strain was identified using the mass spectrometry technique (MALDI-TOF) and it was subsequently compared with the 16S rDNA sequencing technique. Degradation assays were performed with adapted bacteria in an agitated flask containing a synthetic solution with 500 mg.L−1 of free-cyanide (CN−) and initial cell concentration of 2.5 × 1011 CFU.mL−1. Incubation was performed in orbital agitation at 27 °C and 190 rpm for 120 h. In conclusion, the identification techniques elucidated that the isolated strain probably belongs to the Bacillus subtilis species. Finally, cyanide degradation assays showed that the B. subtilis strain adapted to alkaline environments was able to degrade 100% of the free-cyanide in the solution in three days.
Microalgae are alluring biotechnological tool to detoxify the hazardous pollutants present in the environment. Environmental toxic waste is hazardous and causes serious problem to the environment as well as organisms. The microalgal biomass has the potential to remediate these pollutants from the contamination sites through different processes such as biodegradation, accumulation, and immobilization. Microalgal growth is inexpensive because they use sunlight and carbon dioxide; therefore, globally microalgal environmental remediation market found that this industry showed significant growth over last few years and anticipated a continuous growth. Furthermore, research need to be explored for the remediation process to make it more advantageous, economic, feasible, widely accepted by the public, and also elevated level reduced contaminants. This chapter highlights the remediation of environmental pollutants from different sources of contamination using microalgal nanotechnology.KeywordsMicroalgaeEnvironmentPollutantRemediationNanoparticlesContaminants
In this study, we used the Agrobacterium tumefaciens–mediated transformation approach to transfer the activity of the cyanobacterial cyanase enzyme into the micro-alga, Chlamydomonas reinhardtii. In transgenic C. reinhardtii strains, the recombinant cyanase enzyme was proven to be active. In comparison to wild-type control, transgenic type demonstrated higher rates of ammonia release, reduced loss of pigmentation, and a lower percentage of growth retardation when varied amounts of cyanide (up to 200 ppm) were applied to the growth medium. Moreover, cyanase activity increases as concentration of cyanide increase especially in case of transgenic. The maximum activity was indicated in presence of 100 mg/l cyanide it reached eight folds more than wild activity at the same cyanide concentration. Results of this study provide an effective eco-friendly phytoremediation system for detoxification of cyanide using micro-alga compared to previously reported conventional system for removal of cyanide compounds, Also, some factors are taken in consideration like different pH, contact time and the transgenic type has been the priority for removal cyanide at wide range of pH with two folds more than wild type.
Fenton oxidation, coagulation/flocculation/sedimendation plus Fenton oxidation, and Fenton oxidation plus activated carbon adsorption were conducted to develop the effective processes for recycling a biologically treated coking plant effluent. Fenton oxidation enhanced adsorptive capacities of activated carbon for the residual organics and also made them more biodegradable. The Fenton oxidation followed by adsorption and biodegradation in a biological activated carbon (BAC) adsorber was the most cost-effective treatment process to recycle the final effluent for in-plant reuses while meeting the much more stringent discharge limits of the future. Batch experiments were also conducted to determine the effects of copper-loading and fixing methods on the capacity of granular activated carbon (GAC) for removing cyanide from KCN (pH = 11), K3Fe(CN)6 solutions and several Shanghai Coking Plant (SCP) effluent samples. KI-fixed carbon (Cu/KI-GAC) was the best GAC samples tested. Adsorption was the primary mechanism of cyanide removal; catalytic oxidation of the adsorbed cyanide on carbon surface contributed a minor amount of the observed removal. Four small adsorbers containing the base GAC and 0–100% of Cu/KI-GAC were employed for treating a Fenton-oxidized/precipitated SCP effluent sample. After the start-up period (<3 weeks) to establish the effective BAC function in the adsorbers, the effluents became stable and met the discharge limits (CODCr < 50 mg/L and TCN < 0.5 mg/L); with >30% Cu/KI-GAC in the adsorber, the effluent would meet the discharge limits during the start-up phase. The BAC function of the adsorber substantially reduced the carbon replacement cost, making the combined Fenton oxidation and BAC treatment process a cost-effective alternative for recycling the biotreated coking plant effluent.
Occurrence of huge quantity of cyanide in the environment is due to extensive use in metal-finishing and mining industries. The strong affinity of cyanide with metals makes it favorable as an agent for metal-finishing and lixivant for metal leaching. For many years, cyanide has been used as a leaching reagent for the extraction of precious metals, particularly gold and silver. As a high toxicity of the cyanide it appears on the international priority pollution list. Considering the lethal impact of cyanide on the environment as well as human health, environmental authorities have taken a more stringent attitude toward the presence of cyanide in water. The researchers are trying to investigate best removal techniques for treating hazardous materials like cyanide from metal-finishing industrial wastewater and also strive to reuse of this water for agricultural or other purposes. Although cyanide can be removed and recovered by several processes, while biological treatment process gained an impetus of efficient degradation ability. Biological treatment of cyanide has often been offered as a potentially economical, environmentally friendly alternative to conventional methods. For the treatment of cyanide-containing wastewater, the adsorption and biodegradation are two significant methods. The first one, that is, adsorption is better to other wastewater treatment techniques in terms of efficiency, ease of operation, and low cost. The second, biodegradation method of cyanides removal is better than physical and chemical methods. In cyanide biodegradation process; the cyanide is converted to carbon and nitrogen source by various enzymes present in microorganisms. Biological treatments with bacterial whole cells is another important route for cyanide removal from water in which whole cells are used either in bulk phase or are immobilized on a solid support (bioadsorbent). Immobilized whole cells produce biolayer on bioadsorbent surface and when treated with solution having cyanide, the bacterial cells biodegrade it within the cell as well as it gets adsorbed on bioadsorbent surface. This process is termed as simultaneous adsorption and biodegradation process. In this chapter, we are aimed to make comprehensive description about sustainable bioremoval techniques on the removal of most hazardous materials like cyanide which are released from metal-finishing industrial effluents.
Novelty statement:
Ecologically suitable methods for the decontamination of liquid radioactive waste or radioactively contaminated areas are becoming more and more important due to the pollution of the planet. We believe that phytoremediation of radionuclides using microalgae is one of the optimal ecological methods to decontamination of radioactive waste. Microalgae as unicellular organisms have a number of advantages over the other organisms used in bioremediation-high level of tolerance to the environment, fast growth rates, high tolerance to various pH levels, etc. In this study, we used 3 different strains of microalgae for phytoremediation of various radionuclides (137Cs, 60Co, 241Am, and 239Pu). This research was focused on ex situ phytoremediation of radionuclides using microalgae at various pH levels of radioactively contaminated solutions. Due to the ability of microalgae to adapt to sometimes even extreme pH values, this research may be interesting for many institutions and researchers dealing with more environmentally friendly methods of decontamination of radioactive waste.
Coke-oven wastewater contains an array of hazardous pollutants like cyanide, phenol, ammoniacal-N, etc. The main objective of the present study is to assess the effectiveness of phycoremediation technique as tertiary treatment for simultaneous removal of three model pollutants such as phenol, ammoniacal-N, and cyanide from secondary treated coke-oven wastewater. A green route was employed for the treatment of coke-oven wastewater via the use of Tetraspora sp. NITD 18, collected from a contaminated site. Strain susceptibility was tested for the growth in the simulated solution of phenol (10−300 mg/L), ammoniacal-N (100−800 mg/L), and cyanide (1−10 mg/L), and subsequently, optimum concentration was assessed as 100 mg/L, 400 mg/L, and 2 mg/L, respectively. pH 7 and inoculum concentration 10 % was found suitable for the removal of phenol (79.02 ± 6.93 %), ammoniacal-N (74.7 ± 5.07 %), and cyanide (80.4 ± 0.015 %) from their individual solution at optimal initial concentrations after 14 days. For solutions of individual pollutants, preferred pollutants were examined on the basis of production of biomass with respect to time, and found the following order: ammoniacal-N > phenol > cyanide. The solution of mixed pollutants was prepared by mixing the said pollutants at their optimal level of initial concentrations at a suitable pH (7). Such a solution was termed as simulated coke-oven wastewater (SCOW). While the present investigation deals with co-current removal of pollutants from simulated coke-oven wastewater (SCOW) and real secondary treated coke-oven wastewater at laboratory scale, the continuous study on real wastewater at industrial scale with the isolated algal strain is the scope of the future work.
Eco-toxicity testing assesses the potential harmfulness of unknown toxic substances as well as other effects of those substances, such as synergistic, additive, and antagonistic effects using various organisms including water flea, fish, benthic amphipod, and microalgae. Microalgae are important components in the food chains of marine ecosystems. Conventionally, the growth rate of an individual microalgae population is analyzed for 72 h to identify the effects of external stresses, e.g., chemicals, pH, temperature, CO2, etc. However, this method requires counting the number of microalgae every 24 h using a microscope, which is not only labor intensive but also requires substantial expertise. Dunaliella tertiolecta which rapidly changes its morphology when exposed to toxic substances, has been a species of interest among biomass and eco-toxicology researchers. However, such small changes are difficult to visualize and interpret with conventional microscopy or physicochemical techniques. Therefore, we propose a new method which utilizes microalgal morphological changes via lens-free shadow imaging technology (LSIT). To this end, a field-portable cell analyzer, NaviCell, which integrates LSIT was developed. Within this platform, the morphological changes of hundreds of microalgae can be automatically analyzed in parallel within just 3–4 min with over 96% precision and accuracy enabling rapid eco-toxicity evaluation.
A popular Cu(II) based metallo-cage cryptate, Complex 1 [LCu2(ClO4)4], is synthesized by using a bicyclic cryptand, L (synthesized in large scale of ≈ 28 gm/batch) and Cu(ClO4)2 for its application towards the removal of toxic CN¯ from cyanide contaminated water and cyanide containing industrial blast furnace (BF) wastewater. Complex 1, having very low solubility in aqueous medium, showed efficient removal of CN¯ (initial CN¯ conc. of 80 ppm to final conc. of 4.21 ppm; ≈ 95 % removal of CN¯) from standard aqueous solution of CN¯ (NaCN in water) within 10 min, through heterogeneous phase mixing as observed from Ion Selective Electrode (ISE) based measurements. Mechanistic investigation towards the binding of cyanide with complex 1 through spectroscopic studies indicated the initial formation of CN¯ bridged green dimeric copper (II) complex upon addition of one equivalent of CN¯ which subsequently decomposed upon addition of further equivalents of CN¯ to produce a colourless solution. Finally, as a real-time application, complex 1 was treated with cyanide contaminated industrial wastewater in the presence of other interfering anions (e.g. Cl¯, SO4²⁻, NO3¯, NO2¯, SCN¯, F¯etc.) which showed fast and efficient removal of cyanide (initial CN¯ conc. of 6.7 ppm to final conc. of 1.3 ppm; ≈ 77 % removal of CN¯ in 30 min) of BF wastewater from lab scale to pilot plant scale. Interestingly, the complex 1 showed recyclability up to six cycles in terms of removal of cyanide with high efficiency (≈ 72–74 % removal of CN¯).
Cyanide is a known toxic chemical compound that has an adverse effect on living organisms. Nonetheless, it is one of the active reagents in industries such as mining, pharmaceutical, cosmetics, and food processing companies worldwide. The beneficiation of gold and other precious metals from ore generates great amount of cyanide-bearing contaminants, which is released into the environment. The abundance of cyanide contaminants from these industries have created public health concern since the inception of metal extraction from ore. There are strict regulations on the production, transportation, utilization, and disposal of cyanide-bearing contaminants worldwide. The conventional treatment of cyanide waste is either chemical or physical process. The use of these treatment processes has certain pitfalls like operational challenges, an increase in capital cost, and generation of secondary waste. A number of microorganisms have the potential to utilize cyanide as nitrogen and carbon source and transform it into ammonia and carbon dioxide. Biodetoxification might be efficiently, economically and environmentally safe to detoxify cyanide in contaminants and attractive alternative to conventional detoxification method like chemical or physical. This paper reviews the principles and methods of biodetoxification of cyanide contaminants found in the ecosystem.
Cyanide is among the most toxic chemicals widely employed in the cyanidation process to leach precious minerals, such as gold and silver, by the minerals processing companies worldwide. This present article reviews the determination and detoxification of cyanide found in gold mine tailings. Most of the cyanide remains in the solution or the slurries after the cyanidation process. The cyanide species in the gold tailings are classified as free cyanide, weak acid dissociation, and metallocyanide complexes. Several methods, such as colorimetric, titrimetric, and electrochemical, have been developed to determine cyanide concentrations in gold mine effluents. Application of physical, natural, biological, and chemical methods to detoxify cyanide to a permissible limit (50 mg L ⁻¹ ) can be achieved when the chemical compositions of cyanide (type of species) present in the tailings are known. The levels of cyanide concentration determine the impact it will have on the environment.
Microbial community and metabolic potential changes in a biological wastewater treatment reactor were investigated using phylogenetic and functional profile analysis from 16S rRNA-gene-based pyrosequencing. Stirred-tank bioreactors fed by cyanide-containing synthetic solutions were inoculated with a sewage sludge and the cyanide-degrading microbial consortium. A better cyanide degradation was observed in the reactors containing the phylum Proteobacteria, but lower efficiency was observed when Firmicutes and Bacteroidetes were dominant. This study shows the important role of phylum Proteobacteria for the cyanide-containing wastewater treatment in the gold processing plant and contributes the fundamentals about the microbial community exposed to the cyanide.
Petroleum process industries are one of the most energy- and emission-intensive sectors throughout the world. There are natural gas processing plant, crude oil and condensate fractionation plant, liquefied natural gas plant, liquefied petroleum gas plant, etc. that create environmental pollution by processing and handling of petroleum products. The study critically reviewed and discussed the energy and environmental management including pollution control of petroleum process industries of Bangladesh. They produce both gaseous (process gas, waste gas, etc.) and liquid (produced water, waste oil, grease, etc.) pollutants. The study found that the liquid pollutant like waste water is more hazardous and its treatment process is highly complicated due to its higher salinity, more corrosivity and grease-containing characteristics. As part of energy management, the rational use of energy and energy flow diagram of the petroleum industry is presented. Finally, a time frame measure which can be implemented in order to save energy is outlined. The study concluded that the rational use of energy and proper environmental management are essential for achieving energy and environmental sustainability of process industries.
The constantly arising solicitousness for the environmental impact and the potential limitation of petroleum and gas resources has focused the commercial interest on the development of industrially viable microbial strains with fine-tuned physiological capabilities. Synthetic biology, metabolic and protein engineering have become progressively important and valuable platforms in the development of microbial cellular networks for the generation of various pharmaceuticals, chemicals, food ingredients, and biofuels through the conversion of renewable resources. However, despite the comprehensive optimization of the biosynthetic pathways, the mass concentration and the low production rates represent the major obstacles in the exploration of new production hosts, the synthesis of novel enzymatic catalysts of natural and unnatural reactions, and the development of more effective tools for functional proteomics and genomics. Therefore, innovative synthetic biology research and diversified genome engineering approaches are anticipated to play the principal role in the achievement of engineered microbes with robust phenotypes, higher yields, and productivity. Herein, we thoroughly present the nascent technologies in the advancement of bio-engineered microbial cell factories for the optimized synthesis of biotechnologically valuable products.
Various procedures exist for treating cyanides from different industrial waste waters, and comprise several physical, chemical and biological methods. It is still widely discussed and examined due to its potential toxicity and environmental impact. Physical and chemical methods are highly expensive and also cause secondary pollution. The treatment of cyanide by said method is rarely used, owing to cost-effectiveness. Thus, there is a pressing need for the development of an alternative treatment process capable of achieving high removal efficiency without troubling the environment. Several microbial species can degrade cyanide well into less toxic products. Biodegradation of cyanide compounds may take place through various enzymatic pathways, the enzymes of which are produced by microorganisms that utilize cyanides as substrate. The biological methods for the treatment of cyanide are not only cost-effective but also do not produce any secondary pollution. The present chapter describes the mechanism and ardent approaches of proficient biological methods for the removal of cyanide compounds and their advantages over other treatment processes.
The wet market provided fresh foodstuff. Unfortunately, the sullage commonly discharged directly to the drainage without any treatment. Hence, this research was focused on culturing the Scenedesmus sp. and implemented the phycoremediation process to wet market wastewater and to measure the heavy metal removals by Scenedesmus sp. There are two different time collected samples: (1) Sample at 7 a.m. and (2) Sample at 9 a.m.. The five samples were collected for each time sampling from of the Parit Raja Public Market, Batu Pahat wastewater (with additional of five different concentrations of Scenedesmus sp. which are 1.235x10⁶, 1.224x10⁶, 1.220x10⁶, 1.213x10⁶ and 1.203x10⁶ cell/ml). This experiment was conducted within eight days for culturing Scenedesmus sp. and phycoremediation within another eight days. The analysis was done with changes of DO and pH and heavy metals removal during phycoremediation. Based on the result, the optimum efficiency removals for each heavy metal had achieved (36.62-100%) and the optimum concentration for Sample 7 a.m. and Sample 9 a.m. is Concentration 1 (1.235x10⁶ cell/ml) obtained 81.18-100% of heavy metal removals. Concentration of microalgae is statistically correlated well with Fe (p<0.05) while not correlated significantly for Zn and Cu (p>0.05) in influencing high nutrient removal in the wastewater.
Cyanide is the reagent of choice for gold and silver extraction, but also a toxic chemical that may cause
severe environmental pollution problems. Vascular plants possess an enzyme system that detoxifies
cyanide by converting it to the amino acid asparagine. The phytotoxicity of cyanide is indirectly connected
to the efficiency of this enzyme system: Plants only survive cyanide exposure up to a dosage they can
metabolize. Cyanide phyto-toxicity was measured for the subtropical grass Sorghum bicolor. Potassium
cyanide was not toxic when added to the irrigation water at up to 125mg KCN/l (50mg CN/l). In a
degradation test, cyanide was efficiently degraded by sorghum roots and leaves. Cyanide elimination using
plants seems to be a feasible option for gold and silver mine waste and wastewater. Theoretical estimates
indicate that a large area of land is needed. But the process is cost effective, sustainable, and has less critical
emissions than any competing technology. Until now, phytotreatment of gold mining wastewater has only
been tested on a lab scale. With the current knowledge, a pilot-scale demonstration could be implemented
immediately
Summary Cadmium and zinc biosorption, alone or in combination, was investigated with sodium alginate immobilizedChlorella homosphaera cells. Concentrations ranging from 20.0 to 41.0mg/l cadmium, 75.0 and 720.0mg/l zinc were tested and, in all cases, the metal removal achieved values near 100%. When these metals were put in combination a decrease in the rate of absorption was detected. Gold was also tested in the immobilized system and 90% of the initial metal added was recovered in a solution containing 213.0mg/l of the metal, the alginic matrix being responsible for 40% gold uptake.
Heavy metals, depending on their oxidation states, can be highly reactive and, as a consequence, toxic to most organisms. They are produced by an expanding variety of anthropogenic sources suggesting an increasingly important role for this form of pollution. The toxic effect of heavy metals appears to be related to production of reactive oxygen species (ROS) and the resulting unbalanced cellular redox status. Algae respond to heavy metals by induction of several antioxidants, including diverse enzymes such as superoxide dismutase, catalase, glutathione peroxidase and ascorbate peroxidase, and the synthesis of low molecular weight compounds such as carotenoids and glutathione. At high, or acute, levels of metal pollutants, damage to algal cells occurs because ROS levels exceed the capacity of the cell to cope. At lower, or chronic, levels algae accumulate heavy metals and can pass them on to organisms of other trophic levels such as mollusks, crustaceans, and fishes. We review here the evidence linking metal accumulation, cellular toxicity, and the generation of ROS in aquatic environments.
Biosorbent materials are a potential alternative to conventional processes of metal recovery from industrial solutions. Algal biomass ofSargassum natans andAscophyllum nodosum outperformed ion exchange resins in sequestering respectively gold and cobalt from solutions. Non-living biomass ofSaccharomyces cerevisiae andRhizopus arrhizus exhibited higher metal-uptake capacity than the living biomass for the uptake of copper, zinc, cadmium, uranium. The solution pH affected the metal-uptake capacity of the biomass whereas the equilibrium biosorption isotherms were independent of the initial concentration of the metal in the solution. Desorption of the metal from the biosorbent and recycle of the biosorbent have also been demonstrated.
The detoxification of cyanide by algae was examined by exposing cultured suspensions of Arthrospira maxima, Chlorella sp. and Scenedesmus obliquus in growth media to varying concentrations in short-time batch tests. In each experiment, the pH was adjusted to 10.3. The effect of pH, initial concentration of algal cells, temperature and cyanide concentration on microbial detoxification were examined. Under the experimental conditions, initial microbial detoxification rates of 50 and 100 mg/L free cyanide were observed for 25 h. A. maxima did not survive due to its sensitivity to the higher cyanide concentrations in the solutions. S. obliquus removed the cyanide to a greater extent than did Chlorella sp. S. obliquus detoxified 99% of the cyanide, while Chlorella sp. removed about 86% in the same time period. For the raised cyanide concentrations between 100 and 400 mg/L, S. obliquus was the only microorganism tested for 67 h. Kinetic studies of cyanide detoxification showed that microbial removal was linearly correlated with concentration.
A cyanide-metabolizing bacterium, strain DF3, isolated from soil was identified as Alcaligenes xylosoxidans subsp. denitrificans. Whole cells and cell extracts of strain DF3 catalyzed hydrolysis of cyanide to formate and ammonia (HCN + 2H2O----HCOOH + NH3) without forming formamide as a free intermediate. The cyanide-hydrolyzing activity was inducibly produced in cells during growth in cyanide-containing media. Cyanate (OCN-) and a wide range of aliphatic and aromatic nitriles were not hydrolyzed by intact cells of A. xylosoxidans subsp. denitrificans DF3. Strain DF3 hydrolyzed cyanide with great efficacy. Thus, by using resting induced cells at a concentration of 11.3 mg (dry weight) per ml, the cyanide concentration could be reduced from 0.97 M (approximately 25,220 ppm) to less than 77 nM (approximately 0.002 ppm) in 55 h. Enzyme purification established that cyanide hydrolysis by A. xylosoxidans subsp. denitrificans DF3 was due to a single intracellular enzyme. The soluble enzyme was purified approximately 160-fold, and the first 25 NH2-terminal amino acids were determined by automated Edman degradation. The molecular mass of the active enzyme (purity, greater than 97% as determined by amino acid sequencing) was estimated to be greater than 300,000 Da. The cyanide-hydrolyzing enzyme of A. xylosoxidans subsp. denitrificans DF3 was tentatively named cyanidase to distinguish it from known nitrilases (EC 3.5.5.1) which act on organic nitriles.
Several cyanide-tolerant microorganisms have been selected from alkaline wastes and soils contaminated with cyanide. Among them, a fungus identified as Fusarium solani IHEM 8026 shows a good potential for cyanide biodegradation under alkaline conditions (pH 9.2 to 10.7). Results of K(sup14)CN biodegradation studies show that fungal metabolism seems to proceed by a two-step hydrolytic mechanism: (i) the first reaction involves the conversion of cyanide to formamide by a cyanide-hydrolyzing enzyme, cyanide hydratase (EC 4.2.1.66); and (ii) the second reaction consists of the conversion of formamide to formate, which is associated with fungal growth. No growth occurred during the first step of cyanide degradation, suggesting that cyanide is toxic to some degree even in cyanide-degrading microorganisms, such as F. solani. The presence of organic nutrients in the medium has a major influence on the occurrence of the second step. Addition of small amounts of yeast extract led to fungal growth, whereas no growth was observed in media containing cyanide as the sole source of carbon and nitrogen. The simple hydrolytic detoxification pathway identified in the present study could be used for the treatment of many industrial alkaline effluents and wastes containing free cyanide without a prior acidification step, thus limiting the risk of cyanhydric acid volatilization; this should be of great interest from an environmental and health point of view.
This paper describes several processes which may prove satisfactory for the removal of cyanide. Alkaline chlorination is the leading treatment technique and several gold mills are currently installing this system.
Homestake Mine in Lead, South Dakota, has developed and implemented a full scale (5. 5 MGD) attached growth, aerobic, biological treatment process to effectively remove all toxic parameters from cyanidation wastewaters. The process consists of three biological phases: (1) the use of mutant strains of bacteria to degrade cyanide, thiocyanate and ammonia, (2) bio-adsorption of heavy metals and suspended solids on the biofilm and (3) utilization of a bioassay toxicity testing facility to evaluate treatment efficiency and to develop site specific water quality criteria. Emphasis is on the use of compatible living systems to treat and evaluate treatment of toxic wastewaters.
The growth, nutrient (N, P) assimilation and removal of cadmium by immobilized Scenedesmus acutus were investigated. Results obtained with two kinds of immobilization matrices (k-carrageenan and sodium alginate) were compared with control and with suspended cultures of the microalgae. Orthophosphate assimilation of suspended cultures was stimulated by cadmium but nitrate consumption was inhibited. In alginate immobilized cultures cadmium stimulated nitrate consumption but inhibited orthophosphate assimilation. The immobilization material influenced both nutrient assimilation and cadmium removal by Scenedesmus cells. In the first 1.5 h of experimentation, k-carrageenan immobilized cells removed more cadmium than the alginate immobilized cells. However, at a later stage (i.e. after 1.5 h) cadmium removal was higher in alginate immobilized cells.
Experiments were carried out to develop the technological basis for the integrated biodegradation of cyanide and formamide. The ability of both Fusarium oxysporum CCMI 876 and Methylobacterium sp. RXM CCMI 908 to transform cyanide and formamide was analysed and characterised. The Kmi for cyanide hydratase in the immobilised Fusarium oxysporum CCMI 876 was 19±4mM of cyanide and the Vmaxi was 21±5μmolmin−1g−1 (DW) cells. For the entrapped Methylobacterium sp. RXM CCMI 908 the values of the apparent reaction kinetics were Kmi=1.7±0.3mM of cyanide and the Vmaxi=20±2μmolmin−1g−1 (DW) cells. These data were used to design and operate a two-catalyst system to balance cyanide and formamide transformations and assess the system stability. The cyanide was degraded by Fusarium oxysporum CCMI 876 at a rate of 0.059mMh−1 leading to 96% cyanide conversion and leaving a residual 0.21mM. Average 3.76mM of formamide and 0.34mM of formate were formed. This effluent is contacted with Methylobacterium sp. RXM CCMI 908 which used 84% of formamide. Then this compound drops to an average value of 0.62mM. In parallel, formate builds up to nearly 12-fold the initial concentration, correlating with the amount of formamide used. The two systems were merged in a single system which design involved a scale-up criterion and the degradation profiles along the system were determined.
Biological treatment of a synthetic leachate containing cyanide was accomplished in a sequencing batch biofilm reactor (SBBR). A mixed culture of organisms growing on silicone tubing were provided with cyanide as a sole carbon and nitrogen source. Organisms consumed cyanide (20 mg/liter CN−WAD) and produced ammonia in an approximate 1:1 molar yield. The SBBR was operated on a 24-h cycle. Over the course of each cycle, 20 mg/liter of cyanide was degraded to below 0.5 mg/liter. Results from four track studies are presented. It was demonstrated that, when supplied with glucose, the organisms would readily consume excess ammonia. For each mole of glucose added, 10 moles of NH3-N were removed from solution. The SBBR can be used as a mobile system for treatment of leachate from gold-mining operations. Large volumes of low concentration wastewater can be treated in the SBBR since it is not necessary to maintain a consortium of settling organisms. © 1998 Elsevier Science Ltd. All rights reserved
Substances extracted from the earth - stone, iron, bronze - have been so critical to human development that historians name the ages of our past after them. But while scholars have carefully tracked human use of minerals, they have never accounted for the vast environmental damage incurred in mineral production. Few people would guess that a copper mining operation has removed a piece of Utah seven times the weight of all the material dug for the Panama Canal. Few would dream that mines and smelters take up to a tenth of all the energy used each year, or that the waste left by mining measures in the billions of tons - dwarfing the world's total accumulation of more familiar kinds of waste, such as municipal garbage. Indeed, more material is now stripped from the earth by mining than by all the natural erosion of the earth's rivers. The effects of mining operations on the environment are discussed under the following topics: minerals in the global economy, laying waste, at what cost cleaning up, and dipping out. It is concluded that in the long run, the most effective strategy for minimizing new damage is not merely to make mineral extraction cleaner, but to reduce the rich nations needs for virgin (non-recycled) minerals.
There are several water and tailings treatment processes that have been successfully used worldwide for cyanide removal at mining operations. The key to successful implementation of these processes involves consideration of the following:•Site water and cyanide balances under both average and extreme climate conditions.•Goals to be adopted for cyanide levels in treated effluent, including the form of cyanide to be regulated (free vs. WAD vs. total cyanide).•The range of cyanide treatment processes available and their ability to be used individually or in combination to achieve treatment objectives.•Proper treatability testing, design, construction, maintenance and monitoring of both water- and cyanide-management facilities.By carefully considering these aspects of water and cyanide management before, during and after mine operation, operators can reduce the potential for environmental impacts associated with the use of cyanide. Another aspect of cyanide treatment to be considered is the potential environmental impact of the cyanide-related compounds - cyanate, thiocyanate, ammonia, nitrate and nitrite. These compounds may be present in mining solutions to varying extents and may require treatment if water is to be discharged. Each of these cyanide-related compounds is affected differently in the treatment processes discussed, and this should be considered when evaluating cyanide-treatment alternatives for a given site. Table 13 provides a simplified summary of the general applications of various treatment technologies for the removal of iron cyanide and WAD cyanide. This table represents a very simplified summary, but can be used as a conceptual screening tool when evaluating cyanide-treatment processes.
Various bacterial and fungal strains capable of degrading cyanides or having a high potential for adsorbing heavy metals were isolated from water and sediment samples from a mining wastewater deposit in Baia Mare. Some of the isolates were characterised and identified. For those strains displaying the most rapid degradation or the greatest adsorption capacity, important parameters were analysed in synthetic media and in process waters from the Baia Mare pond and the Sasar cyanidation plant. Optimal pH and temperature levels, maximum tolerable cyanide and metal concentrations, as well as possible additional substances required, such as hydrocarbon sources or phosphate were determined. Disruptive factors inhibiting the activity of the organisms and making the complex analysis of the cyanides more difficult were found. With a view towards the development of a pilot plant the immobilization of microorganisms was tested on different support materials.
Accumulation of UO
22
+ by Scenedesmus obliquus 34 was rapid and energy-independent and the biosorption of UO
22
+ could be described by the Freundlich adsorption isotherm below the maximum adsorption capacity (75 mg g-1 dry wt). The optimum pH for uranium uptake was between 5.0_8.5.0.1_2.0 M NaCl enhanced uranyl, while Cu2+, Ni2+, Zn2+, Cd2+ and Mn2+ competed slightly with uranyl. Pretreatment had an unexpected effect on biosorption. After being killed by 0.1 M HCl, S. Obliquus 34 showed 45% of the uptake capacity of the control in which fresh cells were suspended directly in uranyl solution, while the pretreatment of cells by 0.1 M NaOH, 2.0 M NaCl, ethanol or heating decreased uptake slightly. Fresh S. obliquus 34 at 1.2_2.4 mg dry wt mL-1 was able to decrease U from 5.0 to 0.05 mg L-1 after 4_6 equilibrium stages with batch adsorption. Deposited U could be desorbed by pH 4.0 buffer. It is suggested that U was captured by effective groups or by capillary action in the cell wall in the form of [UO2OH]+.
A bacterial coculture capable of growing on thiocyanate has been isolated from thiocyanate adapted bacterial suspension of urban sewage treatment plant. The coculture is composed of two bacteria identified as species Acinetobacter johnsonii and Pseudomonas diminuta. The two end products of thiocyanate conversion are ammonia and sulfate. The thiosulfate has been identified as the sulfur intermediate product of the conversion of thiocyanate to sulfate.
The present study compared the efficiency of two unicellular green algae, Chlorella vulgaris (a commercial species from Carolina Biological Supplies Company) and WW1 (an indigenous species isolated from a local sewage treatment works, tentatively identified as Chlorella miniata) in removing Ni2+ from nickel solutions with concentration ranges similar to that in electroplating effluents. The Ni2+ removal efficiency of C. vulgaris (around 33–41%) was significantly lower than that of WW1 (more than 99%) in nickel solutions from 10 to 40 μg ml−1. The maximum Ni2+ uptake by C. vulgaris and WW1 under the present batch experiment was 641.76 and 1367.62 μg g−1, respectively. According to Langmuir adsorption isotherms the nickel adsorption capacity of WW1 (2985.07 μg g−1) was two times greater than that of C. vulgaris (1282.05 μg g−1). These results demonstrated that WW1 was a more powerful Ni2+ biosorbent than C. vulgaris. In both species, most Ni2+ in solution was sequestered by the algal cells within the first few minutes of treatment. The cellular Ni2+ concentration increased with the concentrations of nickel in solution. After treating Ni-containing wastewater for 24 h, both species were still capable of cell division, but the growth rate was reduced in proportion to the concentrations of nickel in the wastewaters.
Biological treatment is a proven process for the treatment of mining effluents such as tailings, wastewaters, acidic mine drainage etc. Several bacterial species (Pseudomonas sp.) can effectively degrade cyanide into less toxic products. During metabolism, they use cyanide as a nitrogen and carbon source converting it to ammonia and carbonate, if appropriate conditions are maintained. In this study, nine strains of Pseudomonas sp. were isolated and identified from a copper mine. Two (CM5 and CMN2) of the nine bacteria strains were used in a cyanide solution. Some important parameters in the biological treatment process were tested and controlled: pH, cell population and CN− concentration. Tests were conducted to determine the effect of the type of bacterial strains on the treatment of cyanide. Laboratory results indicated that biological treatment with Pseudomonas sp. might be competitive with other chemical treatment processes. This paper presents the results of an investigation of a biological treatment system for cyanide degradation in a laboratory batch process.
The removal of heavy metals by a dry biomass of a brown seaweed was evaluated. A continuous system was used, with an effluent from a Brazilian zinc producing industry, containing zinc (88.0 mg/L), cadmium (1.4 mg/L), and manganese (11. 7 mg/L), as well as high levels of calcium (444 mg/L), magnesium (100 mg/L) and sodium (37.0 mg/L). Preliminary results, in batch conditions, indicated fast uptake kinetics for the heavy metals, whose equilibria were reached in a maximum of 30 minutes. The continuous run was conducted in a laboratory acrylic column, lm high, containing several samplers, filled with the dry biomass. The system operated in upflow condition, at a flow rate of 25 mL/min, f or approximately 70 hours, with high operational stability. The results showed high efficiency in the biosorption of heavy metals. Sodium, calcium and magnesium were not incorporated by the biomass, probably as they are present in the structural polysaccharides of the biomass, thus preventing the establishment of an effective ion-exchange process. Analysis of the obtained results did not indicate selective uptake of the metals, probably due to their marked concentration differences in solution. The continuous laboratory system initially showed an efficiency close to 100% in the biosorption of all heavy metals, followed by a gradual decrease, as a function of the saturation of binding sites in the biomass. A mathematical adjustment of the curves obtained for the uptake of the different metals was used for estimating the amount of biosorbed metals, through mathematical computer integration.
In the history of Turkey the first use of cyanide for gold recovery has been at the Ovacik Gold Mine. During one-year test period, this mine has successfully been mining and processing after a complicated and extensive environmental impact procedure. In Turkey about 2500 ton of sodium cyanide are used with about 240 ton of sodium cyanide being used at this mine annually. During the test period, it has been shown that an effluent quality (CNWAD) between 0.06 ppm (min) and 1 ppm (max) was achievable after cyanide destruction with the Inco Process. It was also found that treated effluent values (CNWAD) of process water (decant) were between 0.04 ppm (min) and 0.59 ppm (max). This paper presents a review of the cyanidation and cyanide destruction processes at the Ovacik Gold Mine.
A bacterial consortium capable of utilising metal cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of metal cyanides (viz. copper cyanide and zinc cyanide) from electroplating waste water. Optimal conditions biodegradation of both the metal-cyanide compounds were pH 7.5, temperature 35°C, inoculum size 109 cells per ml and glucose or sugarcane molasses requirement of 5 mM or 0.6 ml/l, respectively. Metal precipitates obtained during metal-cyanide biodegradation were identified as metal-hydroxides. When the treatment was carried out in a 27 l rotating biological contactor (RBC) in continuous mode, the system could achieve >99.9% removal of 0.5 mM metal cyanide (ca. 52 mg/l cyanide and 30–40 mg/l copper/zinc) in 15 h with sugarcane molasses as carbon source. The RBC treated effluent was found to be safe for discharge in the environment as confirmed by chemical analysis and fish bioassay studies.
The effect of sodium cyanide (NaCN), iron-cyanide complexes and a blast furnace effluent on the growth of the unicellular marine diatom Nitzschia closterium was investigated. Due to the volatile nature of HCN, the free and total cyanide concentrations in all test solutions were monitored daily to ensure that average daily losses of free cyanide did not exceed 5%. The iron-cyanide complexes were less toxic than the NaCN, with 72-h EC50 values of 57, 127 and 275 μg total-CN litre−1 for NaCN, K3Fe(CN)6 and K4Fe(CN)6, respectively. The estimated lowest observed effect concentration (LOEC) for NaCN was 10 μg litre−1. The toxicity of the cyanide complexes was largely due to free cyanide (HCN + CN−) with possible additional toxicity caused by dissociation of the complexes at the algal cell membrane. The toxicity of an effluent from a blast furnace drawdown episode also correlated well with the toxicity of free cyanide.
Biosorption is considered a potential instrument for the removal of metals from waste solutions and for precious metals recovery, an alternative to the conventional processes, such as those based on ion exchange, or adsorption on activated carbon. In this work the state of the art of biosorption investigation is presented and results found in literature are compared.
The rate of degradation of cyanide by certain strains of the Trichoderma spp. was evaluated. For comparison two Fusarium spp., which had previously been demonstrated to degrade metallocyanides were also studied. Studies were carried out to assess the rate of degradation using cyanide as the sole source of carbon or in the presence of glucose. Biodegradation was observed in flask cultures using cyanide as the sole carbon source. Strong evidence of cyanide biodegradation and co-metabolism emerged from studies with flask cultures where glucose was provided as a co-substrate. The rate of degradation of 2000 ppm CN− was enhanced almost three times in the presence of glucose. A concomitant increase in fungal biomass was also observed in all the strains over the experimental period. Growth yield calculations performed provided values that were comparable to those reported in literature for one-carbon substrates.
This chapter focuses on cyanide metabolism in micro-organisms. It is noted that cyanide is a relatively common product of microbial as well as plant metabolism. Cyanide production by micro-organisms has many characteristics typical of secondary metabolism. In addition, it is probably the simplest secondary metabolic system and a continued investigation of cyanide formation should greatly aid a better understanding of microbial secondary metabolism. Cyanide degradation by Chromobacterium violaceum, or C. violaceum, is known to synthesize at least three enzymes capable of metabolizing cyanide. These include rhodanese, γ-cyano-α-aminobutyric acid synthase, and β-cyanoalanine synthase. The concentrations of all three enzymes increase in the post-cyanogenic period. The buildup of β-cyanoalanine is particularly noteworthy in bacteria grown under conditions of high cyanogenesis. The suspensions of harvested C. violaceum cells are also able to form β-cyanoalanine when incubated with cyanide and serine.
A Gram-negative soil bacterium (isolate 26B) has been shown to utilize up to 100 mM thiocyanate as a source of nitrogen when supplied with glucose as the source of carbon and energy. During growth of isolate 26B with thiocyanate as the source of nitrogen, no ammonia, nitrate, nitrite, cyanide, cyanate, sulfate, sulfite, sulfide or carbonyl sulfide was detected in the growth medium. Growth of the bacterium on 14C-labelled thiocyanate (1.6 microCi) and glucose, yielded 14C-labelled carbon dioxide (0.9 microCi). The addition of 2.9 mM thiocyanate to a bacterial suspension in phosphate buffer (50 mM, pH 7.4) resulted in the utilization of 2.1 mM thiocyanate and the production of 2.0 mM ammonia. This activity was inducible and only occurred after growth of the bacterium with thiocyanate as the source of nitrogen. Tetrathionate (0.7 mM) was detected in the medium after the utilization of thiocyanate (2.4 mM) by a suspension of the bacterium in phosphate buffer, and thiosulfate (1.0 mM) was detected as an intermediate. The addition of sulfide or thiosulfate to the bacterial suspension also resulted in the formation of tetrathionate. The utilization of both of these compounds appeared to be constitutive. A pathway for thiocyanate utilization by isolate 26B is proposed which involves the hydrolysis of thiocyanate to produce cyanate and sulfide. The cyanate then undergoes further hydrolysis to form ammonia and carbon dioxide. The sulfide is ultimately oxidized to tetrathionate via a pathway which includes thiosulfate.
Our isolate, Pseudomonas putida, is known to be capable of utilizing cyanides as the sole source of carbon (C) and nitrogen (N) both in the form of free cells and cells immobilized in calcium alginate. In the present study, the cell-free extract(s) were prepared from the cells of P. putida grown in the presence of sodium cyanide. The ability of enzyme(s) to convert cyanides, cyanates, thiocyanates, formamide and cyanide-containing mine waters into ammonia (NH3) was studied at pH 7.5 and pH 9.5. The kinetic analysis of cyanide and formamide conversion into NH3 at pH 7.5 and pH 9.5 by the cell-free extract(s) of P. putida was also studied. The Km and Vmax values for cyanide/formamide were found to be 4.3/8 mM and 142/227 mumol NH3 released mg protein-1 min-1 respectively at pH 7.5 and 5/16.67 mM and 181/434 mumol NH3 released mg protein-1 h-1 respectively at pH 9.5. The study thus concludes that the cell-free extract(s) of P. putida is able to metabolize not only cyanides, cyanates, thiocyanates, and formamide but also cyanide-containing mine waters to NH3.
Two living Chlorella species were used to remove nickel from solution containing 30 micrograms Ni ml-1 in 10 successive cycles. The present study also examined the continued viability of these two algal species after repeated exposure to nickel. The two species of Chlorella were Chlorella vulgaris (commercially available) and WW1 (indigenous species isolated from domestic sewage and was tentatively identified as Chlorella miniata). The nickel removal percentage of WW1 cells was maintained at around 85% in the first five cycles, then declined slightly from the fifth cycle onwards, and finally achieved around 70% removal at the end of the 10th cycle. On the contrary, the removal efficiency of C. vulgaris declined from 50 to 30% during the 10 cycles of nickel bisorption. At the end of these 10 successive cycles, WW1 accumulated a substantial amount of Ni2+ (the cumulative cellular Ni concentration was 0.92% dry w.), while the value was only 0.17% in the case of C. vulgaris. These results suggest that the local isolate, WW1, had more consistent and satisfactory ability for removing Ni than the commercial C. vulgaris. Both algal species were still capable of dividing after each nickel treatment cycle, suggesting that the cells were not killed even when significant amounts of nickel were adsorbed/absorbed. However, Ni exposure adversely affected the physiological activity of algal cells as reflected by the decline in division rate and chlorophyll-a activity in both species. Such negative effects became more obvious as the number of cyclic treatments was increased. Nevertheless, WW1 cells appeared to recover from nickel treatment when re-cultivated in commercial medium for 2 weeks.
A continuous culture experiment was conducted to study interactions between copper-binding ligands released by light-limited Ditylum brightwellii, and toxic effects of Cu on this diatom. Over 6 months, the Cu concentration in the medium has been increased in seven steps (3-173 nM). At each Cu addition, Cu speciation, characteristics of Cu sorption to cellular binding sites, and cell characteristics were determined. Physiological effects of Cu were studied, using indicators for metal detoxification (thiols) and lipid peroxidation (malondialdehyde). Minor amounts of Cu (<1.4%) were chelated by a minimum amount of EDTA (57 nM), required to maintain a stable long-term continuous culture. The responses of D. brightwellii to Cu were monitored. (1) From 3 to 47 nM added Cu, decreasing pools of glutathione, increasing malondialdehyde contents, an increased release of lipophilic ligands, and cell lysis indicated the enhancement of lipid peroxidation. (2) From 47 to 94 nM Cu, a 16-fold increase in high-affinity (strong) hydrophilic ligands was measured (conditional stability constants K' approximately 10(12)) that complexed most Cu (maximum 97%); sexual reproduction was stimulated and cell volumes increased. (3) From 126 nM Cu, glutathione pools increased again, whereas cell division rates decreased slightly. (4) At 142 nM Cu, the number of lysed cells reached a maximum, as did the production of lipophilic compounds that complexed approximately 2% Cu. As the binding sites of the strong ligands became Cu-saturated above 142 nM Cu, larger amounts of Cu were bound to low-affinity (weak) dissolved ligands (3-30%) and cellular binding sites (0.2-2.5%). Probably due to saturation of organic complexes at 142 nM Cu, the MINEQL-calculated Cu2+ concentrations increased markedly; pCu values decreased from >11 to approximately 10; division rates were further inhibited; gamma-glutamylcysteine (phytochelatin precursor) was produced. (5) At 157 nM Cu, phytochelatin synthesis started, and Cu-sorption capacities (cell walls and internal binding sites) increased. (6) At 173 nM Cu, the phytochelatin pool sizes and the number of cellular Cu-binding sites increased further. These results suggest that ligands released by a dense bloom of D. brightwellii, either by active excretion or lysis, would have lower affinities for Cu (K' approximately 10(9)-10(12)) and moderate the availability of Cu less effectively than ligands in natural environments (10(13)-10(14)). In this diatom, the concurring release of ligands, enhanced malondialdehyde production, increasing numbers of presexual cells and cell enlargement may serve as early-warning signals for Cu toxicity, rather than metal-specific phytochelatins that appeared at a stage when cell division was already clearly inhibited.
Experiments were conducted comparing the individual removals of cadmium and copper from water via biosorption using Scenedesmus abundans, a common green algae, to removal in a multi-component system to determine competitive effects, if any, between the metals. The goal was to characterize the biological treatment of water contaminated with heavy metals using live aquatic species. In addition, experiments were performed to measure cell viability as a function of metal concentration and also to compare metal removal using living species to that using nonliving ones. It was shown that, while both living and nonliving S. abundans removed cadmium and copper from water, living algae significantly outperformed nonliving algae. Further, in characterizing biosorption by three concentrations of live S. abundans, capacity curves were created comparing the metal biosorbed per mass algae to the initial metal concentration in solution. The algae concentration was not a factor in the biosorption of either metal individually, such that the capacity of the algae for the metal increased with decreasing algae concentration. At the lowest algae concentration considered, competitive effects were observed at copper and cadmium concentrations above 4 mg/l each. At the highest algae concentration considered, no competitive effects were observed in the range of cadmium and copper concentrations studied (1-7 mg/l). It was concluded that biological treatment of heavy metal contaminated water is possible and that at adequately high algae concentrations, multi-component metal systems can be remediated to the same level as individual metals.
Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.
In gold mining, cyanide has been the preferred lixiviant worldwide since 1887. Although cyanide can be destroyed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. Biological treatment of cyanide is a well-established process and has been commercially used at gold mining operations in North America. Biological treatment processes facilitate growth of microorganisms that are essential for the treatment. The present review describes the advances in the use of biological treatment for the destruction of cyanide in gold mill effluents.
Individual and combined effects of three heavy metals; namely, copper, chromium and nickel, on growth, photosynthesis and chlorophyll a synthesis of the unicellular green alga, Chlorella pyrenoidosa 251, were determined. Within the concentration range of 0.1 to 1.0 mg litre(-1) of the three heavy metals tested on growth, photosynthesis and chlorophyll a synthesis of the alga, the order of toxicity of the three heavy metals was copper > chromium > nickel. The presence of one of the three heavy metals interacted synergistically with the other two heavy metals in various bimetallic combinations on growth, photosynthesis and chlorophyll a synthesis of the alga.