Use of algae for removing heavy metal ions from wastewater: Progress and prospects
ABSTRACT Many algae have immense capability to sorb metals, and there is considerable potential for using them to treat wastewaters. Metal sorption involves binding on the cell surface and to intracellular ligands. The adsorbed metal is several times greater than intracellular metal. Carboxyl group is most important for metal binding. Concentration of metal and biomass in solution, pH, temperature, cations, anions and metabolic stage of the organism affect metal sorption. Algae can effectively remove metals from multi-metal solutions. Dead cells sorb more metal than live cells. Various pretreatments enhance metal sorption capacity of algae. CaCl2 pretreatment is the most suitable and economic method for activation of algal biomass. Algal periphyton has great potential for removing metals from wastewaters. An immobilized or granulated biomass-filled column can be used for several sorption/desorption cycles with unaltered or slightly decreased metal removal. Langmuir and Freundlich models, commonly used for fitting sorption data, cannot precisely describe metal sorption since they ignore the effect of pH, biomass concentration, etc. For commercial application of algal technology for metal removal from wastewaters, emphasis should be given to: (i) selection of strains with high metal sorption capacity, (ii) adequate understanding of sorption mechanisms, (iii) development of low-cost methods for cell immobilization, (iv) development of better models for predicting metal sorption, (v) genetic manipulation of algae for increased number of surface groups or over expression of metal binding proteins, and (vi) economic feasibility.
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- "Biological treatment is a poised to be a dependable alternative method to remove the metal ions because it has many desirable advantages such as easy implementation, low cost, minimal use of chemicals, high efficiency and selectivity to remove only the desired metals (Matagi et al., 1998; Chevalier et al., 2000; Mehta and Gaur, 2005). Biological method of treatment is essentially based on the use of microorganisms which efficiently remove toxicants and toxic heavy metals. "
ABSTRACT: Cadmium is one of the most toxic substances found in aquatic ecosystems. This metal tends to accumulate in photosynthetic plants and fish and transferred to humans causing many diseases. It has to be removed from our environment to reduce any health risks. Dry biomass of the microalga (cyanobacterium) Spirulina platensis were used as biosorbent for the removal of cadmium ions (Cd2+) from aqueous solutions. The effects of different levels of pH (3-9), biomass concentration (0.25-2 g), temperature (18-46 °C), metal concentration (40-200 mg/l) and contact time (30-120 min) were tested. Batch cultures were carried out in triplicate in an orbital shaker at 150 rpm. After centrifuging the biomass, the remaining levels of cadmium ions were measured in the supernatant by Atomic Absorption Spectrometer. Very high levels of removal, reaching up to 87.69% were obtained. The highest percentage of removal was reached at pH 8, 2 g of biosorbent, 26°C, and 60 mg/l of cadmium concentration after 90 minutes of contact time. Langmuir and Freundlich isotherm models were applied to describe the adsorption isotherm of the metal ions by S. platensis. Langmuir model was found to be in better correlation with experimental data (R2 = 0.92). Results of this study indicated that S. platensis is a very good candidate for the removal of heavy metals from aquatic environments. The process is feasible, reliable and eco-friendly.Saudi Journal of Biological Sciences 06/2015; 210. DOI:10.1016/j.sjbs.2015.06.010 · 0.74 Impact Factor
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- "Heavy metals contained in industrial effluents are dangerous particularly in human health perspective due to their toxicity and bio-accumulating effects   . Some of the conventional methods which are still used in the treatment of wastewaters such as ion exchange and chemical precipitation , do not produce significant or desired results when the concentration of heavy metal present is relatively high . In addition, they are also expensive to manage and could sometimes lead to an unfavourable condition such as the formation of toxic chemical sludge as a result of the many chemicals involved in the process. "
ABSTRACT: The aim of this study was to determine the growth and the bioremoval capacity of the green microalga, Botryococcus sp. grown in industrial wastewater contaminated with heavy metals. The freshwater green microalga, Botryococcus sp. was cultured in different concentrations of wastewater (25%, 50% and 100%) with an initial cell concentration of 1000 cells/ml for a period of 12 days. Bold basal medium and sterile distilled water were used as positive and negative control, respectively. The Botryococcus sp. grown in Bold's basal medium showed the highest (P<0.05) average growth rate (7.8 × 106 cells/ml) after a period of 12 days, whereas, the lowest (P<0.05) growth was observed in 50% concentration of wastewater (4.8 × 104 cells/ml). Similar results were obtained for the specific growth rate (µ/day) with an average of 1.93µ/day and 1.22µ/day for the positive control and the 50% concentration respectively. Highest reduction of heavy metals was achieved for chromium which is equivalent to 94%, followed by copper (45%), arsenic (9%) and cadmium (2%). The results of this study suggest the potential of Botryococcus sp. as bioremediator of wastewater contaminated with heavy metals.Journal of Science and Technology 12/2014; 6(2):29-40.
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- "The cultivation of algae in industrial effluent provides an effective form of bioremediation as algae can bioconcentrate metals from waste water (Mehta & Gaur, 2005; Troell et al., 2009; Hubbe, Hasan & Ducoste, 2011) while also capturing carbon and producing sustainable biomass (Roberts, de Nys & Paul, 2013). Integrated algal culture is particularly suited to coal-fired power stations as they are significant sources of both metal-contaminated waste water and CO 2 (Roberts, de Nys & Paul, 2013). "
ABSTRACT: The bioremediation of industrial waste water by macroalgae is a sustainable and renewable approach to the treatment of waste water produced by multiple industries. However, few studies have tested the bioremediation of complex multi-element waste streams from coal-fired power stations by live algae. This study compares the ability of three species of green freshwater macroalgae from the genus Oedogonium, isolated from different geographic regions, to grow in waste water for the bioremediation of metals. The experiments used Ash Dam water from Tarong power station in Queensland, which is contaminated by multiple metals (Al, Cd, Ni and Zn) and metalloids (As and Se) in excess of Australian water quality guidelines. All species had consistent growth rates in Ash Dam water, despite significant differences in their growth rates in "clean" water. A species isolated from the Ash Dam water itself was not better suited to the bioremediation of that waste water. While there were differences in the temporal pattern of the bioconcentration of metals by the three species, over the course of the experiment, all three species bioconcentrated the same elements preferentially and to a similar extent. All species bioconcentrated metals (Cu, Mn, Ni, Cd and Zn) more rapidly than metalloids (As, Mo and Se). Therefore, bioremediation in situ will be most rapid and complete for metals. Overall, all three species of freshwater macroalgae had the ability to grow in waste water and bioconcentrate elements, with a consistent affinity for the key metals that are regulated by Australian and international water quality guidelines. Together, these characteristics make Oedogonium a clear target for scaled bioremediation programs across a range of geographic regions.PeerJ 05/2014; 2:e401. DOI:10.7717/peerj.401 · 2.10 Impact Factor