Please use this identifier to cite or link to this item: http://hdl.handle.net/11189/1899
Title: Continuous biotechnological treatment of cyanide contaminated waters by using a cyanide resistant species of Aspergillus awamori
Other Titles: Environmental Biotechnology – New Approaches and Prospective Applications
Authors: Santos, Bruno AQ 
Ntwampe, Seteno KO 
Doughari, James Hamuel 
Keywords: Aspergillus awamori;Treatment - Contaminated water
Issue Date: 2013
Publisher: InTech Online
Series/Report no.: ;pp 123-146
Abstract: Various industries release a combination of free cyanide and cyanide complexes into the environment via a variety of disposal methods, particularly as wastewater. These industries utilise cyanide based compounds in various operations, including: the beneficiation of metals, electroplating, case hardening, automotive manufacturing, circuitry board manufacturing, and in chemical industries [23]. Cyanide is often found in organic, hydrocarbon chains or as inorganic, transition, alkali and alkali earth metal complexes [20]. Many cyanide complexes are highly unstable, thus temperature, pH and light can degrade the components to form free cyanide which is the most toxic form of cyanide [20, 26]. There is an overwhelming popularity in industry for the use of chemical treatment methods for the treatment of free cyanide and cyanide complexes compared to biochemical treatment methods. Chemical remediation methods like alkaline chlorine oxidation are commonly used to treat cyanide contaminated wastewater [23, 24]. Chemical oxidation is particularly ineffective in the treatment of cyanide-metal complexes containing heavy metals, such as copper, nickel and silver, due to the slow reaction rate [23]. The excess quantity of chlorine used in the treatment process increases the chemical oxygen demand (COD) of the wastewater thereby rendering the water undesirable for reuse, toxic to aquatic life and may produce organic substances. In order to reduce operational costs, some manufacturers partially treat the wastewater, resulting in untreated and/or partially decomposed cyanide being discharged. Other methods of treatment include copper catalysed hydrogen peroxide oxidation, ozonation and electrolytic decomposition [23]. However, these methods are unpopular due to the high capital costs, specialist equipment and maintenance requirements. Several microorganisms, bacteria such as Nocardia sp. and Rhodococcus sp., fungi such as Aspergillus sp. and Fusarium sp. and algae such as Arthrospira maxima and Scenedesmus obliquus, possess enzymatic mechanisms able to bioremediate free cyanide and cyanide complexes [1, 26]. However, limited studies have been conducted using organic waste and fungal strains in cyanide bioremediation. Several studies have been conducted using varying concentrations of free cyanide, with moderate success being achieved in some cases [1]. Since the early 1970’s, progress has been made to develop economically viable continuous remediation processes such as membrane bioreactors (MBRs) [8]. A membrane is generally defined as being a selective barrier. The membrane utilised in a bioreactor can provide either a barrier to limit the transport of certain components, while being permeable to others, thus prevent certain components from contacting a biocatalyst, or contain reactive sites thus being a catalyst itself [5]. The application of MBRs for the production of enzymes has received considerable attention for their diverse industrial use. A number of microorganisms have been studied in MBR applications for wastewater using fungi, such as white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium) [8]. Solid waste generation in South Africa is a problem growing at an exponential rate with the majority of landfill sites reaching maximum capacity. Approximately 427x106 tonnes of solid waste is generated in South Africa every year, of which 40% by mass is organic waste [10]. The average amount of waste generated per person in South Africa is 0.7 kg/annum, which is close to that of developed countries such as the United Kingdom (0.723 kg/annum) and Singapore (0.87 kg/annum), than for developing countries, such as Nepal (0.3 kg/annum) [10]. It is sensible to bioaugment biotechnological processes to utilise organic waste materials, particularly for industries which produce large quantities of it.
Description: Book chapter Petre M (ed): Environmental Biotechnology – New Approaches and Prospective Applications Rijeka, Croatia: InTech Online Publishers, 2013, pp 123-146, ISBN 978-953-51-0972-3
URI: http://hdl.handle.net/11189/1899
ISBN: 978-953-51-0972-3
Appears in Collections:Appsc - Books / Book Chapters

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