Influence of support material on the immobilization of Sulfate-Reducing microbial consortium originated from the effluent of a tannery

KIKOT P; MIGNONE C; VIERA M; DONATI E

Rosario, Santa Fe

Workshop; 1st Argentinean Work Shop in Environmental Science; 2009

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      Heavy metals are released in the environment as a consequence of anthropogenic activities and represent a serious problem for the environment and human life. Heavy metals are present in wastewaters dischargued from industries such as metallurgical, chemical manufacturing, paint, battery, tannery and mining industry in acid-mine drainage that contain high levels of sulfate. Conventional technologies for removing metals from effluents (including precipitation, ion exchange and absorption) are expensive, with low selectivity, ineffective for removing metals at low concentration and generate high sludge volume. Bioremediation with biologically produced H2S offers attractive advantages over the conventional treatment technologies: large volumes of sludge are not generated, higher stability of the metal precipitates in the form of insoluble sulfides and more effective at removing metals at lower concentrations. Sulfate-reducing bacteria (SRB) are heterotrophic microorganisms that use low molecular mass organic acids (such as lactic) and alcohols (such as ethanol) as the carbon/energy substrates. The organic substrate is oxidized either completely to CO2 or to some intermediate compound such as acetic acid using sulfate as a terminal electron acceptor, generating sulfide. The biologically produced H2S react with metals and form insoluble metal sulfide precipitates that can be easily separated. Application of freely suspended cells in a continuous system, however, dictates a high residence time to prevent wash-out of the cells. Immobilized cell reactors appear to be a potential alternative in this area and the supports for biomass growth can be an important tool to improve the microbial equilibrium necessary in reactors employed in the treatment of sulfate-rich wastewaters. The cell immobilization technique is widely used in anaerobic reactors treating wastewaters, when the main objective is to increase the concentration of biomass and the cellular retention time in the reactor. The type of support used for anaerobic biomass immobilization can affect the efficiency of a bioreactor, since the number and type of cells adhering to the support may vary from one support to another. In the present work selection a proper carrier matrix was studied. An evaluation was made of the adhesion of a consortium of sulfate reducing bacteria (enriched from the effluent of a tannery in the area of the Rio Lujan, Argentina) onto six types of support materials: vegetal carbon, polyurethane foam, sand, perlite, vermiculite and glass beads. DGGE were used to characterize the composition of mesophilic anaerobic biofilms developed in different supports. A comparison was made of the quantity of biomass adhering to each material.