Removal of Cr from tannery sludge by indigenous sulfur-oxidizing bacteria

Abstract

The aim of the present study was to examine Cr removal from tannery sludge by bioleaching method using indigenous sulfur-oxidizing bacteria with special emphasis on the influence of bioleaching process on sludge settleability. Chemical leaching with sulfuric acid was designed as the control. The results showed that the inoculation of sulfur-oxidizing bacteria and the addition of elemental sulfur were effective in removing Cr from tannery sludge. After 144 hours of bioleaching, 98% of Cr could be leached. Although it took only 8 hours to reduce the sludge pH from 7.8 to about 2.0 by chemical leaching as compared to 144 hours for bioleaching treatment, chemical leaching removed only 91% of the total Cr. Regardless of bioleaching and chemical leaching treatments, sludge settleability improved considerably with a decrease in sludge pH. Bioleaching treatment performed better than chemical leaching in terms of the percentage of settled sludge and the effluent suspended solids (ESS) content in sludge supernatant. Nevertheless, further work should be carried out to investigate the precise mechanisms leading to such enhanced sludge settleability during sludge bioleaching process.

Detoxification of Electroplating Sludge by Bioleaching: Process and Kinetic Aspects

“…It has been reported that the bioleaching behavior of metals strongly depends on their chemical forms in the original sludge. The experimental data show that the removal efficiencies of heavy metal with respect to concentration of sludge took place in the order of 1% > 2% > 3% > 4% > 5% SL, supporting the observations of Akcil et al [38] and Bakhtiari et al [39]. High SL causes higher shear stress, high toxicity, high mechanical damage to cells, and less oxygen mass transfer, which could result in reducing the bioleaching efficiency [40].…”

Producción Limpia Y Biorremediación Para Disminución De La Contaminación Por Cromo en La Industria De Curtiembres

“…Los procesos de biorremediación para el tratamiento de la contaminación por metales ofrecen una alta especificidad mediante mecanismos de bioadsorción, bioacumulación, biotransformación o biolixiviación (Fang et al 2007, Kaushik et al 2008, Okeke 2008) a formas no tóxicas del metal, además de ser más económicos y seguros que las tecnologías convencionales.…”

“…El potencial aplicativo de los microorganismos como agentes biolixiviadores (removedores de metales), puede usarse para promover la reducción de Cr +6 (Okeke 2008) y la biolixiviación de Cr +3 (Fang et al 2007, Wang et al 2007, tanto por la habilidad de los procesos enzimáticos directamente involucrados como por la producción de metabolitos altamente reductores, que contribuyen a 1 Comunicación personal. Departamento de Gestión ambiental.…”

“…También se han reportado trabajos con efluentes de curtiembres, para la sedimentación de Cr +3 con bacterias acidófilas sulfo-oxidantes, en China (Fang et al 2007), la lixiviación química con ácido sulfúrico se diseñó como el control. Los resultados mostraron que las bacterias sulfooxidantes y la adición de azufre elemental fueron eficaces en la eliminación del cromo.…”