Effect of Heavy Metals on the Growth of Bacteria Isolated from Sewage Sludge Compost Tea

Abstract

The amount of urban sewage sludge is increasing daily. For this reason, it is necessary to have an environmentally friendly use for this residue. Land applications in olive grove soil, poor quality soil, as a compost or a compost tea could be considered as one of the best options, because it has a high content of organic matter. However, the presence of heavy metals in some sewage sludge could be an environmental problem. In this sense, the aim of this work is to check the tolerance of the culturable microbiota present in sewage sludge compost tea to four heavy metals, Cu, Cd, Pb and Zn. Among microbiota isolated, eight strains showed high resistance to Pb, Zn, Cu and Cd, and one microbe ( Rhodococcus sp .) showed a special tolerance to every heavy metal. The strains were divided into six genrera: Rhodococcus , Virgibacillus , Leifsoni , Achromobacter , Cupriavidus and Oceanobacillus sp. Finally, Rhodococcus sp. strain 3 was able to remove different amounts of heavy metals from the culture media with intracellular and surface accumulation of Cu, Zn, Pb and Cd. The application of this bacterial strain in bioremediation processes is discussed.