The effect of solid concentration on bioleaching of metals from sediment was tested in this study in order to assess the Cr, Cu, Pb, and Zn pollution levels after the process. The solid contents of 10, 5, and 2.5% (w/v) were used in the bioleaching tests. After 48 days of flask experiments, Zn, Cr, and Cu, solubilizations were over 90% with 2.5% solid content. The metal pollution remained in the sediment after bioleaching is assessed by using the Pollution Index (PI) due to the values of Ecotox Thresholds of EPA. Bioleaching with 5% and 2.5% solid contents provided low PI values as 0.88 and 0.5 at the end of the experimental period.