The oldest use of polyphenols in the leather industry is based on their ability to stabilize collagen in the skin against rotting. Leather tanning processes are among the most polluting industrial sources in terms of undesirable and toxic parameters (COD, BOD, content of tannic acids, fats, sulphureous residues, chloride, chromium, suspended solids etc.). Tannic acid is a naturally occurring phenolic compound and is widely used in the tanning processes, being one of the main pollutants in leather industry derived wastewaters. Current paper explored the ability of HDPE carrier, functionalized with Cerioporus squamosus microbial strain, to reduce the residual concentration of five natural tannins, widely used in the tanning processes in leather industry: Quebracho, Chestnut, Mimosa, Myrobalan and Gambier, in concentration of 1% in the tested solution. Bio-augmentation experiment of the HDPE structures were carried out in an experimental laboratory installation, and treatment of each aqueous solution, was carried out for 7 straight days, and percentage reduction of residual tannins was calculated at 3 and 7 days. Results highlighted varying degrees of reduction of the residual tannin concentration in the solutions, depending on the tannin tested, the best efficiency being achieved against Myrobalan tannin, with a maximum percentage reduction in residual concentration of 41% after 7 days, followed by Mimosa tannin (34%-7 days), Quebracho (28%-7 days), Chestnut (22%-7 days) and Gambier (9.30%-7 days).