Bioremediation of Hexavalent Chromium and Tannic Acid in Synthetic Tannery Wastewater Using Free and Calcium Alginate–Immobilized Spores and Mycelia of <i>Aspergillus niger</i> and <i>Aspergillus parasiticus</i>

Abstract

ABSTRACT The bioremediation of chromate and tannic acid in synthetic tannery wastewater was studied in a batch culture system using free and immobilized spores and mycelia of A. niger and A. parasiticus. Significant (p< .001) decreases in total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), Cr(VI), and tannic acid concentrations were observed in cultures of both fungi after 96 h of growth. The A. niger culture medium had significantly lower TDS (p< .001), BOD, and tannic acid concentration (p< .05) compared to that of A. parasiticus. Immobilization of both spores and mycelia of the two fungi on Ca-alginate resulted in significantly (p< .05–.001) lower residual Cr(VI) concentrations within 24 h hydraulic retention time (HRT). Chromate removal increased significantly (p< .05) as the number of beads of immobilized spore/mycelia increased from 10 to 100; the increase in Cr(VI) removal ranging from 40.3% to 47.9% with 10 beads and 97.4% to 98.6% with 100 beads. Similarly, tannic acid removal by spores and mycelia of the fungi was significantly (p< .05) enhanced by immobilization. Repeated use of the alginate entrapped spores/mycelia of both fungi up to 3 cycles of 72-h HRT showed no significant change in their ability to carryout Cr(VI) removal.