Removal of chromium and reduction of toxicity to Microtox system from tannery effluent by the use of calcium alginate beads containing humic acid

Removal of chromium (Cr) from tannery effluents by recovery of metal also reduces the ecotoxicological impact. To develop such a process, columns packed with calcium alginate (CA) beads with or without humic acid (HA) have been used as an adsorbent and tannery effluent was passed through it. Concentration of Cr in beads and in different fractions collected after adsorption was measured. Change in total organic carbon content during the process was also noticed. The fractions were also tested for toxicity towards Microtox assay. EC50 values were determined with the help of Microtox analyser 500. Data showed that the CA beads along with HA could be effectively utilised in removal of 54% Cr and also in reducing the toxicity (EC50 (%) in 5 min = >100 in fractions collected after 72 h).