Optimization of Cu, Hg and Cd removal by Enterobacter cloacae by ferric ammonium citrate precipitation

Iron precipitating organisms play a significant role in the formation of ferric hydroxide precipitate, which acts as strong adsorbent for toxic metal. In this respect four different iron precipitating cultures were isolated from Hutti gold mine surface winze water sample on citrate agar medium. The best isolate was screened out for metal removal study on the basis of fast visual iron precipitation. The selected isolate was identified as <i>Enterobacter</i> sp. based on routine biochemical tests and Biolog GN microplate results and as Enterobacter cloacae subsp. <i>dissolvens</i> by 16S rRNA gene sequence analysis (GenBank accession number EU429448). Influence of medium composition, medium initial pH, the influence of inoculum size, effect of various media and ferric ammonium citrate concentration were studied on metal removal in shake flask experiments. Under the optimized conditions studied, <i>E. cloacae</i> showed 94 &#177; 2, 95 &#177; 2 and 70 &#177; 2% of cadmium, copper and mercury removal from a simulated waste in shake flask studies. In lab scale column reactor more than 85% of copper and mercury removal was achieved.