Removal of soluble arsenic by bacterial isolates

Abstract

Thirty-three of 219 strains of arsenic resistant isolates (700 microgram/ml) were able to precipitate arsenic as arsenous sulfide (AsS, As2S2). Three of all were selected and named AsR-17, AsR-19 and AsR-20, resistant to >2400 microgram/ml arsenic. AsR-17 was obligately anaerobic bacteria. AsR-19 and AsR-20 were facultative anaerobic bacteria which capable precipitate arsenic when both of them work together and acts as consortium. Both of the selected strains were almost sensitive to other metal, i.e., Cd, Cu, Cr, Ni and Ag, resist to some metals, e.g., Mn and Zn in concentration of 800 and 100 microgram/ml, respectively. Optimum pH for growth of those selected bacterial isolates was 7 while optimum temperature of AsR-17, AsR-19 and AsR-20 were 35, 40 and 35ํC, respectively. For optimum arsenic concentration for arsenic precipitation were 100 and 200 microgram/ml found in AsR-17 and AsR-19/AsR-20, respectively. Besides, optimum pH and temperature for arsenic precipitation of both of the selected bacterial isolates were 7 and 35ํC, respectively. Percentages of removal arsenic of AsR-17 and AsR-19/AsR-20 were 35.02 and 42.21, respectively at pH7; at temperature 35ํC, were 45.08 and 46.24, respectively