Biosorption of chromium by living cells of Azotobacter s8, Bacillus subtilis and Pseudomonas aeruginosa using batch system reactor

Chromium in wastewater is classified as one of the dangerous contaminants that require further treatment before being discharged to water body. The concentration of chromium in water body, especially river, has increased as many industries utilize chromium as raw material and then discharge their wastewater without any treatment. Biosorption is one of methods that are widely used to treat heavy metal containing wastewater. Bacteria are the most common microorganisms to be used as heavy metal treatment agent. Azotobacter s8, Bacillus subtilis and Pseudomonas putida had been proven to have a heavy metal resistant capability. The screening test showed that Minimum Inhibitory Concentration (MIC) value of chromium for all bacteria ranged from 100 to 250 mg/L of CrCl₃. The chromium biosorption test by bacteria showed that Azotobacter s8 was able to remove 10.53%, and Bacillus subtilis was able to remove 5.68% chromium from 50 mg/L initial concentration, while Pseudomonas putida showed no chromium removal. The chromium biosorption capacity by Azotobacter s8 was 580.08 mg/g and 349.30 mg/g for Bacillus subtilis.