Bioremediation potential of some heavy metals by bacterial strains isolated from municipal wastewater

Standard guidelines were used to assess the physicochemical characteristics of the effluent samples from municipal sewage treatment plant in Diwaniyah city. Physicochemical parameters assessed include temperature that was 29°C, PH value was 27.7, biochemical oxygen demand concentration was 449, chemical oxygen demand was 1470, BOD:COD ratio was 0.3, total suspended solids was 1990, ammonia nitrogen was 0.026, nitrate nitrogen was 8.515, phosphate was 5.579, total dissolved soilds was 1420.6, and lead concentration was 0.0210 and cadmium 0.0112, chromium 0.0410 is of great significance. From 20 samples, six isolates were able to grow in the wastewater agar media. These isolates were identified molecularly using partial sequences of the 16S ribosomal RNA gene as: Escherichia coli strain DAQSE1, Escherichia coli strain DAQSE2, Staphylococcus aureus strain DAQSE3, Pseudomonas aeruginosa strain DAQSE4, Enterobacter cloacae strain DAQSE5, Escherichia coli strain DAQSE6. A batch experiment was conducted to investigate bioremediation ability of some heavy metals by isolated bacterial strains. The results showed removal efficiency for lead ranged from 47% to 100%, and the most efficient strain was Staphylococcus aureus DAQSE3 with 100% removal efficiency. The cadmium removal efficiency ranged from 80% to 100%, with the most efficient Enterobacter cloacae DAQSE5 and Staphylococcus aureus DAQSE3 with 100% removal efficiency. The chromium removal efficiency ranged from 73% to 100%, with the most efficient Enterobacter cloacae DAQSE5 and Staphylococcus aureus DAQSE3 with 100% removal efficiency.