Potential of the Alfalfa (Medicago Sativa‏(‏‎ Rhizobium Bacteria for Nitrate and ‎Phosphate Removal from the Sugarcane Industry Wastewater

To conduct this experiment, rhizospheric bacteria were isolated from the root nodules of alfalfa ‎plants (Medicago sativa) in the Khuzestan province during the spring season. For the molecular ‎identification of superior isolates, DNA extraction and expression of 16S rDNA were performed. ‎To investigate nitrate (NO3-) and phosphate (PO43-) removal, 120 mL vials were filled with 50 mL of ‎laboratory wastewater containing specified concentrations of nitrate (25, 50, 100, and 200 mgL-1) ‎and phosphate (5, 10, 20, and 30 mgL-1). The removal percentage was examined over 1, 2, and 3 ‎hours. Results revealed that three rhizobial bacteria, including Sinorhizobium meliloti (bacterium 3) ‎‎(Query ID= DQ-145546.1), Sinorhizobium medicae (bacterium 2) (Query ID= CP-000738.1), and ‎Sinorhizobium meliloti (bacterium 1) (Query ID= CP 021215.1), were isolated and identified. The ‎highest removal efficiency was recorded within 3 hours at 44.61%. With an increase in ‎concentration, the removal efficiency decreased, reaching its lowest value (14.82%) at 200 mg L-1 ‎compared to other concentrations (p < 0.05). Besides, the bacterial type or mixture did not ‎significantly affect the nitrate removal percentage (p>0.05). At a concentration of 25 mg L-1, the ‎highest removal percentage (63.08%) was measured in the presence of bacteria at 3 hours. ‎Furthermore, the highest phosphate removal percentage was obtained at 37.4% at 5%, within 3 ‎hours, and a mixture of 3 bacteria. Furthermore, the efficiency of the mixture of 3 bacteria was ‎higher compared to bacterium 2 (p<0.05). Besides bacteria 1 and 3 with a removal percentage of ‎‎16.23% were ranked higher (p > 0.05). At higher concentrations and increased time, the nitrate and ‎phosphate removal percentages exhibited a consistent and fluctuating trend, respectively (p > 0.05). ‎Ribosome bacteria performed better in nitrate removal compared to phosphate (p ‎‏>‏‎ 0.05). ‎Considering that wastewater from agricultural and industrial centers contains a mixture of ‎nitrogenous and phosphorous substances, it appears that the use of a consortium of these bacteria ‎with different characteristics and compatibilities enhances the efficiency of purification and removal ‎of these parameters.‎