Continuous Fixed Bed Bioreactor for the Degradation of Textile Dyes: Phytotoxicity Assessment

This study explores a novel bioremediation approach using a continuous upflow fixed bed bioreactor with date pedicels as a biosupport material. Date pedicels offer a dual advantage: providing microbial support and potentially acting as a biostimulant due to their inherent nutrients. This research is divided into two phases: with and without microbial introduction. The bioreactor’s efficiency in removing two common textile dyes, RB19 and DR227, was evaluated under various conditions: fixed bed high, the effect of the initial concentration of the pollutant, and recycling the RB19 solution within the bioreactor. Optimization studies revealed an 83% removal yield of RB19 dye with an initial pollutant concentration of 100 mg·L−1 using activated sludge as inoculum. The bioreactor developed its own bacterial consortium without initial inoculation. Microscopic analysis confirmed the presence of a diverse microbial community, including protozoa (Aspidisca and Paramecium), nematodes, and diatoms. The bioreactor exhibited efficient removal of RB19 across a range of initial concentrations (20–100 mg/L) with similar removal efficiencies (around 65%). Interestingly, the removal efficiency for DR227 was concentration-dependent. The bioreactor demonstrated the ability to enhance the biodegradability of treated RB19 solutions. Phytotoxicity tests using watercress and lettuce seeds revealed no negative impacts on plant growth. SEM and FTIR analyses were conducted to examine the biosupport material before and after biotreatment.