Immobilization of mixed cells by Flaxseeds (Linum usitatissimum) extract as new nonconventional biocarrier for biodegradation of sodium dodecyl sulfate

Flaxseeds as a new nonconventional biocarrier was used for the first time to immobilize mixed bacterial cells for biodegradation of sodium dodecyl sulfate (SDS) in actual wastewaters. The results revealed that SDS elimination efficiency in domestic wastewater (DWW) and household detergents manufacturing wastewater (HWW) were 98.8% and 94.5%, respectively. The immobilized cells were repeatedly used for 60 batches without notable loss of their bioactivity, mechanical and chemical stability. Seven kinetic models were applied to depict the interrelation between cells growth and substrate consumption which were; Blackman, Monod, Haldane, Teissier, Moser, Han-Levenspiel, and Contois Models. Teissier model fit well the experimental data with lowest sum of squares error (SSE) of 2.41 × 10−14 indicating exponential growth of biocatalyst inside the biocarrier. Endogenous rate constant (Kd), and yield coefficient (Y) were found to be 0.0039 h−1, and 0.44 h−1, respectively. Values of first order rate constant (K1), effective diffusivity (De), mass transfer coefficient, effectiveness factor (η), and Thiele modulus (Φ) were found to be 1.55 × 10−5 s−1, 6.44×10−7 cm2/s, 2.14×10−6 cm/s, 0.88, and 0.49, respectively. Values of oxygen uptake rate (OUR), volumetric oxygen mass transfer coefficient (KLa) and oxygen transfer rate (OTR) were 0.0013 mg O2/L. s, 0.0222 s−1 and 0.00111 mg O2/L. s, respectively. Experimental and predicted results of (OUR) were in a good agreement with determination coefficient (R2) of 0.94.