Abstract
The presence of cyclic organic compounds, including phenol, in the wastewater of many industries has made phenol removal an important issue. Meanwhile, the biological methods of removing phenol have attracted the attention of researchers in recent years. Recently, the use of immobilized microbial cells is proposed as a new approach in industrial wastewater treatment. In this research, the aim is to study the effect of immobilized beads size on the phenol biodegradation efficiency and specific microbial growth rate. For this purpose, electrospray technique was used to immobilize activated sludge in hybrid matrix of alginate and polyvinyl alcohol (PVA). The fabricated alginate/PVA beads were characterized using Fourier transform infrared spectroscopy (FTIR). Evaluation of the results related to the free and immobilized cell systems in the shake flask experiments showed that at low phenol concentrations the immobilized cell system had the same performance as the free cell system, while the immobilized cell system at higher concentrations had a better performance in removing phenol so that at a concentration of 2000 mg/L, removal percentage has increased from 15% to 25-34%. On the other hand, in this survey, the kinetic behavior of activated sludge was in good agreement with Haldane's equation. Moreover, the maximum specific growth rate was measured 0.033 and 0.041 (h(-1)) beside 544 and 636 mg/L substrate inhibition constant, for free and immobilized cell systems, respectively. This result shows that the phenol biodegradation has been improved by using the cell immobilization technique especially with applying the smaller beads, which is due to improved mass transfer and microbial cell protection from harsh environments.