Biodegradation of P-Cresol by Mixed Culture in Batch Reactor - Effect of the Three Nitrogen Sources Used
Résumé
Phenols are distributed either as nature or artificial mono-aromatic compounds in various environmental sites as major pollutants. Their existence in wastes from industrial processes such as oil refineries, coking plants, wastewater treatment plants, petroleum-based processing, phenols resin industry manufacturing and plants, has been well established. Many processes have been used for the remediation of Phenolic compounds. Conventional methods of treatment have been largely chemical or physical, but these processes have led to secondary effluent problems and costly. Biological treatment is an effective method that is used where many micro-organisms can be growing on Phenolic compounds as the sole source of carbon. The temperature (30°C), the stirring velocity (200 r/min), NaH2PO4 concentration (3 g. L-1), MgSO4 concentration (0.1 g. L-1), initial concentration of p-cersol (100 mg. L-1) and KH2PO4 concentration (3 g. L-1) for (NH4)2SO4, (3 g. L-1) for NH4NO3, (3 g. L- 1) for NH4Cl; while the initial concentration of nitrogen sources ((NH4)2SO4, NH4NO3, NH4Cl) was varied in the following range, 0 - 2 g. L-1. All experiments were carried out at a given initial bacterial concentration, 0.08 g.L-1 (based on optical density determination, 0.079). Irrespective of the culture conditions, total p-cresol degradation (100 m g. L-1) was recorded for culture time ranging from 32.5 to 49 h. the optimal concentration were therefore, 1 g. L-1 for all nitrogen sources, leading to a specific growth rate of 0.3 h- 1. Higher maximum specific growth rate values were recorded during this work, if compared to those reported in the available literature, even those dealing with mixed culture. This result showed the relevance of the specific microbial consortium used. Two mathematical models were used to describe the length of lag phase versus initial nitrogen concentration; the growth length of lag phase was fitted using polynomial models, the correlation coefficient was varied in the following range, 0.99 - 1.