Chapter 9 Removal of phenol from wastewater by microbial granules

Abstract

This chapter analyzes the removal of phenol from wastewater by microbial granules. Phenol is an important industrial chemical and is used in the production of polycarbonate resins, explosives, paints, inks, perfumes, wood preservatives, textiles, drugs, and as an antibacterial and antifungal agent. Because of its widespread use and its ubiquity, phenol is a major pollutant of the environment. In view of the widespread occurrence of phenol, microorganisms can be found in many environments that are able to use phenol as a carbon and energy source. Aerobic degradation of phenol by microorganisms is mainly based on the ortho- and meta-cleavage pathways. During the first step of the aerobic phenol degradation pathway, molecular oxygen is used by the phenol hydroxylase enzyme to add a second hydroxyl group in the ortho-position to the one already present to produce catechol, which can then be degraded by either the ortho- or the metacleavage pathways. In aerobic phenol degradation, the highly reactive molecular oxygen is used for the initial attack on the aromatic ring and for the final ring cleavage step. Pure cultures of anaerobically respiring bacteria can completely oxidize phenol to carbon dioxide using nitrate, ferric iron, or sulfate as terminal electron acceptor. At least two phenol degradation pathways have been suggested to occur under methanogenic conditions.