High-Rate Biodegradation of Phenol by Aerobically Grown Microbial Granules.

This study demonstrates that aerobic granules can be developed to achieve high phenol loading rates in a sequencing batch reactor. The reactor was started at a loading rate of 1.5 kg phenol m-3 d-1 with phenol-enriched activated sludge as inoculum. Granules first appeared on Day 9 after startup and quickly grew to become the dominant biomass in the reactor. The phenol loading was then adjusted stepwise to a final value of 2.5 kg phenol m-3 d-1. At this high loading, phenol was completely degraded and high biomass concentration was maintained in the reactor. The biomass continued to possess a good settling ability, with a sludge volume index of 60.5 mL g SS-1 (SS stands for suspended solids). Granules remained stable, without significant deterioration in granule structure and physiology, even at the maximum phenol loading rate tested. The applied selection pressure enabled the micro-organisms to aggregate into granules, and the compact structure of the aerobic granules served both to retain biomass and protect the microbial cells against the phenol toxicity. High specific phenol degradation rates exceeding 1 g phenol g VSS-1 d-1 (VSS stands for volatile suspended solids) were sustained up to phenol concentrations of 500 mg l-1, and significant rates continued to be achieved up to a phenol concentration of 1,900 mg L-1. The phenol-degrading aerobic granules can be exploited to design compact high-rate aerobic granulation systems for the treatment of industrial wastewaters containing high concentrations of phenol and other inhibitory chemicals. [ABSTRACT FROM AUTHOR]

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