Effect of the Organic Matter to Ammonia Ratio on Aerobic Granulation during 4-Chlorophenol Degradation in a Sequencing Batch Reactor

The influence of the chemical oxygen demand (COD)/N ratio on the performance of a granular sequencing batch reactor (SBR) system degrading 4-chlorophenol (4CP) was evaluated. Two SBR were operated under the same conditions, but with two different COD/N ratios, 150 and 20. It was observed that successful granule formation was obtained when activated sludge was initially acclimated to 4CP without using a co-substrate, and then hydrodynamic pressure selection was used to generate granules. Removal efficiencies of 4CP were >99.7%, and the specific degradation rates were up to 87mg4CP/(mgvolatile suspended solid) per hour. It was found that nitrogen limitation had no effect on the removal efficiencies of 4CP and on the specific degradation rates. However, the results indicated that under nitrogen-limited conditions, higher granule sizes and a denser biomass were promoted.