Biodegradation of high phenol containing synthetic wastewater by an aerobic fixed bed reactor

The continuous aerobic degradation of phenol, mixed with readily degradable synthetic wastewater was studied over a period of 400 days at 25 ± 5 °C temperature in a fixed bed biofilm reactor using ‘Liapor’ clay beads as packing material. The phenol concentration added to the reactor ranged from 0.19 to 5.17 g/l and was achieved by a gradual increase of phenol in wastewater, thus adapting the microbial flora to high contaminant concentrations. A maximal removal rate of 2.92 g phenol/(l d) at a hydraulic retention time (HRT) of 0.95 days and a total organic loading rate (OLR) of 15.3 g COD/(l d) with a phenol concentration of 4.9 g/l was observed. However, this was not a stable rate at such high phenol loading. At the end of reactor operation on day 405, the phenol removal rate was 2.3 g/(l d) at a influent phenol concentration of 4.9 g/l. There were no phenol intermediates present in the reactor, as evident from corresponding COD, phenol removal and the absence of fatty acids. Omission of organic nitrogen compounds or of urea in influent feed was not favourable for optimal phenol removal. The phenol degradation profile that was studied in shake flasks indicated that the presence of a acetate which represent as an intermediate of phenol degradation retarded the phenol degradation. The highest phenol degradation rate observed in batch assays was 3.54 g/(l d).