Degradation of phenol and cresols at low temperatures using a suspended-carrier biofilm process

Degradation of phenol and o-, m- and p-cresol at a concentration of 150 mg l(-1) of each compound was studied in a suspended-carrier biofilm process consisting of two aerobic stages. The fungus Mortierella sarnyensis Mil'ko dominated the microflora in the first reactor, while bacteria dominated in the second reactor. The process was studied at 4, 7, 11 and 15 degrees C. The results from the experiments showed the process to be relatively efficient even at 4 degrees C. The degradation rate was 33% of that at 15 degrees C for o-cresol. Both phenol and the cresols were degraded in the first reactor and a new peak appeared in the HPLC-chromatograms indicating the formation of one or more intermediate compounds in the first stage. These compounds were however degraded to below the detection limit in the second reactor. Small new peaks appeared in the chromatograms of the outlet from the second reactor at the maximum loading rates.