Phenol removal in packed bed reactor under denitrifying conditions

Detailed studies on the efficiency of phenol degradation by a biofilm in an anaerobic packed bed reactor were carried out. The efficiency of phenol degradation depended on both the concentration of phenol in the medium and the phenol load in anaerobic packed bed reactor. Increasing phenol concentrations from 200 to 1,250 mg l(-1) and retention time (Tr)= 12 h were paralleled by increasing efficiency of the process, which reached a maximum value of 1,390 mg l(-1) day(-1) at 700 mg phenol l(-1). The highest concentration of phenol used inhibited growth by approximately 95%. When the phenol load in medium containing 200, 300, 400 and 500 mg l(-1) was increased through a shortening of the retention time (Tr from 24 to 2 h) a maximum efficiency of phenol degradation of 2,200 mg l(-1) day(-1) was obtained at Tr=4 h and phenol concentrations in the medium of 200 mg l(-1). Phenol in concentrations from 300 to 500 mg l(-1) was fully degraded at Tr>9 h and phenol load reaching 530-1330 mg l(-1) day(-1) for the individual concentrations. The post-denitrification effluent leaving packed bed reactor in spite of the absence or even trace amounts of phenol in it requires further purification.