REMOVAL OF FECAL-COLIFORMS IN A TRICKLING BIOFILTRATION PROCESS

Biofiltration is a relatively new process, and very Little information is available on its capacity to eliminate coliforms. The objective of this paper is to present some results on the fecal coliforms removal of a full scale biofiltration process BIODROF(R). A sampling campaign was set up at one of the two Communaute Urbaine de Quebec (CUQ) wastew ater treatment plants. The liquid treatment line consists of the follo wing main processes: primary settlers, biofilters (BIODROF(R)) and ult raviolet disinfection units. A total of 74 samples were collected for both influent and effluent of the biofiltration process during 22 days between January and August 1993. They were analysed for fecal colifor ms, suspended solids (SS), chemical oxygen demand (GOD), transmittance , turbidity, temperature and pH. The average fecal coliforms reduction observed was 56% which is low compared to removal efficiencies found in the literature for biological treatment processes. The reduction of fecal coliforms seems to be independant of the wastewater characteris tics and removal of SS or GOD. The mechanism of reduction would be sim ilar to the retention mechanism of SS.