Document Type: Original Research Paper
The aim of the present study was to assess the bio-trickling filter startup for the treatment of
wastewater produced by Pegah Dairy Company at psychrophilic condition. The startup time of a bio-trickling
filter is directly proportional to the concentration of microbial population. Abio-trickling column with a height of
150 cm was packed with lava rocks with the liquid recirculated through the packing. The startup flow rate for the
pilot was 0.0035 L/min, with hydraulic retention time (HRT) of 10 days at 7-13ºC. Results indicated that for HRT
of 10 days, the efficiency of chemical oxygen demand (COD) removal was more than 85% for less than 100 g
COD/m3/h. Subsequently, dairy wastewater was added to the reminder of activated sludge with the HRT of 8
days, and the nutrients were added to the pilot tank with a daily ratio of carbon/nitrogen/phosphorous: 100/5/1.
For the subsequent 5 days, the pilot was maintained in a steady state. The results revealed that the pilot startup
was performed completely.