Ali Oboodi, Ehsan Fathi, Hassan Nezammahalleh
In the present work, a novel down-flow biofilter with four identical layers was developed for the de-nitrification of 100 mg L-1 nitrate contaminated wastewater, flowing horizontally from one layer to another in a continuous fashion. This biofilter can be applied for long-term continuous wastewater treatment without any need to whole system shutdown and backwashing. The clogged layer or the deactivated section can be easily spotted and repaired while the system is under continuous operation. To attain a short startup period, the effect of two main constructional parameters, namely, filter media and inoculants source, were then investigated.. Two studied filter media were sand and woodchips. The pure culture of Saccharomyces cerevisiae and the mixed cultures of activated sludge and wastewater were three common inoculants under investigation. The biofilter packed with woodchips seeded with the wastewater resulted in the least startup period of about 3 days with a steady nitrate removal efficiency of 90 %.