Fixed film biological systems have been used for the treatment of wastewater for many years. These systems have been extensively and generally effectively used for the removal of carbon from wastewater sources. In recent years the legislative demands for nutrient removal, both in Australia and overseas, has seen a move away for biological fixed film systems to activated sludge (suspended growth) systems because of the perceived inability of fixed film systems to provide appropriate nutrient removal. However extensive research has been conducted into this field.
The most common approach to biological denitrification in fixed film treatment systems has been to place an anoxic zone either before (pre-anoxic) or after (post-anoxic) the aeration system (i.e. Trickling Filter, Rotating Biological Contactor, etc.). However this previous research has focused on the use of an external carbon source in the post anoxic zones to provide the carbon requirements for the biological denitrification reaction. This project was aimed at determining the nitrogen removal potential of fixed film biological treatment systems without the need for an additional carbon source.
Following a literature survey and mathematical modelling of three different trickling filter – anoxic vessel configurations, the pre-anoxic system was determined as the best system for denitrification in fixed film domestic wastewater treatment systems without an additional carbon source.
It is however recommended that the models created in this project be applied to an experimental system to determine their accuracy. This experimental verification of the modelling performed is expected to be undertaken in the second half of this year.