Nitrogen compounds are removed using two-phase upflow open-bed quick filters, biofilters with filter medium in the biological cleaning phase of nutritive removal.The ammonia content of the wastewater is oxidized to nitrate by microorganisms bond to the filter medium of the nitrification biofilters while air is being introduced.
The microorganisms exploit the easily degradable added organic substance (methanol) for denitrification under anoxic conditions provided in the post denitrification biofilters.The filtration units are rinsed regularly with an increased amount of purified wastewater and process air to remove excess microorganisms and to prevent the filter medium (the filter bed) from clogging.
Comparative laboratory tests were conducted on the currently used BIOLIT and the prospective new, Bionature Rock® denitrification granulated medium. According to the results both the endogenous and the acetate respiration values are higher for Bionature Rock®. The results show that the filtering medium currently used in the technology has less favourable properties in terms of the attachment of microorganisms.
The results clearly demonstrate that the surface of the new type of medium had 20 times more biomass growth on average (0.28 g on the old and 5.4 g on the new medium). Consequently, it can be concluded that the new type of medium has much more favourable surface characteristic than the one currently in use. Based on the tests, it can be stated that Bionature Rock® has been found to be a more suitable biological medium, presumably because of its natural origin, than the medium called BIOLIT, which is produced artificially.