The biological conventional removal of nitrogen is achieved through nitrification and denitrification steps using several types of technologies, including fixed-film reactors. This type of technology allows the nitrifying bacteria to grow on a media that remains inside the reactor. This process requires tight control and is known to progressively clog during treatment as the filtered particles accumulate and biofilm grows on the media. Thus, clogging management is generally considered as a key factor in biofiltration. So, increasing the filtration time and reducing the number of backwashes are possible ways of achieving a more efficient nitrification step. The objective of the work presented here is to verify the influence of a media, named K5, added to the Biostyr® beads inside a biofilter. With a greater density than Biostyr® beads, this media stays at the bottom of the biofilter and improves operating conditions, reducing both the headloss during filtration time and the number of backwashes. The addition of such media in biofilters may reduce significantly the energy consumption of the process and the risk of hydraulic short-circuiting while limiting biofilter clogging.

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