With the exception of ammonia removal in submerged biofilters,
removal of all measured forms of nitrogen was significant in
both operating conditions during treatment 1 (Wilcoxon p < 0.01,
except for TKN and ammonia in flood/drain biofilters p < 0.05).
However there were no significant differences between flood/drain
and submerged biofilters in the concentration of any form of nitrogen
in the outlet water (Fig. 2).