The nitrogenous compounds found in the effluent of the
anaerobic
filters chiefly included ammoniacal-N and organic
nitrogen. In turn, the analysis of the output of the sand
filters
revealed an increase in the concentration of the most oxidized
form (NNO
3), which points to an acute process of nitrification
(Table 4). With the discharge of 600 L m2 day1, at least 74% of the
nitrogen compounds present in the sand
filter effluents were
composed of nitrate (Fig. 4). This high efficiency, according to Kang
(2004), can be attributed to the large average area of the sand
particles, which makes a greater adhesion surface available for