According to Hammer and Knight (1994) this
volatilization occurred when pH of input effluent range
between 7.8-8.4. As pH of our input effluent varies
from 7.44-7.66, this mechanism was limited. In our case
absolutely no ammoniac smell was detected.
Fig 5a showed the changes in TKN removal
during the experiment. S treatment showed a good
performance in terms of TKN removal. The average
TKN removal for S and SP was 97.7% and 94.93%
respectively and the corresponding output effluent
TKN concentration was between 0.52±0.07-1.85±0.07
mg/Land 0.8±0.41-2.97±0.31 mg/Lrespectively for S
and SP, from the second week. The average TKN
removal for P was 80.14% and the corresponding
output effluent TKN concentration was between
4.56±0.52-13.5±2.42 mg/L, for the same period, for
average output effluent TKN concentration. The
reduction of organic nitrogen suggested an intense
mineralization.
Fig 5b below showed the change of the conversion
ratio of nitrogen during the experiment. The conversion
ratio of nitrogen was calculated as the ratio of nitrate
output on NTK input. This ratio reached 100% after 49
days for S and SP treatment, whereas it was 60% with
P. TKN was mainly transformed into nitrate, a more
assimilate nitrogen form for plants. The output effluent
nitrate concentration rose from 6.12±2.35 to
229.97±36.49 mg/Land from 4.4±0.65 to 235.88±7.59 mg/
Lrespectively for S and SP. The output effluent nitrate
concentration for P rose from 1.8±0.5 to 127.57±23.71
mg/L. The average inlet nitrate concentration was 2.78
mg/L.