corresponding to an OLR of 5.9 kg COD/m3
d . TA in
the reactor was 1.8 g/l, whereas the alkalinity ratio was
0.32 andthe levels of VFA were lower than 0.3 g/l. The
COD removal efficiency achieved under these conditions
was around93%.
Period4 (days 349–395) was relatedto a temporary
decrease in the influent flow. During this period the
appliedOLR was around3.6 kg COD/m3
dwith COD
removal efficiencies of 85.5%.
3.2.4. Fifth period: mature process
Finally, period5 represents 239 days of stable
operation at full rate, i.e., treating the whole amount
of wastewaters discharged by this laboratory. The COD
removal efficiencies were always higher than 90%, with
an alkalinity ratio of 0.30. The appliedOLR variedfrom
2.5 to 6.5 kg COD/m3
d, depending on the variation of
the influent COD (Figs. 3 and4), the average value
being 4.7 kg COD/m3
d. TA was always higher than
1.5 g/l. Nitrogen concentration in the effluent ranged
between 150 and500 mg/l, a large fraction of it being
ammonia.
The complete OLR balance referredto the influent,
biogas and effluent corresponding to the last day of
operation, day 634, was the following: 6.5, 5.6 and
0.9 kg COD/m3
d, respectively. Taking into account that
the methane content in the biogas was 68%, the biogas
generated during this day was 45.5 m3
.
The effluent of the AF reactor was successfully treated
in the SBR unit. The COD andnitrogen obtainedfor the
final effluent of the whole plant was most of the time
below 200 and10 mg/l, respectively, which was adequate
for discharge [5]