Treatment Plants for Denitrification
rv,s = (0.5 g N/(kg VSS · h)) · 4 kg VSS/m 3 = 2 g N/(m 3 · h)= 0.048 kg N/(m 3 · d)
The tank volume, V2, is found from Expression (7.28):
V2 = (180 kg N/d)/(0.048 kg N/(m 3 . d))= 3,750 m 3
7.3.7 Computerized process design
Combined nitrification-denitrification plants with several tanks and recycles, or
with alternating operation, are suitable for an analysis of the operation by means of
computer models. The interaction between the three different processes, each of
which has opposite interests, is complicated and the design is difficult to carry out,
without the extra computational capacity supplied by a computer model.
The present computer models cannot be used for the design of the plants, but they
can be used to analyze the effect of the diurnal variations, rain, temperature
changes, or inhibition on the chosen design. As a result of a computer analysis, it
may also be necessary to make changes in the dimensions of the plant, or in its mode
of operation.
The models are also suitable for optimization of the operation of existing plants. The
effect of changes in the oxygen concentration, recycle, phase length or other controls
can be tested and optimized before they are taken into use on the plant itself. In the
long term, further developed models can be directly incorporated in the control of
the plants.
Fig 7.24 shows a comparison between a model calculation and a direct measurement in a tank on an alternating plant with nitrogen removal. In order to obtain the
shown compliance, a comprehensive analysis and calibration are required, as further illustrated by Example 7.8 /16/.
Example 7.8.
Model calculation by means of a computer model /19/.
The work comprises 3 main activities:
- Characterization of the wastewater
- Characterization of activated sludge
- Determination of process constants through tests
The influent to the plant is wastewater which is preprecipitated with polymerized aluminium chloride. The preprecipitated sludge is hydrolyzed and the dissolved hydrolyzate
is added to the denitrification phase to increase both the rate and capacity of the denitrification. The design of the plant is shown in Fig 7.25.
Characterization of wastewater. Diurnal variations in the influent to the alternating
tanks have been measured. The COD, Kjeldahl nitrogen and ammonium as well as SS
261
rv,s = (0.5 g N/(kg VSS · h)) · 4 kg VSS/m 3 = 2 g N/(m 3 · h)= 0.048 kg N/(m 3 · d)
The tank volume, V2, is found from Expression (7.28):
V2 = (180 kg N/d)/(0.048 kg N/(m 3 . d))= 3,750 m 3
7.3.7 Computerized process design
Combined nitrification-denitrification plants with several tanks and recycles, or
with alternating operation, are suitable for an analysis of the operation by means of
computer models. The interaction between the three different processes, each of
which has opposite interests, is complicated and the design is difficult to carry out,
without the extra computational capacity supplied by a computer model.
The present computer models cannot be used for the design of the plants, but they
can be used to analyze the effect of the diurnal variations, rain, temperature
changes, or inhibition on the chosen design. As a result of a computer analysis, it
may also be necessary to make changes in the dimensions of the plant, or in its mode
of operation.
The models are also suitable for optimization of the operation of existing plants. The
effect of changes in the oxygen concentration, recycle, phase length or other controls
can be tested and optimized before they are taken into use on the plant itself. In the
long term, further developed models can be directly incorporated in the control of
the plants.
Fig 7.24 shows a comparison between a model calculation and a direct measurement in a tank on an alternating plant with nitrogen removal. In order to obtain the
shown compliance, a comprehensive analysis and calibration are required, as further illustrated by Example 7.8 /16/.
Example 7.8.
Model calculation by means of a computer model /19/.
The work comprises 3 main activities:
- Characterization of the wastewater
- Characterization of activated sludge
- Determination of process constants through tests
The influent to the plant is wastewater which is preprecipitated with polymerized aluminium chloride. The preprecipitated sludge is hydrolyzed and the dissolved hydrolyzate
is added to the denitrification phase to increase both the rate and capacity of the denitrification. The design of the plant is shown in Fig 7.25.
Characterization of wastewater. Diurnal variations in the influent to the alternating
tanks have been measured. The COD, Kjeldahl nitrogen and ammonium as well as SS
261