Treatment Plants for Denitrification
- Oxygen recovery by denitrification with raw wastewater carbon
-Alkalinity
-Removal rate
7.3.1 C/N ratio
By denitrification, organic matter and nitrogen are removed. As a certain amount of
organic matter should be used for the denitrification process, the C/N ratio is
important for the success of the process.
In connection with an evaluation of a denitrification plant, the COD /N - or the
BOD /N - ratio in the influent is often calculated for the part of the nitrogen to be
removed which is unambiguous for separate denitrification plants. For plants with
combined sludge, the C/N ratio should be calculated for the influent into the
denitrification tank in the case of pre-denitrification- see Fig 7.12. In the case of post
denitrification with combined sludge, it is the influent into the nitrification tank
which is used for the C/N calculation.
The C/N ratio in the influent can be used for a rough evaluation of process
possibilities and to find out if it is necessary to add an external carbon source.
The C/N ratio in the influent, (C/Nh, is calculated using symbols from Fig 7.4, and
hence
(COD/TN)I = Ccoo,t/CrN,l
(7.13)
or as
(BOD/TN)I = Csoo,1/CrN,l
(7.14)
A more detailed analysis of the consumption of organic matter and the removal of
nitrogen will give a better understanding in cases where the composition of the
wastewater deviates from the ordinary one, or where a new type of plant is being
considered.
In a denitrification plant, organic matter will be used for three purposes:
1. Conversion of nitrate (or nitrite) into nitrogen gas.
2. Sludge production.
3. Respiration with oxygen.
If the quantity of these three consumptions is known, the necessary C/N ratio for
the plant concerned can be calculated. A surplus of organic matter in relation to
nitrogen can only be used for respiration with oxygen or for sludge production, and
it may leave the treatment plant with the treated water and hence, in respect of
organic matter, reduce the quality of the effluent.
Based on the equations of reaction, the realized C/N ratio can be calculated for a
current process, that is, the amount of organic matter which has been removed and
249
- Oxygen recovery by denitrification with raw wastewater carbon
-Alkalinity
-Removal rate
7.3.1 C/N ratio
By denitrification, organic matter and nitrogen are removed. As a certain amount of
organic matter should be used for the denitrification process, the C/N ratio is
important for the success of the process.
In connection with an evaluation of a denitrification plant, the COD /N - or the
BOD /N - ratio in the influent is often calculated for the part of the nitrogen to be
removed which is unambiguous for separate denitrification plants. For plants with
combined sludge, the C/N ratio should be calculated for the influent into the
denitrification tank in the case of pre-denitrification- see Fig 7.12. In the case of post
denitrification with combined sludge, it is the influent into the nitrification tank
which is used for the C/N calculation.
The C/N ratio in the influent can be used for a rough evaluation of process
possibilities and to find out if it is necessary to add an external carbon source.
The C/N ratio in the influent, (C/Nh, is calculated using symbols from Fig 7.4, and
hence
(COD/TN)I = Ccoo,t/CrN,l
(7.13)
or as
(BOD/TN)I = Csoo,1/CrN,l
(7.14)
A more detailed analysis of the consumption of organic matter and the removal of
nitrogen will give a better understanding in cases where the composition of the
wastewater deviates from the ordinary one, or where a new type of plant is being
considered.
In a denitrification plant, organic matter will be used for three purposes:
1. Conversion of nitrate (or nitrite) into nitrogen gas.
2. Sludge production.
3. Respiration with oxygen.
If the quantity of these three consumptions is known, the necessary C/N ratio for
the plant concerned can be calculated. A surplus of organic matter in relation to
nitrogen can only be used for respiration with oxygen or for sludge production, and
it may leave the treatment plant with the treated water and hence, in respect of
organic matter, reduce the quality of the effluent.
Based on the equations of reaction, the realized C/N ratio can be calculated for a
current process, that is, the amount of organic matter which has been removed and
249