Design of denitrifying plants
r ----v -- ____ . , . .
- - -
1
I
I
I
I
L - - - - ·
I
I
L----- ----...J
Backwash
Fig 7.18 Denitrifying filter with backwash.
(Filter medium: Sand or porous materials resembling Leca)
.I.~·
Fig 7.19 Fluidized filter for denitrification.
(Carrier: Sand).
floes without carrier (granules). Full-scale experiences with denitrifying filters are
few. Often an external carbon source is added in the form of methanol, acetic acid or
industrial wastewater.
The combination with nitrification will normally be performed in a pre-denitrification process, that is, with a nitrifying filter after the denitrifying filter and recycle of
the nitrified water. As the nitrifying filter should not be loaded with too large
amounts of organic matter, it is necessary that the effluent from the denitrifying filter
only has a minor content of suspended solids. The requirement of recycle means
that denitrifying filters without settling of the wastewater flow, that is, filters with
backwash (Fig 7.18) or fluidized filters (Fig 7.19) are superior. For the other types,
the recycle will mean that the settling tanks will be very large (and hence very
expensive).
7.3. Design of denitrifying plants
For the design of denitrifying plants, a number of special process conditions should
be taken into consideration. In this section the following is discussed:
- C/N ratio
- Oxygen/ stirring
- Nitrogen gas in settling tanks
248
r ----v -- ____ . , . .
- - -
1
I
I
I
I
L - - - - ·
I
I
L----- ----...J
Backwash
Fig 7.18 Denitrifying filter with backwash.
(Filter medium: Sand or porous materials resembling Leca)
.I.~·
Fig 7.19 Fluidized filter for denitrification.
(Carrier: Sand).
floes without carrier (granules). Full-scale experiences with denitrifying filters are
few. Often an external carbon source is added in the form of methanol, acetic acid or
industrial wastewater.
The combination with nitrification will normally be performed in a pre-denitrification process, that is, with a nitrifying filter after the denitrifying filter and recycle of
the nitrified water. As the nitrifying filter should not be loaded with too large
amounts of organic matter, it is necessary that the effluent from the denitrifying filter
only has a minor content of suspended solids. The requirement of recycle means
that denitrifying filters without settling of the wastewater flow, that is, filters with
backwash (Fig 7.18) or fluidized filters (Fig 7.19) are superior. For the other types,
the recycle will mean that the settling tanks will be very large (and hence very
expensive).
7.3. Design of denitrifying plants
For the design of denitrifying plants, a number of special process conditions should
be taken into consideration. In this section the following is discussed:
- C/N ratio
- Oxygen/ stirring
- Nitrogen gas in settling tanks
248