Types of plants for denitrification
b) Denitrification with combined sludge
Fig 7.7
jllo I
j
..
Design of a denitrification plant with separate and combined activated sludge,
respectively.
be made for the denitrification to occur, may be established in the new filter types
whereas the conventional trickling filters are difficult to adapt to the process.
Fig 7.8 shows the principle for the different filter technologies. It should be noted
that denitrification in biofilters normally takes place with a separate sludge system.
Fig 7.8 only shows the design of the filters for denitrification. The separation of the
treated water and surplus sludge from the process takes place in conventional
secondary settling tanks for the rotating discs whereas for the submerged filters and
for the fluidized filters the top can be designed to function as a separation unit.
Fig7.8
242
Rotating discs
discs ---:fl)~
. ~
'rotation
biofilm
......,
shaft
Submerged filter
3-5 mm
grains of sand
biofitm
Fluidized filter
0.5-1.0 mm
grains of sand
biofitm
Filter types for denitrification.