Activated Sludge Treatment Plants
4.3.2 Single tank activated sludge plants
Activated sludge plants can be built as one combined tank functioning both as
aeration tank and settling tank. In certain plant types the two tanks are integrated
to such an extent that they may in principle be considered as one tank with several
functions. Fig 4.7 gives examples of these plant designs.
When making calculations on the processes in these plants, the problem is that an
attempt must be made to "divide" the tank into two halves, the aeration part, Vz,
and the settling part, V2.'J. to achieve a basic layout as shown in Fig 4.6, however
without recycle flow, Q4. In this type of plant it is usually impossible to define this
and the return sludge concentration, )4, .
The plant types with a certain physical separation between the two functions will
allow for this separation of the volume, that is, types c and d and partly type e in Fig
4.7. In the plant types a and b there is no physical, but a temporal separation
between aeration tank and settling tank. If, for example, the oxidation ditch, type a,
half of the time is used as a settling tank we may assume:
Fig 4.7
a
Plane
Section
lD---~ Oxidation ditch, single
b
-- -----------· .......... .
-----..1 V 2+V2.~ -- ~
:~~~:~:~:~{~~{~:;:· ~:~~:·~~=~~~~~= ~~~ :: ----~
SBR (Sequencing Batch Reactor)
c
d
e
~
Ponds
Single tank activated sludge plants. Basically the processes in the tanks are not
influenced by the geometry of the plant.
129
4.3.2 Single tank activated sludge plants
Activated sludge plants can be built as one combined tank functioning both as
aeration tank and settling tank. In certain plant types the two tanks are integrated
to such an extent that they may in principle be considered as one tank with several
functions. Fig 4.7 gives examples of these plant designs.
When making calculations on the processes in these plants, the problem is that an
attempt must be made to "divide" the tank into two halves, the aeration part, Vz,
and the settling part, V2.'J. to achieve a basic layout as shown in Fig 4.6, however
without recycle flow, Q4. In this type of plant it is usually impossible to define this
and the return sludge concentration, )4, .
The plant types with a certain physical separation between the two functions will
allow for this separation of the volume, that is, types c and d and partly type e in Fig
4.7. In the plant types a and b there is no physical, but a temporal separation
between aeration tank and settling tank. If, for example, the oxidation ditch, type a,
half of the time is used as a settling tank we may assume:
Fig 4.7
a
Plane
Section
lD---~ Oxidation ditch, single
b
-- -----------· .......... .
-----..1 V 2+V2.~ -- ~
:~~~:~:~:~{~~{~:;:· ~:~~:·~~=~~~~~= ~~~ :: ----~
SBR (Sequencing Batch Reactor)
c
d
e
~
Ponds
Single tank activated sludge plants. Basically the processes in the tanks are not
influenced by the geometry of the plant.
129