07
x7 ~----~~~--------~
Activated Sludge Treabnent Plants
C7
Os
Xs
Cs
Fig 4.10 Contact stabilization, schematic layout.
The sludge mass in the plant is:
The mass balances for the contact stabilization processes become more complicated
because two tanks have to be included for each process. A contribution from
hydrolysis to a mass balance is for example:
Detailed calculations for the contact stabilization plant can only be carried out by
means of mathematical computer models.
4.3.4 Biosorption plants
These plants are very heavily loaded activated sludge plants where the hydraulic
retention time of the wastewater in the aeration tank is 0.2-0.5 h. In such a highly
loaded plant most of the suspended organic matter is removed whereas only a
minor treabnent of the dissolved organic matter takes place. The sludge in a
biosorption plant is very active, often much more than in the following low-loaded
activated sludge plant /3/.
The particles of the wastewater are very quickly adsorbed (1-2 minutes) to the
activated sludge floes so that a model description of this adsorption will usually not
be necessary. The efficiency of the process is controlled by the following settlement.
It will usually be designed in such a way that a larger amount of suspended solids
will be discharged to the effluent than from an ordinary activated sludge settlement.
The reason is that biosorption is only used as a pretreabnent and is normally
followed by an activated sludge plant. A plant with a biofilter may also be used as
the 2nd stage.
Fig 4.11 shows examples of biosorption plants. The sludge production in a biosorption plant, as the one shown in Fig 4.11a, is bigger than in a similar single activated
sludge plant. Biosorption saves the energy which would otherwise have been used
for oxidation of the extra sludge production. The bigger sludge production by
biosorption can be used for increased biogas production. It could also be foreseen
that the sludge production from biosorption could be used for a hydrolysis process
133
x7 ~----~~~--------~
Activated Sludge Treabnent Plants
C7
Os
Xs
Cs
Fig 4.10 Contact stabilization, schematic layout.
The sludge mass in the plant is:
The mass balances for the contact stabilization processes become more complicated
because two tanks have to be included for each process. A contribution from
hydrolysis to a mass balance is for example:
Detailed calculations for the contact stabilization plant can only be carried out by
means of mathematical computer models.
4.3.4 Biosorption plants
These plants are very heavily loaded activated sludge plants where the hydraulic
retention time of the wastewater in the aeration tank is 0.2-0.5 h. In such a highly
loaded plant most of the suspended organic matter is removed whereas only a
minor treabnent of the dissolved organic matter takes place. The sludge in a
biosorption plant is very active, often much more than in the following low-loaded
activated sludge plant /3/.
The particles of the wastewater are very quickly adsorbed (1-2 minutes) to the
activated sludge floes so that a model description of this adsorption will usually not
be necessary. The efficiency of the process is controlled by the following settlement.
It will usually be designed in such a way that a larger amount of suspended solids
will be discharged to the effluent than from an ordinary activated sludge settlement.
The reason is that biosorption is only used as a pretreabnent and is normally
followed by an activated sludge plant. A plant with a biofilter may also be used as
the 2nd stage.
Fig 4.11 shows examples of biosorption plants. The sludge production in a biosorption plant, as the one shown in Fig 4.11a, is bigger than in a similar single activated
sludge plant. Biosorption saves the energy which would otherwise have been used
for oxidation of the extra sludge production. The bigger sludge production by
biosorption can be used for increased biogas production. It could also be foreseen
that the sludge production from biosorption could be used for a hydrolysis process
133