9. Anaerobic Wastewater Treatment
By Mogens Henze
Anaerobic wastewater treatment is not the same as anaerobic sludge treatment. The
reason is that a larger part of the organic matter in the wastewater is dissolved in
anaerobic wastewater treatment. When dissolved organic matter is to be removed,
it means that treatment processes are to be used which ensure a good and a
sufficiently long contact between the dissolved substances in the wastewater and
the microorganisms carrying out the anaerobic processes. It means that for anaerobic wastewater treatment there is a big difference between the hydraulic retention
time and the sludge age which is usually not the case in anaerobic sludge treatment.
The first anaerobic treatment plant for industrial wastewater was built in 1929 for
the treatment of wastewater from yeast production in Slagelse, Denmark. Even if
this plant was in operation for almost 30 years, the development went very slowly.
The development of this process did not gather momentum until the Dutch UASB
plant type was introduced around 1980.
Anaerobic treatment processes are cheap in operation and yield a gas production of
a considerable value. The processes are especially favourable for concentrated
wastewater where an aerobic oxidation of the organic matter would otherwise
result in high electricity costs.
It is a further advantage if the wastewater to be treated is warm, as the necessary
tank volume is hereby reduced. A method to reduce the tank volume is to utilize
processes where it is possible to maintain a high sludge concentration in the tank.
The development within anaerobic processes is thus moving towards such processes, for example sludge blanket plants and fluidized filters of which many are
already known from other branches of biotechnology and from chemical technology /11/.
Anaerobic wastewater treatment plants are by and large only used for the treatment
of industrial wastewater. Experiments with the treatment of municipal wastewater
have not yet resulted in an increase in the use of the process. This is due to the fact
that the effluent quality is not acceptable so that further aerobic treatment is normally required.
By percentage, plants for anaerobic industrial wastewater treatment remove a lot of
organic matter and almost no nutrients.
Anaerobic plants must therefore be considered as pretreatment plants which are to
be followed by other treatment processes/plants.
285
By Mogens Henze
Anaerobic wastewater treatment is not the same as anaerobic sludge treatment. The
reason is that a larger part of the organic matter in the wastewater is dissolved in
anaerobic wastewater treatment. When dissolved organic matter is to be removed,
it means that treatment processes are to be used which ensure a good and a
sufficiently long contact between the dissolved substances in the wastewater and
the microorganisms carrying out the anaerobic processes. It means that for anaerobic wastewater treatment there is a big difference between the hydraulic retention
time and the sludge age which is usually not the case in anaerobic sludge treatment.
The first anaerobic treatment plant for industrial wastewater was built in 1929 for
the treatment of wastewater from yeast production in Slagelse, Denmark. Even if
this plant was in operation for almost 30 years, the development went very slowly.
The development of this process did not gather momentum until the Dutch UASB
plant type was introduced around 1980.
Anaerobic treatment processes are cheap in operation and yield a gas production of
a considerable value. The processes are especially favourable for concentrated
wastewater where an aerobic oxidation of the organic matter would otherwise
result in high electricity costs.
It is a further advantage if the wastewater to be treated is warm, as the necessary
tank volume is hereby reduced. A method to reduce the tank volume is to utilize
processes where it is possible to maintain a high sludge concentration in the tank.
The development within anaerobic processes is thus moving towards such processes, for example sludge blanket plants and fluidized filters of which many are
already known from other branches of biotechnology and from chemical technology /11/.
Anaerobic wastewater treatment plants are by and large only used for the treatment
of industrial wastewater. Experiments with the treatment of municipal wastewater
have not yet resulted in an increase in the use of the process. This is due to the fact
that the effluent quality is not acceptable so that further aerobic treatment is normally required.
By percentage, plants for anaerobic industrial wastewater treatment remove a lot of
organic matter and almost no nutrients.
Anaerobic plants must therefore be considered as pretreatment plants which are to
be followed by other treatment processes/plants.
285