d. temperature
e. growth rate
f. freely
suspended
life forms
Basic Biological Processes
If the temperature in the plant is below the temperature at which an
organism can grow, the organism concerned will die.
In an activated sludge plant, the conditions are kept constant by
drawing off surplus sludge. This is one of the mechanisms to remove
organisms from the process. Other mechanisms are grazing (predation) and suspended solids in the effluent. If an organism is to
survive in the treatment plant, it must be able to reproduce at a faster
rate than the rate at which it is removed from the plant. Therefore
the growth rate of the organism is important for its survival in the
treatment plant. Organisms which degrade complicated, organic
compounds, for example toxic waste, will often have a slow growth
rate as a result of a heavy work load and small yield. The same
applies to nitrifying bacteria in respect of their conversion of ammonium. In respect of the treatment efficiency for special substances in
activated sludge plants, the minimum growth rate at which organisms can survive in the plant concerned is of vital importance.
Organisms which require a surface to grow on cannot survive in an
activated sludge plant in the long run.
Similar to the biofilters, the two selection mechanisms, substrate and temperature,
are variables. Two other mechanisms depend to a certain extent on the mode of
operation of the plant, that is, the oxygen conditions and the growth rate. The
oxygen conditions vary with the varying content of organic matter in the wastewater, or through the regulation of aeration. The necessary minimum growth rate
varies with the sludge concentration in the reaction tank.
3.2. Conversions in biological treatment
plants
A number of biologically dependent conversions are of vital importance in biological treatment plants. It concerns
- biological growth
- hydrolysis
-decay
To this, adsorption should be added, which (even if this does not concern an actual
conversion) may also influence the process.
61
e. growth rate
f. freely
suspended
life forms
Basic Biological Processes
If the temperature in the plant is below the temperature at which an
organism can grow, the organism concerned will die.
In an activated sludge plant, the conditions are kept constant by
drawing off surplus sludge. This is one of the mechanisms to remove
organisms from the process. Other mechanisms are grazing (predation) and suspended solids in the effluent. If an organism is to
survive in the treatment plant, it must be able to reproduce at a faster
rate than the rate at which it is removed from the plant. Therefore
the growth rate of the organism is important for its survival in the
treatment plant. Organisms which degrade complicated, organic
compounds, for example toxic waste, will often have a slow growth
rate as a result of a heavy work load and small yield. The same
applies to nitrifying bacteria in respect of their conversion of ammonium. In respect of the treatment efficiency for special substances in
activated sludge plants, the minimum growth rate at which organisms can survive in the plant concerned is of vital importance.
Organisms which require a surface to grow on cannot survive in an
activated sludge plant in the long run.
Similar to the biofilters, the two selection mechanisms, substrate and temperature,
are variables. Two other mechanisms depend to a certain extent on the mode of
operation of the plant, that is, the oxygen conditions and the growth rate. The
oxygen conditions vary with the varying content of organic matter in the wastewater, or through the regulation of aeration. The necessary minimum growth rate
varies with the sludge concentration in the reaction tank.
3.2. Conversions in biological treatment
plants
A number of biologically dependent conversions are of vital importance in biological treatment plants. It concerns
- biological growth
- hydrolysis
-decay
To this, adsorption should be added, which (even if this does not concern an actual
conversion) may also influence the process.
61