Anaerobic Wastewater Treatment
Design of anaerobic filter areas
By means of the mass balance in Expression (9.6), the size of the anaerobic filter can
be calculated.
The necessary area of the carrier, A2•, is:
(9.11)
Knowing the sludge specific removal rate, l')(,M, the sludge concentration in the
biofilm, X2•, and the thickness of the biofilm, L:z. the necessary filter area, A2•, can
easily be calculated. The only problem is that normally we do not know X2• and L2.
By using the specific filter area= A2•/V:z. Expression (9.11) can be transformed to
(9.12)
The volume of the anaerobic filter, V:z. is:
(9.13)
The specific filter surface area, ro, and the sludge concentration, X:z, is found in Table
9.4. The sludge specific removal rate, rx,M can be estimated from Table 9.7. Subsequently the area as well as the volume of the filter can be estimated.
The organic matter removed in the filter, Q1 · C1- Q3 · C3, can approximatly be
expressed as Q1 · (C1- Ss,J),
where cl is the biodegradable substance in the influent,
Ss,3 is the dissolved biodegradable substance in the effluent.
Hereby the suspended organic substance in the effluent, XJ, is understood to be the
yield of the biological removal which is not quite wrong, especially for plants
without separate withdrawal of excess sludge.
Hence expression (9.13) can be written:
(9.14)
It clearly appears from the above design that the area in anaerobic filters is of less
importance. The filter medium functions as the carrier for the sludge (biomass), and
diffusional limitations in the film hardly ever occur. It means that what is decisive
for the anaerobic filters is the total sludge concentration which can be obtained in
the filter whereas the area of the filter medium is of no special importance.
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Design of anaerobic filter areas
By means of the mass balance in Expression (9.6), the size of the anaerobic filter can
be calculated.
The necessary area of the carrier, A2•, is:
(9.11)
Knowing the sludge specific removal rate, l')(,M, the sludge concentration in the
biofilm, X2•, and the thickness of the biofilm, L:z. the necessary filter area, A2•, can
easily be calculated. The only problem is that normally we do not know X2• and L2.
By using the specific filter area= A2•/V:z. Expression (9.11) can be transformed to
(9.12)
The volume of the anaerobic filter, V:z. is:
(9.13)
The specific filter surface area, ro, and the sludge concentration, X:z, is found in Table
9.4. The sludge specific removal rate, rx,M can be estimated from Table 9.7. Subsequently the area as well as the volume of the filter can be estimated.
The organic matter removed in the filter, Q1 · C1- Q3 · C3, can approximatly be
expressed as Q1 · (C1- Ss,J),
where cl is the biodegradable substance in the influent,
Ss,3 is the dissolved biodegradable substance in the effluent.
Hereby the suspended organic substance in the effluent, XJ, is understood to be the
yield of the biological removal which is not quite wrong, especially for plants
without separate withdrawal of excess sludge.
Hence expression (9.13) can be written:
(9.14)
It clearly appears from the above design that the area in anaerobic filters is of less
importance. The filter medium functions as the carrier for the sludge (biomass), and
diffusional limitations in the film hardly ever occur. It means that what is decisive
for the anaerobic filters is the total sludge concentration which can be obtained in
the filter whereas the area of the filter medium is of no special importance.
301