Biological Storage in the Mathematical Analysis of Activated Sludge Behaviour
371
CONCLUSION
The need for a mathematical description of the behaviour of activated sludge is
obvious if we want to introduce better regulation, automation and maybe process control
in our plants.
It is obvious that such analysis can lead to erroneous conclusions if we neglect any of
the basic mechanisms of biological degradation.
Our measurements on different plants have shown that at least one point is not
covered by the usual model described in the literature: the decay between the occurrence
peak of BOD 5 load and peak of the respiratory activity.
In this paper, we made an attempt to evolve a more sophisticated model which by
taking account of the ability of bacterial cells to store externally or internally part of the
available food, leads to much better fit between the calculated and observed
measurements.
We do not think we have solved all the problems raised by the description of the
complex mechanisms involved in biological treatment; nevertheless we hope to have
brought to light a new point and to open a challenge for more work in this path.
REFERENCES
1 STANNIER & DOUDOROFF, Precis de microbiologie gonorale, Masson Ed.
2 BROUZES, "Automated activated sludge plants with respiratory metabolism control", Paper 115
(Fourth Inte Conf. WPR Prague) (1969).
3 ZANDER and JOHNSON, "Process control for activated sludge", Proc. Purdue Ind. Waste Conf. p.
403 (1967).
4 NILS WESTBERG, "An introductory study of regulation in the activated sludge process", Water
Research Perg. Press Vol 3 p.613 (1969).
5 TUCCK and CHUDOBA, "Purification efficiency in aeration tanks with complete mixing and
piston flow", Water Research Vol. 3 p.559 (1969).
APPENDIX
Definition of Symbols
AR
b
c
ke
kb
kn
ks
Lon
Los
Ls
Ma
P
q
Q
r
Respiratory activity
Mass of volatile solids corresponding to 1 g BOD (mg RV/mg BOD 5 )
Concentration rate of sedimentation basin
Endogenous respiration rate (d
_1 )
Constant
Constant
Constant
: Non-soluble BOD 5 of influent (mg/1)
Soluble BOD5 of influent (mg/1)
Interstitial BOD 5 of aerator (mg/1)
Active mass in sludge (mg/1)
Maximum rate constant of undissolved reserve ( d )
Maximum rate constant of "dissolved reserve" (d )
Volume flow of influent (cu.m/h)
: Recirculation rate
371
CONCLUSION
The need for a mathematical description of the behaviour of activated sludge is
obvious if we want to introduce better regulation, automation and maybe process control
in our plants.
It is obvious that such analysis can lead to erroneous conclusions if we neglect any of
the basic mechanisms of biological degradation.
Our measurements on different plants have shown that at least one point is not
covered by the usual model described in the literature: the decay between the occurrence
peak of BOD 5 load and peak of the respiratory activity.
In this paper, we made an attempt to evolve a more sophisticated model which by
taking account of the ability of bacterial cells to store externally or internally part of the
available food, leads to much better fit between the calculated and observed
measurements.
We do not think we have solved all the problems raised by the description of the
complex mechanisms involved in biological treatment; nevertheless we hope to have
brought to light a new point and to open a challenge for more work in this path.
REFERENCES
1 STANNIER & DOUDOROFF, Precis de microbiologie gonorale, Masson Ed.
2 BROUZES, "Automated activated sludge plants with respiratory metabolism control", Paper 115
(Fourth Inte Conf. WPR Prague) (1969).
3 ZANDER and JOHNSON, "Process control for activated sludge", Proc. Purdue Ind. Waste Conf. p.
403 (1967).
4 NILS WESTBERG, "An introductory study of regulation in the activated sludge process", Water
Research Perg. Press Vol 3 p.613 (1969).
5 TUCCK and CHUDOBA, "Purification efficiency in aeration tanks with complete mixing and
piston flow", Water Research Vol. 3 p.559 (1969).
APPENDIX
Definition of Symbols
AR
b
c
ke
kb
kn
ks
Lon
Los
Ls
Ma
P
q
Q
r
Respiratory activity
Mass of volatile solids corresponding to 1 g BOD (mg RV/mg BOD 5 )
Concentration rate of sedimentation basin
Endogenous respiration rate (d
_1 )
Constant
Constant
Constant
: Non-soluble BOD 5 of influent (mg/1)
Soluble BOD5 of influent (mg/1)
Interstitial BOD 5 of aerator (mg/1)
Active mass in sludge (mg/1)
Maximum rate constant of undissolved reserve ( d )
Maximum rate constant of "dissolved reserve" (d )
Volume flow of influent (cu.m/h)
: Recirculation rate