V
Volume, L
3
V S
Volume of final clarifier, L
3
W
0
BOD loading to a second-stage filter, M/T
X
Microbial concentration, M/L
3
ÀX
Average microbial concentration in the plug flow process, M/L
3
X c
Sludge concentration in the final clarifier effluent, M/L
3
X c
Bacterial concentration within the biofilm, M/L
3
X r
Return sludge concentration, M/L
3
X v
Volatile biological solid concentration, M/L
3
X θ
Sludge production rate for a complete mix model with no sludge recycle,
M/L
3
X θc
Sludge production rate for a complete mix model with sludge recycle, M/L
3
X v
MLVSS, mixed liquor volatile suspended solids, mg/L
Y
Growth yield coefficient, mass microbial growth per unit mass substrate
utilized
Y
Depth of a stagnant liquid layer outside the slime-liquid interface, L
Y c
Depth of a biofilm within the cellular matrix, L
Y e
Effective depth of biofilm at which S c ¼ S i , L
Z
Direction z
α
Specific consumption of oxygen, M/L
3 t
ΔG
Gibbs free energy, kcal/electron mole
μ.
Net specific growth rate, change of microbial concentration per unit time per
unit microbial concentration, 1/t
P
A coefficient
P s
Sludge produced, M/T
θ
Temperature coefficient
θ
Hydraulic retention time, t
θ c
Sludge retention time, sludge age, or mean cell residence time, t
θ T
Temperature coefficient, a constant
1 Concepts and Physical Behavior
Current practice in the secondary treatment of wastewater for pollution control calls
for the use of biological oxidation to remove organic substances. When it comes to
selecting the method of biological oxidation, the pollution control engineer has at his
or her disposal a variety of treatment processes, among which activated sludge and
trickling filters are currently the most popular. In this section, the function and
limitations of the activated sludge processes are reviewed. The principles of biological oxidation and of the energy flow concept are described, and the relationship of
synthesis and respiration is discussed in relation to the importance of activated
sludge process control. Other biological treatment processes will be dealt with in
later sections.
3 Biological Processes
77
Volume, L
3
V S
Volume of final clarifier, L
3
W
0
BOD loading to a second-stage filter, M/T
X
Microbial concentration, M/L
3
ÀX
Average microbial concentration in the plug flow process, M/L
3
X c
Sludge concentration in the final clarifier effluent, M/L
3
X c
Bacterial concentration within the biofilm, M/L
3
X r
Return sludge concentration, M/L
3
X v
Volatile biological solid concentration, M/L
3
X θ
Sludge production rate for a complete mix model with no sludge recycle,
M/L
3
X θc
Sludge production rate for a complete mix model with sludge recycle, M/L
3
X v
MLVSS, mixed liquor volatile suspended solids, mg/L
Y
Growth yield coefficient, mass microbial growth per unit mass substrate
utilized
Y
Depth of a stagnant liquid layer outside the slime-liquid interface, L
Y c
Depth of a biofilm within the cellular matrix, L
Y e
Effective depth of biofilm at which S c ¼ S i , L
Z
Direction z
α
Specific consumption of oxygen, M/L
3 t
ΔG
Gibbs free energy, kcal/electron mole
μ.
Net specific growth rate, change of microbial concentration per unit time per
unit microbial concentration, 1/t
P
A coefficient
P s
Sludge produced, M/T
θ
Temperature coefficient
θ
Hydraulic retention time, t
θ c
Sludge retention time, sludge age, or mean cell residence time, t
θ T
Temperature coefficient, a constant
1 Concepts and Physical Behavior
Current practice in the secondary treatment of wastewater for pollution control calls
for the use of biological oxidation to remove organic substances. When it comes to
selecting the method of biological oxidation, the pollution control engineer has at his
or her disposal a variety of treatment processes, among which activated sludge and
trickling filters are currently the most popular. In this section, the function and
limitations of the activated sludge processes are reviewed. The principles of biological oxidation and of the energy flow concept are described, and the relationship of
synthesis and respiration is discussed in relation to the importance of activated
sludge process control. Other biological treatment processes will be dealt with in
later sections.
3 Biological Processes
77