Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

Civil Engineering (CE): Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

The document Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Environmental Engineering.
All you need of Civil Engineering (CE) at this link: Civil Engineering (CE)

BASIC EQUATION FOR BIOLOGICAL TREATMENT OF WASTEWATER 

According to Monod kinetics, 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.1)
 Where, s is the substrate concentration, ks is the substrate concentration when µ(=µmax/2), µmax is the maximum µ when substrate is not limiting. Also, solid production rate Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)  is related to substrate utilization rate Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) by 
 following relationship: 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.2) 
 Where, Sr is the mass of soluble substrate (i.e. BOD), Y is the yield coefficient (kg of new cells formed/kg BOD removed). However owing to large treatment time in many of the large treatment units, substantial number of cells may die because of endogenous respiration. Therefore, 

Net production rate Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.3)

Where, Kd is the endogenous respiration decay rate constant. For growth phase only, 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.3)

Case 1- S>>Ks    

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)(4.2.4)
 i.e. removal rate is independent of substrate concentration and that the removal rate depends on X only. 

Case 2: S<< KS 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.5)

Here, removal rate depends both upon X and S. Where, X is the mass of biomass in the system (usually represented by MLSS i.e. Mixed Liquor Suspended Solid), µ is the specific growth rate constant (time-1). 

Major Terms [a] Hydraulic detention time,

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.6)

[b] Sludge age or mean residence time(θC)

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)(4.2.7)

Where, x (=X/V) the concentration of microbial solution in the system, x’ is the concentration of solids withdrawn. 

For the flow through system, x’ = x and Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

For the flow system with recycling, x’ < x and  Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

[c] Food to microorganism ratio 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) (4.2.8)

 

Problem 4.2.1: An aerated activated sludge tank is being operated under following conditions: Q=4400 m3/d, MLSS=3500 mg/l, Y=0.5, tank volume =770 m3, Endogeneous decay rate constant kd=0.09 d-1.
 (a) Estimate weight of solids produced per day for the conditions in which BOD is reduced from 350 mg/l to 130 mg/l.
 (b) Estimate θc.
 (c) Estimate F/M ratio. 

Solution: 

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

=241.4 kg/d. 

θc  = mass of solid in the system/ mass of solid leaving the system per day = Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)

Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE)= 0.359 (kg BOD/kg MLSS) 

θc = 11.17 day.

The document Anaerobic & Aerobic Treatment Biochemical Kinetics Notes | Study Environmental Engineering - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Environmental Engineering.
All you need of Civil Engineering (CE) at this link: Civil Engineering (CE)
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