1. Reactor analysis (Mass balances, Flow models, Reactors)

2. Classifications of reactor
Batch reactor
Continuous-flow stirred-tank reactor
Tubular reactor
CFSTR in series
Packed bed reactor)
Fluidized bed reactor
Exothermic, Endothermic
Homogeneous, Heterogeneous
Catalytic, Non-catalytic

3. Principal applications of reactor types used for water/wastewater treatment

4. REACTIONS, REACTION RATES, AND REACTION, RATE COEFFICIENTS
Types of Reactions
Homogeneous Reactions
irreversible or reversible
Heterogeneous Reactions
1. Transport of reactants from the bulk fluid to the fluid-solid interface
(external surface of catalyst particle)
2. Intraparticle transport of reactants into the catalyst particle (if it is porous)
3. Adsorption of reactants at interior sites of the catalyst particle
4. Chemical reaction of adsorbed reactants to adsorbed products (surface reaction)
5. Desorption of adsorbed products
6. Transport of products from the interior sites to the outer surface of the catalyst particle

5. Rate of Reaction For homogeneous reactions
If the volume remains constant (i.e., isothermal conditions, no evaporation)
For heterogeneous reactions

6. For reactions involving two or more reactants with unequal stoichiometric coefficients
Reaction Order

7. Effects of Temperature on Reaction Rate Coefficients
van’t Hoff-Arrhenius relationship

8. Analysis of Reaction Rate coefficient
Differential method
Integral method

10. 1. Mass balance
At Steady-State

11. 2. Modeling 1) Batch reactor with reaction
1) Batch reactor with reaction
For 1st order reaction : rc = kC

12. 2) CFSTR with reaction
Integrating factor
At steady-state condition

13. 3) CFSTR in series with reaction a) Analytical approach
b) Graphical approach
a) Analyltical solution

14. Combining 2 eq.

15. b) Graphical solution

16. 4) PFR with reaction

18. Comparison of Complete-Mix and Plug-Flow Reactors with Reaction
Required reactor volumes expressed in terms of Q/k for CFSTRs in series
and PFR for various removal efficiencies for 1st order kinetics

19. 3. TREATMENT PROCESSES INVOLVING MASS TRANSFER
1) Basic Principle of Mass Transfer
Principal applications of mass transfer operations and processes in wastewater treatment

20. Diffusion
Symbol
Values(cm2/s)
Molecular diffusion
Eddy diffusion
Dispersion D De Dm
10-8 ∼ 10-4
10-4 ∼ 10-2
102 ∼ 106

21. 2) Gas-Liquid Mass Transfer
: two-film theory, penetration model, surface-renewal model
The Two-Film Theory

22. Under steady-state conditions, the rate of mass transfer of a gas through the gas
film must be equal to the rate transfer through the liquid film.

23. If the two expressions above are equated
Henry’s law
overall driving force
The transfer of mass is controlled by the liquid film
The transfer of mass is controlled by the gas film
The relationship between the overall liquid and gas phase transfer coefficients

24. the flux of a slightly soluble gas from the gas to the liquid phase (liquid film
controls transfer rate)
The corresponding rate of mass transfer per unit volume per unit time
: depends on water quality and the type of aeration equipment and is unique for each situation

25. Absorption of Gases (a) (b)
Definition sketch for the absorption of a gas: (a)under turbulent conditions where the concentration of gas in the gaseous and liquid phases is uniform
(b)under quiescent conditions

27. Absorption of Gases under Quiescent Conditions
molecular diffusion

28. Approximate coefficients of molecular diffusion and coefficients of
diffusion for gases of low solubility in water at 20 ℃
Desorption (Removal) of Gases
the volatilization of a gas from a supersatured liquid

29. 3) Liquid-Solid Mass Transfer
Adsorption
Granular or powdered activated carbon
PAC : diameter of less than mm (200 sieve),
GAC : diameter greater than 0.1 mm (~140 sieve)

30. Comparison of granular and powdered activated carbon

31. Fundamentals of Adsorption
The adsorption process
bulk solution transport
film diffusion transport
pore transport
adsorption
Adsorption forces
Coulombic-unlike charges Point charge and a dipole
Dipole-dipole interactions Point charge neutral species
London or van der Waals forces Covalent bonding with reaction
Hydrogen bonding

32. Development of Adsorption Isotherms
Freundlich, Langmuir, Brunauer, Emmet, and Teller (BET isotherm)
Freundlich isotherm is used most commonly to describe the adsorption characteristics of the activated carbon used in water and wastewater treatment.

33. Freundlich isotherm
Determination of the constant
in Isotherm
log (x/m) versus log Ce

34. Langmuir isotherm
developed by assuming
a fixed number of accessible sites are available on the adsorbent surface,
all of which have the same energy
(2) adsorption is reversible
Determination of the constant
in Isotherm

37. Types of activated carbon contactors
Activated Carbon Treatment Process Applications
Removal of refractory organic compounds, as well as residual amounts of
inorganic compounds such as nitrogen, sulfides, and heavy metals
Removal of taste and odor compounds
GAC
Fixed-bed
Expanded-bed
Types of activated carbon contactors