1. ERT 417 Waste Treatment In Bioprocess Industry
Semester /2012
Huzairy Hassan
School of Bioprocess Engineering
UniMAP

2. Chemical Treatment Processes of Industrial Waste

3. Hasil Pembelajaran / Learning (Course) Outcomes:
At the end of the course, students are expected to acquire these abilitities:
1. Ability to calculate the physical, chemical, and biological properties of waste material and describe its toxicology.
2. Ability to calculate and design the basic structure of waste treatment unit operations.
3. Ability to compare and evaluate methods for a particular waste for treatment.
4. Ability to interpret, and propose the common waste management practice in industry and describe the legal framework structure

4. “Compare and choose the chemical treatment methods for waste treatment in industries. Calculate and design the basic structure of waste treatment unit operations”.
Chemical treatment / Unit operation

5. Introduction
Chemical treatment usually are used in combination with the Physical Unit Operations;
- Screening, coarse solids reduction, mixing and flocculation, gravity separation, grit removal, sedimentation, flotation, aeration, etc.
and also with Biological Unit Operations.

7. Role of Chemical Unit Processes in Wastewater Treatment
Chemical coagulation
Chemical precipitation
Chemical disinfection
Chemical oxidation
Advanced oxidation process
Ion exchange
Chemical neutralization, scale control, and stabilization

8. Application of chemical Unit Processes in wastewater treatment

9. Considerations & Issues of Chemical Treatment….
“Chemical treatment – additive processes”
Handling, treatment and disposal of the large volumes of sludge produced
Net increase in dissolved constituents
Increase in cost of energy & chemical costs
TDS concentration increase;
ex: chlorine additives

10. CHEMICAL COAGULATION

11. Chemical Coagulation Colloidal particles found in wastewater :
- net negative surface charge,
to 1 µm in size
- attractive body forces between particles < repelling forces
- this stable conditions, Brownian motion (i.e., random movement) keeps the particles in suspension.
Coagulation is the process of destabilizing colloidal particles so that particle growth can occur as a result of particle collisions.

12. Nature of particles in wastewater
Suspended particles > 1.0 µm, can be removed by gravity sedimentation
Colloidal particles cannot be removed by sedimentation (need coagulants & flocculant aids)
Characteristics of Colloidal Particles:
a) Particle size and number
0.01 to 1.0 µm
number in untreated wastewater and after primary sedimentation
= 106 to 1012 /mL
b) Particle shape and flexibility
spherical, ellipsoids, disklike, various length, D, and random coils .
shapes affect electrical properties, particle-particle interaction, and
particle-solvent interaction

13. c) Particle-solvent interaction
Hydrophobic – have relatively little attraction for water
Hydrophilic – much greater attraction for water
Association colloids – made up of surface-active agents, ex: soaps, synthetic detergents, and dyestuff which form organized aggregates known as micelles.

14. Basic definitions
Chemical coagulation – all reactions and mechanisms involved in the chemical destabilization of particles and in the formation of larger particles through perikinetic flocculation (aggregation of particles in the size range from 0.01 to 1 µm )
Coagulant – chemical that is added to destabilize the colloidal particles in wastewater so that floc formation can occur.
Flocculant – chemical, typically organic, added to enhance the flocculation process.
Coagulant & Flocculant : natural and synthetic organic polymers, metal salts, and prehydrolized metal salts (ex:alum, ferric sulfate, polyaluminum chloride (PACl) and polyiron chloride (PICl), etc )

15. gravity sedimentation and filtration
Flocculants are also used to enhance the performance of granular medium filters and dewatering of digested biosolids, Filter aids
Flocculation: the process of increasing the size of particles as a result of particle collisions.
Microflocculation
(perikinetic flocculation)
- Particle aggregation is brought about by the random thermal motion of fluid molecules known as Brownian motion
Macroflocculation
(orthokinetic flocculation)
- Particle aggregation is brought about by inducing velocity gradients and mixing in the fluid containing the particles to be flocculated
Reaching 1-10 µm size, then separated by
gravity sedimentation and filtration

16. a) Isomorphous replacement
Development Surface Charge
a) Isomorphous replacement
- occurs in clays and other soil particles, ions in lattice structure replaced with ions from solution, ex: Si4+ replaced with Al3+
b) Structural imperfections
- occurs in clay or similar particles, due to broken bonds on crystal edge (imperfections in crystal formation)
c) Preferential Adsorption
- when oil droplets, gas bubbles, or other inert substances are dispersed in water, they will acquire –ve charge through adsorption of ions (hydroxyl ions)
d) Ionization
- ionization of carboxyl and amino groups (at different level of pH)

17. Measurement of surface potential
Electrical double layer

18. Particle-particle interactions

19. Particle Destabilization
1) Particle Destabilization and Aggregation with Polyelectrolytes
Actions of polyelectrolytes:
a) Charge neutralization
- act as coagulants that neutralize or lower the charge of the
wastewater particles
- normally the wastewater particles are –ve charge, so,
cationic (+ve charge) polyelectrolytes are used.
- polyelectrolytes must be adsorbed to the particles – used
sufficient and high intensity of mixing (prevent folding back
of polyelectrolytes)

20. b) Polymer bridge formation
Anionic or nonionic
polyelectrolytes

21. c) Charge neutralization and Polymer bridge formation - use cationic polyelectrolytes having extremely high molecular weight - can form both charge neutralization and polymer bridge

22. a) Addition of potential determining ions
2) Particle Destabilization with Potential-determining Ions and electrolytes
a) Addition of potential determining ions
- add strong acids or bases to reduce charge of metal oxides
or hydroxides to near 0 so that coagulation can occur
- not feasible due to massive concentrations of ions to be added
b) Use of Electrolytes
- added to coagulate colloidal suspension
- cause decrease in zeta potential and corresponding decrease in repulsive forces.
- also not feasible in waste treatment.

23. - Addition of alum or ferric sulfate (Fe3+ & Al3+)
3) Particle destabilization and removal with Hydrolyzed metal ions
- Addition of alum or ferric sulfate (Fe3+ & Al3+)
- Complex formation of metal ion hydrolysis products
Letterman, 1991

24. Action of hydrolyzed metal ions:
i) Adsorption and charge neutralization
- mononuclear and polynuclear metal hydrolysis species adsorb on the colloidal particles.
ii) Adsorption and interparticle bridging
- involve the adsorption of polynuclear metal hydrolysis species and polymer species which in turn will form particle-polymer bridges
- if enough coagulant requirement & charge neutralization, metal hydroxides precipitates and soluble metal hydrolysis products form
- if sufficient metal salts added, large amount of metal hydroxide floc will form settle
iii) Enmeshment (trapped) in sweep floc
- floc particles settle and sweep through water containing colloidal partilces
- colloidal particles enmesh in the floc – removed by sedimetation.

25. CHEMICAL PRECIPITATION
FOR IMPROVED
PLANT PERFORMANCE

26. Chemical Precipitations

27. 1) Alum
Alkalinity
(or Magnesium
bicarbonate)
Precipitate

28. The quantity of alkalinity (as CaCO3 having Mw = 100) required to react with 10 mg/L of alum is;
!! Note: If less than this amount of alkalinity is available,
it must be added, ex: Lime

29. 2) Lime
- Reactions for carbonic acid – clarification;
- Alkalinity;

30. 3) Ferrous sulfate and lime
Ferrous sulfate alone added to wastewater;
FeSO4 ·7H2O + Ca(HCO3) Fe(HCO3)2 + CaSO4 + 7H2O
Addition of Ferrous sulfate & lime
Fe(HCO3) Ca(OH) Fe(OH)2 + 2CaCO3 + 2H2O
Ferrous
bicarbonate
(soluble)
Ferrous sulfate
(soluble)
Calcium
carbonate
(soluble)
Calcium
sulfate
(soluble)
Ferrous
bicarbonate
(soluble)
Calcium
carbonate
(somewhat
soluble)
Calcium
hydroxide
(slightly soluble)
Ferrous
hydroxide
(very slightly
soluble)

31. 4) Ferric chloride 2FeCl3 + 3Ca(HCO3)2 2Fe(OH)3 + 3CaCl2 + 6CO2

32. Example 6.1 – Estimation of sludge volume from chemical precipitation of untreated wastewater
a) Estimate the mass and volume of sludge produced from untreated wastewater without and with the use of ferric chloride for the enhanced removal of TSS.
b) Also estimate the amount of lime required for the specified ferric chloride dose.
- Assume that 60% of the TSS is removed in the primary settling tank without the addition of chemicals, and that the addition of ferric chloride results in an increased removal of TSS to 85%.
- Also, assume that the following data apply to this situation:

33. Wastewater flow rate = 1000 m3 /d Wastewater TSS = 220 mg/L
Wastewater alkalinity as CaCO3 = 136 mg/L
Ferric chloride (FeCl3) added = 40 kg/1000m3
Raw sludge properties:
Specific gravity = 1.03
Moisture content = 94 %
6. Chemical sludge properties:
Specific gravity = 1.05
Moisture content = 92.5 %

34. Solutions: ?

35. Recommended design for Primary Sedimentation
Types of Precipitation
Percentage removal %
TSS
BOD
Bacteria
Chemical Precipitation
80 – 90 %
50 – 80 %
Precipitation without chemical additives
50 – 70 %
25 – 40 %
25 – 75 %

36. Surface Loading Rate (SLR) or “surface settling rate” or “surface overflow rate” : is a hydraulic loading factor expressed in terms of flow per surface area.

37. CHEMICAL PRECIPITATION FOR PHOSPHORUS REMOVAL

38. Introduction
The removal of phosphorus from wastewater involves the incorporation of phosphate into TSS and the subsequent removal of these solids.
Incorporation into
Chemical precipitates
Incorporation into
biological solids

39. Phosphate Precipitation
Addition of salts of multivalent metal ions, ex: Ca(II), Al(III), and Fe(III).
1) Phosphate precipitation with Calcium
- Calcium is added in the form of lime Ca(OH)2.
- usually, when lime is added, it reacts with natural bicarbonate alkalinity to precipitate CaCO3.
- As pH > 10, excess calcium ions will react with phosphate, to precipitate hydroxylapatite [Ca10(PO4)6(OH)2].
- Quantity of lime required to precipitate P - independent of phosphate amount present, but dependent of wastewater alkalinity (about 1.4 – 1.5 times total alkalinity as CaCO3)
- because need high pH- not feasible.

40. 2) Phosphate precipitation with Aluminum and Iron
Because many competing reactions and effects of pH, alkalinity, trace elements, etc., Eqs 6-20 & 6-21 cannot be used to estimate the required chemical dosages.
So, achieved by bench-scale tests Figure 6-12.

41. Solid lines: Conc. of residual soluble phosphates after precipitation
Shaded area: pure metal phosphates are precipitated
Solid lines: Conc. of residual soluble phosphates after precipitation

42. Example 6.2 – Determination of Alum Dosage for Phosphorus Removal
Determine the amount of liquid alum required to precipitate phosphorus in a wastewater that contains 8 mg P/L.
Also determine the required alum storage capacity if a 30-d supply is to be stored at the treatment facility. Based on laboratory testing, 1.5 mole of Al will be required per mole of P. The flow rate is m3/d. the following data are for the liquid alum supply.
Formula for liquid alum Al2(SO4)3 ·18H2O
Alum strength = 48 %
Density of liquid alum solution = 1.2 kg/L

43. Solution: ?

48. CHEMICAL OXIDATION

49. Chemical Oxidation
Use of Ozone (O3), Hydrogen peroxide (H2O2), Permanganate (MnO4), Chloride dioxide (ClO2), Chlorine (Cl2) or (HOCl), and Oxygen (O2)
To reduce /degrade BOD, COD, ammonia, nonbiodegradable organic compounds.

50. Fundamentals of chemical oxidation
Oxidation-reduction reactions (redox)
Cu2+ + Zn Cu + Zn2+
2) Half-reaction potentials

51. ¤ ¤ ¤ ¤ Go back and read Example 6.4 and 6.5 (revision)↗

53. Thank you