1. Physical/Chemical Waste Treatment
Walter J. Wujcik, Ph.D., P.E.
Drexel University

2. Text Chapters 28 – Wastewater Quantity & Quality
26 – Water Supply Treatment
29 – Wastewater Treatment

3. What Can Physical/Chemical Treatment Processes Be Used For?
Treat wastewater
Contaminated groundwater treatment
Potable water treatment
Industrial process water treatment

4. PE Exam Problem Solving
Apply principles of engineering to design oriented problems
Multiple choice
Morning – general test
Afternoon – specialty tests

5. Physical/Chemical Processes
Physical processes
Sedimentation
Filtration
Flocculation
Air stripping
Carbon adsorption
Chemical processes
Coagulation
Ion exchange
Chemical oxidation

6. Physical Treatment Processes
Physical treatment processes are those in which the application of physical forces (gravity, buoyancy, friction) predominate.

7. Chemical Treatment Processes
Chemical treatment processes are those in which the removal or conversion of contaminants is brought about by the addition of chemicals or by other chemical reactions.

8. Classification of Particles
Suspended solids – the settleable solids that will settle to the bottom of an Imhoff cone in 60 minutes.
Colloidal solids –generally require biological oxidation or coagulation, followed by sedimentation for removal (organics & inorganics).
Dissolved solids - consist of both inorganic and organic molecules and ions that are present in true solution in water.

9. Remove in Size Order
Suspended
Colloidal
Dissolved

10. Treatment Type Destruction technologies
Transfer technologies (residuals)

11. Suspended Particles
Screening
Sedimentation
Filtration

12. Colloidal Particles Biological treatment (organics)
Coagulation/flocculation followed by sedimentation

13. Dissolved Particles Organic Molecules Inorganic molecules
Air stripping
Chemical oxidation
Carbon adsorption
Inorganic molecules
Ion exchange
Reverse osmosis

14. Selection of Treatment Technology
Wastewater characteristics
Discharge requirements
Site specific constraints
Capital and operating costs

15. Wastewater Characteristics
Flow – batch or continuous; frequency; volume; and rate
Chemical composition
High strength vs. low strength (variability)
Solids to dissolved sized particles
Biodegradable or non-biodegradable

16. Discharge Requirements
End of pipe – NPDES (direct stream discharge) limits vs. pretreatment ordinance limits (industrial discharges)
End of process – Categorical standards

17. Site Specific Constraints
Available space/land for treatment facility
Proximity to residential community (odor potential)
Level of technical skills available for operating treatment facility
Anticipated need for future expansion

18. Capital and Operating Costs
Funds available (now vs. future)

19. Chapter 28 Problems
Problem 1a
Problem 6a, b, & c

20. Sedimentation Class 1 – Discrete particles
Class 2 – Flocculant settling
Class 3 – Zone settling
Class 4 – Compression settling

21. Settling Velocity
Forces on the particle
Gravity
Buoyant
Drag

22. “Ideal” Settling Tank Flow is horizontal Uniform velocity
Uniform concentration of solids at inlet
Particles reaching bottom stayed removed
No flocculation

23. Settling Velocity – Class 1
Overflow rate
Function of tank area, independent of depth, independent of detention
More complex considerations with Class 2, 3, and 4 sedimentation

24. Settling - Activated sludge
Dual purpose
Removal of solids
Return of biomass

25. Design Standards Pennsylvania standards Ten States standards
Other states

26. Sedimentation Problems
Chapter 29
3a, b, & c 4
Chapter 26
3a, b, c, & d

27. Coagulation
Coagulation – electrochemical process of destabilizing a colloidal suspension brought about by:
Addition of multivalent metal salts (inorganic polymers)
Addition of polyelectrolytes (polymer)
Addition of electrolyte

28. Flocculation
Physical process of bringing particles together after charge is reduced

29. Coagulant Reactions Hydrolysis lowers pH
Inorganic coagulants destroy alkalinity

30. Flocculant Settling
Flash mix tank
Flocculation basin
Settling tank

31. Flocculation Problem
Chapter 26
Problem 5a, b, & c

32. Precipitation Softening
Chapter 26
Problem 8a, b, & c

33. Dissolved Contaminants
Organics – Carbon Adsorption, air stripping, oxidation
Inorganics – Ion exchange, reverse osmosis

34. Carbon Adsorption
Remove organics difficult to remove by biological treatment
Remove organics to more stringent effluent levels than achievable by bio processes
Adsorption is the removal of solute particles from solution
GAC particles have high surface area

35. Freundlich Isotherm Empirically derived Perform isotherm tests
Theoretical carbon capacity
Select carbon

36. Isotherm Tests Pulverize GAC
Equal aliquots of wastewater to be treated
Carbon dosages appropriate to situation (10 to 5,000 mg/L)
Cover flasks & agitate
Filter flask contents
Analyze filtrate for compounds of interest

37. Continuous Column Tests
Design conditions
Breakpoint
Breakthrough point

38. Carbon System Design Upflow vs. Downflow Multiple units
Typical design parameters
Flow rates ~ 2-4 gal/min/ft3 bed volume
Bed depths > 4 ft.
Detention time minutes

39. Factors affecting GAC Performance
Temperature pH
Biological activity

40. Carbon Adsorption Limitations
Presence of multiple contaminants can affect process performance
Costs are high if used as the primary treatment on waste streams with high contaminant concentration levels
Water soluble compounds and small molecules are not adsorbed well

41. Ion Exchange
Removes unwanted ions from raw water by transferring them to a solid material, the ion exchange resin, which accepts them while giving back an equivalent number of desirable ions stored on the resin
Ion exchange is used for metals removal (strict discharge limits) and specific ions removal (e.g., ammonia, cyanide, etc.)

42. Ion Exchange Cations are exchanged for hydrogen or sodium ions
Cationic resin – acid for regeneration
Anions are exchanged for hydroxyl ions
Anionic resin – caustic for regeneration
Ion exchange resins loose some exchange capacity after each regeneration

43. Typical Operating Cycle
Treatment (i.e., adsorption)
Resin bed adsorption (leakage of contaminant)
Backwash (solids removal)
Regeneration
Rinse cycle
Treatment

44. Freundlich isotherm Empirically derived Perform isotherm tests
Theoretical resin capacity
Select ion exchange resin

45. Ion Exchange System Design
Minimum depth – 2 to 2.5 feet
Flow rate – 2 to 5 gal/min – ft3
Regenerant flow rate - 1 to 2 gal/min – ft3
Rinse flow rate – 30 to – 3 gal/min – ft3