1. Introduction to Environmental Engineering and Science (3rd ed.)
Chapter 5. Water Pollution

2. Population lacking access to safe drinking water

3. Properties of water Dipolar Density (maximum: 4oC)
Melting and Boiling points
Specific heat (4,184 J/kgoC)
Heat of vaporization (2,258 kJ/kg)
Water as a solvent
Greenhouse effect

4. The Hydrologic Cycle
Figure: 05-03

5. Per capita water availability
Figure: 05-04

6. Fresh water use in the U.S., 1990.
Figure: 05-05

7. Water Pollutants Pathogens (Table 5.4)
Oxygen-Demanding Wastes (BOD, COD)
Nutrients: eutrophication, NO3-, NO2-
Salts
Thermal Pollution
Heavy Metals: Hg, Pb, Cd, and As
Pesticides: insecticides, herbicides, rodenticides, and fungicides; DDT, DDE, 2,4-D, 2,4,5-T, and dioxin

9. Figure: 05-UN01

10. Water Pollutants Volatile Organic Chemicals (VOCs)
Emerging Contaminants:
- EDCs (endocrine disrupting compounds)
- PBDEs (polybrominated biphenyl ethers)
- PFCAs (perfluorocarboxylates)

11. Figure: 05-UN03

12. Fraction of impaired river and stream
Figure: 05-07

13. Extent of impaired lake
Figure: 05-08

14. Biochemical Oxygen Demand
Definition: the amount of oxygen required by microorganisms to oxidize organic wastes aerobically.
Aerobic decomposition by microorganisms
O.M. + O2 → CO2 +H2O + new cells + stable products (NO3-, PO43-, SO42-, …)
Anaerobic decomposition by by microorganisms
O.M. → CO2 +H2O + new cells + unstable products (CH4, NH3, H2S, …)

15. Five-day BOD (BOD5) Test:
BOD5 = (DOi – DOf)/P
Unseeded/seeded BOD5 test (Examples 5.1 & 5.2)
Figure: 05-09

16. Figure: 05-09

17. First-Order Reaction:
Lt=L0e-kt
Figure: 05-10

18. Figure: 05-11
(Example 5.3)

19. Figure: 05-11

20. Temperature dependence of BOD5
kT = k20Ɵ(T-20)
where Ɵ = 1.047, T: oC
(Example 5.4)

22. Nitrification By Nitrosomonas 2NH3 + 3O2 → 2NO2- + 2H+ + 2H2O
By Nitrosobacter
2NO2- + O2 → 2NO3-
CBOD (carbonaceous BOD)
NBOD (nitrogenous BOD)
Figure: 05-12

23. Changes in nitrogen forms under aerobic conditions
(Example 5.5)

25. Total BOD = Carbonaceous and nitrogenous BODs
Figure: 05-13

26. Total Kjeldahl Nitrogen (TKN)
TKN = organic N + NH3-N
Ultimate NBOD ≈ 4.57×TKN
ThOD and COD
ThOD: stoichiometric calculation
COD: a strong chemical oxidizing agent
COD ≥ BOD

27. The effect of oxygen-demanding wastes on rivers
Rate of deoxygenation = kdLt = kdL0e-kdt
where L0 = (QwLw + QrLr)/(Qw+Qr)
Figure: 05-14

28. Reaeration Rate of reaeration = krD where kr = 3.9u1/2/H3/2
kr = reaeration coefficient at 20 oC
u = average stream velocity
H = average stream depth
(Table 5.9) (Table 5.10)

30. The Oxygen Sag Curve dD/dt = kdL0e-kdt - krD
Eqs 5.31 (solution) and 5.32 (maximum deficit)
Figure: 05-15

31. Figure: 05-16

32. Unhealthful drop on DO by increasing BOD from a waste source
Figure: 05-17

33. The Oxygen Sag Curve over Temperature
Figure: 05-18

34. Thermal Stratification
Figure: 05-20

35. Stratification and Dissolved Oxygen
Figure: 05-22

36. Acidification vs. Bicarbonate Buffering
Figure: 05-23

37. saturated water in aquifer
Groundwater:
saturated water in aquifer
Figure: 05-26

38. Confined vs. Unconfined Aquifer
Figure: 05-27

39. Porosity, specific yield, and storage coefficient
Porosity = volume of voids/ total volume
Specific yield = the volume of water that can be drained from an unconfined aquifer per unit area per unit decline in the water table
Storage coefficient = the volume of water that can be drained from a confined aquifer per unit area per unit decline of head.

40. Hydraulic Gradient: i
Figure: 05-28

41. A two-dimensional flow net
Figure: 05-29

42. Using three wells to determine the gradient
Figure: 05-30

43. Darcy’s law Q = KA(dh/dL) = KiA Darcy’s velocity = q = Q/A = Ki
Average linear velocity = v = q/n
(Table 5.12)
(Example 5.12)

46. Dispersion and Retardation
Figure: 05-34

47. An instantaneous source in a flow field
Figure: 05-35

48. Retardation
Figure: 05-36

49. Plume separation due to retardation
Figure: 05-37

50. Cone of Depression
Figure: 05-40

51. Cone of Depression:
confined aquifer
Figure: 05-43

52. Capture-Zone:
The outer envelop of the streamlines that converge on the well (Eq. 5.56)
Figure: 05-44

53. Control of Groundwater Plumes:
Hydrodynamic Control
Figure: 05-50

54. Contaminants in Aquifer: Table 5.13
Nonaqueous-Phase Liquids (NAPLs): Table 5.14
Figure: 05-51

55. Figure: 05-51

56. Figure: 05-51

57. Groundwater Remediation Technologies:
1. Conventional Pump-and-Treat systems
Figure: 05-52

58. Groundwater Remediation Technologies: 2. Soil Vapor Extraction (SVE)
Figure: 05-53

59. Groundwater Remediation Technologies:
3. Air Sparging + SVE
Figure: 05-54

60. Groundwater Remediation Technologies:
4. Air Sparging with Horizontal Wells
Figure: 05-55

61. Groundwater Remediation Technologies: 5. In Situ Bioremediation
Figure: 05-56

62. Groundwater Remediation Technologies:
6. Permeable Reactive Barriers (PRBs)
e.g., reduction of chlorinated solvents and Cr6+ by Fe(0)
Figure: 05-57

63. Groundwater Remediation Technologies: Other Remediation Technologies
Solubilization & mobilization
Thermal desorption
Steam extraction
Electrokinetic
Isolation: impermeable barriers, vitrification, encapsulation, soil solidification
Chemical oxidation
Phytoremediation, biosparging, …