Pathogen Removal

Pathogen removal in wetlands is due to the same factors described in Chapter 3 for pond systems, and Equation 3.25 can be used to estimate pathogen removal in these wetlands. The actual removal should be more effective due to the additional filtration provided by the plants and litter layer in a wetland. Table 3.9 contains performance data for both FWS and SSF systems. The principal removal

TABLE 6.6

Removal of Metals with Length in a Free Water Surface Constructed Wetland at Nucice (Prague)

TABLE 6.6

Removal of Metals with Length in a Free Water Surface Constructed Wetland at Nucice (Prague)

Metal

0 m

5 m

16 m

32 m

48 m

60 m

62 m

Aluminum

451

126

65

47

46

<40

<40

Copper

11.3

4.1

3.0

<2.0

<2.0

<2.0

<2.0

Manganese

27B

47

52

39

41

45

53

Zinc

19B

106

12

7.3

3.6

<5.0

<5.0

Source: Vymazal, J. and Krasa, P., Water Sci. Technol, 48(5), 299-305, 2003. With permission.

Source: Vymazal, J. and Krasa, P., Water Sci. Technol, 48(5), 299-305, 2003. With permission.

TABLE 6.7

Reduction of Temperature through Free Water Surface Constructed Wetlands at Sacramento County, California, and Mt. Angel, Oregon

Sacramento County, California Mt. Angel, Oregon

TABLE 6.7

Reduction of Temperature through Free Water Surface Constructed Wetlands at Sacramento County, California, and Mt. Angel, Oregon

Sacramento County, California Mt. Angel, Oregon

Ina

Out

Reduction

Inb

Out

Reduction

Month

("F)

("F)

("F)

("F)

("F)

("F)

January

57.7

4B.0

9.7

45.3

44.2

1.1

February

62.4

51.3

11.1

50.2

50.4

-0.2

March

59.0

55.6

3.4

53.5

52.4

1.1

April

64.9

61.1

3.B

63.3

60.9

2.4

May

67.5

59.9

7.6

67.0

62.5

4.5

June

72.1

71.B

0.3

72.B

6B.0

4.B

July

74.B

73.6

1.2

73.7

69.1

4.6

August

7B.4

72.7

5.7

73.1

66.9

6.2

September

76.1

6B.5

7.6

70.3

64.5

5.B

October

64.2

5B.6

5.6

59.5

55.9

3.6

November

60.6

57.2

3.4

52.2

50.6

1.6

December

56.3

50.2

6.1

4B.4

47.5

0.9

Average

5.5

3.0

a Five-year average 1994 to 1998 (Nolte Associates, 1999). b Four-year average 1999 to 2002 (City of Mt. Angel, Oregon).

mechanism in SSF wetlands is physical entrapment and filtration. As shown in Table 3.9, the finer textured material used at Iselin, Pennsylvania, was clearly superior to the gravel used at Santee, California. Removals of both bacteria and

TABLE 6.8

Removal of Organic Priority Pollutants in Constructed Wetlands

TABLE 6.8

Removal of Organic Priority Pollutants in Constructed Wetlands

Compound

Initial Concentration

(%)

Benzene

721

81

Biphenyl

821

96

Chlorobenzene

531

81

Dimethyl-phthalate

1033

81

Ethylbenzene

430

88

Naphthalene

707

90

p-Nitrotoluene

986

99

Toluene

591

88

p-Xylene

398

82

Bromoform

641

93

Chloroform

838

69

1,2-Dichloroethane

822

49

Tetrachloroethlyene

457

75

1,1,1-Trichloroethane

756

68

Source: Reed, S.C. et al., Natural Systems for Waste Management and Treatment, 2nd ed., McGraw-Hill, New York, 1995. With permission.

Source: Reed, S.C. et al., Natural Systems for Waste Management and Treatment, 2nd ed., McGraw-Hill, New York, 1995. With permission.

virus are equally efficient in both SSF and FWS wetlands. The pilot FWS wetlands at Arcata, California, removed about 95% of the fecal coliforms and 92% of the virus with an HRT of about 3.3 d; at the pilot study in Santee, California, the SSF wetland achieved >98% removal of coliforms and >99% virus removal with an HRT of about 6 d.

0 0

Post a comment