Trace Organics Removal

As described in Section 3.3 of Chapter 3 in this book, the removal of trace organic compounds occurs via volatilization or adsorption and biodegradation. The adsorption occurs primarily on the organic matter present in the system. Table 3.6 in Chapter 3 presents the removal of organic chemicals in land treatment systems; removal exceeds 95%, except in a very few cases where >90% was observed. The removal in constructed wetlands is even more effective as the HRT in wetland systems is measured in days as compared to the minutes or hours for land treatment concepts, and significant organic materials for adsorption are almost always present. As a result, the opportunities for volatilization and adsorption/biodegradation are enhanced in the wetland process. Removals observed in

TABLE 6.5

Metals Removal in Free Water Surface Constructed Wetlands

TABLE 6.5

Metals Removal in Free Water Surface Constructed Wetlands

Location

Removal

(%)

Prague

Aluminum

451

<40

91

Sacramento County, California

Antimony

C.43

0.18

58

Sacramento County, California

Arsenic

2.37a

2.80

-18

Brookhaven, New York

Cadmium

43

0.6

99

Sacramento County, California

Cadmium

C.C8

0.03

63

Brookhaven, New York

Chromium

160

20

88

Sacramento County, California

Chromium

1.43

1.11

23

Brookhaven, New York

Copper

151C

60

96

Sacramento County, California

Copper

7.44

3.17

57

Brookhaven, New York

Iron

643C

2140

67

Sacramento County, California

Lead

1.14

0.23

80

Brookhaven, New York

Lead

1.7

0.4

76

Brookhaven, New York

Manganese

21C

120

43

Sacramento County, California

Mercury

C.C11

0.004

64

Brookhaven, New York

Nickel

35

10

71

Sacramento County, California

Nickel

5.80

6.84

-18

Sacramento County, California

Silver

0.53

0.09

83

Brookhaven, New York

Zinc

22CC

230

90

Sacramento County, California

Zinc

35.82

6.74

81

a During the 5 years of monitoring, the influent arsenic dropped from 3.25 to 2.33 |g/L, while the effluent arsenic varied from 2.34 to 3.77 |g/L.

Source: Data from USEPA (1999), Nolte Associates (1999), and Hendry et al. (1979).

pilot-scale constructed wetlands with a 24-hr HRT are presented in Table 6.8. The removals should be even higher and comparable to those in Table 3.6 at the several day HRT commonly used for wetland design.

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