HFVF Systems

In mid-1990s, a HF-VF hybrid system was introduced in Denmark (Figure 38). The large HF bed is placed first to remove organics and suspended solids and to provide denitrification. An intermittently loaded small VF bed is designed for further removal of organics and SS and to nitrify ammonia to nitrate. However, in order to remove total nitrogen, the nitrified effluent from the VF bed must be recycled to the sedimentation tank.

Table 6 Performance of the VF-HF Colecott hybrid system

Inflow

VF1out

VF2out

HFout

Efficiency

Parameter

(mgl1)

(mgl1)

(mgl1)

(mgl1)

(%)

COD

462

210

66

47

89

bod5

269

171

43

23

91

TSS

53

28

3

1

98

NHÍ-N

45

28

16

7

84

NO3-N

0.1

4.7

3.8

2.7

NO2-N

0.1

0.2

0.1

0.1

PO4

18

16

15

11

39

From Vymazal J (2005) Constructed wetlands with horizontal subsurface flow and hybrid systems for wastewater treatment. Ecological Engineering 25: 478-490.

Data from O'Hogain S (2003) The design, operation and performance of a municipal hybrid reed bed treatment system. Water Science and Technology 48(5): 119-126.

Two-stage H-V CW

Two-stage H-V CW

Figure 38 Sketch of a two-stage CW consisting of a HSSF unit for removal of TSS and BOD followed by pulse loading VF unit for nitrification. Enhanced nitrogen removal can be achieved by recycling of the nitrified effluent in the first bed and hence get denitrification there. From Brix H and Johansen NH (1999) Treatment of domestic sewage in a two-stage constructed wetland - design parameters. In: Vymazal J (ed.) Nutrient Cycling and Retention and Constructed Wetland, pp.155-165. Leiden, The Netherlands: Backhuys Publishers.

Figure 38 Sketch of a two-stage CW consisting of a HSSF unit for removal of TSS and BOD followed by pulse loading VF unit for nitrification. Enhanced nitrogen removal can be achieved by recycling of the nitrified effluent in the first bed and hence get denitrification there. From Brix H and Johansen NH (1999) Treatment of domestic sewage in a two-stage constructed wetland - design parameters. In: Vymazal J (ed.) Nutrient Cycling and Retention and Constructed Wetland, pp.155-165. Leiden, The Netherlands: Backhuys Publishers.

See also: Biodegradation; Denitrification; Freshwater Marshes; Nitrification; Soil Movement by Tillage and Other Agricultural Activities.

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