Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Kinh tế đất ngập nước thường thấp hơn nhiều so với các công nghệ cạnh tranh. Thiết bị cơ khí luôn luôn tốn kém năng lượng hơn, và sẽ luôn luôn đắt hơn để hoạt động, hơn một hệ thống đất ngập nước thụ động (Type A) (Brix, 1999). Việc trao đổi cơ bản là đất cho năng lượng (Campbell và Ogden, 1999). Kết quả là, chi phí vòng đời của một dự án đất ngập nước, được đại diện bởi giá trị hiện tại của chi phí vốn và điều hành, là rất thường xuyên khá thuận lợi so với. | 23 Economics The economics of treatment wetlands consists of two major factors capital costs and operating costs. The capital cost components of free water surface FWS and subsurface flow SSF wetlands are essentially the same except for the cost of the gravel required for SSF wetlands Campbell and Ogden 1999 U.S. ePa 2000a . However SSF systems have generally been implemented for smaller flows than FWS systems. For instance the system database compiled by the Water Environment Research Foundation WERF has 214 FWS wetlands with a median design flow of 1 050 m3 d 707 HSSF wetlands with a median design flow of 9.5 m3 d and 566 VF wetlands with a median design flow of only 2.1 m3 d Wallace and Knight 2006 . System areas from the WERF database show 330 FWS wetlands with a median area of 1.6 ha 16 000 m2 710 horizontal subsurface flow HSSF wetlands with a median area of 140 m2 and 544 vertical flow VF wetlands with a median area of 44 m2. Therefore SSF wetlands do not enjoy the economy of scale experienced by FWS wetlands. There is now enough information to determine approximate capital cost functions that represent these scale effects. Because wetland systems are constructed using local labor and local materials it is not possible to offer precise universal cost estimates that will apply to all treatment systems. Generally the basic components of a wetland treatment system earthwork gravel in the case of SSF wetlands liners and plants are produced in regional markets that are distance sensitive. For instance the installed cost per cubic meter of gravel is highly dependent on the distance between the source of supply a local gravel pit and the site of wetland construction. Labor costs are also highly variable. To assess the feasibility of a wetland treatment system local cost figures should be used to compare the capital and operating costs of a wetland system against that of other treatment technologies. Within the United States Construction Cost Indices CCI are .
