tailieunhanh - TREATMENT WETLANDS - CHAPTER 20

Tiêu chuẩn quy tắc đã được các phương pháp phổ biến nhất cho các vùng đất ngập nước SSF kích thước bởi vì những phương pháp được nhanh chóng và toán học đơn giản. Điều này đã dẫn đến việc sử dụng rộng rãi (và đôi khi lạm dụng) các phương pháp quy. Tiêu chuẩn quy tắc chỉ hợp lý khi chúng được dựa trên việc thực hiện quan sát một số lượng lớn các vùng đất ngập nước được xây dựng để các chi tiết kỹ thuật vật lý như nhau xử lý cùng loại của nước thải theo. | 20 Sizing of SSF Wetlands The design of subsurface flow SSF wetlands may be roughly divided into two categories sizing calculations and physical specifications. Sizing requires characterization of the incoming water and regional climate as well as the goals of wetland treatment as discussed in Chapter 16. This chapter discusses different sizing methodologies for SSF wetlands. Chapter 21 deals with the physical considerations including the number of cells layout liners bed depth media size plants and water level control. It is recognized that SSF wetlands are not stand-alone treatment devices but rather form part of an overall treatment process. For HSSF wetlands primary treatment at a minimum is required to remove settleable and floating solids prior to the wetland bed. This is typically provided through the use of settling tanks. Some projects may employ a higher level of pretreatment through the use of activated sludge systems lagoons or other treatment processes. Vertical flow VF wetlands may or may not have such preliminary treatment stages and biosolids systems will receive material of different quality depending on the nature of the overall treatment process. This chapter focuses on the sizing of SSF wetland components recognizing that this will be only one part of the overall treatment process. To date most SSF wetlands have been sized using prescriptive criteria. The most common approach has been to tie the required wetland size to a parameter that presumably defines the influent conditions. Influent loadings population equivalents detention time and number of bedrooms have all been used to create these scaling factors. Prescriptive criteria represent a reasonable approach to wetland sizing when there is a large body of preexisting performance data for well-defined pollutants loading charts and a more detailed understanding of the internal dynamics of the wetland is not necessary. As a result prescriptive criteria are used mainly for the design of SSF .