Hydraulic performance of biofilter systems for stormwater management

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Determining the influence of catchment characteristics Ascendant Hierarchical Classification (AHC) was used to show group patterns in the dataset, and thus to tease out the factors which have significant explanatory power on the variation observed. It was conducted on the following parameters: K fs shallow , K fs deep, K lab deep ini , age of the system, size ratio, volume of water per year, total volume of water and total volume of water per area (m²) of systems. Multiple regressions were used in order to explain the variation of K fs shallow as a function of explanatory variables (K lab ini , age, size ratio, volume of water per year, total volume of water per m²) in order to understand possible correlation between the current K and characteristics of the system and its catchment. 14
3 Results and discussion 3.1 Biofilter design Most of the systems studied were not designed strictly according to current guidelines in term of ratio size of the system/size of the catchment (many were constructed prior to the availability of these current guidelines). For example, the Victorian (Melbourne Water, 2005) guidelines recommend a biofilter :catchment area ratio of at least 1.65 %, but the 30 Victorian systems surveyed show a ratio between 0.1% and 21.9%, with an average of 5.3 % and a median of 2.5% (Table 3). Biofilters are thus generally over sized, although the extended depths are often considerably less than the recommended range of 100-200mm. However, given their irregular geometry, exact measurement of the ‘effective’ or ‘average’ ponding depth was not feasible. Field hydraulic conductivity measurement shows that 39% (using the shallow ring method) (42% using the deep ring method) of the biofilters have a K fs below 50 mm/h, 44% (27%) between 50 and 200 mm/h and 17% (30%) above 200 mm/h (Table 3). In summary, most of the systems (~60%) have a hydraulic conductivity either within or exceeding the currently used guidelines (Melbourne Water, 2005; Wong et al., 2006). 15
Page 1 and 2: Hydraulic performance of biofilter
Page 3 and 4: Executive summary Biofiltration sys
Page 5 and 6: Table of contents 1 Introduction ..
Page 7 and 8: The potential for clogging of the s
Page 9 and 10: 2 Method 2.1 Sampling locations Thi
Page 11 and 12: K fs is then found using the follow
Page 13: Laboratory measurements have inhere
Page 17 and 18: The influence of this result on the
Page 19 and 20: Table 4 : K value and Cv for each s
Page 21 and 22: (2003). Since both field measuremen
Page 23 and 24: Systems with low initial hydraulic
Page 25 and 26: 4 Conclusions Whilst biofilters hav
Page 27 and 28: 6 References Achleitner S., Engelha

Hydraulic performance of biofilter systems for stormwater management

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