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Performance evaluation of environmentally compatible stormwater filtration systems
Samuel, M.P.; Senthilvel, S. & Mathew, A.C.
Abstract
A horizontal flow multimedia stormwater filter
was developed and tested for hydraulic efficiency and
pollutant removal efficiency. Suitability of different natural
fibres such as jute, sisal, hemp, coir and oil palm was
studied as filter media. Furthermore, the efficacy of different
fabric filter screens made up of both woven and
nonwoven textiles was also assessed. A new terminology,
Universal Performance Index, was introduced. Analysis of
these indices showed that jute medium, nonwoven sisal
screen and media proportion 1:1:1 performed better. All of
the filter combinations exhibited 100 % sediment removal
at lower sediment concentration in the inflow. Percentage
of discarded flow versus reference flow for the stormwater
filter combinations showed that the device performed better
at lower flow rates. It was also observed that the hydraulic
efficiency was directly proportional to the slope and
inversely proportional to the cross-sectional area of the
filter. Hydraulic efficiency showed a diminishing trend as
the sediment level in inflow increases. By using matrix
ranking method, the gravel–coir fibre–sand filter in 1:1:1
proportion with woven sisal hemp screens was selected as
the best filter combination. The field evaluation of the filter
showed 97.24 % efficiency in normalizing pH and 13.27 %
efficiency in reducing electrical conductivity. The removal
percentages of magnesium and sodium were 32 and 34 %,
respectively. But higher removal efficiencies above 70 %
were recorded for total solids, nitrates and sulphates.
Keywords
Filter; Stormwater; Fibre; Fabric; Pollutant; Water quality; Hydraulic efficiency
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