Performance of Dual Flow Grass Filters Integrated with Groundwater Recharge System for Stormwater Treatment – A Laboratory a

Manoj P. Samuel, S. Senthilvel and A. C. Mathew


A dual flow multimedia stormwater filter integrated with a groundwater recharge system was developed and tested for hydraulic efficiency and pollutant removal efficiency. The influent stormwater first flows horizontally through the circular layers of planted grass and bio-fibres. Subsequently the flow direction changes into vertical direction so that water moves through layers of pebbles and sand and finally it gets recharged to the deep aquifers. The media in the sequence of Vegetative medium: Bio-fibre- Pebble: Sand were filled in 9 proportions and tested for the best performing combination. Three grass species, viz., Typha (Typha angustifolia), Vetiver (Chrysopogon zizanioides) and St. Augustine grass (Stenotaphrum secundatum) were tested as the best performing vegetative medium. The adsorption behaviour of Coconut (Cocos nucifera) fibre, which was filled in the middle layer, was found out by a series of column and batch studies. The dual flow filter showed an increasing trend in hydraulic efficiency with increase in flow rate. The chemical removal efficiency of recharge dual flow filter was found very high in case of K+ (81.6 %) and Na (77.55%). The pH normalizing efficiency and EC reduction efficiency were also recorded high. The average removal percentage of Ca2+ was moderate, while that of Mg2+ was very low. The filter proportions 1:1- 1:2 (plant: fibre- pebble: sand) showed much superior performance compared to all other proportions. Based on the estimated annual costs and returns, all the financial viability criteria (IRR, NPV and BCR) were found favourable and affordable to farmers for investment on developed filtration system

Keyword: Recharge filter, vegetati

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