Storm Water Purification in an Urban City of India using a Bio-retention Filter

Abstract

Bio-retention filtration system is the leading water conservation strategy that makes use of biogeochemical technique within a vegetation ecosystem to retain soil moisture, purify and conserve storm water in urban cities. The present study was aimed at designing a bio-retention filter basin in Kharghar node of Navi Mumbai, Maharashtra, India. The analysis was carried out for both minor (5-year average recurrence interval) and major (100-year average recurrence interval) floods. Total discharge was computed using the rational formula and it was estimated as 0.023 m3/s for minor flood condition and as 0.037 m3/s for major flood condition. The maximum infiltration rate was computed as 0.0047 m3/s considering sandy loam soil as the filter media. A flow width of 1.6 m was considered in designing the bio-retention filter. 100 mm diameter polyvinyl chloride pipe was proposed as they are the best in terms of performance and have advantage over other pipes. No liner is required for filter according to the soil condition of Kharghar. A transition layer of 100 mm gravel was suggested to provide better efficiency and durability for the bio retention system. The vegetation for the bio-retention basin can be Doob or Bermuda grass (Cynodon dactylon) as it has the highest water retention capacity as per Indian conditions.