Surfactants and personal care products removal in pilot scale horizontal and vertical flow constructed wetlands while treating greywater

Abstract

Studies were conducted on pilot scale horizontal (HFCW) and vertical subsurface flow constructed wetland (VFCW) systems for the treatment of greywater. The fate of emerging contaminants in these systems was evaluated. Sodium dodecyl sulphate (SDS), propylene glycol (PG) and trimethyl amine (TMA) were selected as the target emerging contaminants. Pilot plants were designed to treat 2.5m3/day of greywater generated in a student’s hostel, with a hydraulic retention time (HRT) ranging from 8.9days to 14.9days. The greywater passed through a pre-treatment (settling tank) unit before entering the horizontal and vertical flow constructed wetlands (10.1m×2.55m×1.2m). The substrate material in wet land systems was a mixture of sand, brick bats and gravel, and systems were planted with reed plant (Phragmites australis). Performance of systems was evaluated for the removal of organics, nutrients, bacterial contamination and emerging contaminants. Accumulations of emerging contaminants in soil and plant tissues were also studied. Performance was monitored over a year to study the effect of operating conditions such as hydraulic retention time, external organic load, and the seasons. It was found that the vertical flow system was marginally more efficient in treating the pollutants when compared to horizontal flow system. Removal efficiencies of SDS, PG and TMA in VFCW for different operating conditions were around 89%, 95% and 98%, respectively. In the case of HFCW, removal efficiencies were 85%, 90% and 95% for SDS, PG and TMA, respectively. The treated water from both the systems was meeting the USEPA standard limits for reuse.