Urban wastewater treatment using vermi-biofiltration system

Abstract

This work illustrates the potential of a novel vermi-biofiltration system in treatment of urban wastewater. A small-scale vermi-biofiltration reactor was constructed using vertical subsurface-flow constructed wetlands (VSFCWs) aided with local earthworms Perionyx sansibaricus. The coco-grass: Cyprus rotundus (density 0.14 plants/in. 2) was used to construct VSFCW. Another reactor without earthworms acted as experimental control. The wastewater was treated through this system for a total of eight repetitive cycles and after each cycle the changes in pH, electrical conductivity (EC), total dissolved solids (TDS), and total suspended solids (TSS), chemical oxygen demand (COD), NO 3 − and PO 4 3− of water were measured. Vermi-biofiltration caused significant decrease in level of TSS (88.6%), TDS (99.8%), COD (90%), NO 3 − (92.7%) and PO 4 3− (98.3%). There were about 38.8, 20.8, 80.6, 50.8 and 144.6% more removal of TSS, TDS, NO 3 −, PO 4 3− and COD, respectively in vermi-biofiltration than control. Results thus suggested that vermin-biofiltration system is more efficient than VSFCW in terms of contamination removal efficacy. However, this work provides a preliminary idea of using earthworms in wastewater treatment system and further detailed studies are required on some key issues (e.g., loading rate, flow alternation impacts and earthworm stocking density) of this system.