Performance of Vertical Flow Constructed Wetlands Planted with Indigenous Species for Decentralized Wastewater Treatment and Biomass Production in Kerala, India

Abstract

This study evaluates the performance of tropical subsurface vertical flow constructed wetlands (VFCW) having indigenous plants as decentralized ecological treatment systems for municipal wastewater treatment combined with biomass production. The VFCW mesocosms were planted with lignocellulosic grass species suitable to climatic conditions of Kerala such as Cumbu Napier Hybrid grass (Pennisetum purpureum), Gamba grass (Andropogon gayanus) and Palisade grass (Urochloa brizantha). The VFCWs were operated at a hydraulic loading rate (HLR) of 0.1md-1 and hydraulic retention time (HRT) of 1 day. During the study period, the planted VFCWs attained significant pollutant removal efficiency than the control system with an unplanted filter bed. The VFCW planted with Cumbu Napier Hybrid grass obtained average removal efficiencies of TSS (89.80%), BOD (89.90%), COD (78.10%), Nitrates (69.07%), TN (44.33%), and Phosphates (51.20%). In the VFCW system planted with Palisade grass, the average removal efficiencies observed were Turbidity (98.70%), TSS (89.50%), BOD (87.90%), COD (72.70%), Nitrates (62.07%), TN (43%), and Phosphates (47%). The treated effluent concentration from both the units conformed to the USEPA guidelines for non-potable water reuse standards. The average biomass yield of Cumbu Napier Hybrid grass during the study period was found to be significantly higher when compared to Gamba grass and Palisade grass.

Keywords

• ecological sanitation, indigenous species, biomass production, vertical flow constructed wetlands