SUBSURFACE FLOW CONSTRUCTED WETLAND SYSTEM VEGETATED WITH PHRAGMITES KARKA IN THE TREATMENT OF DYE-RICH WASTEWATER

Abstract

Some major parts of tropical Africa, especially in West Africa are nowadays grappling with the problem of degradation of the quality of fresh water by the introduction of effluents containing dyes from textile industries. In this study a low cost and economical method of treating dye-rich effluent using locally available macrophyte was investigated. The pilot Constructed Wetland (CW) consists of 1200 × 1000 × 1000 mm plastic tanks, filled with 500 mm deep 10-15 mm size granite overlaid with 150 mm thick sand (C_u = 1.15 and C_{c =} 6.8) substrate. The substrates had an hydraulic conductivity of 0.002 m/s. The pilot CW was planted with Phragmites Karka Retz. at 200 mm c/c to provide a high density bed. Irrigation was done intermittently at 6 days retention period with 0.05 m³ indigo dye rich wastewater from the local tie and dye textile industries and plant growth monitored. Physico-chemical parameters, Cr, Pb, Cu, Zn and Fe removal were also evaluated. The study revealed a 24 % growth rate reduction in the plants irrigated with indigo dye-rich wastewater. Reduction of TDS (50 %), TSS (66 %), EC (46 %) were also observed and the heavy metals evaluated showed an uptake of 64 %, 68 %, 78 %, 58 %, and 68 % for Cr, Pb, Zn, Cu, and Fe respectively by the CW. Phragmites karka as a macrophyte in Constructed Wetland was found to be efficient in dye-rich wastewater treatment.