A laboratory treatment study of acid mine water of wetlands with emergent macrophyte (Typha angustata)

Abstract

Acid mine drainage (AMD) is a serious environmental problem in mining regions throughout the world. In this study laboratory experiments were carried out to test the capacity of 1 m³ bench-scale wetland test cells of substrate (containing powdered goat manure, wood chips and soil) and well grown emergent macrophyte (Typha angustata) to treat AMD. Artificially simulated AMD experiments were carried out for different water column heights (100, 150 and 200 mm). The performance of the system was evaluated for 24, 48, 72, 96 and 168 hour retention periods. Within a 24 h retention period the pH rose from 2.93 to 6.33 and alkalinity rose from 0 to 230.78 mg/l as CaCO₃; electric conductivity decreased by 32.47 to 33.86%; turbidity decreased by 33.33 to 48.35%; sulphate reduced by 26.97 to 30.80%; acidity reduced by 82.22 to 100% and hardness reduction was 20.00 to 31.33%. The percentage of metal removal observed in the treated water was: for Fe 84.22 to 84.84%; for Cu 78.19 to 94.18%; Zn 78.45 to 79.12%; Pb 89.24 to 93.12%; Co 62.65 to 76.67%; Ni 45.27 to 76.46%; Mn 44.28 to 53.77%. It was observed that most of the improvements take place within a 24 h retention period. Efficient removal of pollutants was achieved and residual concentrations in the wetland test cells were decreased below the relevant permissible level subscribed by Bureau of Indian Standards and Ministry of Environment and Forests (MOEF) after 24 hours of retention period (except for lead where the input concentration was higher).

Keywords:

• Acid mine drainage (AMD)
• Treatment constructed wetland
• T. angustata
• Bench-scale experiment