Performance of Different Macrophytes and Support Media in Constructed Wetlands for High Turbidity Reduction from Mine Spoil Rainwater

Abstract

Surface runoff in mining areas transports dissolved and suspended particles into water bodies, known as mine spoil rainwater, contributing to increases in turbidity. The aim of this study was to evaluate the effectiveness of horizontal flow wetlands, free water surface (FWS), and subsurface flow (HSSF) in reducing turbidity >1500 NTU from a synthetic mine spoil rainwater. Macrophytes, support media, hydraulic retention time (HRT), and hydraulic loading rate (HLR) were analyzed. The HSSF T. domingensis in gravel #1 achieved a 99% reduction for 4-day HRT, with residual turbidity of 7 ± 3 NTU for 27.43 L m−2 d−1 HLR. The FWS P. stratiotes achieved a 99% reduction for 6-day HRT, with residual turbidity of 11 ± 5 NTU for 36.53 L m−2 d−1 HLR. P. stratiotes free root structures promoted interception of suspended colloidal particles, resulting in a better performance. The dense root structure of T. domingensis spreading through the pores of the substrate provided better efficiency than N. humboldtiana. However, N. humboldtiana proved to be promising as a native species. The use of small granulometry alkaline support media (9 to 19 mm) was highlighted. Therefore, this research proves the efficiency of constructed wetlands in reducing high turbidity and provides optimized parameters for this technology application.