Abstract
Constructed wetlands (CW) have been widely used to treat different types of water, including acid mine drainage (AMD). However, little is known about their performance in the removal of As from AMD. In this study, a laboratory-scale horizontal subsurface flow (HSSF) CW system was tested to evaluate its capacity to treat highly acidic, As-rich contaminated water resembling AMD. Vegetated and non-vegetated cells, having limestone or zeolite as the main supporting media, were built and operated to evaluate the effect of the media type and the presence of Phragmites australis on the removal of arsenic, iron (Fe), lead (Pb), and zinc (Zn), and on the neutralization capacity. The four types of cells were highly effective in the removal of As and Pb (removal > 99%), and Fe (removal > 98%), whereas Zn removal rates depended on the cell type. Limestone cells raised the pH from ~1.9 to ~7.5, while zeolite cells raised it to ~4. These results suggest that the media type has a key role in the neutralization capacity, and that the presence of vegetation affected mainly the removal of Zn. Knowledge from this study will contribute to guiding the implementation of HSSF CW for treating As-rich AMD.
Highlights
The presence of As in water sources is a worldwide threat due to its toxicity and carcinogenic effects [1]
The purpose of this study is to evaluate the performance of a laboratory-scale horizontal subsurface flow (HSSF) constructed wetlands (CW) system with alternative media in the treatment of arsenic-rich, highly acidic contaminated water
The removal rates were > 99% for As and Pb, > 98% for Fe, and fluctuated between 23% and 75% for Zn depending on the cell type
Summary
The presence of As in water sources is a worldwide threat due to its toxicity and carcinogenic effects [1]. Constructed wetlands, as natural water treatment systems, have low investment and operation costs [3]. As such, they offer a sustainable alternative for water treatment. The main application of constructed wetlands (CW) has been the treatment of different wastewaters, they have high potential to treat metal-contaminated water [4]. The main use of CW for this purpose has been in acid mine drainage (AMD) treatment. In these waters, As may be present in a wide range of
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