ABSTRACT Purun tikus (Eleocharis dulcis) is one of the natural vegetation found in the acid sulfate swamp of South Kalimantan. The plant is potentially able to act biofilter due to it may grow and adapt well to land flooded with acidic water. In this study, purun tikus was used as an integral part of subsurface flow constructed wetland system (SSFCW). This engineering system is deliberately designed using subsurface flow and made by using the natural processes including wetland vegetation, soil, and a collection of associated microbes found at the wetland to alleviate the wastewater treatment process. This study intended to determine the ability of Purun tikus when planted in a constructed wetland to absorb iron (Fe) of coal acid mine drainage. The study used vertical (VF) and horizontal (HF) subsurface flow (SSF) constructed wetland (CW) under batch hydraulic loading regimes. The results of study showed that the Fe content of Purun tikus plants positively correlated with time length (day) of treatment. Purun tikus had the highest Fe concentration at the sixth day for vertical flow SSFCW batch and 13th day for horizontal flow SSFCW batch. Key words: coal acid mine drainage, constructed wetland (CW), iron (Fe), puruntikus (E.dulcis) Abbreviations: Subsurface Flow Constructed Wetland System (SSFCW), vertical (VF), horizontal (HF), subsurface flow (SSF), constructed wetland (CW).