White hard clam (Meretrix lyrata) shells media to improve phosphorus removal in lab-scale horizontal sub-surface flow constructed wetlands: Performance, removal pathways, and lifespan.

•P removal from simulated wastewater using lab-scale HSSF-CWs was examined.•Paspalum atratum was utilized as the emergent wetland plant for very first time.•WHC-based HSSF-CW planted with Paspalum atratum removed up to 89.9% of inflow P.•WHC sorption was the dominant P removal pathway in HSSF-CWs.•Utilizing WHC as a reactive filter media apparently extended lifespans of HSSF-CWs.