The ornamental plant Alternanthera ficoidea (also named A. tenella), which is common and widespread throughout the tropics and is being increasingly regarded as an invasive, problematic weed, has been explored as a bioagent in greywater treatment. In the recently developed SHEFROL® bioreactor, it was seen to treat greywater of varying strengths (250-1,300 mg/L chemical oxygen demand, COD) quickly and substantially to the extent of 75-77%. Biological oxygen demand (BOD), nitrogen, phosphorus, suspended solids, and heavy metals copper, nickel, manganese, and zinc were also removed to the extents of 83.5, 94.9, 33.1, 27.0, 44.8, 27.5, 38.2, and 43.2%, respectively. As all this was achieved in a single pot, single step, and in a simple reactor operation, at hydraulic retention times of a mere 6 h, it shows the process to be several times more efficient as well as potentially less expensive than the conventional treatment systems which utilize macrophytes in tanks or constructed wetlands.