Oilfield wastewater contaminants removal efficiencies of three indigenous plants species in a free water surface flow constructed wetland

Although the role of plants in wetland ecosystems is largely known, not many native plant species have been used in constructed wetlands, especially in sub-Saharan Africa to treat oilfield wastewater, an emerging contaminant of considerable concern to both academics and policy makers owing to its deleterious effects on aquatic organisms and human health. This study assessed the contaminant removal efficiencies of three indigenous wetland plants (Typha latifolia, Ruellia simplex and Alternanthera philoxeroides) in a small-field-scale free water surface flow constructed wetland to polish effluent treated in a conventional oily wastewater treatment plant. Statistical significant differences in removal efficiencies were recorded between the planted wetlands and the unplanted wetland for all parameters examined, with the exception of total phosphorus. The results also showed that the removal efficiencies for oil and grease, biochemical oxygen demand, chemical oxygen demand and total dissolved solids were highest in wetland planted with Alternanthera philoxeroides followed by Typha latifolia planted wetland. Whereas the removal of nitrate and total phosphorus were highest in wetland planted with Typha latifolia, the removal of coliform bacteria was highest in Ruellia simplex planted wetland. The study showed that free water surface flow constructed wetland has the potential to improve quality of effluent treated with conventional oily wastewater treatment plant. The study is very significant because it has extensive practical application in the oil and gas industry in terms of improving the contaminant removal efficiency and thereby limiting adverse environmental and human health impacts. Also, wetland treatment systems are nature-based solution to environmental problems because they are built on sound ecological principles and for that matter they are sustainable in terms of the capital cost involved, energy consumption and technological requirement.