Large-scale remediation of oil-contaminated water using floating treatment wetlands

The contamination of water with hydrocarbons resulting from oil exploration and production highlights the need for efficient and environmentally friendly technology to mitigate this form of water pollution. Floating treatment wetlands are a sustainable approach for remediating contaminated water. In this large-scale study, we used four different plants, Phragmites australis, Typha domingensis, Leptochloa fusca, and Brachiaria mutica, to vegetate a floating mat with an area of 3058 m(2) made from locally sourced materials. The floating treatment wetlands constructed in this manner were used to treat an oil-contaminated water stabilization pit resulting from oil and gas exploration activities in District Chakwal, Pakistan. The plants and the water in the pit were inoculated with a consortium of 10 different hydrocarbon-degrading bacteria. The application of floating treatment wetlands to the pit reduced chemical oxygen demand, biochemical oxygen demand, total dissolved solids, hydrocarbon content, and heavy metals by 97.4%, 98.9%, 82.4%, 99.1%, and 80%, respectively, within 18 months. All plants survived and showed growth, but maximum development and biomass production were exhibited by P. australis. Moreover, the bacteria used for inoculation were able to persist and show degradation activity in the water as well as in the rhizoplane, roots, and shoots of the plants. We conclude that floating treatment wetlands can be applied to oil-contaminated water stabilization pits for affordable and effective water treatment.