Enhanced remediation of sewage effluent by endophyte-assisted floating treatment wetlands

Abstract

The use of floating treatment wetlands (FTWs) is a promising approach for the remediation of sewage effluent. The efficiency of FTWs can be improved by the combined use of plants and pollutant-degrading bacteria. The aim of this study was to evaluate the influence of inoculation of endophytic bacteria on the detoxification of sewage effluent in FTWs. A terrestrial plant, Brachiaria mutica, was vegetated on a floating mat and inoculated with three endophytic bacterial strains, Acinetobacter sp. strain BRSI56, Bacillus cereus strain BRSI57, and Bacillus licheniformis strain BRSI58, to develop FTWs for the remediation of sewage effluent of Faisalabad city (Pakistan). Results indicated that B. mutica has the potential to remove both organic and inorganic contaminants from sewage effluent. However, endophytic inoculation in FTWs further enhanced the removal efficiency. Maximum reduction in chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total nitrogen (N), and phosphate (PO4) was achieved by the combined use of plants and bacteria. Moreover, the inoculated bacteria showed persistence in water as well as colonization in the root and shoot of the plant. Treated effluent met the national wastewater discharge standards of Pakistan and can be discharged in the environment without any environmental risks. This study provides useful evidence of endophyte-assisted FTWs to be the most sustainable and affordable approach for in situ remediation of sewage effluent.