Bioremediation of brewery wastewater using hydroponics planted with vetiver grass in Addis Ababa, Ethiopia

Background: Bioremediation is the use of biological interventions for mitigation of the noxious effects caused by pollutants in the environment including wastewater. It is very useful approach for a variety of applications in the area of environmental protection. It has become an attractive alternative to the conventional cleanup technologies that employ plants and their associated microorganisms to remove, contain, or render harmless environmental contaminants. Methods: Three parallel hydroponic treatment systems (each 2 m long x 0.75 m wide x 0.65 m deep) and one control unit were filled with brewery wastewater to an effective depth of 0.5 m. Two sets of floating polystyrene platform were used for each treatment unit to support vetiver tillers for conducting bioremediation study. The wastewater was fed to the hydroponic treatment units at hydraulic loading rate of 10 cm d(-1) and hydraulic residence time of 5 days. Influent and effluent samples were collected once a month for 7 months, and analyzed to determine the various parameters relating to the water quality including plant growth and nutrient analyses. Results: Vetiver grass grew and established with well-developed root and shoots in the hydroponics under fluctuations of brewery wastewater loads and showed phytoremedial capacity to remove pollutants. Removal efficiencies for BOD 5 and COD were significant (p < 0.05), up to 73% (748-1642 mg l(-1) inlet), and up to 58% (835-2602 mgl(-1) inlet), respectively. Significant removal efficiencies (p < 0.05) ranged from 26 to 46% (14-21 mgl(-1) inlet) for TKN, 28-46% (13-19 mgl(-1) inlet) for NH 4(+)-N, 35-58% (4-11 mgl(-1) inlet) for NO3--N, and 42-63% (4-8 mgl(-1) inlet) for PO4-3-P were recorded. Nutrient accumulation in the samples harvested were varied between 7.4 and 8.3 g N kg(-1) dry weight and 6.4-7.5 g P kg(-1) dry weight in the hydroponic treatment units during the study period. Conclusions: This study has shown suitability of vetiver grass for organics and nutrient removal in the bioremediation of brewery wastewater using hydroponics technique in addition to production of valuable biomass. Bioremediation using hydroponics is green and environmentally sustainable approach that offers promising alternative for wastewater treatment in developing countries including Ethiopia.