removal of petroleum hydrocarbon from water by combined cultivation of azolla and bacteria

Background: pollution of water resources with petroleum hydrocarbons causes adverse effects on ecosystems and human health. physico-chemical methods for removing thin layers of oil on the water surface are not cost-effective. azolla is one of the plants that grows and reproduces on the surface of water and has many roots that can be a suitable place for microbial growth and decomposition of oil compounds. objectives: the aim of this study was to remove petroleum hydrocarbons from water by co-culture of azolla and bacteria. methods: commercial diesel fuel was used as a source of total petroleum hydrocarbon (tph) pollution in water. isolated bacteria from diesel fuel-contaminated soil were identified by biochemical test results according to standard methods. experiments were conducted in separate runs, including culturing bacteria alone, azolla alone, and co-culture of azolla-bacteria. concentrations of 100, 500, and 1000 mgl-1 of tph in water and contact times of 5.0, 10.0, and 15.0 days were examined. results: in the case of azolla culture alone, the mean tph removal was 40%. in the case of bacteria culture alone and tph concentration of 1000 mgl^-1, the minimum removal was 35% for pseudomonas aeruginosa and the maximum was 60% for alcaligenes faecalis. in the case of co-culture with tph concentration of 1000 mgl^-1, the minimum removal was 80% for p. aeruginosa-azolla and the maximum was 100% for a. faecalis-azolla. in the case of co-culture, the removal was 100% for tph concentrations of 100 and 500 mgl^-1 at contact times of 5.0 and 10.0 days, respectively. conclusions: co-culture of azolla and bacteria was effective for the complete removal of petroleum hydrocarbons (100 and 500 mgl-1) from water. this method can be used to clean up and remove petroleum hydrocarbons from water.