BACKGROUND: Organobentonite is efficient for organic pollution removal; however, it is infrequently applied in waste-water treatment engineering because of its high cost of modification and the difficulty of separation from treated water. This study investigated a new process for simultaneously removing phosphate and organic pollutants by flocculation with the aid of organobentonite. RESULTS: The results showed that low amounts of surfactant-modified organobentonite could cheaply enhance simultaneous phosphate removal and phenanthrene removal. During the process, some of the alum cations were exchanged to the inner surface of the lamellar bentonite and the mechanism of phosphate adsorption on alum was changed to ligand exchange, which improved phosphate adsorption. Moreover, the coagulant helped clay sedimentation, and settlement speed of the floc itself was accelerated. It was found that the optimal removal efficiency was obtained at an alum concentration of 0.2 mmol L-1 and pH 5.3, with more than 90% phosphate and 98% phenanthrene removed and residual turbidity kept below 10 NTU. CONCLUSION: Results showed that the proposed process was suitable for simultaneously removing non-biodegradable organic pollutants such as phenanthrene and phosphate from water after the bioprocess in waste-water treatment. (C) 2009 Society of Chemical Industry