(1) At an ozone dose of 1.6 mg/L with a PAC dose of 50 mg/L, the DOF separator can achieve very good removals of turbidity, colour, organic matter, total bacteria and aliform bacteria from the secondary effluent. The treated water quality is compar able to, or better than, that by a conventional tertiary treatment process and meets the standard for domestic re-use (2) Generation of micro bubbles of ozone-rich air and creation of well dispersed onditions are considered to be the main reason for the high efficiency of disinfed tion and separation in the DOF separator. () With its compact structure, low HRT and high efficiency of pollutant removal, the DOF separator is recommendable to be used as a treatment unit in an onsite or decentralised system for tertiary wastewater treatment and reuse. Acknowledgements This study was supported by the National Natural Science Foundation of China(Grant No.50138020). References Bauer, M. et al. (1998). Enhanced rapid gravity filtration and dissolved air flotation for pre-treatment of river Thames reservoir water. Water Sci. TechnoL., 37(2). 35-42 Betzer, N, Argaman, Y and Kott, Y.(1980). Effluent treatment and algae recovery by ozone-induced flotation. Water Res, 14(8). 1003-1009 Goel, S et al. (1995). Biodegradation of NOM: effect of NOM source and ozone dose. J. AWWA, 87(1) 90-105. Gogate, P.R. and Pandit, A B(2004). A review of imperative technologies for wastewater treatment 1: oxidation technologies at ambient conditions. Adv. Environ. Res, 8. 501-551 Hargesheimer, EE. and Watson. S.B.(1996). Drinking water treatment options for taste and odor control. Warer res,30(6,1423-1430. Jin, P K. and Wang, X C.(2004). Effect of ozonation and hydroxyl peroxide oxidation on the structure of mic acids and their removal. /WA 4th Water Congress, Marrakech. 2004. Johnson, B.A. et aL. (1995). Pilot plant testing of dissolved air flotation for treating Boston,s low-turbidity surface water supply. Water Sci. TechnoL. 31(3-4), 83-92. Lens, P. Zeeman, G and Lettinga, G(2001). Decentralized Sanitation and Reuse- Concepts, Systems and Implementation, IWA Publishing, London, UK. wen, D M. et aL.(1995). NOM characterization and treatability. J AWWA, 87(1). 46-63 Rashid, F, Iqbal, M.S. and Bhatti, MS(1990). Mini ozonizer for instant production of ozone required for oxidation reactions and its application in the foam flotation-separation technique. Anal. Chim. Acta, 238. Schmidt, P D. et aL.(1995). DAF treatment of a reservoir water supply: Comparison with in-line direct filtration and control of organic matter. Water Sci. Technol., 31(3-4). 103-1l Standardization Administration of China(SAC)(2002). Urban Wastewater Reuse: Water Qualiry Standard for Urban Water Consumption(GB/T18920-20 Yu, Q. er al. (1994). The chemistry of ozone conditioning in the selective flotation of macroscopic fossil esin from Utah Wasatch Plateau coal. Coal Prep, 15(1), 35-50(1) At an ozone dose of 1.6 mg/L with a PAC dose of 50 mg/L, the DOF separator can achieve very good removals of turbidity, colour, organic matter, total bacteria and coliform bacteria from the secondary effluent. The treated water quality is compar￾able to, or better than, that by a conventional tertiary treatment process and meets the standard for domestic re-use. (2) Generation of micro bubbles of ozone-rich air and creation of well dispersed conditions are considered to be the main reason for the high efficiency of disinfec￾tion and separation in the DOF separator. (3) With its compact structure, low HRT and high efficiency of pollutant removal, the DOF separator is recommendable to be used as a treatment unit in an onsite or decentralised system for tertiary wastewater treatment and reuse. Acknowledgements This study was supported by the National Natural Science Foundation of China (Grant No. 50138020). References Bauer, M.J. et al. (1998). Enhanced rapid gravity filtration and dissolved air flotation for pre-treatment of river Thames reservoir water. Water Sci. Technol., 37(2), 35 – 42. Betzer, N., Argaman, Y. and Kott, Y. (1980). Effluent treatment and algae recovery by ozone-induced flotation. Water Res., 14(8), 1003 –1009. Goel, S. et al. (1995). Biodegradation of NOM: effect of NOM source and ozone dose. J. AWWA, 87(1), 90 –105. Gogate, P.R. and Pandit, A.B. (2004). A review of imperative technologies for wastewater treatment I: oxidation technologies at ambient conditions. Adv. Environ. Res., 8, 501 – 551. Hargesheimer, E.E. and Watson, S.B. (1996). Drinking water treatment options for taste and odor control. Water Res., 30(6), 1423– 1430. Jin, P.K. and Wang, X.C. (2004). Effect of ozonation and hydroxyl peroxide oxidation on the structure of humic acids and their removal. IWA 4th Water Congress, Marrakech, 2004. Johnson, B.A. et al. (1995). Pilot plant testing of dissolved air flotation for treating Boston’s low-turbidity surface water supply. Water Sci. Technol., 31(3– 4), 83 – 92. Lens, P., Zeeman, G. and Lettinga, G. (2001). Decentralized Sanitation and Reuse – Concepts, Systems and Implementation, IWA Publishing, London, UK. Owen, D.M. et al. (1995). NOM characterization and treatability. J. AWWA, 87(1), 46 –63. Rashid, F., Iqbal, M.S. and Bhatti, M.S. (1990). Mini ozonizer for instant production of ozone required for oxidation reactions and its application in the foam flotation-separation technique. Anal. Chim. Acta, 238, 427 –430. Schmidt, P.D. et al. (1995). DAF treatment of a reservoir water supply: Comparison with in-line direct filtration and control of organic matter. Water Sci. Technol., 31(3– 4), 103 –111. Standardization Administration of China (SAC) (2002). Urban Wastewater Reuse: Water Quality Standard for Urban Water Consumption (GB/T18920-2002). Yu, Q. et al. (1994). The chemistry of ozone conditioning in the selective flotation of macroscopic fossil resin from Utah Wasatch Plateau coal. Coal Prep, 15(l), 35 –50. P.K. Jin et al. 157