آب و فاضلاب (Sep 2007)
Evaluation of Dissolved Air Flotation (DAF) for Pretreatment of the Karoon River Water
Abstract
The efficiency of a pilot dissolved air flotation (DAF) unit is evaluated. It is the objective of the present study to determine the removal efficiency of DAF in removing turbidity and organic matter from theKaroonRiverfeeding a water treatment plant. Water quality investigations over the study period revealed that, thanks to the self-purification process in the river, the Karoon water quality is acceptable with respect to total organic carbon (TOC) (never exceeding 2.89 mg/l) but its turbidity has great fluctuations (from as low as 42 to 1,000 NTU) due to the nature of the river. Its true color is in desirable conditions. Suspended solids removal efficiency of the pilot DAF unit varied from 38% to 95%, with an average level of 72%. The results from this study indicate that DAF removal efficiency is inversely related to the volume of inflow of solids into the system so that increasing TSS decreases removal efficiency. The high turbidity level in the absence of a primary sedimentation unit causes the flotation system to lose its desired efficiency. FAD cannot be, therefore, recommended for water treatment plants fed by the Karoon water unless a pretreatment unit is used. Furthermore, as FAD's TOC removal efficiency varies by up to 82%, and since part of the organic content includes volatile organic matter causing odors and undesirable taste, FAD is recommended as a complementary process in the treatment of high quality water.
