A Novel Approach to the Evaluation of Sediment Basin Floating Surface Skimmer Flow Rates

A floating surface skimmer is a device that regulates dewatering in a sediment basin. Skimmers decant from the top of the water column, allowing for greater capture of suspended sediment. Skimmer dewatering rates depend on design and vary by manufacturer. Theoretical flow rates yield errors when estimating dewatering times; therefore, there is a need to conduct experimental testing to obtain accurate flow rates. This study evaluated the discharge rates of eight skimmers with varying inlet sizes across different orifice openings using an adjustable slider. Testing was conducted in a 29.8 m3 (1053 ft3) evaluation tank assessing inlet sizes ranging from 3.8 cm (1.5 in.) to 20.3 cm (8 in.). For the five largest skimmers, four adjustable slider configurations were assessed, while three slider configurations were assessed for the three smallest skimmers. Each configuration was triplicated for 87 total experiments. Results indicate that skimmers can achieve flow rates ranging as high as 2622 m3/d (92,585 ft3/d) to as low as 28 m3/d (981 ft3/d) across all sizes. Collected data was used to model flow characteristics and develop two interactive skimmer sizing tools for designers and engineers. An alternative flow rate calculation method was also considered to maximize data analysis efficiency.