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HYDRAULIC CHARACTERISTICS OF SEWER SEDIMENT GATE-FLUSHING TANKS: LABORATORY FLUME STUDIES
Citation:
Fan*, C Y., R Field*, Q. Guo, AND R. Raghavan. HYDRAULIC CHARACTERISTICS OF SEWER SEDIMENT GATE-FLUSHING TANKS: LABORATORY FLUME STUDIES. Presented at International Scientific Committee of the Int. Association of Hydraulics Engineering and Research, 3rd Int. Symp on Environmental Hydaulics: A Special These in, Tempe, AZ, 12/5-8/2001.
Description:
The objective of this study was to test the performance of gate-flushing tanks, simulated in a laboratory flume, to remove sediments from combined sewers and storage tanks. A significant amount of sediment/debris/sludge may accumulate at the bottom of a sewer during dry weather or small storms. Accumulated sewer sediment, if not flushed to a designated collector beforehand, may be washed directly to receiving waters during times of high-storm flow. A large fraction of the sediment may be biodegradable and a host of contaminants are adsorbed onto the sediment. The direct discharge of this sediment to receiving waters will cause serious water quality problems. A gate-flushing tank was installed at the head-end of a laboratory hydraulic flume. Tests were conducted under 40 fluising conditions. Noncohesive sediment of similar size to that of sewer sediments were used in the tests. Total weight and spatial distribution of flushed sediment were measured. The speed and height of the flushing surge were also measured using video imaging. Up to 50% of the sediment originally in the flume was flushed away under the various testing conditions. These laboratory test results will be used to compare performance with other types of flushing devices and sewer sediments. A simplified hydraulic surge model was developed that compared well with laboratory results. The most appropriate sediment flushing/transport model was also identified from the laboratory results. The hydraulic and sediment transport models, after improvements in spatial and temporal variations, will be used to guide the design and placement of sewer sediment flushing devices.