Experiments on a 4-ft (1.2-m) diameter model circular clarifier operating at overflow rates and suspension concentrations corresponding to municipal treatment practice show that baffles designed to function as wave traps suppress low-frequency, large-amplitude density waves observed in these units. Simultaneous measurements of solids removal show substantial improvement. This work establishes the relationship between density waves and the deviation from ideal clarifier performance that earlier papers on internal waves by our research group suggested. The power spectrum of the internal waves and the effect of operating variables such as overflow rate, scraper speed, and suspended solid on the spectrum and solids removal are discussed.

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