Lecture 6

Design of floating thickeners is based on the

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Unformatted text preview: results from experimental tests. Design of floating thickeners is based on the knowledge of: • Wastewater flow rate and solid loading • Air-to-solid ratio (typically expressed as volume of air/mass of solids or mass of air/mass of solids) • Overflow rate (or rise velocity of solids) • Final solid loading in sludge PIERO M. ARMENANTE NJIT Air-to-Solid Ratio (A/S Ratio) • The A/S ratio is the amount of air that must be generated in the wastewater to produce the desired separation of the solids (expressed as volume of air/mass of solids or mass of air/mass of solids) • The A/S ratio must be determined experimentally from test runs • Once the A/S ratio is known it is possible to calculate the pressure required to dissolve enough air in the wastewater to produce the desired amount of air during decompression • Typical A/S ratios are in the range 0.005 - 0.060 mL air/mg solids (0.0065 - 0.08 mg air/mg solids) PIERO M. ARMENANTE NJIT Nomenclature for Flotation f = correction factor to account for non-saturation of water by air at pressure P Fair = net mass flow rate of air available for flotation (mg/h) Fsolids = incoming mass flow rate of solids (mg/h) P = pressure of pressurized wastewater (atm) Po = pressure after depressurization (atm), typically equal to the atmospheric pressure Q...
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