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Water and Wastewater Engineering - Sciences Club

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WASTEWATER PLANT RESIDUALS MANAGEMENT 27-65<br />

6% <strong>and</strong> a specific gravity of 1.03. The sludge is to be pumped 112 m to an anaerobic<br />

digester. Assume a Hazen-Williams C � 100 <strong>and</strong> a pumping time of 1/2 hour once<br />

per day.<br />

27-14. To improve the performance of the digester in Problem 27-13, it has been proposed that a<br />

more uniform feed be employed by using a clock control to operate a pump for 5 minutes<br />

at an interval of 96 minutes. Determine the pumping flow rate <strong>and</strong> the approximate number<br />

of cycles per day. (The spreadsheet solver tool may be useful for this solution.) Use<br />

this flow rate to select a pipe diameter <strong>and</strong> estimate the friction headloss.<br />

27-15. Design a pretreatment lime stabilization system for Quirm. The daily sludge flow<br />

rate of 112 m 3 is to be treated in one batch. The primary sludge has a solids concentration<br />

of 6% <strong>and</strong> a specific gravity of 1.02. Determine the volume of tank, mixer size<br />

(kW, rpm, turbine dia.), lime feed rate, <strong>and</strong> lime storage volume for two-week delivery.<br />

27-16. Design a pretreatment lime stabilization system for Pseudopolis. The daily sludge<br />

flow rate of 216 m 3<br />

is to be treated in one batch. Half of the sludge volume is<br />

primary sludge with a solids concentration of 4.3% <strong>and</strong> a specific gravity of 1.02.<br />

The other half of the volume is WAS with a solids concentration of 1.3% <strong>and</strong> a<br />

specific gravity of 1.005. Determine the volume of tank, mixer size (kW, rpm,<br />

turbine dia.), lime feed rate, <strong>and</strong> lime storage volume for two-week delivery.<br />

27-17. In the preliminary analysis of alternatives for stabilizing the WAS sludge from<br />

Sunset’s activated sludge plant, your boss has asked you to design an aerobic<br />

digester. The sludge flow rate is 62.3 m 3 / d. The solids concentration is 2.8%, <strong>and</strong><br />

the specific gravity of the sludge is 1.01. Use the following data for the design:<br />

Winter conditions govern<br />

Te mperature of digester contents � 20 � C<br />

VSS � 0.8 TSS<br />

VSS reduction goal � 40%<br />

Influent BOD � 2,600 mg/L<br />

Fraction of influent BOD consisting of primary solids � 0.35<br />

S l udge concentration is 70% of the incoming thickened sludge concentration<br />

Diffused air mixing is to be used<br />

27-18. In the preliminary analysis of alternatives for stabilizing a mixture of primary <strong>and</strong> WAS<br />

sludge from Knight Falls’ activated sludge plant, your boss has asked you to design an<br />

aerobic digester. The sludge flow rate is 404 m 3 /d. The solids concentration 2.8% <strong>and</strong><br />

the specific gravity of the sludge is 1.01. Use the following data for the design:<br />

Winter conditions govern<br />

Te mperature of digester contents � 15 � C<br />

VSS � 0.7 TSS<br />

VSS reduction goal � 40%<br />

Influent BOD � 1,700 mg/L<br />

Fraction of influent BOD consisting of primary solids � 0.28<br />

S l udge concentration is 70% of the incoming thickened sludge concentration<br />

Diffused air mixing is to be used

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