# HW4 - 4 The organic concentration in a water sample...

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CEE 3510 Prob. Set No. 4 Due: March 3, 2010 1. Using free energy principles explain why anaerobic digestion (with the production of CH 4 ) is used to treat organic sludges produced during biological wastewater treatment. 2. Human wastewater production is about 0.2 lbs oxygen consuming material per day per person. Assuming that the city of Ithaca (population approximately 65, 000) discharged its domestic waste directly (without treatment) to Cayuga Lake, how long would it take to utilize all of the oxygen in the lake. Cayuga Lake has a volume of 2.4 x 10 12 gallons and initial dissolved oxygen concentration of 10 mg/L. Assume that there is no photosynthetic oxygen production nor any atmospheric reaeration. Also assume that the oxygen concentration is uniform throughout the lake. 3. If domestic sewage has an approximate formulation of C 10 H 19 O 3 N, estimate the NOD (nitrogenous oxygen demand) of a sample, which contains 100 mg/L of domestic sewage as BOD L . Assume complete biodegradability of the sewage.

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Unformatted text preview: 4. The organic concentration in a water sample, measured as BOD L is 4 mg/L. If the BOD reaction rate is 0.3/day, what will be the concentration of organic matter remaining at the end of 5 days (L t )? How much oxygen will be used in this period to oxidize the waste (y t )? 5. A water sample has a BOD 5 of 10 mg/L. The sample was diluted 1/10 with dilution water and put in a BOD bottle. Initial DO (dissolved oxygen) in the BOD bottle was 8 mg/L. The sample also contained 2 mg/L NH 3-N (before dilution). Assume the sample was typical domestic sewage. What was the final DO in the BOD bottle? 6. A BOD test is performed on an undiluted sample at 20 o C and 35 o C. BOD 5 at 20 o C was 4.15 mg/L. BOD 5 at 35 o C was 6.56 mg/L. From this data determine the BOD L of the sample. Assume that nitrification was inhibited and that the temperature correction factor ( θ29 equals 1.05. 7. Do Stella Exercise #2 1 2...
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HW4 - 4 The organic concentration in a water sample...

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