13. Free settling of sludge is 0.25 cm/min. Using an original height of 25 cm, the sludge settled to height of 18 cm after the free-settling period. The sludge was found to settle to a height of 10 cm after 110 min. This particular sludge was found to settle completely to a height of 4 cm. The time to settle to a height of 1/5 of its original height in a cylindrical tank whose diameter is 85% of its depth if it is 85% full and consider 1000 cu ft of sludge in the tank is a. 62.4 hours b. 54.2 hours c. 46.2 hours d. 65.4 hours

13. Free settling of sludge is 0.25 cm/min. Using an original height of 25 cm, the sludge settled to height of 18 cm after the free-settling period. The sludge was found to settle to a height of 10 cm after 110 min. This particular sludge was found to settle completely to a height of 4 cm. The time to settle to a height of 1/5 of its original height in a cylindrical tank whose diameter is 85% of its depth if it is 85% full and consider 1000 cu ft of sludge in the tank is a. 62.4 hours b. 54.2 hours c. 46.2 hours d. 65.4 hours

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Free settling rate of a sludge is 0.25 cm/min. Using an original height of 25 cm, the sludge settledto a height of 18 cm after the free‐settling period. The sludge was found to settle to a height of10 cm after 110 min. This particular sludge was found to settle completely to a height of 4 cm.Calculate the time to settle to a height of 1/5 of its original height in a cylindrical tank whosediameter is 85% of its depth if it is 85% full. Consider 100 cubic feet of sludge in the tank.
A two litre graduated cylinder was used to determine the Sludge Volume Index (SVI) of an activated sludge sample. The settled volume was 800 ml and the MLSS concentration was 2800 mg/lt. The SVI of sludge is
a) An activated sludge plant with recycle is evaluating its secondary clarification system. Settling column tests are conducted and analyzed for settling velocities at different initial solids concentrations. The data are provided below. The plant flow rate is 10,000 m3/d, with a recirculation ratio of 0.5. The MLSS in the reactor is 4000 mg/L. The desired underflow concentration is 17,000 mg/L. Solids concentration mg/L Settling velocity m/h 1500 6.5 3000 5.1 4500 4 6000 2.95 7500 2 9000 1.4 12,000 0.5 15,000 0.27 17,000 0.2 b) Design secondary clarifiers for the activated sludge plant of problem a), with a recycle ratio of 0.6. Calculate the required surface area if two clarifiers are used. Also calculate underflow rate, underflow velocity, and overflow rates. Clearly state your assumptions.
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11.8 A 1- L cylinder is used to measure the settleability of 0.5% suspended solids sludge. After 30 min the settled sludge solids occupy 600 mL. Calculate the SVI
Given a settling tank operating at 80% TSS removal efficiency, an inflow of 0.5 m3/s, and an influent concentration of 100 mg/L. Assuming steady state operations, at what flow would operators have to remove sludge in order to achieve a TSS concentration of 1500 mg/L in the sludge? Answer: 0.027 m3/s
The permeameter in a permeability test setup involves a sample 200mm diameter and a length of 30mm. The height of water is kept constant at 400mm. In a duration of 4 min, water was collected in the graduated flask having a volume of 450cu.m. Determine the Hydraulic Conductivity.
A mixed liquor sample form an activated sludge plant was settled in a one-litre measuring cylinder for 30 minutes after which time, a volume of 350 m/ of sludge was recorded. When 50 m/ of the mixed liquor were filtered through a GFC paper for the determination of MLSS the gain in weight of the paper was 0.1375 g. Determine the SVI.
A sample of 1 litre is drawn from the aeration tank and is then allowed to settle for 30 min. The settled sludge occupies 300 ml at the bottom. This sludge, when dried, is found to have a mass of 3.2 g. The Sludge Density Index is mg/ml (round off to two decimal places).
A conventional activated sludge plant is designed to treat 28000 kiloliters per day at a settled sewage of BOD equal to 220 mg/l. The effluent BOD is 15 mg/l. F/M ratio is 0.22, MLSS is 3000 mg/1. The hydraulic retention time of the sludge will be
A sand sample of 35 sq. cm cross sectional area and 20 cm long was tested in a constant head permeameter. Under a head of 60 cm, the discharge was 120 ml in 6 min. The dry weight of sand used for the test was 1120 g, and Gs = 2.68 1. Determine the hydraulic conductivity in cm/sec. 2. Determine the discharge velocity in cm/sec 3. Determine the seepage velocity in cm/sec