One of the drawbacks for treating domestic wastewater in an activated sludge treatment is its lowered temperature during winter seasons. The efficiency of biological treatment decreases with a decrease in water temperature due to slow microbial growth. One approach to overcome this drawback is to heat water. Assume that a wastewater with a flow rate of 6000 m³/d will be heated to increase its temperature from 15 °C to 25 °C in an aim to improve the biological treatment efficiency in an activated sludge treatment during winter season. Based on information given in the problem; a) Calculate the daily heat necessary as kcal/d to increase the temperature of wastewater from 10 °C to 25 °C. b) Estimate the cost of heating as TL per cubic meter (m³) wastewater treated if coal is used as an energy source. Do you think the cost you calculated for heating wastewater is feasible? Heat of coal = 7800 kcal/kg c) Assume 2 m³ of wastewater is evaporated daily during heating process, calculate the annual heat loss through evaporation as kcal/y.

One of the drawbacks for treating domestic wastewater in an activated sludge treatment is its lowered temperature during winter seasons. The efficiency of biological treatment decreases with a decrease in water temperature due to slow microbial growth. One approach to overcome this drawback is to heat water. Assume that a wastewater with a flow rate of 6000 m³/d will be heated to increase its temperature from 15 °C to 25 °C in an aim to improve the biological treatment efficiency in an activated sludge treatment during winter season. Based on information given in the problem; a) Calculate the daily heat necessary as kcal/d to increase the temperature of wastewater from 10 °C to 25 °C. b) Estimate the cost of heating as TL per cubic meter (m³) wastewater treated if coal is used as an energy source. Do you think the cost you calculated for heating wastewater is feasible? Heat of coal = 7800 kcal/kg c) Assume 2 m³ of wastewater is evaporated daily during heating process, calculate the annual heat loss through evaporation as kcal/y.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.3DP

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