Problems

15.1 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of ammonia nitrogen in the effluent is 1.039 mg/L. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.2 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of total nitrogen in the effluent is 2.53 mg/L. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.3 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of total nitrogen in the effluent is 2.53 mg/L. Assume all kinetic parameters. Calculate the concentration of oxygen right after the aeration is cut off.

15.4 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of ammonia nitrogen in the effluent is 1.039 mg/L. Assume all kinetic parameters are known. Calculate the concentration of oxygen right after the aeration is cut off.

15.5 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. The concentration of total nitrogen in the effluent is 2.53 mg/L. Assuming all kinetic parameters are known, calculate the fraction of nitrate nitrogen destroyed in the denitri-fication process.

15.6 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of total nitrogen in the effluent is 2.53 mg/L. Assuming all kinetic parameters are known except Ydn, calculate Ydn.

15.7 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of ammonia nitrogen in the effluent is 1.039 mg/L. Assuming all kinetic parameters are known except Ydn, calculate Ydn.

15.8 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 0.5 mg/L

of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of total nitrogen in the effluent is 2.53 mg/L. Assume all kinetic parameters. The concentration of oxygen right after the aeration is cut off is 2.0 mg/L. Calculate the concentration of ammonia nitrogen in the effluent.

15.9 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 0.5 mg/L of NO2-N. The total nitrate nitrogen is destroyed by 95% and the concentration of ammonia nitrogen in the effluent is 1.039 mg/L. Assume all kinetic parameters are known. The concentration of oxygen right after the aeration is cut off is 2.0 mg/L. Calculate the concentration of total nitrogen in the effluent.

15.10 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 2.0 mg/L of dissolved oxygen. The concentration of total nitrogen in the effluent is 2.53 mg/L. Assuming all kinetic parameters are known and that the nitrate nitrogen is destroyed by 95%, calculate the concentration of nitrite nitrogen that appeared right after aeration is stopped.

15.11 After cutting off the aeration to a nitrification plant, the dissolved oxygen concentration is 2.0 mg/L. Calculate the millimoles per liter of sewage needed for the carbonaceous reaction in this last stage of aerobic reaction before denitrification sets in.

15.12 After cutting off the aeration to a nitrification plant, the dissolved oxygen concentration is 2.0 mg/L. The BOD5 sewage needed for the carbonaceous reaction in this last stage of aerobic reaction before denitrification sets in is 1.34 mg/L. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.13 The BOD5 sewage needed for the carbonaceous reaction in the last stage of aerobic reaction before denitrification sets in is 1.34 mg/L. Assuming all kinetic parameters are known, calculate the dissolved oxygen concentration right after the aeration is cut off.

15.14 The millimoles per liter of sewage needed for the carbonaceous reaction in the last stage of aerobic reaction before denitrification sets in is 0.005. Assuming all kinetic parameters are known, calculate the dissolved oxygen concentration right after the aeration is cut off.

15.15 After cutting off the aeration to a nitrification plant, the dissolved oxygen concentration is 2.0 mg/L. The millimoles per liter of sewage needed for the carbonaceous reaction in the last stage of aerobic reaction before denitrification sets in is 0.005. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.16 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. Assume that an effluent total nitrogen not to exceed 3.0 mg/L is required by the permitting agency. The BOD5 required to satisfy the carbon requirement is 79.15 mg/L. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.17 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 0.5 mg/L of NO2-N. Assume that an effluent total nitrogen not to exceed 3.0 mg/L is required by the permitting agency. The BOD5 required to satisfy the carbon requirement is 79.15 mg/L. Assuming all kinetic parameters are known, calculate the dissolved oxygen concentration remaining right after the aeration is cut off.

15.18 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N and 2.0 mg/L of dissolved oxygen. Assume that an effluent total nitrogen not to exceed 3.0 mg/L is required by the permitting agency. The BOD5 required to satisfy the carbon requirement is 79.15 mg/L. Assuming all kinetic parameters are known, calculate the nitrite nitrogen concentration right after the aeration is cut off.

15.19 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. Assume that an effluent total nitrogen not to exceed 3.0 mg/L is required by the permitting agency. The BOD5 required to satisfy the carbon requirement is 79.15 mg/L. Assuming all kinetic parameters are known except Fdn, calculate Fdn.

15.20 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 4.21 mmol/L. Assuming all kinetic parameters are known except Yc, calculate Yc.

15.21 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 4.21 mmol/L. Assuming all kinetic parameters are known except Ym, calculate Ym.

15.22 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 4.21 mmol/L. Assuming all kinetic parameters are known except Yn, calculate Yn.

15.23 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. The BOD5 required for nitrification was found to be 4.21 mmol/L. Assuming all kinetic parameters are known, calculate the concentration of nitrate nitrogen subjected to denitrification.

15.24 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be

134.72 mg/L. Assuming all kinetic parameters are known except Yc, calculate Yc. Make appropriate assumptions for the ratio of BOD5 to BOD„.

15.25 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 134.72 mg/L. Assuming all kinetic parameters are known except Ym, calculate Ym. Make appropriate assumptions for the ratio of BOD5 to BOD„.

15.26 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 134.72 mg/L. Assuming all kinetic parameters are known except Y„, calculate Y„. Make appropriate assumptions for the ratio of BOD5 to BOD„.

15.27 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. The BOD5 required for nitrification was found to be 134.72 mg/L. Assuming all kinetic parameters are known, calculate the concentration of nitrate nitrogen subjected to denitrification. Make appropriate assumptions for the ratio of BOD5 to BOD„.

15.28 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The BOD5 required for nitrification was found to be 134.72 mg/L. Assuming all kinetic parameters are known, calculate the ratio of BOD5 to BOD„.

15.29 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The amount of bicarbonate alkalinity required for nitrification is 25.0 mg/L as calcium carbonate. Assuming all kinetic parameters are known except Ym, calculate Ym.

15.30 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. From previous experience, the concentration of nitrate nitrogen after nitrification is 30 mg/L. The amount of bicarbonate alkalinity required for nitrification is 25.0 mg/L as calcium carbonate. Assuming all kinetic parameters are known except Y„, calculate Y„.

15.31 A domestic wastewater with a flow of 20,000 m /d is to be denitrified. After settling in the primary clarifier, its BOD5 was reduced to 150 mg/L. The amount of bicarbonate alkalinity required for nitrification is 25.0 mg/L as calcium carbonate. Assuming all kinetic parameters are known, calculate the nitrate nitrogen concentration subjected to denitrification.

15.32 An activated sludge process is used to nitrify an influent with the following characteristics to 2.0 mg/L ammonia: Q0 = 1 mgd, BOD5 = 200 mg/L, TKN = 60 mg/L, and minimum operating temperature = 10°C. The effluent is to have a BOD5 of 5.0 mg/L. The DO is to be maintained at 2.0 mg/L.

Assume KsO — 1.3 mg/L. The MCRT needed to attain the limiting 2 8 concentration of ammonia nitrogen concentration is 1.34(10 ) days. What do you conclude about this MCRT? Calculate the limiting ammonia nitrogen concentration.

15.33 An activated sludge process is used to nitrify an influent with the following characteristics to 2.0 mg/L ammonia: Q0 — 1 mgd, BOD5 — 200 mg/L, and TKN — 60 mg/L. The effluent is to have a BOD5 of 5.0 mg/L. The DO is to be maintained at 2.0 mg/L. Assume KsO — 1.3 mg/L. The MCRT needed to attain the limiting concentration of ammonia nitrogen is 1.34(108) days and the limiting ammonia nitrogen concentration is 1.26 mg/L. At what temperature was the unit operated?

15.34 An activated sludge process is used to nitrify an influent with the following characteristics to 2.0 mg/L ammonia: Q0 — 1 mgd, BOD5 — 200 mg/L,

TKN — 60 mg/L, and minimum operating temperature — 10°C. The effluent is to have a BOD5 of 5.0 mg/L. Assume KsO — 1.3 mg/L. The MCRT

28 needed to attain the limiting concentration of ammonia nitrogen is 1.34(10)

days and the limiting ammonia nitrogen concentration is 1.26 mg/L. Calculate the dissolved oxygen concentration at which the unit was operated.

15.35 An activated sludge process is used to nitrify an influent with the following characteristics to 2.0 mg/L ammonia: Q0 — 1 mgd, BOD5 — 200 mg/L, TKN — 60 mg/L, and minimum operating temperature — 10°C. The effluent is to have a BOD5 of 5.0 mg/L. The DO is to be maintained at 2.0 mg/L. Assume KsO — 1.3 mg/L. Calculate the MCRT needed to attain the effluent ammonia nitrogen concentration from the nitrification tank of 2.0 mg/L.

15.36 An activated sludge process is used to nitrify an influent with the following characteristics to around 2.0 mg/L ammonia: Q0 — 1 mgd, BOD5 — 200 mg/L, TKN — 60 mg/L, and minimum operating temperature — 10°C. The effluent is to have a BOD5 of 5.0 mg/L. The DO is to be maintained at 2.0 mg/L. Assume KsO — 1.3 mg/L. If the MCRT is 20 days, calculate the ammonia nitrogen concentration from the nitrification tank.

15.37 A domestic wastewater with a flow of 20,000 m /d is nitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. Assume an effluent total nitrogen not to exceed 3.0 mg/L and an effluent BOD5 not to exceed 10 mg/L. Calculate the volume of the reactor based on the heterotrophic reaction.

15.38 A domestic wastewater with a flow of 20,000 m /d is nitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. Assume an effluent total nitrogen not to exceed 3.0 mg/L and an effluent BOD5 not to exceed 10 mg/L. Calculate the volume of the reactor based on the nitrifiers.

15.39 A domestic wastewater with a flow of 20,000 m /d is nitrified. The effluent from the nitrification tank contains 30 mg/L of NO3-N, 2.0 mg/L of dissolved oxygen, and 0.5 mg/L of NO2-N. Assume an effluent total nitrogen not to exceed 3.0 mg/L and an effluent BOD5 not to exceed 10 mg/L. Calculate the volume of the reactor based on the denitrifiers.

15.40 A bench-scale kinetic study was conducted on a particular carbonaceous waste producing the result below. Calculate Yc, kdc, pcm, and Ksc.

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