In a municipal wastewater treatment plant, the influent flow rate into a complete mixing activated sludge system is 50 L/sec, its solid concentration MLSS is 30 mg/L, and the BOD5 in the influent is 245 mg/L. The MLSS concentration at the bottom of the secondary clarifier is 15,000 mg/L and 10 mg/L at the top of the clarifier. The flow rate of returned activated sludge is 20 L/sec. a. What is the concentration of the MLSS in the activated sludge reactor (assuming that it is fully mixed and has constant concentration)? b. What is the activated sludge basin volume if the hydraulic retention time in the basin is 10 hours and the system is operated at the R/Q ratio given in the problem? c. If the cross section of the basin is 20 m² (perpendicular to the flow), how long the basin will be? d. The plant has 96% BOD5 removal. What is the effluent BOD5? e. The flowrate of the waste activated sludge (WAS) is 0.2 L/sec. How many solids (in kg) are wasted every day through the secondary clarifier effluent and how many through the WAS of the clarifier?

In a municipal wastewater treatment plant, the influent flow rate into a complete mixing activated sludge system is 50 L/sec, its solid concentration MLSS is 30 mg/L, and the BOD5 in the influent is 245 mg/L. The MLSS concentration at the bottom of the secondary clarifier is 15,000 mg/L and 10 mg/L at the top of the clarifier. The flow rate of returned activated sludge is 20 L/sec. a. What is the concentration of the MLSS in the activated sludge reactor (assuming that it is fully mixed and has constant concentration)? b. What is the activated sludge basin volume if the hydraulic retention time in the basin is 10 hours and the system is operated at the R/Q ratio given in the problem? c. If the cross section of the basin is 20 m² (perpendicular to the flow), how long the basin will be? d. The plant has 96% BOD5 removal. What is the effluent BOD5? e. The flowrate of the waste activated sludge (WAS) is 0.2 L/sec. How many solids (in kg) are wasted every day through the secondary clarifier effluent and how many through the WAS of the clarifier?

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Publisher:DUNLAP, Richard A.

Chapter14: Ocean Thermal Energy Conversion And Ocean Salinity Gradient Energy

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Problem 20P

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Concept explainers

Integrated Solid Waste Management

Integrated Solid Waste Management (ISWM) is a thorough waste suppression, compost, removal and recycling Program. An effective ISWM system considers how to suppress, manage and recycle solid waste in a manner that is most efficiently to protect human health and the surrounding. ISWM system requires evaluation of public wants and demands and then selecting and merging the most effective waste management activities for the proposed demands. The main ISWM activities for solid waste management are Waste prevention, Recycling and Composting, and Combustion and Removal and waste collection in a properly planned, constructed, managed and mitigated landfill areas. Each of these requires careful designing, financing, accumulation, and delivery of activities.

Question

In a municipal wastewater treatment plant, the influent flow rate into a
complete mixing activated sludge system is 50 L/sec, its solid concentration MLSS is
30 mg/L, and the BODs in the influent is 245 mg/L. The MLSS concentration at the
bottom of the secondary clarifier is 15,000 mg/L and 10 mg/L at the top of the
|clarifier. The flow rate of returned activated sludge is 20 L/sec.
a. What is the concentration of the MLSS in the activated sludge reactor (assuming
that it is fully mixed and has constant concentration)?
b. What is the activated sludge basin volume if the hydraulic retention time in the
basin is 10 hours and the system is operated at the R/Q ratio given in the
problem?
|c. If the cross section of the basin is 20 m² (perpendicular to the flow), how long the
basin will be?
d. The plant has 96% BOD5 removal. What is the effluent BOD5?
e. The flowrate of the waste activated sludge (WAS) is 0.2 L/sec. How many solids
(in kg) are wasted every day through the secondary clarifier effluent and how
many through the WAS of the clarifier?

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