Chemistry Homework Solutions
Problem
#86793

Waste water mass balance problem

Info:
BOD: Biochemical Oxygen Demand
BOD5  is the total amount of oxygen consumed by microorganisms during the first five days of biodegradation

BOD5 = (DOi – Dof)/(P)    this is the five-day BOD of a diluted sample
Where DOi = the initial dissolved oxygen (DO) of the diluted wastewater
            DOf = the final DO of the diluted wastewater, 5 days later
            P      = the dilution fraction =   (volume of wastewater)/(volume of wastewater plus dilution water)
A standard BOD bottle holds 300 mL, so P is just the volume of wastewater divided by 300 mL

5.36)
Consider a lake with 100 X 10^6 m^2 of surface area for which the only source of phosphorus is the effluent from a wastewater treatment plant. The effluent flow rate is 0.4 m^3/s and its phosphorus concentration is 10.0 mg/L (10.0 g/m^3). The lake is also fed by a stream having 20 m^3/s of flow with no phosphorus. If the phosphorus settling rate is estimated to be 10 m/yr, estimate the average phosphorus concentration in the lake. What level of phosphorus removal at the treatment plant would be required to keep the average lake concentration below 0.010 mg/L?  

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5.36.doc
Info:

BOD: Biochemical Oxygen Demand

BOD5 is the total amount of oxygen consumed by microorganisms during
the first five days of biodegradation

BOD5 = (DOi – Dof)/(P) this is the five-day BOD of a diluted sample

Where DOi = the initial dissolved oxygen (DO) of the diluted wastewater

DOf = the final DO of the diluted wastewater, 5 days later

P = the dilution fraction = (volume of
wastewater)/(volume of wastewater plus dilution water)

A standard BOD bottle holds 300 mL, so P is just the volume of
wastewater divided by 300 mL

5.36)

Consider a lake with 100 X 10^6 m^2 of surface area for which the only
source of phosphorus is the effluent from a wastewater treatment plant.
The effluent flow rate is 0.4 m^3/s and its phosphorus concentration is
10.0 mg/L (10.0 g/m^3). The lake is also fed by a stream having 20 m^3/s
of flow with no phosphorus. If the phosphorus settling rate is estimated
to be 10 m/yr, estimate the average phosphorus concentration in the
lake. What level of phosphorus removal at the treatment plant would be
required to keep the average lake concentration below 0.010 mg/L?

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Waste water mass balance problem

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