Question

3. [20] You have been conducting a water quality study of Lake Arjun, which has a surface area of 8.9 ×105 m2 . The average depth of the lake is 9 m. The lake is fed by a stream having a flow rate of 1.02 m3 /s and a phosphorus concentration of 0.023 mg/L. Runoff from the homes along the lake adds phosphorus at an average annual rate of 1.25 g/s. The river flows from the lake at a flow rate of 1.02 m3 /s. The average phosphorus concentration in the lake is 13.2 µg/L. Assume evaporation and precipitation negate each other. What is the calculated average settling rate of phosphorus?

Answer #1

Consider a 20 * 105 m3 lake fed by a
polluted stream having a flow rate of 4.2 m3/s and
pollutant concentration equal to 25 mg/L. There is also a sewage
outfall that discharges 0.5 m3/s of wastewater having a
pollutant concentration of 275 mg/L. The stream and sewage wastes
have a second order decay rate of 0.32/day. Assuming the pollutant
is completely mixed in the lake and assuming no evaporation or
other water losses or gains, find the steady-state...

Consider a lake that is fed by mix of two streams: one stream
has a flow rate of N m3/s and BOD concentration of 10 mg/L. The
other is a sewage outfall that discharges 0.6 m3/s and a BOD
concentration of 40 mg/L. Assuming the pollution is completely
mixed in the stream, find the resulting BOD concentration

Part I. Indicate whether true or false (T or F).
____ Storm water detention ponds typically are designed to
regulate the outflow peak rate at or below a single target value,
such as the pre-development (pre-land use change) peak runoff rate
for a specified return period event. Detention storage alters the
peak but not the volume of the outflow hydrograph.
_____ Typical rating curves for weirs are concave upward.
Typical rating curves for orifices are concave downward.
____ A sediment...

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