Question

A water treatment plant has five identical rapid sand filters.
Each is square in plan and has a capacity of 1 MGD. The application
rate is to be 4 gal/min-ft^{2} and the total wetted depth
is 10 ft. Each filter will be backwashed every day for 5 min. The
rate of rise of the backwash water is 2 ft/min.

A) What should be the cross-section dimensions of each filter?

B) What percentage of the plant's filtered water will be used for backwashing?

Answer #1

1) A drinking water treatment plant uses a cubic rapid mix,
rectangular flocculation basin, and rectangular sedimentation basin
to treat 10.0 mgd of water. Size the volume for each basin using
the characteristic detention time and flow through velocity
requirements. What is the rapid mix volume for Dt = 30 sec? What is
the floc. basin volume for Dt = 30 min? What is the floc. basin
cross-sectional area for a velocity = 10.0 ft/min? What is the sed.
basin...

Problem #3: Biochemical Oxygen Demand (BOD) and Stream
Quality
A wastewater
treatment plant designed for a community of 45,000 people has a
flow of 100 gal/person/day and a BOD5 loading of 0.2
lb/person/day. The upstream characteristics of the receiving waters
are:
stream flow rate =
20 cfs and BOD5 = 2 mg/L
The water quality
standards require the in-stream BOD5 to be less than 7
mg/L in this stretch of the river.
The minimum BOD
removal efficiency that the treatment...

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