A primary settling tank at a wastewater treatment plant has one influent flow (Qin) and two effluent flows (Qout and Qw) as indicated in the schematic below. The tank has an influent concentration (cin) of 220 mg/L of suspended solids, an effluent concentration (cout) of 45 mg/L of suspended solids, and a waste concentration (cw) of 10,000 mg/L of suspended solids. If the influent flow rate is 450 m3/hr, what is the waste flow rate

Question

Engineering

Shawn

11 December, 21:16

A primary settling tank at a wastewater treatment plant has one influent flow (Qin) and two effluent flows (Qout and Qw) as indicated in the schematic below. The tank has an influent concentration (cin) of 220 mg/L of suspended solids, an effluent concentration (cout) of 45 mg/L of suspended solids, and a waste concentration (cw) of 10,000 mg/L of suspended solids. If the influent flow rate is 450 m3/hr, what is the waste flow rate

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Marissa · Answer 1

The waste flow rate is 81.05 m3/h

Explanation:

According to the given data we have the following:

Influent SS concentration (CIn) : 220 mg/L

Influent flow rate (QIn) : 450 m3/h

Effluent concentration (Cout) : 45 mg/L

Waste sludge concentration (Cw) : 10,000 mg/L

Qout + Qw = 450 m3/h

CIn QIn=Cout Qout + Cw Qw

220*450=45Qout + 1000Qw

45Qout+1000Qw=99,000

Therefore, Qout=398.95 m3/h

Qw=81.05 m3/h

The waste flow rate is 81.05 m3/h