A small town discharges its sewage effluent in a nearby river. The river has an initial background BOD of 23.5 mg/L. The oxygen deficit just upstream from the point of discharge of the sewerage is 4 mg/L. The river is flowing at a speed of 43 km/day. You have been asked to determine the impact of this town’s sewerage discharge on the river given that the deoxygenation rate coefficient kd is 0.3/day, and the reaeration rate coefficient kr is 0.5/day. a) A sensitive fish species inhabits the river 120 km from the point of discharge. Determine if the impact of the BOD will have led to the minimum DO before or after the location of the fish species. b) Find the minimum DO due to the effluent discharge. c) Discuss the oxygen deficit in relation to the location of the fish species and whether the fish are at risk due to the discharge upstream.
A small town discharges its sewage effluent in a nearby river. The river has an initial background BOD of 23.5 mg/L.
The oxygen deficit just upstream from the point of discharge of the sewerage is 4 mg/L. The river is flowing at a
speed of 43 km/day. You have been asked to determine the impact of this town’s sewerage discharge on the river
given that the deoxygenation rate coefficient kd is 0.3/day, and the reaeration rate coefficient kr is 0.5/day.
a) A sensitive fish species inhabits the river 120 km from the point of discharge. Determine if the impact of the
BOD will have led to the minimum DO before or after the location of the fish species.
b) Find the minimum DO due to the effluent discharge.
c) Discuss the oxygen deficit in relation to the location of the fish species and whether the fish are at risk due to
the discharge upstream.
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