Question

A river containing 1.7 mg BODL/L and 6.8 mg DO/L receives a 6.4-ft3 /s agricultural effluent containing 210 mg BODL/L and 2.5 mg DO/L. The river is on average 175 ft wide, 4 ft deep, and it flows at 0.12 ft/s. We assume for simplicity that the temperature of the river and effluent is 20°C, with DOsat (20°C) = 9.1 mg/L, kd = 0.3 d-1 , and ka = 0.25 d-1 . a) Following the steps below, you are asked to calculate the time critic (tc), deficit critic (Dc), and minimum DO (DOmin) that will be reached downstream the point source pollution.b) The river runs into a natural preserve 25 miles downstream the effluent discharge, where the DO, per local regulation, must be no lower than 5.0 mg/L. Determine whether the agricultural effluent discharge would results in a violation of the regulation (1 mile = 5,280 ft).

Answer 1