Question

1)A 20,000-kg fertilizer spill has occurred into a well-mixed 5 Ha lake with an average depth of 8 m. The lake is fed by two streams and has an average detention time of 3 weeks.

3)A 20,000-kg fertilizer spill has occurred into a well-mixed 5 Ha lake with an average depth of 8 m. The lake is fed by two streams and has an average detention time of 3 weeks a)Determine the initial concentration of fertilizer in the lake, in mg/L b)How long does it take for the concentration to be reduced to 10% of the initial concentration due only to flushing (no reaction)? c)How long does it take for 95% of the initial mass of fertilizer to be flushed from the lake?

Answer 1

Given data: concentration of fertilizer = 20,000 kg volume of lake = Area * depth = 5Ha * 8m = 5 * 10^4 * 8 = 4 * 10^5 m^3 = 4 * 10^3 lit Detention time, of take = 3 weeks (a): Initial concentration of lake = 20,000 * 10/4 * 10^8 = 200/4 = 50 mg/lit (b): Total concentration_50 * 4 * 10^8 mg_21 days 10% concentration_? 50 * 4 * 10^8_21 days 0.1 * 50 * 4 * 10^8 rightarrow x x = 21 * 0. * 520 * 4 * 10^8/50 * 4 * 10^8 x = 2.1 days \r\n (c): 100% initial mass_20,000 kg_21 days 95% mass_20,000 kg 20,000_21 days 0.95 * 20,000_x(How many days) x = 0.95 * 20.,000 * 21/20,000 x = 19.95 days