Steady state concentration of non-reactive pollutant

Question

Problem:

A company has been discharging a non-reactive pollutant at a concentration of 15 g/m³ to a lagoon for several years. The wastewater flow rate is 0.1 mega-liters (ML) per day and the lagoon detention time is 10 days. The lagoon is assumed to be completely mixed. The overflow from the lagoon discharges into an adjacent river.

Required:

Please determine:

1.  The steady state concentration of the non-reactive pollutant in the effluent from the lagoon that overflows into the river.

2. The concentration of the non-reactive pollutant in the effluent leaving the lagoon 10 days after the influent concentration is suddenly increased to 150 g/m³

Note: Please provide full description.