Problem:
A local river carries a nonreactive pollutant at a concentration equal to Cs and at a flow rate equal to Qs. An industrial operations plant discharges at Qp the same pollutant to the river at a concentration equal to Cp. Just downstream from this plant's outfall is a tributary contributing flow to the river at a rate equal to QT and pollutant concentration of CT. A local community currently withdraws water at a rate of QC from this surface water system at it most downstream location for its drinking water needs. With pollutant discovered in the river, the community currently mixes fresh drinking water with river water to meet the drinking water standard for the pollutant.
Required:
Question 1: Determine the downstream concentration of the pollutant.
Question 2: If the community measures a pollutant concentration in the river equal to 100 ppb, at what ratio (volumetric %) must this community mix the river water with fresh water to meet a drinking water standard of 70 ppb?
Note: Please provide equation and explain comprehensively and give step by step solution.