A well-mixed sewage lagoon (a shallow pond) is receiving 430 m³ /d of untreated sewage. the lagoon has a surface area of 10 ha (hectares) and a depth of 1.0 m. the pollutant concentration in the raw sewage discharging into the lagoon is 180 mg/l. the organic matter in the sewage degrades biologically (decays) in the lagoon according to first-order kinetics. the reaction rate constant (decay coefficient) is 0.70 d⁻¹. assuming no other water losses or gains (evaporation, seepage, or rainfall) and that the lagoon is completely mixed, find the steady-state concentration of the pollutant in the lagoon effluent.
