Question

The wastewater coming from small development was treated by the string of 2 ponds. The initial flow to the first pond was 12.5 m/hr, and wastewater was carrying 112 mg/L of nonconservative pollutant. Assume the following: steady state, complete mixed, decay (1° kinetics), k = 0.2 d1. First pond volume was V1= 434 m3, and second pond volume was of V2 = 952 m2 (a) Find concentrations of pollutant after leaving first pond and after leaving second pond (b) When we will redesign this system and instead 2 ponds we will put one pond only with combined volume (Vi + V2 what will be the concentration of this pollutant leaving this pond V), For full credit provide sketches that express problems (a) and (b) and full calculations

Answer 1

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Giren flow of waste water flow = 12.5m Concentration of pollutant before entering into the for = 112 mgle lo 112mg Q1 = 12:57 (Vi=4341 952m)__ ? now 12.5m3 Derention tich period period of of first first pond = 434m = 34.72 hr pond I = 1.45 days Detention reuod of second pond = 952m's = 76.16 hr 125m hr - 3.173 days that mix is complerely mixed and becay C i kinetics) .K=0. 2ď Given Concentration of pollentant afrer Leaving first pond is 4 = Lo - 112oogle = 186.866 mg/l Akti (+0.2 (1.45 Concentration of pollutant arrest Leaving second pond is t2 = L = 86.866 = 153.113 moll) tkt If we Redesign the pond with combined volume of Varety = = 434 m² +952m² = 1386 m3 Detention period of this Redesigned pond= 4 = 1386m It 0-2 (3.173) 6 Redesigned pond - do 12.5 m = 110.88 ohr = 4.62 days A Concentration 4= LO (AKE of Poliurant atret Leaving this pond is = 112 mg/ 58.212 mall 140.2 (4.62) 7 Lt = 58 212 male