La.) Predičt thể trophič štătě ôf å (surface area) reservoir that is in steady state and receives a total of 100 kg of Phosphorus per year from runoff from its watershed. The amount of Phosphorus leaving the system over the dam leaving the reservoir is 80 kg of

Poorly treated municipal wastewater is continuously discharged directly into a lake. The discharge from the wastewater plant into the lake occurs at a flow of Qd = 1 m3/hr. The concentration of phosphate (PO43, M = 95 g/mol) in the discharge flow (Cxd) that is decaying with first-order kinetics is 100 mg/L. The lake is a well-mixed water body of 100 m3. (Phosphate is naturally uptaken by algae with a first- order decay rate constant equal to 0.20/day.) The concentration of phosphate in the incoming river (Cx,r) is 10 mg P/L. The incoming river flow rate is Q, = 10 m3/hr. %3D a) Which of the following equations represent the correct mass balance equation? O va = CxQr - CxdQd -QoutCxvout" kCx,outV %3D O 0 = Cx,Qr + CxdQd -QoutCxvout" kCx,outV X,r O 0 = CxQr + CxdQd -QoutCxvout- kV O 0 = Cx,dQr + Cx,,Qd -QoutCxout- kCxoutV

Question 1: Is the dissolved oxygen level in the pond adequate for the fishes to thrive? Discuss the impact of low DO levels of water to aquatic organisms. Question 2: In typical aquatic environment, when dissolved organic matter is high, dissolved oxygen level tends to be low. Explain why this inverse relationship occurs.

Fifteen kilograms of contaminant is spilled into a stream 5 m wide and 1 m deep. The flow in the river is 2 m3/s, the longitudinal diffusion coefficient is 3 m2/s, and the decay constant is 50 d−1.  A) Determine the maximum concentration in the stream at a drinking-water intake 1 km downstream from the spill. B) How would this concentration be affected if the decay constant is actually one- half of the estimated value?