Answer Happy

Sewage flows at 4m/s with a BODs of 60mg/L and a dissolved oxygen (DO) value of 1.8mg/L, into a river. Upstream of the sewage outfall the river flows at 20m/s with a BODs value of 4mg/L and it is saturated with dissolved oxygen. The saturated DO level in the river is 12mg/L. a) Calculate the BODs and DO values in the river at the confluence. (7 Marks) Downstream the river flows with a mean velocity 1.5m/s. The BOD reaction rate constant is 0.4 day and the re-aeration constant is 0.6 day? b) Calculate the maximum dissolved oxygen deficit, D., in the river and how far downstream of the outfall that it occurs. Additionally, suggest how this figure may differ in the real-world from your modelled calculations. (10 Marks) c) In up to 8 sentences, define 4 different types of water pollutants and describe their common sources, and consequences. (5 Marks) d) Describe the role of water temperature in aggravating pollutant impact, and suggest how this could be controlled from an industrial point of view. (3 Marks)