## Self Assessment Quiz

Q14.1. A city discharge 30MGD sewage into a river with a flow of 10 cum/s. Stream velocity 3 kM/hr. 5 day sewage BOD 200 mg/L an river BOD 1 mg/L. Sewage contains no DO and river is 90% saturated in DO. Oxygen solubility at 15°C is 9 mg/L BOD removal rate 0.3/day and reaeration constant 0.7/day. Determine max sag and where it occurs, also what is the  BOD at critical and DO at critical.

Q14.2. A city discharge 30 MGD sewage into a river with a flow of 10 cum/s. Stream velocity 3 kM/hr. 5 day sewage BOD 200 mg/L an river BOD 1 mg/L. Sewage contains no DO and river is 90% saturated in DO. Oxygen solubility at 25°C is 6 mg/L BOD removal rate 0.5/day and reaeration constant 0.7/day. Determine max sag where it occurs, BOD at critical and DO at critical.

Q14.3. A city discharge 30MGD sewage into a river with a flow of 10 cum/s. Stream velocity 3 kM/hr. 5 day sewage COD 500 mg/L a river COD 3 mg/L. Sewage contains no DO and river is 90% saturated in DO. Oxygen solubility at 25°C is 6 mg/L BOD removal rate 0.5/day and COD removal rate 0.3/day and reaeration constant 0.7/day. Determine max sag where it occurs, BOD at critical and DO at critical