(Solved): Q3 (25 marks) A city has a secondary level wastewater treatment plant (WWTP) with a rated capacity ...

Q3 (25 marks) A city has a secondary level wastewater treatment plant (WWTP) with a rated capacity of 10,000 m³/d with the treated effluent from WWTP discharging to a river with a flow of 500,000 m³/d. The current effluent discharge limits for CBOD5, TSS and total phosphorus (TP) as 15 mg/L, 15 mg/l and 1 mg/L respectively. A study has established the background TP concentration of 0.02 mg/L in the river and recommends that downstream concentration should not deteriorate more than 20% of the upstream concentration to keep the water quality intact. Determine what level does the effluent TP limit needs to be adjusted to in order to meet the above condition. Also comment on the potential changes or upgrades required to the WWTP to meet this condition. (25 marks)