(Solved): A circular primary clarifier needs to be designed to treat domestic wastewater with average and pea ...

A circular primary clarifier needs to be designed to treat domestic wastewater with average and peak flow rates of 6,750 and $21,820{\mathrm{m}}^3/$ day, respectively. The side water depth is $3.5\mathrm{m}$, and the diameter is $30\mathrm{m}$. The influent BOD is $250\mathrm{mg}/\mathrm{L}$ and the clarified water leaves the tank with the $\mathrm{BOD}$ of $150\mathrm{mg}/\mathrm{L}$. (i) Calculate the weir loading, surface overflow rate and retention time, at average flow. (ii) Check if the design parameters are within the accepted limits. (iii) If the design is not suitable, what is the minimum diameter that should be used to achieve the accepted range of design parameters? (iv) Calculate the clarifier BOD removal efficiency. (I0 marks)