An aerated lagoon with a liquid volume of 3000 m3 is designed to accommodate an inlet flow rate of 105 L/min. BOD (biological oxygen demand) is a non-conservative pollutant that is of key importance at the lagoon and its average inlet concentration is 212 mg/L. Assume a reaction rate of 0.30 d-1 for BOD removal in the lagoon and the aeration rate significantly mixing mixes the lagoon.
(1) What is the concentration of BOD at the exit of the lagoon?
(2) If the provincial limit for release into waterways is 25 mg/L, what would you suggest to change and/or implement?