A sewage lagoon that has a surface area of 10 ha and a depth of 1 m is receiving 8640 m3
· d−1 of sewage
containing 100 mg · L−1 of biodegradable contaminant. At steady state, the effluent from the lagoon must
not exceed 20 mg · L−1 of biodegradable contaminant. Assuming the lagoon is well mixed and that there
are no losses or gains of water in the lagoon other than the sewage input, what biodegradation reaction rate
coefficient (d−1) must be achieved for a first-order reaction?