Managing a salt-water aquarium. A tank at the New Jersey State Aquarium has a volume of 2.9 million liters. Bacteria are used to remove nitrate that would otherwise build up to toxic levels. Aquarium water is first pumped into a 2 700-L deaeration tank containing bacteria that consume O₂ in the presence of added methanol:

Anoxic (deoxygenated) water from the deaeration tank flows into a 1 500-L denitrification reactor containing colonies of Pseudomonas bacteria in a porous medium. Methanol is injected continuously and nitrate is converted into nitrite and then into nitrogen:

(a) Deaeration can be thought of as a slow, bacteria-mediated titration of O₂ by CH₃OH. The concentration of O₂ in seawater at 24^oC is 220 μM. How many liters of CH₃OH (FM 32.04, density = 0.791 g/mL) are required by Reaction 1 for 2.9 million liters of aquarium water?

(b) Write the net reaction showing nitrate plus methanol going to nitrogen. How many liters of CH₃OH are required by the net reaction for 2.9 million liters of aquarium water with a nitrate concentration of 8 100 μM?

(c) In addition to consuming methanol for Reactions 1 through 3, the bacteria require 30% more methanol for their own growth. What is the total volume of methanol required to denitrify 2.9 million liters of aquarium water?

Transcribed Image Text:

Bacteria 2CH3OH + 302 2CO2 + 4H20 Methanol