When ferrous iron is present in solution in raw drinking water, it needs to be removed, otherwise the ferric hydroxide that forms after oxidation will precipitate everywhere in the distribution pipes and home plumbing. The balanced oxidation reaction of Fe2+ with O2 is 4 Fe2+ + O2 + 10 H2O = 4 Fe(OH)3(s) + 8H+

If Fe2+ is present in the water at 2 mg/L at water treatment plant running at 2 mgd, what is the mass of Fe(OH)3(s) sludge is produced if it is 80% by weight water?