1. You are in charge of designing the disinfection system for your water treatment plant. You have decided to use ozone for you design, and will inject 2 mg/L ozone into the contractor. Your design needs to have Ct of 20 mg*min/L to properly disinfect the water. The decay rate constant for ozone has been found to be 4.25×10-3 L/mg/min. Assume that the hydraulic efficiency of all chambers (t10/to) = 0.65. Suggest a design that incorporates multiple cells and achieves the desired disinfection goals. You should report the number of cells and the volume of each cell. (Hint: Don’t forget to consider the decay rate of ozone!)
2.Your water treatment plant has been treating its water with 1 mg/L ozone to oxidize arsenite compounds to As(V) for subsequent removal.
a.If the water concentration changes to have the following concentrations, will this process still work?
As(III) = 80 mg/L
Fe(II) = 3.0 mg/L
H2S = 0.5 mg/L
Hints:
1.Reaction of ozone with iron should be of the form (a-f are stoichiometric coefficents):
a H2O + b Fe2+ + c O3 d Fe(OH3) + e O2 + f H+
2.For all oxidation reactions, mass and charge must be conserved
Molecular weights (g/mol)
Fe – 55.845
As – 74.9216
Mn – 54.938
O3 – 48
b. A vendor proposes that you can oxidize more of the metal ions if you switch to permanganate. Do you believe her? Justify your answer.
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