For me its unclear what you want to know.
Do you want to how much Aluminium sulfate correspond to a solution of 17% Aluminiumoxide, if it would be existing.
What does 1:1 mean 1 kg water and 1 kg Sulfate?
If so you have to calculate the corresponding moles. if yo have that you can convert to the mass of the aluminium oxide. You need the density of your solution if you use the volumes. If stay with mass then you can calculate how much water you really need.