Some questions to the pool chemists on sodium bromide + sodium persulfate:
In bromine spas, sodium persulfate, as opposed to potassium persulfate, is said to not re-activate used up bromine (organic bromides).
On the other hand, the combination of sodium bromide + sodium persulfate is used in pool water desinfection, see patents http://www.google.com/patents/US6149821 and http://www.google.com/patents/US20040084383. The latter mentions that the combination needs some time ("aging"), up to some hours to fully develop the bromine from the added sodium bromide.
Is the sodium persulfate just slower than the potassium type or does it really make a difference to generate bromine from "new" versus "used" bromide?
So, would you have to re-add sodium bromide when re-adding sodium persulfate?