Yes the Bougainvillea may have been affected adversely by the chlorine contained in the swimming pool's water.If my pool had chlorine I wouldn't either swim in it.It is too bad both for you and your plants.
Now another hypothesis is that this summer there were 3 major heat waves that tired the plants and trees all over the south Europe.Your Bougainvillea may have not been the exception.
Also Bougainvilleas originate from arid regions.Experiment with your plant by not watering it(if it is on the ground and not in a pot).You can help it overcome any stress by spraying it with seaweed extract.It's easy,organic and very efficient.Take care not to stain your clothes though.

Bougainvilleas bloom 2-5 times/year depending on the variety and conditions.It doesn't bloom all over the year.Just be patient until the next flowering buds appear.

Good luck

I think that your problem is clearly overwatering. The swimming pool was there before you moved, and the previous owner surely used it. Traditionally, in the mediterranean countries we have a different way of watering plants. We tend to use no sprinkler systems except for vegetables and greens, as most of our typical plants can't stand continuous watering. We usually water plants twice a week in the hottest days of the summer, and once a week the rest of the year, or even less in winter. I can leave my bouganvillea (in a pot in the balcony) about three weeks without watering when I go on holidays every august and nothing happens, it won't die.