Once the chlorine from the bleach has destroyed the algae and the toxins, the water can be boiled to drive off the chlorine.
The toxin only way that the toxin can be removed is trough reverse osmosis and then charcoal filtering. Many water treatment plants the treatment consist of mixing the contaminated water with uncontaminated water until it reaches a level below the approved threshold.
But don’t boil it too long or you concentrate the fluoride.