I guess my initial concern is that, if the water has been properly treated and maintained, and there's still the likelihood of algael growth thereafter, then the water is not secured, and is being contaminated somehow. That being the case, where one lifeform can grow, so can others.

If, however, the water is secured such that no algae are present despite the presense of sunlight, then it is likely nothing else made it through the processing cycle that would somehow have survived. In addition to the algae, I would be looking for suspended 'floaties' in the water before consuming it as well.

High levels of UV and Ion Exchange mechanisms will breakdown all organic components in water, whether organisms, or by-products or organisms. You hit it with enough juice, it will render anything organic inert. Heat ain't the only way to get rid of it.