Solar energy may be used in a water stabilisation pond to treat waste water without chemicals or electricity. A further environmental advantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although algae may produce toxic chemicals that make the water unusable.
What is a possible negative effect of algae in water stabilization ponds? For what reason would solar energy be used in a water stabilisation pond? What is a reason why the water from a water stabilisation pond may be unusable?