Read this: 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.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): For what reason would solar energy be used in a water stabilisation pond?
to treat waste water without chemicals or electricity