WEF Discussion Forums
Operation and Maintenance
High DO in Lagoons
I think it is just normal to have those values of DO. We are getting the same values here in our lagoon ponds in the Philippines. Especially, during sunny days. You can refer to the Standard Methods for the Examination of Wastewater, p.5-5. It mentioned that supersaturation is normal for cold waters and photosynthetic waters.
I hope this would help
Typically when I have seen supersaturated DO readings in a facultative lagoon it has been during times of low rainfall and high temperatures. What you are probably seeing is lagoon turnover. I can't remember the exact process but it is due to the carbon dioxide being stripped off the upper layer of water. I would assume they took the DO reading sometime around midday. Another way to test this is to check the pH when you get a high DO reading. If the pH is also high this is a typical sign of turnover. Also this is a natural occurance. The only thing I know is to change the time of sample collection to early morning to late evening.