[2112]

 I hope someone can assist with the head scratching occurrence.
 I recently encountered an issue whereby a large container of waste water containing small amounts of Ammonium Nitrate, Aluminium and Hexamine started a small reaction within the container.  The temperature within the container rose to 75c resulting in  a small amount of gas which smelled like formaldehyde  omitting from the water container. The outside temperature was 40c but the container was semi submerged.
My question is because the smell of Formaldehyde I assume the hexamine has reacted with something but with what?
There were  elements of cow dung evident  and broken masonry/cement    close to the container which could have entered the container. Could this have been a contributing factor?
What other elements would cause hexamine to react in this way?
If anyone can assist I would be most grateful.

[Hunter2]

Hexamin also called Hexatetramethylentetramin goes in water under hydrolysis.

C₆H12₂N₄ + 6 H₂O => 6 CH₂O + 4 NH₃

This is not surprising. The Formaldehyde will developed.