Confidence votes 4.8K. The base meanining of un pigeonnier is a dovecote (a structure where doves, or similar birds, are bred or housed). But you will also find un pigeonnier used to mean a garret-flat, or any small flat near the top of a building (especially if it is a low-rent sort of place).
Duckweed creates an anaerobic environment. When it comes to wastewater lagoons, the lack of dissolved oxygen is bad. (Read our previous article, Troubleshooting Low Lagoon Dissolved Oxygen, for an in-depth look.) Duckweed is a DO killer, blocking the oxygen-transferring interface between the surface of the lagoon and the atmosphere.
Dissolved oxygen is a molecule of O2 that is dissolved into the water. It is invisible to our naked eye. It is not the bubbles in water, nor the oxygen component of the water molecule H2O. Dissolved oxygen can get into the water two ways, through atmospheric oxygen mixing into a stream in turbulent areas or by the release of oxygen from aquatic plants during photosynthesis. All animals need oxygen to survive.