Mechanisms for the Purification of Effluents with High Nitrogen Content by a Plant Cover of Water Hyacinths (Eichhornia Crassipes)

The mechanisms for the purification of three effluents containing a high level of ammoniacal nitrogen by water hyacinths ( Eichhornia crassipes ) have been studied. The pollutants (nitrogen, phosphorus, COD and suspended solids) were eliminated by means of the creation of a favourable ecosystem. The liberation of oxygen and the root support provided by the rhizosphere allow a nitrifying bacterial flora to develop. Denitrification can occur when there is no more available nitrogen, namely at the bottom of the pond or when a high BOD mobilises all the available oxygen in the pond. Ammoniacal nitrogen is eliminated by plants (