Résumé
Microalgae can be grown with wastewater in order to reduce the production cost, and recycle nitrogen and phosphorus from waste. Indeed, microalgal systems show great potential for extensive nutrient removal in wastewater treatment. High Rate Algal Ponds (HRAPs) however contain other organisms whose impact can be strong on the process dynamics. This work quantifies the role played by detritivores and algivores through a modelling approach. We present a model, in the framework of Activated Sludge Model, intended to describe the interaction between microalgae, zooplankton, and bacteria. The model is calibrated and tested with experimental data from a HARP fed with a WWTP. We show first that detritivores can have a positive role while they clarify the medium and provide light access to the algae stimulating micro-algae growth. The interaction microalgae/zoo-plankton is, however, much more complicated and grazing maintains a pressure on microalgae, and reduces the removal process efficiency.