5. Conclusion

The HRAP system replaces existing systems such as activated sludge, which is costly and energy-intensive, and stabilization basins, which are not very efficient. The HRAP's low construction and operating costs make it a suitable wastewater treatment solution for sparsely populated areas. The valorization of the biomass produced for agriculture or energy production also places the system in a circular economy perspective.

Numerous studies carried out on HRAPs operated under real-life conditions in France, Spain, Australia and New Zealand reveal that the wide range of interacting microorganisms, uncontrolled populations of microalgae and bacteria, and solar conditions all contribute to the complexity of the system and the variability of its performance. The HRAP is nevertheless a promising technology, and a better understanding of the behavior of microorganisms and...