**5. Conclusions**

The correct operation strategies in a biological process (e.g., temperature, nutrient concentra‐ tions, bacterial population's interaction and reactor configuration) allow abate high organic carbon and nitrogen concentrations in wastewaters, which poses a problem and changes from a problem to an opportunity. The aforementioned process can be applied to every anaero‐ bic digestion process with inhibitory ammonia concentrations because the need of expensive freshwater can be replaced by recycled treated water with savings of freshwater consumption and operational costs.

Finally, new solutions for ammonia removal using biological treatments reevaluate the tech‐ nical and economical optimization of the anaerobic digestion projects; the latter were dis‐ carded in the past because they showed a negative total annual worth or low biogas potential. Thus, this new process contributes to all different energy matrixes.
