6. Conclusion

The aim of this article was to provide an overview of the various options available for biological wastewater treatment.

Depending on the nature and extent of the organic pollution, various processes can be used to purify urban and industrial wastewater, depending on its physico-chemical characteristics and the degree of purification required.

The choice between these solutions will have to take account not only of technical considerations, such as the relative efficiency of the various processes, but also of economic considerations, including not only estimated investment costs but also operating costs.

We feel it's important to stress that there are no universal solutions, and that extrapolating a treatment process used in one plant or by one urban agglomeration to others is difficult, if not virtually impossible....