This paper presents results of two years of investigations on three types of wastewater stabilization pond treatment systems, purifying a raw urban wastewater, in the arid climate of Marrakesh. The systems tested were: two lined water hyacinth ponds, two lined facultative ponds and one anaerobic pond. During the course of the experiment, organic load, nutrients and parasitical load were studied. Results show that the macrophytic ponds were more efficient to reduce organic load (90% of TSS and 78% of COD) that the microphtic ponds; these ones were more efficient to eliminate nutrients (NTK 71%, NH4 60%, Ptotal 80% and PO4 62%). The anaerobic pond presents a lower efficiency, less than 40% for organic and less than 20% for nutrients. About sanitary concerns, all of the year, the macrophytic and microphytic pond effluents correspond to B category (WHO, 1989). The anaerobic pond yields B category effluent except in autumn when it corresponds to C category.

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