The wastewater treatment by infiltration-percolation plant at Ben Sergao (a suburb of Agadir, Morocco) foreshadows the installation which will be able to be built for Greater Agadir (first fraction: 40,000 m3/d). The present plant treats 1,000 m3/d of highly concentrated raw effluents which after being decanted in an anaerobic stabilization pond are infiltrated into 5 infiltration basins of 1,500 m2 each, constituted by a bed 2 metres thick of eolian sand drained at its base.
The decanted water infiltrates at the rate of one metre per day. With this process 100 % of the suspended matter, and 95 % of the chemical oxygen demand are removed, 85 % of the nitrogen is oxidized. The parasites are entirely eliminated and the number of fecal coliforms and streptococci is made 10,000 to 100,000 times smaller. A series of experiments of irrigation by the treated effluents is under way.