SOURCES ET ORIGINES DE LA POLLUTION DE L’EAU DU FLEUVE NIGER AU NIVEAU DE LA VILLE DE NIAMEY

Abstract

The Niger stream, main source of provision in water of the city of Niamey, is threatened by various and multiform pollutions following the dismissals in the stream of the urban worn-out waters without previous treatment. The main objective of this survey is to diagnose the management of the sewages in the sources of their production and to study the features of the outlets of the dismissals of waters used of the city of Niamey clearing in Niger stream. To make itself/themselves, the gait assigned for this survey is based on the investigation of the land and the in-situ measures of the physico-chemical parameters as well as the debit of the dismissals of the worn-out waters. The investigation shows that the city of Niamey doesn't have any station of purification of the urban worn-out waters functional. Besides, on a number of nineteen (19) establishments investigated, only a minority of establishments, to the number of five (5), have functional purification station, of which one only is in stop of working. To the descended this survey the results watch that the city of Niamey rejects until 13 540 m3j-1 of waters used through thirty-two (32) points of the dismissals identified along the strands of the Niger stream in the city of Niamey. To these outlets, does the in-situ measures show that the pH varies from 5 to 8,45. The electric conductivity (THIS) varies 220 μS cm-1 to 8 095 μS cm-1; the Totals of the Salt Dissoutses (SDR) vary 112 ppm to 4 070 ppm and the chloride of sodium (NaCl) varies between 0,45% and 15,9%. The results descended of the investigation of the land testify a bad management of waters used since the sources where they are generated. As for the results gotten by the different measures, the value of some parameters to know EC, NaCl and SDR passes the one fixed by the World organization of Health (WHO), while the one of pH is on this side of the fork fixed by this one. To the look of these results, measures of treatment of these worn-out waters must be taken before their tipping in the Niger stream.