Effects of Latrines on Water Quality in the Phreatic Nappe in N’Djamena City: (5 th District), Chad

Abstract

Water is a precious natural resource, essential for many uses (crucial for various purposes). Its use for food or hygiene purposes requires excellent physico-chemical and microbiological quality. The region has a high population density compared to other cities in Chad. In order to determine the effect of latrines on groundwater quality in the N’Djamena city, specifically in the 5 th district, 13 water points were selected for physicochemical and bacteriological analyses. Physico-chemical parameters such as pH, temperature and conductivity were measured in situ using a multi-parameter device. Major ion analysis was carried out at the Laboratoire National des Eaux in N ’ Djamena . Anions (Cl − , SO 4 2 − , NO 3 − ) were analysed using a Dr6000 spectrophotometer, and cations (Ca 2+ , Mg 2 + , Na + , K + ) using a flame photometer and a volumetric dosing method. The result show that, the pH ranged from 5.89 to 6.78, with an average of 6.40. EC values range from 441 µS/cm to 1647 µS/cm, with an average of 830.76 µS/cm. A temperature values vary from 29˚C to 32˚C, with an average of 30˚C. The turbidity values range from 0.48 NTU to 10.6 NTU, with an average of 2.30 NTU. Ca 2+ range from 20.8 mg/L to 160 mg/L, with an average of 73.23 mg/L (20). Mg 2+ ranged from 3.4 mg/L to 18 mg/L, with an average of 6.85 mg/L. The Na + ranged from 1.8 mg/L to 14.5 mg/L with an average of 3.83 mg/L. The iron content ranges from 0.06 mg/L to 0.83 mg/L, with an average of 0.29 mg/L. The average values are compared with world health organisation (WHO) drinking water quality standards. The results of chemical analyses on the Piper diagram show that the dominant chemical facies are calcium-magnesium bicarbonate. Bacteriological parameters were analysed using the membrane filter method. The samples contained E. coli , total coliforms and aerobic flora in excess of the WHO norm. The microbiological analyses clearly confirmed a high concentration of germs in the borehole water. Because the distance between the latrines and the water points was not respected, the pathogenic germs reached the water table, making the groundwater unhealthy. As a result, suitable water treatment is required before drinking form.