Qualitative Assessment and Typology of the Water Resource Used for the Production of Drinking Water in Duékoué, Western Côte d’Ivoire

Abstract

The objective of this study was to evaluate the typology of water through physicochemical and bacteriological characterization with the aim of highlighting its vulnerability as a drinking water resource. The methodology adopted was to evaluate the level of pollution by monitoring the spatiotemporal variation of the water pollution indicator levels of Lake Dohou. The sampling frequency is monthly for one year, from November 2017 to October 2018, in order to obtain a fairly representative image of water quality and its seasonal evolution in eight (8) well-defined stations. The parameters were determined using the standard methods defined by the French Association for Standardization (AFNOR). This study shows that the waters are acidic, with an average pH of 5.81 and a low electrical conductivity of between 42.67 ± 4.30 and 59.62 ± 21.84 μS•cm −1. At all stations, seasonal mean water transparencies are low (<1 m). It is also noted that 99.7% of the water samples collected had total nitrogen (TN) levels above the limit of 4 mg•L −1. All of the lake's waters have non-compliant BOD5 (<3 mgO 2 •L −1) for raw water intended for the production of drinking water. Sites D6 and D7 have COD/BOD5 ratio greater than 3, which indicates the presence of non-biodegradable organic matter in these areas. Total coliforms, Escherichia coli and Enterococci were present in 100% (28/28) water samples at concentrations ranging from 2300 to 173,000 CFU/100 mL, from 100 to 1650 CFU/100 mL and from 20 to 1140 CFU 1/100 mL respectively. For Salmonella pathogens, they were detected in 50% of the dry season samples and in 100% of the rainy season samples. This almost permanent presence of this pathogenic germ denotes a poor quality of water with reference to this parameter.

Typology of the Phytoplankton Community of Dohou Lake, Drinking Water Supply Source in Duékoué Town (Western Côte d’Ivoire)

“…According to some authors, the acidity of inland waters is related to the supply of humic acids from soil leaching, wastewater discharge and macrophyte decomposition under the action of bacteria (Korfali & Davies, 2003). These results are consistent with those of Kouamé et al (2019) obtained on the same lake. In general, natural waters have pH values between 4.5 and 9 (Kortatsi, 2007).…”

“…In addition, during the rainy season, the arrival of runoff water loaded with solids and suspended matter would contribute to disturbing lake water, resulting in low average transparency values. Our results are similar to those of Kouamé et al (2019) on Dohou lake. Nitrogen compounds (total nitrogen, nitrate, nitrite) are essential constituents of organic matter and enter into the composition of cellular proteins.…”

“…This variation in the oxygenation of the lake water may be due either to exchanges at the air-water interface, to the diffusion within the body of water or to the photosynthetic activity of the algae which, in the presence of sunlight, captures the atmospheric CO 2 to transform it into O 2 to aerate the medium or to a consumption of oxygen dissolved by aerobic bacteria for the degradation of organic matter (Amon, 2017). The values of this parameter are similar to those found by Kouamé et al (2019) on the same lake. The average transparency of the lake water does not exceed 1 meter during the study period.…”

Heavy Metals Contamination of an Aquatic Environment and Health Risks Assessment in Two Fish Species: Case of the Guessabo Lake, Western Côte d'Ivoire

“…The region enjoys a humid tropical climate with a dry season and a rainy season. Medium-fertility ferritic soils are favourable for the development of agriculture in this area 21 . There are also soils developed on basic rocks potentially rich in mineral salts and hydromorphic soils located in the lowlands.…”