Assessment of Bacterial Load in Urban Wastewater in Drainage Canals in the Cities of Abidjan, Bouake and Yamousoukro, Côte d'Ivoire

Abstract

The microbiological quality of urban wastewater presents important environmental, health and political challenges. The lack of a water treatment system leads to a lack of knowledge about the variability of the microbiological quality of wastewater in the major cities of Côte d'Ivoire. Aims: The purpose of this study is to assess the level of microbiological pollution of urban wastewater in the drainage channels of the different agglomerations. Methodology: Indicators of environmental pollution (mesophilic aerobic germs) and faecal contamination (fecal coliforms and intestinal enterococci) were analyzed at 14 upstream and downstream sites in cities of Abidjan, Bouaké, Yamoussoukro during rainy periods and in the dry season. Results: Our results show an important pollution translated by the abundance of bacterial indicators of which the aerobic mesophilic germs can reach average loads going from 3x107 cfu/100 mL to 7x109 cfu/100 mL and the witnesses of fecal contaminations can reach average loads going from 3x105 cfu/100 mL to 7x107 cfu/100 mL for the fecal coliforms and from 6x105 cfu/100mL to 1x107 cfu/100mL for the intestinal enterococci These average bacterial loads fluctuate according to the configuration of the sewerage systems and the hydrological conditions. In the rainy season, a significant dilution of certain indicators, precisely mesophilic aerobic germs and intestinal enterococcus, can be observed. The number of microorganisms encountered exceeds the values indicated by the WHO guidelines (WHO, 2017) and the standards in force for wastewater discharge. Conclusion: Creation of strong treatment systems for wastewater to manage them before any discharge in waterbodies have to be a priority. This could reduce the risks of pollution from an environmental and health point of view. The microorganisms encountered can cause mild or serious infections.