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Pollution des eaux et rivières et impact sur les populations riveraines: cas de la rivière Mgoua dans la zone industrielle de Douala-Bassa

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par Gisèle BAOK
Université de Dschang-FASA - Master en gestion de l'eau option environment 2007

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Water is an essential resource for life. However, the activities of humans contribute to the degradation of water and therefore diminish the availability of water for future generations. Douala, the economic capital of Cameroon is the most industrialised and most populated town of the country. Industries that reject their waste water without previous treatment degrad the river water quality and put the neighbouring populations in danger. As part of this study, we worked in the catchment area of river Mgoua with a surface area of 782 ha. The Mgoua river takes rise from a heavily industrialized zone and receives pollutants from both industrial and domestic sources.

The objectives of this work were to determine the sources of pollution of the river, characterize the river, determine the risks the neighbouring populations are facing due to the pollution of the river and propose an institutional framework for integrated management of water resources in the catchment.

Surveys were conducted at the level of the industries and the river neighbouring households. Samples were taken from the river at five different points, once a week from April 22 to May 26 2006. These samples were subject to physico-chemical and bacteriological analysis. A stakeholder analysis was carried in order to serve as a base for an institutional framework to an integrated management of the basin.

The survey conducted among 95 waterside households and industries showed that the origin of the pollution of the river is both domestic and industrial. Indeed, all the industries (15) except one send out waste water without appropriate treatment into the river. As concerns the population, 54% use the river to dispose waste water, 15% use the river to dispose sewage water, knowing that 53% of households have latrines situated near the river. Solid household wastes are disposed directly in the river by 47% of households. The neighbouring riversides suffer from, flood, diseases link to the quality of water, mosquitoes, smell and unhygienic conditions. The study indicates that about 71% of the population use well water mainly for cooking, bathing, washing clothes etc; and that diarrhea and malaria are the most common diseases.

The five sets of sample have shown that the values of the physico-chemical parameters for each of the sample do not respect the norms required for surface water (The mean values of chemical oxygen demand and biological oxygen demand in five days are greater than those of moderately polluted surface water respectively by 1717% and 736%). The pollution is significant immediately after the industries. Then we have a mean value of 211mg/l for total dissolved solids (TDS) and a maximum value of 421 mg/l for the chemical oxygen demand (COD). Downstream, the pollution increase, values such as 87 mg/l for biological oxygen demand in five days (BOD5), 111mg/l for chemical oxygen demand (COD), 228mg/l for suspended materials and 211.8mg/l for turbidity were found.

We propose setting up a management committee of the Mgoua catchment which will be composed of resource persons in integrated water resource management. The committee will benefit technically from the services of the state and will propose possible solutions to ameliorate the quality of the river and by so doing, improve the quality of life in the catchment. The forum shall be composed of representatives of all the stakeholders in the hydrologic system of river Mgoua.

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