The present study aims to present a complete diagnosis of the state of water supply and sanitation in the Dschang city. After an inventory of the actor practices starting from existing documentations of the Dschang urban council, 87,000 inhabitants, we identified consumers through physical field identification of the water supplies and sanitation in November 2007. All wells were mapped, 300 households surveyed and water quality analysed. It appears that water is basically supplied through connection on the conventional "CAMWATER" network. Over 52.2% of households not connected to network used 728 alternative points for water assessment (705 wells and 23 springs), and drawn drinking water especially from springs. Bacteriological quality varies greatly from one water point to another. Water coming from depth soils and managed water points are relatively more improved in quality. For the 250 sanitation installations surveyed, 70% of households use pit latrines with open bottom; 116 latrines are located in a radius of 15 m around the wells and springs. For the wastewater drainage and treatment, no device is constructed. The difficulties of supplying safe drinking water and the precarious conditions of sanitation seemed to be the origin of many water borne-diseases in this city.

The evaluation of environmental impact of urban waste management systems is the objective of this work. The case of Yaounde is analysed in this paper. Four systems of management have been considered for the analyses. System 1 is the traditional collection and landfill disposal. In system 2 the biogas produced in the landfill is recovered to produce electricity. In systems 3 and 4, in addition to the collection, a centralised composting or biogas plant has been introduced before the landfill disposal of refuse. Life Cycle Assessment (LCA), has proven more adapted to evaluate these four systems. The stages which have been studied are : the collection, the transportation, the treatment, the transportation of compost on a distance of 70 km, the landfill disposal of refuse. The analysis of the different outputs has allowed to take into account six impact classes allocated by the waste management systems studied. These impact classes constitute the environmental criteria taking into account the multicriteria analysis of the four systems. At the environmental level, system 2 has been shown as the most effective. L’évaluation des incidences environnementales des systèmes de gestion des déchets urbains constitue l’objectif de ce travail. Le cas de la ville de Yaoundé au Cameroun a été spécifiquement analysé. Quatre systèmes de gestion ont servi de base aux analyses effectuées. Le système 1 est constitué par la collecte traditionnelle et la mise en décharge des déchets bruts. Dans le système 2 le biogaz qui est produit après la mise en décharge est récupéré pour produire de l’électricité. Les systèmes 3 et 4, considèrent après la collecte, une étape de traitement par compostage et méthanisation en réacteur et de mise en décharge des déchets ultimes. La méthode d’analyse de cycle de vie (ACV), a été utilisée pour évaluer ces quatre systèmes. Pour cela, les étapes suivantes ont été étudiées : la collecte, le transport, le traitement, le transport des sous-produits sur une distance de 70 km, la mise en décharge des résidus. L’analyse des différents rejets a permis de recenser six classes d’impact pour les systèmes de gestion des déchets étudiés. Ces classes d’impact constituent les critères environnementaux pour l’évaluation environnementale des quatre systèmes en utilisant les outils d’analyse multicritère. Les résultats obtenus indiquent que sur le plan environnemental, le système 2 se dégage comme le plus performant.

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The authors here analyse the emission of greenhouse gases (GHG) resulting from the various treatment of municipal solid waste found in the town of Yaounde. Four management systems have been taken as the basis for analyses. System 1 is the traditional collection and landfill disposal, while in system 2 the hiogas produced in the landfill is recuperated to produce electricity. In systems 3 and 4, in addition to the collection, we have introduced a centralised composting or biogas plant before the landfilling disposal of refuse. A Life Cycle Inventory (LCI) of the four systems was made; this enable us to quantify the flux of matter and of energy, consumed or produced by the systems. Following this, only the greenhouse effect was taken into account to evaluate the ecological consequences of the MSW management systems. The method used to evaluate this impact takes into consideration on the one hand, GHG emissions or avoided emission following the substitution of fuel with methane recovered from landfills or produced in the digesters, and on the other hand, sequestrated carbon in the soil following the regular deposit of compost. Landfilling without recuperation of methane is the most emitting solution for greenhouse gas: it leads to the emission of 1.7 ton of carbon dioxide equivalent (tCO2E) per ton of household waste. Composting and methanisation allow one to have a comparable level of emission reduction, either respectively 1.8 and 2 tCO2E/t of MSW. In order to reduce the emission of GHG in the waste management systems, it is advisable to avoid first of all the emissions of methane coming from the landfills. System 2 seems to be a solution that would reduce the emissions of GHG at low cost (2.2 to 4 $/tCO2E). System 2 is calculated as the most effective at the environmental and economic level in the context of Yaounde. Therefore traditional collection, landfill disposal and biogas recuperation to produce electricity is preferable in moist tropical climates.

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