This report assessed two toilet-linked biogas digesters to determine the presence of pathogenic microorganisms and nutrient value of the effluent slurry. These were Kokebe Tsebah Senior Secondary School and Higher 12 Medium Technical and Vocational Training Institute in Addis Ababa. The parameters analyzed were temperature, pH, biochemical oxygen demand, chemical oxygen demand, nitrate, phosphorous, potassium, total coliform and fecal coliform. They were all measured using standard methods. The efficiency of both digesters was evaluated based on concentration and percentage removal of the above parameters. The report shows that the efficiency of removal is better in Kokebe Tsebah digester than the higher 12 digester. The assessment of nutrients showed that there are enough amounts of nutrients like nitrate, potassium and phosphate that can increase soil fertility if applied to vegetables and crops.
In general, the results showed that Fermented slurry, sometimes called bio-slurry, is an excellent organic fertilizer which can make an important contribution to better crop yields and lasting soil fertility. Although the nutrient content of the slurry is high and it is important for use as a fertilizer, the high number of total coliforms and fecal coliforms found can contaminate the environment in which the effluent is being released. As a conclusion, effluent slurry of digesters could be a potential source of environmental pollution in general and human infection in particular. Therefore, in order to avoid pollution and utilize the slurry as a source of fertilizer the report ends with recommendations.