Characterization of Depotted Faecal Sludge into the Environment and Design of a Suitable Treatment System: Case of Nomayos Area in Yaounde City

Abstract

Aims: The aim of this study is to contribute to the establishment of a sustainable system of treating faecal sludge derived from autonomous sanitation system; this through co-composting with sawdust, using an analytical formula to obtain the appropriate ratio of mixing sludge and sawdust. Study Design: In other to meet that objective, we have spent eight weeks in the site of Nomayos, area in Yaounde city, support of the present study. For this period, we followed the movement of the depotted trucks of faecal sludge then recorded the quantities these waste and taken samples for the analysis laboratory. Place and Duration of Study: Physics and chemistry laboratory, University of Yaounde I and Research Center, National Advanced School of Public Work, between August 2016 and October 2016. Methodology: Data were collected and we counted 467 trucks emptying during this period. The analysis of these data collected from the field shows that the waste disposal site of Nomayos swallows up more than 140 m3 per day of faecal sludge which correspond to 10 emptying per day. We also noticed that, 85.87% of the faecal sludge came from septic tanks where they had spent several years. Results: The samples analysis showed that the faecal sludge dumps in this area had the organics fraction (TVS/TS) of 3.25% and the mineralization rates of 96.75%. This proves that, the waste had low organics fraction and had spent many years in the septic tanks before collection. The biodegradability index (COD/BOD5) of this waste was 21, greater than one showed that the waste was not totally biodegradable. We have proposed as recommended treatment system for this type of faecal sludge, considering ecological sanitation system for a sustainable development, the unplanted drying bed after which we performed co-composting with sawdust to stabilize the substrate and lagoon system for leachate treatment. This system presents a potential production of 21.0 tons per day of desiccated faecal sludge; 18.9 tons per day of compost and 120 m3 per day of leachate treatment. Conclusion: The realization of our proposed treatment system, will make it possible to solve this problem of pollution on a large scale.