Sludge accumulation in stabilisation ponds in the Soudano–Sahelian climate of Burkina Faso

Sludge accumulation in waste stabilisation ponds based on local conditions is of great interest for successful sludge management, and accurate accumulation data are essential for WSP design based on reasonable data for model development in relation to the effect of climate variability. For this purpose, a series of three ponds treating domestic wastewater in the Soudano–Sahelian climate of Burkina Faso were monitored for sludge accumulation. After five and a half years of operation, the rates of sludge accumulation in the ponds were evaluated at 0.019, 0.009 and 0.007 m3 per capita per year, respectively, for the anaerobic (AP), facultative (FP) and maturation pond (MP). The corresponding rates of accumulation in dry weight (dw) per person per year were calculated to 1.3, 0.43 and 0.26 kg dw per capita per year, respectively, in AP, FP and MP. A coefficient of high biodegradability of sludge was found in the AP. In contrast to the seasonal evolution of sludge accumulation reported in Mediterranean climatic conditions characterised by a succession of winter and summer, in Sahelian climate regions, a continuous digestion of sludge during its accumulation was observed, due to the warmer Sahelian conditions prevailing most of the year.