Assessment of Faecal Sludge Characteristics from On-Site Sanitation Systems Prior the Design of a Low Cost Treatment Plant in the 1st District of N’Djamena, Chad

Abstract

Faecal sludge management is a major sanitation challenge in N’Djamena, Chad, where on-site sanitation systems are widely used and local design data for treatment facilities remain limited. This study quantified faecal sludge production and characterised selected physicochemical properties in the 1st District of N’Djamena to provide baseline information for the preliminary sizing of a low-cost treatment plant. A household survey was conducted between February and June 2025, and faecal sludge production was estimated using a specific-production approach. Sludge samples from traditional pit latrines, ventilated improved pit latrines, and septic tanks were collected in April 2025 and assessed for pH, temperature, and electrical conductivity using standard analytical procedures. The sanitation-system distribution reported in the study was 60% traditional pit latrines, 5% ventilated improved pit latrines, and 35% septic tanks. Annual faecal sludge production was estimated at 30,409.51 m³. Mean pH values were 7.37, 8.05, and 7.69 for traditional pit latrines, ventilated improved pit latrines, and septic tanks, respectively. Corresponding electrical conductivities were 6,500, 6,300, and 2,684 µS/cm, while measured temperatures were 34.5, 34.5, and 33.0 °C. These results indicate marked variation among sanitation systems and provide preliminary site-specific information relevant to treatment-process selection and facility sizing. Further characterisation is required before a definitive biological treatment design can be established.