Spatial Distribution Model for Helminth Eggs in Swaswa Waste Stabilization Pond Sludge System Located in Dodoma, the Capital City of Tanzania

Waste stabilization ponds (WSPs) are widely used for Municipal wastewater treatment in semi-arid Tanzania and generate sludge with significant agricultural reuse potential; however, spatial distribution of helminth eggs within WSP sludge remains poorly understood, limiting safe reuse decisions. The SWASWA Waste Stabilization Pond system have been analysed using Inverse Distance Weighting (IDW), multiple regression, and model validation techniques integrating UTM coordinates, altitude, pond depth, pH, and temperature. Helminth egg concentrations declined from the inlet (14.00±2.00 eggs/L) through anaerobic (8.08±3.08 eggs/L) and facultative zones (3.96±1.90 eggs/L) to the final effluent (4.00±1.00 eggs/L), achieving 71.43% removal efficiency; however, all sites exceeded the WHO guideline of ≤1 egg/L. UTM Northing, pond depth and altitude were the strongest predictors, while temperature and pH were insignificant. The final model explained 67.0% of spatial variability (Adjusted R²=0.620) and showed strong predictive performance (R²=0.728; RMSE=1.96 eggs/L), identifying high-risk anaerobic zones (>8 eggs/L). The study concludes that sludge reuse without additional treatment poses health risks. Zone-specific treatment and routine georeferenced monitoring are recommended prior to any sludge reuse. This spatial modelling framework contributes the first spatially explicit helminth risk-zoning framework for WSP sludge management in semi-arid sub-Saharan Africa, supporting United Nations Sustainable Development Goals (SDG 6.3).