Variations in physicochemical properties, microbiological profiles, and nutrient dynamics in the Temi River, Arusha, Tanzania: Sources and implications

This study thoroughly investigates the physicochemical properties, microbiological profiles, and nutrient dynamics of the Temi River in Tanzania. The sources and implications of fluctuations in dissolved organic carbon (DOC) and nutrients during the wet and dry seasons are carefully analysed. Water samples were collected from various geographically referenced points along the river, and analyses were performed using the APHA Standard Methods for Water and Wastewater Testing. The results show that most parameters increased downstream in both seasons, with the highest DOC levels reaching 352.11 mg/L in the wet season, followed by a significant decrease to 126.00 mg/L during the dry season. Key ion concentrations, such as K+, Na+, Mg2+, and Ca2+, peaked at 114 mg/L during the wet season and dropped to 40.51 mg/L in the dry season. The floodplain area displayed higher biochemical oxygen demand (BOD) values, exceeding the WHO maximum permissible level of 10 mg/L, while other regions remained below this threshold. Stable isotope analysis indicated that DOC primarily originated from plant materials, with soil and wastewater sources contributing to fluctuations in nutrient concentrations. Notably, high levels of faecal coliforms (FC) were present in both seasons, indicating inadequate domestic sewage disposal and poor hygienic practices, which pose significant health risks. This comprehensive research provides a solid foundation for understanding the health risks linked to the Temi River for domestic use.