Rainwater harvesting for domestic use in suburb areas of Dar es salaam, Tanzania: a case study of Wazo Hill

Abstract

Despite the increasing reliance of rainwater harvesting in semi-urban areas, there is a lack of comprehensive localized data on the safety of harvested rainwater, particularly in areas such as Wazo Hill where communities predominantly depend on it. This study evaluates the quality of harvested rooftop rainwater intended for human consumption and assesses its compliance with the World health Organization (WHO) and Draft East Africa Standards (DEAS) for drinking water. Rainwater samples were collected from various catchment surfaces and storage systems located in Wazo Hill, Tanzania. A stratified random sampling technique was employed to select the households equipped with rainwater harvesting systems and sampling locations were georeferenced using a Portable GPS device (Garmin Oregon 700). A total of eighty-four (84) samples were analyzed for physicochemical parameters, including pH, turbidity, electrical conductivity, Total Dissolved Solids (TDS) and selected heavy metals (lead, chromium and iron). Microbial assessment focused on fecal coliforms and total coliforms. The results reveled that while physicochemical parameters generally conformed to WHO and DEAS guidelines for drinking water, microbial contamination was predominant. Fecal coliforms concentrations ranged from 40.1 to 48.0 CFU/100 mL and total coliforms ranged from 15.5 and 19.8 CFU/100 mL, both exceeded recommended thresholds. The likely sources of the microbial contamination were identified as fecal matter from birds, rodents and reptiles accessing the catchment areas as stated by other studies. These findings highlight the needs for appropriate treatment such as disinfecting prior to the consumption of harvested rainwater, regular monitoring and maintenance of harvesting and storage systems are recommended to ensure the microbial safety and overall quality of rainwater used for domestic purposes.