Sustainable Greywater Treatment and Reuse for Irrigation in Rural Tanzania - A Case Study of Tumaini Open School

Abstract

Climate change is expected to intensify water scarcity and increase pressure on water and food security, highlighting the need for alternative water sources for agricultural irrigation. Tumaini Open School in Tabora, Tanzania, experiences water scarcity and unreliable water supply, while greywater is currently discharged directly into the envi ronment. This project investigated the potential for treating and reusing greywater for irrigation at the school through a system adapted to the local context. The total weekly greywater generation was estimated to be 6000 L/week in Area I (student area) and 3400 L/week in Area III (staff area) based on questionnaires and volumetric measurements. Laundry and shower greywater contributed the largest share of the total greywater generation. Water quality assessment showed that laundry grey water was the most contaminated source in both areas particularly with respect to tur bidity and electrical conductivity (EC). A prototype was constructed and operated for 15 consecutive days in order to evaluate the feasibility of a sand filter in terms of treat ment performance. The prototype reduced average turbidity of kitchen greywater from 261 to 19 FNU, indicating effective removal of suspended particles. However, EC in creased from 494 to 796 µS/cm after treatment, suggesting that dissolved salts were not removed by the filter. A social acceptance questionnaire indicated positive attitudes towards greywater reuse, especially with sufficient information and training prior to implementation. Based on the results from the volumetric measurements, prototype performance and water quality assessment, a treatment system was proposed. A septic tank followed by an intermittent sand filter (ISF) was dimensioned for Area I and Area III. The treat ment system was estimated to provide sufficient treatment with regards to E. coli and human health risks based on quantitative microbial risk assessment (QMRA). Overall, the study indicates that greywater reuse has the potential to completely replace munic ipal water for irrigation during the wet season and reduce municipal water demand by approximately 85% during the dry season.