From drops to drums Assessing rainwater storage's quality and quantity for addressing water demands in dry periods – A case study from Arusha Tanzania

Sustainable Development Goal 6 highlight the importance of providing reliable, affordable, and safe source of clean drinking water and sanitation for all by 2030. In Tanzania there is a dire need of a water supply strategy due to high levels of natural fluoride contamination in ground water (upto 74 mg/L) and the challenge of meeting water demand during 5 months long dry period. This study assesses social and technical feasibility of implementing rainwater harvesting (RWH) along with treatment technologies that includes Denutritor® to remove ammonia/pesticides and ultrafiltration to eliminate carbon. This integrated technology known as “Mbinguni Maji” is aimed for the long-term water storage to supply drinking water throughout the dry season. The methodology involves i) Assessing the technical feasibility of RWH using database from QGIS and Water Productivity Open-access portal (WaPOR) from the Food and Agricultural Organization of the United Nations; ii) conducting pilot demonstration in 5 different locations in Tanzania; and iii) conducting socio-economic survey for social acceptance of the technology through detailed questionnaires administered to residential homes, medical facilities, schools, hotels, and water kiosk owner. The result indicates that, from technical perspective, there is ample rainfall (average of 1036 mm/year) to supply water throughout the dry season, primarily for drinking and cooking purpose only (upto a maximum of 10 lpcd). The pilot demonstration confirms that the Mbinguni Maji RWH technology produce water that meets WHO water quality standards. The produced water is free from nutrients like carbon and ammonia, ensuring the possibility of long-term storage without bacterial and algal growth. Furthermore, Lab scale demonstration of Denutritor® show promising result of removing nitrite, ammonia even at high elevated temperature (30 °C), which can be effectively applied in Tanzania. In terms of social acceptance, RWH technology is already widely practised in Tanzania during the rainy season. However, the initial investment costs and operation & maintenance (O&M) concerns hinder the usage of RWH technology. Therefore, to ensure the long-term sustainability of RWH technologies, there is a need of development of comprehensive business plan and community awareness campaign.