Gravity-Driven Membranes, a Potential Option for Community-level Drinking Water Treatment

In the urgency to achieve the targets under SDG 6, technologies that work in specific contexts will need to be implemented and scaled up. One such technology is the GDM (Gravity-Driven Membrane). GDM offers a potential solution for providing clean water in low-resource settings. It utilises gravity to drive water through membrane filters to treat contaminated water sources, making them safer for consumption. This innovative approach addresses the dual challenges of water quality and accessibility, particularly in areas where traditional water treatment methods may be unfeasible due to high turbidity (water that is cloudy, opaque, or thick with suspended matter). 

A notable example of GDM technology in action exists in Uganda's Busia and Namayingo districts. Here, many households rely on Lake Victoria as their primary water source, despite the high contamination levels that made the water unsafe for consumption previously. Groundwater sources, which could provoide an alternative, are too saline for consumption. Families therefore frequently used untreated lake water, putting themselves at risk from pathogens such as E. coli from fecal matter, which cause diarrheal diseases.

In response to these challenges, the Swiss Federal Institute of Aquatic Science and Technology, Eawag, in collaboration with Water School Uganda, Africa Water Solutions and Get Water Uganda, installed GDM systems at five water kiosks, primarily serving local primary schools and nearby communities. Each kiosk featured a GDM setup designed to treat lake water, effectively reducing turbidity and organic contamination in a single process. With an 80 m² membrane surface and a 10 m³ tank capacity, the system reliably produces 6-8 m³ of treated water daily, meeting the needs of approximately 70 households since almost a decade.
Access to clean water was improved through the distribution of treated water at the kiosks, where users filled 20-liter jerrycans. Water ATMs were also introduced, allowing for 24-hour access using NFC tokens, enhancing convenience and transparency in cash flow.

To ensure sustainability, a community-centred management model was implemented. A locally elected committee manages operations, monitors revenue, and handles minor maintenance, supported by local NGOs and school staff who incorporate WASH education into their curriculum. Water pricing is set to cover basic operational costs without overburdening the community.

This case study illustrates the potential of GDM technology in providing reliable and safe water access, showcasing its potential to transform water supply in resource-limited environments. Despite the potential of GDM, it is important to note that it does not remove geogenic contamination (Fluoride or Arsenic), chemical contamination (pesticides, industrial chemicals, cyanobacterial toxins) or salinity from the water. These needs other specializes means to treat. Eawag has developed a manual that explains implementation and management of GDM in details that can be downloaded here, and a series of videos that can be watched here.