£120,000 Flush Forward Challenge launches to test off-grid sanitation in UK

Challenge Works has launched a new UK programme to investigate whether off-grid sanitation technologies could reduce sewage pollution, nutrient contamination and drinking water use. The Gates Foundation-funded Flush Forward Challenge will provide up to £120,000 to organisations exploring alternatives to conventional non-sewered sanitation. Up to three organisations will receive £40,000 each to undertake six months of research and planning focused on local sanitation challenges. The programme will specifically investigate the potential for Reinvented Toilet technologies, which can process human waste without connections to mains water, sewers or mains electricity.

One million UK homes remain off the sewer network

Challenge Works estimates that around one million UK homes are not connected to mains sewers and instead rely on septic tanks, cesspits or small sewage treatment plants. Septic tanks provide primary treatment, with surrounding ground responsible for much of the remaining treatment process. Outputs can still contain pathogens and nutrients including nitrogen and phosphorus, which can enter the surrounding environment. Challenge Works estimates that with septic tanks typically lasting between 20 and 40 years, around 25,000 to 50,000 systems could require replacement each year. The Flush Forward Challenge will examine whether newer non-sewered technologies could provide an alternative as existing systems reach the end of their operational lives.

Reinvented Toilet technology targets off-grid treatment

Reinvented Toilet technologies are designed to treat toilet waste without requiring connections to conventional sewer networks, piped water or mains electricity. Despite the name, the technologies generally focus on waste treatment rather than simply redesigning the toilet itself. Systems range from compact treatment equipment incorporated into individual bathrooms to larger waste-processing installations that could potentially replace septic tanks. Some are covered by ISO 30500, the international standard for non-sewered sanitation systems. The technologies are designed to remove pathogens and environmental contaminants while recovering water and, depending on the system, resources including nitrogen, phosphorus or biochar.

Challenge targets sewage pollution and water consumption

The programme is being launched against the backdrop of continuing pressure on UK water and wastewater infrastructure. According to figures cited by Challenge Works, England and Wales recorded 386,466 wastewater discharge events during 2025, lasting a combined 2.65 million hours. Nitrogen and phosphorus in sewage can contribute to eutrophication when they enter waterways. Excessive nutrient concentrations encourage algal growth, which can reduce dissolved oxygen and damage aquatic ecosystems. Water consumption is another focus for the programme. Challenge Works estimates that more than 2.4 billion litres of drinking water are used for toilet flushing in the UK every day, creating an opportunity for sanitation technologies that require significantly less water.

£40,000 available for each successful organisation

Up to three organisations will each receive £40,000 to fund six months of staff support, alongside systems-thinking training, mentoring and regional analysis. Participants will investigate non-sewered sanitation challenges in their areas and bring together stakeholders to identify potential interventions. The programme is seeking applications from organisations directly dealing with the environmental or social impacts of non-sewered sanitation. Potential participants include councils, environmental organisations, river trusts, national parks and small water companies operating as New Appointments and Variations (NAVs). Challenge Works is particularly interested in regions with significant nitrogen or phosphorus problems combined with a high prevalence of septic tanks or other alternative sanitation systems.

Challenge Works seeks evidence for UK deployment

Catherine Duncan, Senior Programme Manager at Challenge Works, said the programme would allow organisations experiencing these problems directly to investigate whether newer technologies could provide viable alternatives.

“Septic tanks and municipal sewers are 19th century inventions that are not meeting the expectations of people or the needs of the environment. “Organisations working in areas affected by non-sewered sanitation understand the pressures facing their environments and communities better than anyone. Through the Flush Forward Challenge, we want to give these problem owners the funding, evidence and practical support they need to explore whether a new generation of non-sewered sanitation technologies could offer a better way forward.”

Duncan said the programme would also help identify the UK locations and circumstances in which off-grid treatment could provide the greatest benefits.

“Reinvented Toilet technologies have the potential to treat waste safely without relying on water, sewer or mains power connections. By working with organisations that manage issues first-hand, we can build a clearer picture of where the technologies could make a meaningful difference in the UK.”

Potential role in housing and nutrient neutrality

Beyond replacing existing septic tanks, the programme will investigate whether non-sewered treatment could support development in locations constrained by sewer capacity or nutrient neutrality requirements. Treating waste locally could potentially reduce the amount of nitrogen and phosphorus entering sensitive catchments. Participants will assess Reinvented Toilet systems alongside other potential interventions, including technologies accredited under ISO 30500. The objective is to produce an evidence-led assessment of how different approaches could address specific regional sanitation problems rather than prescribing a single technology.

UK could provide testing ground for wider adoption

The programme will also examine whether deployment in mature markets such as the UK could help establish confidence in Reinvented Toilet technologies. Challenge Works argues that established regulatory systems and markets could provide an environment in which technologies can demonstrate their performance and develop commercially. Successful adoption could ultimately help reduce production costs and support deployment in countries where access to conventional sanitation infrastructure remains limited. According to UNICEF figures cited by the programme, around 3.4 billion people globally lack access to safe sanitation. The Flush Forward Challenge builds on the Reinvent the Toilet Challenge launched by the Gates Foundation in 2011. It is being delivered by Challenge Works in partnership with Bluechain Consulting and Cranfield University.

Applications open until December 2026

Entries opened on 5 October 2026 and will close at 12 noon GMT on 16 December 2026. Successful organisations will receive funding and technical support to investigate their regional sanitation challenges and develop potential pathways for deploying new treatment technologies. Further information and application details are available through the Flush Forward Challenge website.