In Nyeri County, Kenya, a team of Dutch and Kenyan partners is testing a water technology innovation that could transform local fish farming. Supported by Partners for Water, the Affordable Recirculating Aquaculture System pilot project (A-RAS-2) is led by the Food Systems and Poverty Alleviation (FOSPA) Foundation in Africa, in collaboration with FOSPA-Kenya and Systemic Consultancy. The project addresses Kenya’s severe protein deficit and the recurring challenges of drought. Project leads Katrine Soma and Charles Mbauni share how it works.

A systems approach

At its core, A-RAS-2 offers small-scale fish farmers a water-efficient, nutrient-reusing, solar-powered alternative to traditional ponds. The pilot project aims to demonstrate that these systems can produce up to 25 times more fish while using only 2–5 percent of the water required in conventional ponds and providing manure for the farmer’s mixed farming systems.

But A-RAS- 2 is more than just a new water technology, it adopts a systems approach built on a deep understanding of the local food system and its interlinked challenges. Beyond addressing farmer’s needs, the project strengthens multiple links in the chain. It stimulates local entrepreneurship in producing technology components and fish marketing and improves consumers access to affordable, nutritious food. On a wider scale, it contributes to climate-neutral, resource-efficient food production with the potential to save over 216 million cubic metres of water per year across Kenya.

From research to practice

For nearly a decade, social scientist Katrine Soma has studied Kenya’s food systems with a particular focus on fish. She works at Wageningen Social and Economic Research and is the chair and founder of the FOSPA-Africa Foundation in the Netherlands. Working closely alongside her is Charles Mbauni, chairman of the Nyeri Fish Farmers Cooperative Society and co-founder and chair of FOSPA-Kenya.

“I have worked in Kenya since 2018, researching bottlenecks in the fish food system,” explains Soma. “Through FOSPA-Africa, Charles and I combine research and implementation hand in hand.”

Mbauni adds: “As chairman of the cooperative, I saw first-hand the challenges in water use, fish growth and costly technology. That is how the idea of an affordable recirculating aquaculture system was born.”

Transforming challenges into innovations

“Kenya, like much of the Horn of Africa, faces chronic food insecurity, mostly driven by climate change and recurring droughts,” says Mbauni. “Protein is in particularly short supply. When drought strikes, traditional sources such as beef and sheep are no longer sustainable due to their high water footprint.”

Recognizing this, the government launched the ‘Eat More Fish’ campaign to promote fish consumption,” explains Soma. Mbauni adds: “Demand for fish is high and far exceeds local production. In fact, 70 per cent of fish consumed in Kenya is imported.”

Against this backdrop, A-RAS offers a breakthrough. “Traditional ponds are about 300m2 and stock no more than five fish per cubic metre, producing around 280 kilograms per pond,” notes Mbauni. “By contrast, A-RAS can reach densities of nearly 200 fish per cubic metre, producing more than 7,000 kilograms in the same space.”

“This is an enormous difference,” says Soma. “It means more fish, more protein, and at the same time we release land and water for other purposes”.

Practical, affordable and circular water technology

The technology is both innovative and pragmatic. “Recirculating aquaculture systems are usually expensive,” says Soma. “We focused on affordability – using local materials, cheaper or second-hand parts and high quality components where essential.” The result is a mix of simple tanks and advanced yet affordable water management.

“The tanks are made locally and in a simple yet durable manner,” explains Mbauni. “At the same time, the air and water pumps are high quality and supplied by Dutch entrepreneurs.” A settling tank filters solid waste, which is reused as fertiliser. A nitrification tank with microorganism removes nitrogen. Different oxygenation technologies are being tested, including nano and microbubbles.

Mbauni continuous: “Each system has six tanks with fish at different growth stages, allowing farmers to maintain a steady income throughout the year. This enables them to reinvest in quality feed essential for water and fish health.”

Soma concludes: “In the end, it is high-tech translated into practical, affordable solutions. And because the system runs on solar energy for water recirculation, it is climate neutral,”

Consortium and partners

The pilot project builds on a feasibility study carried out by FOSPA-Africa together with AquaFarmingConsult and Wageningen University & Research, supported by Partners for Water.

In this second phase, the consortium consists of FOSPA-Africa, FOSPA-Kenya and Systemic Consultancy. FOSPA-Africa brings together research, implementation and technical and financial expertise to refine the water technology and develop accessible business models for scaling.

Engaging stakeholders

From the start, farmers have been at the heart of the project. Mbauni represents a cooperative of around 1,000 fish farmers whose feedback informs every stage of the process. To ensure diversity, five farmers were involved in both the feasibility study and the pilot, among them women, young farmers and a disabled farmer.

“Working with the cooperative means we know immediately what works and what doesn’t,” says Soma. “Farmers tell us: this is a good idea, that is not. This direct communication saves time and ensures solutions are truly practical and acceptable.”

This bottom-up approach goes beyond farmers. In Kibera, Nairobi’s largest informal settlement, local leaders, consumers and women vendors co-created solutions for fish distribution. “Our solution is not an external, foreign thing,” says Mbauni. “It’s embedded in the community, where people trust and support each other.”

Next steps

To advance the project, the consortium has built a new A-RAS-2 facility in Nyeri County. “This enables gathering of reliable data and refining oxygenation technologies, with the first results expected next year,” says Soma.

On this basis, the project aims to scale up across Kenya, moving from fish production to a complete food system with feed, fingerlings, processing and training hubs. “We’re developing financing models to make the systems accessible for small-scale farmers,” notes Mbauni. “The long-term goal is to turn proven pilots into a nationwide movement, with potential expansion to neighbouring countries such as Uganda and Ethiopia.”

Innovation in progress series

The Partners for Water 5 programme (2022 – 2027) follows several projects that received the Partners for Water subsidy from start to finish. Over the next few years, these projects will take you on their journey of testing the feasibility or application of innovative solutions to enhance water safety and water security abroad. You’ll be able to gain insights into their processes, collaborations with local partners and their potential solutions; as well as their struggles, challenges and their lessons learned. Discover all projects. 

In Kenya, 12.8 million people suffer from excessive fluoride exposure due to contaminated drinking water. This leads to health issues like bone deformation and discoloured teeth, as well as reduced job prospects. Now, for the first time, a consortium of four organisations has developed a unique, low-cost household filter that removes both bacteria and fluoride, without using electricity or wastewater. Funded by Partners for Water, this innovation seems to be a game changer. Nazava Water Filters’ Lieselotte Heederik and Marleen Ophorst explain more.

“Empowering households by giving them the opportunity to take control of their own water quality is the mission of Nazava Water Filters” explains Heederik, the organisation’s co-founder. Pursuing this goal, the consortium (consisting of Resilience BV, Nazava Water Filters Ltd, Harbauer Limited, and Delft University of Technology) has developed an innovative filter. It combines Nazava’s proven ceramic technology for removing bacteria with HAPaqua’s fluoride-absorbing unit, based on hydroxyapatite. Ophorst, Nazava Water Filters’ Project Manager, adds: “We believe in decentralised solutions that make safe drinking water – free from bacteria and fluoride – accessible to households in areas where that is far from guaranteed.”

Social enterprise with a mission

“Nazava is a for-profit social enterprise that has deliberately chosen a commercial model to deliver a social mission,” explains Heederik. “We believe this contributes to product sustainability and customer satisfaction. If our product doesn’t work, our customers will tell us. And if they don’t want it, they won’t buy it. The market keeps us accountable for quality and relevance.”

“Simultaneously, we are driven by a sense of justice,” Ophorst shares. “This combination makes us quite unique. There are very few companies in the water sector that combine a social mission with a commercial approach while focusing specifically on household-level solutions.”

Collaboration is key

According to Ophorst, the collaboration between the four partners runs smoothly: “Each organisation brings its own expertise. We all have a clear role and learn a lot from each other.” TU Delft contributes academic research, Harbauer brings fluoride removal expertise, and Resilience drives the project and oversees management. “We are truly complementary,” confirms Heederik. “That’s what makes the partnership strong.”

Why not reverse osmosis?

“Traditionally, fluoride contamination in drinking water is treated through reverse osmosis. But this isn’t a sustainable solution,” shares Heederik. “It’s expensive, energy-intensive, and produces wastewater.” The consortium’s solution is a true game changer. “Our filter works by gravity, completely without electricity,” says Ophorst. “That makes it much more accessible for both urban and rural households, but also allows NGOs working on water security to reach far more people, simply by reducing costs.”

Users at the centre

A major pillar of the project is involving end users. “For one month we tested our product among 50 households in Nakuru” says Ophorst. “Each week we asked them for honest feedback: ‘Don’t tell us what you think we want to hear, tell us what you really think.’” That open approach paid off. “Users even helped us think through improvements for rural communities lacking basic infrastructure and they also referred new customers who would benefit from this solution.”

“We remain in touch with our 50 first users,” Ophorst continues. “We’re still monitoring long-term performance; the amount of fluoride the filter continues to remove depends on the original water quality and how much is filtered.”

High demand and future prospects

Heederik and Ophorst have presented the project at various international conferences, including World Water Week in Stockholm and the World Water Forum in Bali, as well as events in Kenya. “At every conference, we’re reminded just how high the demand is for a sustainable bacteria and fluoride filter,” says Heederik. “We even received a call from a representative of the Nairobi dental association, showing interest in our product. That really confirms the scale of the problem.”

“People are recommending the filter to friends and family, and demand is growing,” says Ophorst. “This makes me incredibly proud of what we’ve achieved over the past year and of the whole team involved.”

A game changer in the making

Although the product is still in the testing phase, early signs are promising. “We have a solution that is scalable, sustainable, and truly meets people’s needs,” says Ophorst. “People are already calling to ask: ‘Is it available yet?’” The consortium has submitted a new funding application to test the filter with users from diverse socio-economic backgrounds.

Heederik concludes with a clear invitation: “We’re actively looking for financial, technical, and operational partners who want to help bring this game changer forward. So we can bring the smiles back to the faces of children in Kenya.”

“Too much fluoride in water can cause brown teeth and other health issues. In Kenya’s Rift Valley, people live with that reality every day.” Begüm Tanis and Guus Wiersma from TU Delft explain how they are working on a practical water solution to provide safe drinking water: a household water filter designed to tackle both excess fluoride and bacterial contamination. Supported by the Partners for Water programme, the project aims to improve water security while reducing costs and plastic waste.

Wiersma, project coordinator, and Tanis, assistant professor, both work at TU Delft’s Water Management Department. They are part of a consortium comprising Harbauer Limited, Resilience BV, Nazava Water Filters Ltd., and Delft University of Technology. Their shared goal? Safe, affordable drinking water—without the environmental cost.

Synergising proven water solutions

“The two components of the solution are both already existing technologies,” explains Wiersma. “We combined Nazava’s ceramic filter, which is highly effective at removing bacteria and viruses, with the HAPaqua system.” The latter is an adsorbent filter designed to reduce fluoride levels, using Hydroxyapatite as its base material.

Tanis adds: “The system operates with granular material through which the water flows, allowing the fluoride to bind to the granules. As the water passes through the filter, the fluoride is captured by the material, resulting in water with significantly reduced fluoride content.”

Addressing a critical health concern

The project targets Kenya’s Rift Valley, where naturally occurring fluoride in the groundwater often exceeds safe levels. “Most people in the region are aware that consuming too much fluoride can lead to health problems, such as brown or mottled teeth—also known as dental fluorosis,” explains Wiersma.
Tanis adds: “In the past, many residents relied on bone char (charcoal made from animal bones) to filter out fluoride. But this method has several drawbacks, including health concerns, inconsistent quality, and limited filtration capacity.”

“The impact on the daily lives of users will be significant,” says Wiersma. He shares that the initial response from the communities has been very open and positive.

Benefits beyond clean water

The filter can be used with various water sources, including rainwater, groundwater, and even surface water. However, the impact of this innovation goes beyond simply providing safe drinking water. “Currently, people buy bottled water when they can afford it. But with the Nazava filter, you can treat up to 7,000 litres of water,” Tanis explains. “That’s quite a lot.” “This saves households money by reducing the need to purchase expensive bottled water, but also significantly cuts down on plastic waste,” adds Wiersma.

Testing in real conditions

Rather than conducting tests in the Netherlands using artificially contaminated water, the team set up a laboratory in Nakuru, Kenya, to test the filters with naturally fluoridated water. “By testing on location, you get the most accurate results, because you’re using the actual water the filters are designed to treat,” explains Tanis.

The team collected water from two different boreholes, each with distinct fluoride concentrations. “We continuously used water from the same sources for each test, ensuring that the fluoride concentration in the inflow remained relatively constant,” Tanis adds. “This allowed us to reliably compare the performance of the filters under consistent conditions.”

The team also collaborated with Egerton University in Nakuru, where a local student joined the project as an intern. In addition, an undergraduate student from TU Delft spent several months in Kenya working with the prototypes and conducting water quality testing.

“It’s a great opportunity for students to work on applied, real-world projects,” says Wiersma. “The students supported us in testing two different prototypes and also conducted additional tests to examine preferential flow,” adds Tanis. “The outcomes of both the students’ tests and our tests were promising, showing that the filters effectively removed fluoride.”

Royal recognition

During a state visit to Kenya, Queen Máxima of the Netherlands and the Minister for Foreign Trade and Development Reinette Klever, were also introduced to the water solution. “Queen Máxima’s response was very positive,” says Wiersma enthusiastically. “It was great to show them our prototype. The Queen’s interest could help raise awareness of the fluoride contamination issues in the Rift Valley.”

Looking ahead: scaling for wider impact

The team has applied for the next round of Partners for Water funding to continue testing and improving the solution before scaling up. “Initially, we’ll focus on Kenya,” says Tanis, “but the Rift Valley stretches from Ethiopia through Kenya and Tanzania all the way down to Mozambique. People face the same issue throughout the region, so if you have a solution that works, why not scale it up?” Wiersma concludes: “Ultimately, our goal is to provide access to safe drinking water for everyone, while simultaneously reducing the plastic burden on the environment.”