The Stone prize: innovative approaches to sustainable water purification and supply

By Trupthi Basavaraj and Rachel Findlay,
New Philanthropy Capital

When confronted by the sheer scale of the issues facing the water sector in developing countries, it is hard not to feel a little bit powerless. Globally, 780 million people, amounting to 11% of the world’s population, use unsafe drinking water or have no water source at all, and it has become increasingly apparent that more traditional models of water delivery are not always the most viable solution. It is estimated, for example, that 40% of the pumps built in Africa are broken at any given point, and each pump can take up to a month to be repaired.

For the Stone Family Foundation, the answer is to identify and support water initiatives that harness the power of the private sector, as these have the potential to create and sustain impact. To this end, the Foundation established the £100,000 Stone Prize for Innovation and Entrepreneurship in Water, administered by NPC. After an 8 month process to create a shortlist from a pool of 179 applications across 39 countries, the Foundation recently announced its Prize winner: Dispensers for Safe Water (DSW) for its innovative Chlorine Dispenser System. The dispenser is filled with dilute chlorine and placed near a communal water source, allowing individuals to treat their water free of cost with the correct dose of chlorine.

This simple, low-cost solutiong has already reached approximately 424,000 people across 800 villages in Kenya. Thirty months after dispenser installation, 55-60% of household drinking water samples in these communities tested positive for chlorine. At scale, the chlorine dispensers would cost less than US$0.50 per person per year, including both hardware costs and recurring costs of chlorine refills, dispenser management and maintenance.

But what makes this initiative truly exciting is its financial model. Having found that people are unwilling to pay for chlorine, DSW has devised two innovative ways for generating revenue. The first is selling carbon credits generated through the dispensers by reducing the demand for boiling water using firewood. The second is to bundle the dispenser as part of wider package of agricultural goods sold by its partner, One Acre Fund. If successful, both models offer new and exciting ways of making water purification accessible and sustainable for low-income communities. It will also allow DSW to expand the Kenya Chlorine Dispenser System program.

The Foundation also found four other initiatives that it hopes to support outside the Prize framework, for example, through social investment or smaller grants to further test aspects of the initiative. These are:

  • Spring Health—rural water kiosks, India: Spring Health is a social enterprise that uses low-cost electro-chlorination technology to purify water. It partners with village kiosks and installs 3,000 litre cement tanks next to each shop, which the shopkeeper then fills from his well. Local staff visit each village by motorcycle every three days to purify the water and the shopkeeper sells it for Rs.2 (about US$0.04) per 10 litre jerry can, or provides a home delivery service.
  • Aquaya Institute—Water Business Kits, Kenya: Aquaya is looking to catalyse a market of independent small-scale businesses to purify and sell clean water. To do this, it has developed a ‘Water Business Kit’ for Kenya, that provides entrepreneurs with a detailed business plan describing all the steps and requirements necessary to open and operate a water treatment business—including advice on hardware selection and sourcing, financing, regulatory compliance and marketing.
  • Next Drop—information on piped water supply, India: Next Drop tackles the lack of information available to consumers and water utilities on the performance of piped water systems. In most Indian cities, piped water supply is only sporadically available, leaving consumers waiting for hours for water. For Rs.10 (US$0.2) a month, Next Drop texts customers 30-60 minutes before water becomes available. Water utility engineers can also use Next Drop’s software to record the status of different valves and identify issues in water supply. In the long term, it hopes to work with the water utility to improve the overall quality and level of service delivery.
  • Population Services International (PSI)—Sanosil Water Disinfectant, Myanmar: PSI has introduced Sanosil, a new tasteless and odourless water disinfectant, as a substitute for chlorine, which had proved unpopular with households in Myanmar. Sanosil is sold to water vendors who use it to purify their water, which they will then sell on for a small premium to peri-urban and urban households—potentially increasing their monthly income by 30%. PSI is planning to develop a brand for the Sanosil-treated water as well as different marketing materials and strategies—the direct sale of Sanosil to vendors will then be franchised out to local entrepreneurs or water vendor cooperatives.

We are excited about these initiatives but also recognise the limitations and risks involved in supporting innovative and entrepreneurial approaches. Actors working in this area not only need to develop a sustainable business model but have to create a new market. We feel this holds promise to really start addressing the needs of the millions without access to clean water.




Author: RWSN Secretariat

RWSN is a global network of rural water supply professionals. Visit to find out more

One thought on “The Stone prize: innovative approaches to sustainable water purification and supply”

  1. thanks for sharing us your knowledge. we really need to have a good water purification system now that millions of people are dying from different diseases they acquired from drinking unfiltered water

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