Clean water solutions for low- and middle-income countries don’t have to be expensive, but they have to be available. The statistics are sad: 1.7 billion people use a drinking water source contaminated with feces, and more than 500,000 people die of waterborne disease each year, most of them younger than 5 years old.
Clean water straight from the tap is as good as it gets. But until everyone has gold-standard infrastructure, there are lower cost solutions available. Boiling water over a wood fire is one of the most widely used methods in low- and middle-income countries, but it is also a health hazard for those working in poorly ventilated kitchens. Cooking fires also exacerbate deforestation. Instead, we’ve rounded up ten low-cost technologies to treat water, and not one requires boiling. Most of these are for household use, but a few are for community-wide treatment.
Do you know of other methods? Please let us know in a comment below.
Ceramic Filters
A filter maker presses clay in a hydraulic press in Indonesia. Photo courtesy of Pelita Indonesia
Clay, sawdust and a plastic bucket can make a water filter that catches dirt and disease-causing microbes. In the classic design, mix clay with a combustible material like sawdust or rice husks, give it a flower pot shape and fire it in a kiln. The sawdust or rice husks burn away, leaving tiny pores in the ceramic through which water filters.
Potters for Peace promotes an open source system called CT Filtron, distributed in Ghana, that treats water with silver-enhanced ceramic filtration. CT Filtron is one of 25 ceramic filters archived for comparison in our Solutions Library.
Bamboo Charcoal
In this spin on the charcoal filter, a team of E4C members in Bangalore propose a filter made of locally available materials including charred bamboo, gravel and natural adsorbents. “The process we propose is indigenous, eco-friendly, low cost and entails minimum maintenance,” the team wrote in a message to E4C. They estimate that their filter can handle 30 liters of water per hour, and it would be affordable for average households in the region.
Solar Disinfection (SODIS)
Clear PET plastic bottles of water disinfect in the sunlight in a community in Indonesia. SODIS Eawag (CC by 3.0)
If cost is a bigger concern than time or convenience, the cheapest way to treat water is to leave it in a plastic bottle in the sunlight. Leave clear bottles in the sun for a few hours and UV radiation and heat kills the microbes that cause diarrhea and other waterborne illness. The Sodis (for solar disinfection) method was deployed in some parts of Haiti after the earthquake in 2010, and it is used in emergencies and impoverished regions worldwide.
“It is the combined effect of UV irradiation and high temperature that leads to antimicrobial action,” according to a paper published in 2020 in the journal ACS Catalysis.
WADI Solar Disinfection Indicator
Solar disinfection is one of the cheapest ways to kill microbes in water, but it is possible to make mistakes. Clouds, shade and the placement of the bottles and the murkiness of the water can change the amount of time needed to disinfect. To take solar disinfection to the next level and remove the guesswork, try WADI. WADI, by Helioz, is a device that measures solar radiation levels to indicate when the water is sterilized. Just look for the happy smiley face on WADI’s display.
Yet there may be room for competing designs in this category: we came across this prototype of a solar indicator at IEEE’s Global Humanitarian Technology Conference in Seattle, Washington (USA).
Portable Solar Distiller
Not to be confused with solar sterilization or disinfection, solar distillation purifies even muddy, salty or otherwise undrinkable water through evaporation and condensation. Thepower ofdistillation to purify saltwater makes it unique among the treatment methods featured on this page.
A solar still can actually be a cheap and simple piece of shaped plastic or glass, or they can be more highly designed devices such as Henry Glogau’s award-winning portable solar distiller featured in the video above. “The portable design merges local resource production with community architecture, providing freshwater and a shaded gathering place,” according to the video’s description.
To work, the still places water contaminated with salt or other impurities in direct sunlight where it heats and evaporates. The water vapor is trapped and condenses into droplets that run off into a container. This simple process takes huge amounts of energy, which is why solar stills can make more sense than stills powered by other fuels.
For another take on the solar still, see the Eliodomestico terracota household still in our Solutions Library.
Bicycle-Powered Water Filter
Bicycles in all their glorious versatility and simplicity are a favorite at E4C, and we were pleased to find a small but thriving supply of bicycle water filter videos, including this one by mechanical engineering students at the University of Maine. The Clean Water Team developed the bike-powered filter, and their project page describes the build, including a bill of materials.
For more bicycle action, see our list of ten things you can do with a bicycle.
Emergency Homemade Filter
The plastic bottle makes yet another appearance as a water treatment device, this time as a simple filter that can remove sediment and even disease-causing microbes. Simply cut the bottom from the bottle, fill it with layers of gravel, sand cloth and charcoal, filter the water through it and hope for the best.
Slow Sand Filtration
Slow sand filtration has the advantage of working on an entire community’s water source, not just individual households. West Virginia University offers a technical brief on slow sand filtration systems, including a design summary.
A slow sand filtration system is a combination of several parts: water storage tanks, an aerator, pre-filters, sand filters, disinfection stages, and filtered water storage tanks. The number of filters and filter types that are used in a given slow sand filtration system will depend on the quality of the source water and will be different for each community.
WATA Sodium Hypochlorite System
Chlorine is one of the most versatile and effective clean water solutions in LMICs and everywhere else. Chlorine can work in a community water supply to kill microbes before it enters people’s jerry cans or home water supplies. And it keeps the water safe from new contaminations long after it is added.
Community-wide water treatment with chlorine is now possible using only water, salt, electricity and a portable device called WATA. The system converts a measure of salt and water into sodium hypochlorite (bleach) by the process of electrolysis, passing an electric current through the saline soluiton. Designed by the Antenna Foundation in Geneva, Switzerland, WATA produces enough chlorine in two hours to treat 2,500 liters of water. The product has been tested for more than 10 years, it is commercially available and comes in five sizes depending upon the quantity of active chlorine desired (from 0.5 liters to 60 liters).
Aguaclara Reach Water Treatment Plant
TheAguaClara Reach Full Scale Plant is a compact gravity-fed water treatment system that uses a five-step process to treat and filter water. The system adds a coagulant to the water to settle out sediment and other particles, then runs the water through a sand filter and adds chlorine before storing it.
This community treatment plant can serve 1,000 to 50,000 people.
E4C’s Solutions Library
Please see E4C’s Solutions Library for more clean water solutions suitable for communities in low- and middle-income countries. In our database you can view standardized information about hundreds of products and compare similar technologies side by side.
