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What We Learned About Water Purification

According to the Centers for Disease Control and Prevention, 780 million people worldwide lack access to clean water — a harrowing figure. Thankfully, many nonprofits are at the vanguard of providing clean water to communities who otherwise lack access. The ImpactMatters team has been looking at a subset of these nonprofits, which provide water purification systems to extremely poor beneficiaries so they can get clean water. But what is the true impact of these water purification programs? Should donors be putting their limited dollars in these nonprofits’ hands? To answer these questions, we analyzed 11 nonprofits to start with, working across four continents, and learned a few interesting things in the process.

First, a little background on what we did. We calculated impact by estimating how much it cost each nonprofit to provide one person one year of clean water (known as a person-year). Our calculation is a function of several factors, including: the cost to install and monitor the water purification device, how effective the device is at purifying water, how long the device lasts, and how many people a device serves who otherwise would not have had access to clean water. [This is a simplification; for a detailed explanation, read our full methodology.] Then, we compared this cost to an estimated market value of water — i.e., what the beneficiaries would have had to pay for a year of clean water if it had not been provided by the nonprofit.1 If a nonprofit provides a person-year of clean water for less than 125 percent of the market rate, we consider it cost-effective (4 stars); if it provides clean water for less than 75 percent, we consider it highly cost-effective (5 stars).

All but one of the nonprofits we analyzed received a 5-star rating

What we learned

1. Not all water purifiers are created equal

We use the term “water purifier” broadly. In reality, some water purification technologies only physically filter out unwanted particles while others also chemically disinfect water to kill harmful microorganisms. In an ideal world, both filtration and disinfection would be provided to ensure water is always fit for drinking. However, all the nonprofits we analyzed focused on the filtration stage.

Different filter types have different lifespans and uptake rates. For example, certain hollow fiber membrane filters have been observed to last only one year in the field, as opposed to concrete biosand filters, which have been observed to last 10. The choice of filter type is one of the major factors that determine a nonprofit’s impact.

2. Providing water purification devices is often one piece of a larger effort to improve water and sanitation conditions

Nonprofits that provide water purifiers often engage in full water, sanitation, and hygiene (WASH) programs. As you can imagine, clean water is closely related to local sanitation infrastructure and hygiene practices, such as waste management and hand washing. 

3. Clean water goes beyond being an end in and of itself

Nonprofits whose goal is providing clean water often frame their message not just for water’s sake, but for the health benefits that come with access to clean water. The World Health Organization, for example, estimates that 1.4 million child deaths due to diarrhea could be averted with safe water. Water is also directly linked to gender equality; in communities without immediate access to clean water, it is often women and girls who make the miles-long journey to the nearest (often still unclean) water source.

What we need to learn

1. How much does water cost?

We weren’t able to find hard data on the market value of water in the countries where these filters are provided. For the purpose of benchmarking cost-effectiveness, we estimated market costs by applying a standard markup to provider costs — you can see a full explanation of our reasoning here — but actual data on what beneficiaries would otherwise have to pay for water remains unknown. 

2. What pieces are missing from our picture of the field?

When nonprofits run full WASH programs, they often don’t report their data in a disaggregated enough way that would allow us to calculate impact on an isolated outcome like person-years of clean water (much less a group of outcomes covering the WASH spectrum). Maybe this skews our picture of the field in some way — perhaps programs that are integrated into full WASH agendas enjoy benefits of scale, and we’re actually underestimating the field as a whole by not having data on those programs. 

We also have a broader data collection problem that goes beyond the presence of WASH programs. We were only able to analyze eight nonprofits at this time — we eventually want to do more, but right now the data just aren’t there. This could be clouding our view of the field as well. Maybe nonprofits who report data are more effective than those who don’t. 

3. What are the long-term impacts?

A successful clean water program relies as much on behavior change as it does on purification technology. Water purifiers are fundamentally a user-facing product, and so their efficacy is going to depend on the user, the local culture and pre-existing norms around water. While we have good research on things like the efficacy and uptake rates of certain purifiers, we don’t have as good an estimate of how this changes communities in the long term. How do these water purifiers move a community toward truly sustainable access to clean water?

1We realize that without the nonprofit, most beneficiaries would not actually be buying a year of clean water — that’s captured in our estimate of the counterfactual. The point of the benchmark is instead to compare nonprofit costs to hypothetical market alternatives. See here for a full discussion of how we benchmark cost-effectiveness.