Clean water is the foundation of health.

Our water program provides sustainable access to clean drinking water sources that serve as the cornerstone of the community’s health.


Eradicating Contaminated Drinking Water

Biological contaminants are the main threat to drinking water sources in the Andes, with springs, streams, and lakes containing fecal coliform bacteria, parasites, and other harmful pathogens. A central part of our mission involves helping combat this pervasive health risk by producing and installing biosand water filters for use in the remote homes and schools of the Andes. Community-scale water filtration systems are much less successful in these types of communities because they rely on chlorination systems and large-scale infrastructure, both of which require significant ongoing maintenance and financial support. Even when implemented successfully, these solutions are less than suitable because chlorination at normal dilution rates does not eradicate dangerous parasites like Giardia and Cryptosporidium. By contrast, biosand filters eliminate almost all bacteria, viruses, and parasites.

The Biosand Filter

Initially designed in the 1990s by Dr. David Manz of the University of Calgary, biosand water filters have been promoted since 2001 by the Centre for Affordable Water and Sanitation Technology (CAWST) as an extremely effective method of converting water containing biological contaminants into safe drinking water. Through its comprehensive extension and training programs, CAWST has fostered adoption of this lifesaving technology in more than 55 countries. Inspired by this, we began our water treatment efforts by building and installing over 150 biosand filters in high Andean communities between 2008 and 2009. We soon realized, however, that the heavy concrete design of the CAWST biosand filter made it highly impractical for transportation to less accessible areas – the very areas that are often most in need of clean drinking water.

In 2011 DESEA Peru director Sandy Hart, with the help of volunteers Matt Hastie and Pat Teti, designed a biosand filter using 315-millimeter (12-inch) diameter PVC pipe, giving rise to a highly portable and equally efficient iteration to the original concrete filter. The new design and materials comply with the specifications of CAWST’s widely tested concrete filter and weigh in at a mere 10 kilograms (22 pounds). After initial development, DESEA Peru thoroughly tested the PVC model to confirm its performance as on par with its concrete predecessor. We’ve since installed filters in 570 Andean households and schools, and our PVC design has been trialed by other organizations throughout Peru as well as in Ecuador, Palestine, and Afghanistan.

Biosand Filter Manual


Water Treatment and Maintenance 

Total Installations


Program Purpose

To Eradicate Contaminated Water

How the Biosand Filter Works

The biosand water filtration system involves the slow percolation of water within a 90-centimeter (35-inch) tall container through a column of fine sand (with gravel drainage layers), including a biologically active layer at the sand surface. Based on in-house and independent studies, CAWST reports that biosand filters are able to remove high percentages of bacteria, viruses, and parasites (including Giardia, Cryptosporidium, other protozoa, and helminths). Our PVC water filter is capable of producing up to 15 liters of treated drinking water per hour and is designed to function effectively with minimal maintenance for over 30 years.

CAWST Biosand Filters Remove:


of bacteria


of viruses


of parasites

Maintenance and Usage

We build our PVC biosand filters in our workshop in Lamay, Peru, about a one-hour drive from Cusco. Filter recipients pay a nominal fee of $6 USD as a contribution to the purchase of materials and the construction of the filter. Recipients assist by transporting materials to their homes, washing the sand and gravel, and helping with the installation of their filter. All recipients also participate in training to ensure proper sanitation practices and filter maintenance. Our nurses monitor filter usage and maintenance along with community health workers (qhalis) for an initial evaluation period that eventually gives way to independent qhali supervision.

Empowering Through Teaching

In high Andean communities, water supply systems, where present, consist of concrete, spring-capture structures and piped, gravity-fed systems delivering water to outdoor basins. These systems tend to receive little to no maintenance, and after years of inattention borne of community members’ lack of relevant expertise, much of this infrastructure is in desperate need of cleaning and repair. We strive to remedy this situation by arming communities with the knowledge necessary to assume proper upkeep of existing water supply infrastructure.