Biosand household filters are a fairly recent invention, but have undergone extensive testing at the University of Calgary in Canada as well as in Haiti. The system is efficient and has proven itself so effective that the filter has become one of the most widely distributed devices for household water treatment in developing countries around the world, and the usage is continuing to spread. The filters were first used in Haiti in 1999 and their usage is spreading throughout the country as people become more aware of their effectiveness. There are currently over 8000 filters distributed throughout Haiti by various organizations.

The Biosand filter has gained recognition for various reasons. It is a simple design that uses basic materials that are readily available and inexpensive. The simplicity of design allows for easy production and ease of transport. There are no moving parts, it requires no electricity and only one square foot of space to sit on. The use is very simple to the point that even young children can use and understand the importance of the filter. With proper usage education and simple, regular maintenance a filter will last for an indefinite period of time. The filter is able to solve the problem of treating multiple water sources and because it removes all four types of pathogens – bacteria, protozoa, viruses and worms – the water can be used for drinking, bathing, cooking and other general household use. Two weeks after installation a Biosand filter will remove 98.9% of all bacteria present in the water, but upon installation testing has shown that the filter will remove all worms and protozoa, most viruses and a high percentage of bacteria which leads to an immediate improvement in water quality.

How does it work? (courtisy of CAWST)

1. Water is poured into the top of the filter as needed, where a diffuser plate placed above the sand bed dissipates the initial force of the water. Traveling slowly through the sand bed, the water then passes through several layers of gravel and collects in a pipe at the base of the filter. At this point, the water is propelled through plastic piping encased in the concrete exterior, and out of the filter, for the user to collect.



2. As with all slow sand filters, the removal of pathogens occurs in the BioSand filter due to a combination of biological and mechanical processes. When water is poured into the top of the filter, the organic material it is carrying is trapped at the surface of the fine sand, forming a biological layer or 'schmutzdecke'. Over a period of one to three weeks, micro-organisms colonize the schmutzdecke, where organic food and oxygen derived from the water abounds.

The people of Haiti live in harsh conditions and have very limited access to clean water sources. As a vulnerable population, which combined with significantly contaminated water sources that are a leading cause of disease transmission, they will only be faced with illness and death. Taking measures to reduce the dose of pathogens that they are receiving will go a long way towards reducing illness and subsequent death.

The Biosand filter’s simple technology, its proven effectiveness and availability of production materials are what make it a viable option for Haiti. In a country where education is limited, people of all ages, including young children, are able to use the filter and understand how it works.