Clay Pot Water Filter

Overview

The Clay Pot Water Filter is central to the success and determination of Abundant Water. Our vision is not to simply provide water filtration systems to villages in need, but to establish a model in which potters in villages can make the water filters themselves.

With modest seed funding, our pioneering project manager worked alongside an experienced Lao potter and together they developed clay-pot water filters that consistently tests as safe and effective in rigorous laboratory testing. Firing regimes were developed to produce a low- cost filter with minimal environmental impact allowing for filters to be manufactured in a village setting.

Working with local potters and responding to village feedback enabled Abundant Water to develop a filter that not only has a greater flow rate but is more versatile and adaptable. This enables Abundant Water to provide filtration systems not only for village households but also for schools.

How it works

The Clay Pot Water Filter (CPWF) purifies water by passing it through the pores of the ceramic, which acts as a physical filter. This porous ceramic is made possible by incorporating a ‘burn-out’ material such as sawdust, coffee grounds or rice husks in the clay. This is then fired at a temperature low enough to prevent vitrification of the ceramic but high enough to completely burn out the incorporated material. This results in a honeycomb structure with pores small enough to prevent bacteria from passing through but large enough to allow for a reasonable flow rate of water.

CPWF made in this way are able to filter all particles and microorganisms larger than one micron. This includes silt, bacteria, protozoa and ameba. It is unable to filter viruses, salt or chemicals, such as arsenic, but is able to filter all bacteria, which cause a majority of water-borne diseases.

Activities

Key Findings

Clay Pot Water Filters (CPWF) have been researched and manufactured for over 30 years. The Abundant Water (AW) filter integrates basic filtration technology developed and proven through Australian National University research. This research demonstrated viable filters can be manufactured from readily available materials and traditional firing techniques without the need for moulds, machinery or industrial kilns.

This research enabled Sunny, a young engineer, with no pottery experience to work together with a Lao potter to make viable filters using traditional Lao pottery techniques. The ‘open-source’ AW approach has allowed the Lao potters to take ownership of the process, adapt the technology, and design it to meet their village needs. As a result, the AW project emphasises sharing the CPWF with indigenous potters, encouraging local ownership and through this ownership further encouraging indigenous testing, quality control, distribution, use and education campaigns.

The Clay Pot Water Filter is made from a mixture of local terra-cotta clay, sawdust or other combustible materials such as rice husks and coffee grounds. AW potters have been using coffee grounds provided by coffee shops in Vientianne. The simplicity in its design and materials means that the filter can be produced without the need for a kiln or expensive materials. This opens the possibility for these pots to be produced in any village setting where resources such as rice husks and coffee grounds are easily accessible. The flexibility of the technology allows it to be produced by anyone with basic pottery training, and to be fired in traditional ‘open-air’ fires using readily available material like rice straw or cow dung. Thus, the filters are low-cost, low maintenance and easily replaced, factors which make the Abundant Water filter program suited to indigenous and developing communities around the world.

Technical Overview

The AW ceramic water filter has passed through many transformations in a short time as the Lao partners adapt the innovation to their traditions and marketplace. Initially, pots were small and hand-formed so the potter could master the technology. The primary consideration in these early stages was filtration rate, so that the pots were able to produce enough water clear of fecal matter/bacteria. In achieving this, the potter began to focus on increasing the flow-rate to enable the CPWF to produce adequate quantities of water for domestic use. Once the manufacturing issues of quality control and repeatability were resolved a feedback team of Lao potters and villagers were consulted and began to advise us on a design and form of filter that suited the Lao village conditions.

Initially the filter was in the form of a ceramic water filter bowl sitting inside a water receptacle. However, after receiving advice from the feedback team, this has given way to a ceramic water filter candle that is fitted with a rubber thong gasket inside a bucket, sitting on top of a storage bucket. This latest redevelopment of the filter is easier to reliably manufacture and allows for greater water pressure and increased water flow. It can be made by hand, and because it is smaller than a bowl or bucket-shaped filter, is easier to fire. Firing is achieved in an outdoor fire with the candle filters stacked on a mesh base, burnt in a fire fueled by rice straw and sticks. The technique does not require a kiln, uses freely available material, and is very low cost. Temperatures are controlled at between 800 and 900 degrees Celsius for approximately 2 hours.

The latest iteration of the clay-pot water filter produces a candle (cylindrical) filter that uses commonly available and cheap plumbing fittings to connect to hoses and pipes. This enables this system to perform effectively in both gravity-feed and syphon applications, in homes as well as in schools.