Building a Bio Sand Filter (BSF) to purify water

Anthony Higgs has been a lifelong friend of Andrew MacGregor, Sandy’s son, and when Anthony described his work to Sandy in SE Asia about building Bio Sand Filters (BSF) to purify water Sandy immediately introduced Anthony to Steve Carroll. Arrangements were made to have Anthony come to Ban Xai, source material and conduct workshops for both Thao Moua andYang Xang to build BSFs so that they could show all the villagers how they could obtain safe drinking water without boiling (thus saving time and firewood).


Below is a diary of the process ( by Anthony) with pictures. Thank you Anthony for your contribution.

  • Shopping for pipes or suitable water containers & container to use as a show-model.
  • Visited all the pipe factories but their pipes were wrong size, too thick & too long.
  • We decided to use a plastic water container (22 gallon) with plastic tub on top. This meant pipe joiners to go through the wall of the plastic container with an O ring and therefore no need for cement, waterproofing, sand, etc.
  • With his instruction I went to ministry of Foreign Affairs Government building with Thao to inform them of my teaching Xang & Thao the BSF.
  • We layed everything out and collected stones, gravel from in front of the workshop and sand from the river and washed them ready for the show-model filter.
  • Thao and I sorted the stones for the show-model filter.
  • Stone collecting, sorting & washing takes the rest of the day with one size stone still needed and washed as well as river sand to be collected and washed.
  • Two government officials were picked up who wanted to see what we were doing. at the workshop
  • River sand was collected and washed by the river.
  • The water container was prepared by washing inside with soap, hole made on the side for 1/2 inch pvc pipe & fittings.
  • Stones were washed again & loaded. River sand was washed again and added to the container completing the filter
  • The top receptor was added after a small hole was made in the base.
  • The filter was completed and ready to run water through it to further clean and to allow the schmutzdeche to grow over a 3 week period.
  • We reviewed the whole process and had Thao read the step by step procedure for constructing and making the BSF and the importance of maintaining the schmutzdeche. We discussed the idea of him building one for his family which would give him a ton of confidence.
  • Out to the workshop to cleanup and run 40lts of water through the filter to wash any lingering turbidity through the filter.
  • Final debriefing.

YANG ANTHONY and THAO in their MiVAC shirts made in Cambodia, organised by Michael Hayes and donated by Beryl Goddard