Biosand Filter Description

bsf
Source: CAWST

Description
Biosand filters are a small, household sized adaptation of slow sand filters such that they can be run intermittently.

The filter consists of a layer of gravel overlain with prepared sand media contained within a filter body or box, usually constructed on concrete. A shallow layer of water sits atop the sand, where a biofilm (schmutzdecke) is created that further filters the water of harmful microorganisms.

Operating the filter is very simple: remove the lid, pour a bucket of water into the filter, and immediately collect the treated water in a clean container.

Development
Invented by David Manz, PhD. University of Calgary

Performance

Amount of Water Treated
Household biosand filters typically provide 30 liters of water per hour, which is sufficient for a family of five. Flow rate may decrease over time as the filter becomes clogged, but can be restored with cleaning.

Contaminant Removal
Biosand filters have been shown to remove more than 90 percent of fecal coliform, 100 percent of protozoa and helminthes, 95 to 99 percent of zinc, copper, cadmium, and lead, and all suspended sediments. Biosand filters have also been shown to remove 76 to 91 percent of arsenic, reducing it to acceptable concentrations. These filters do not sufficiently remove dissolved compounds such as salt and fluoride or organic chemicals such as pesticides and fertilizers. The biological layer’s effectiveness is influenced by temperature. Ammonia oxidation stops below 6° Celsius and alternative treatment methods are required below 2° Celsius. Additionally, because biosand filters are not able to handle high turbidity, they may become clogged and ineffective during monsoon or rainy seasons.

Ease of Use
Biosand filters require daily fillings during the 2 to 3 weeks when the biological layer is growing. Biosand filters also require regular cleaning, which involves agitating the water above the biological layer. The filter will require 2 to 3 weeks of nonuse after agitation to allow for the regrowth of the biological layer. On occasion, the sand in the filter needs to be cleaned as well. There are several different methods to clean the sand, though all of them require significant labor, significant training, or high cost. User error has also been found to affect the filters’ efficiency, especially because of the required 2 to 3 week nonuse period for growing the biological layer. Biosand filters can be fabricated locally in almost all regions because they use common materials.

Benefits & Drawbacks

Advantages
  • Removal of turbidity, colour, odour
  • Good microbial removal
  • High flow rate
  • Can be constructed of local materials
  • Income generation
  • Durable
  • Minimal maintanence
Drawbacks
  • Not 100% microbial removal, may require post-disinfection
  • Limited transportation due to weight
  • Turbidity should not exceed 50 NTU

Costs

  • Capital Costs: $12.00 - $30.00 US
  • Operation and Maintenance: Minimal
Comments:
There may be educational and training costs associated with teaching users how to properly maintain their filters. Costs may vary across regions depending on the availability of materials and labor.

Resources

References & Links
  • Biological Sand Filters: Low-Cost Bioremediation Technique for Production of Clean Drinking Water, [PDF or HTML]

  • UN Habitat: Best Practice Brief

  • The Use and Performance of the Biosand Filter in the Artibonite Valley of Haiti: A Field Study of 107 Households, [PDF]

  • BSF Manufacturing & Installation Report. [PDF]

  • Rotary District #6290 Biosand Filter Reference Material

  • Evaluation of the Biosand Filter for Reducing Risks of Diarrheal Illness and Improving Drinking Water Quality in Communities of The Dominican Republic. [PDF]

  • FBF International's Water Filter Testing Report

  • Nicaraguan Study of the Biosand Water Filter. [PDF]

  • Health Impact Study, Dominican Republic. [PDF]

  • Dominican Republic Field Report [PDF]

  • Targeting individuals: away from the concept of community involvement: The success of household sand filtration [PDF]

  • History of Dominican Republic Biosand Project. [PDF]

  • Site Visit amd Status Report, Cuba. [PDF]

  • Biosand Water Filter in Dalive. [Google video]

Biosand Projects

Training

CAWST BSF Training Workshop [photographs]

Canada
Centre for Affordable Water and Sanitation Technology

Box #12, 2916 5th Avenue NE, Calgary, Alberta, Canada
Tel: +01 (403) 243 3285; Fax: +01 (403) 243-6199
Email: cawst [at] cawst [dot] org

Cameroon
Life and Water Development Group

India
DHAN Foundation

Philippines
Women's Global Green Action Network
A Single Drop

Contact Information

Centre for Affordable Water and Sanitation Technology
Box #12, 2916 5th Avenue NE, Calgary, Alberta, Canada
Tel: +01 (403) 243 3285; Fax: +01 (403) 243-6199
Email: cawst [at] cawst [dot] org