BSF info: Does the biosand filter add minerals to the water?

[Catherine Bourgault]

Hi all, 

Some questions have been raised during the last ABINET LEX (in Cameroon) on some technical aspects of the BSF. 

Here are some of the questions I have captured through the week with the answer. Further information can be found on the CAWST biosand filter info website:  https://www.biosandfilters.info/faq   

Question: Does the biosand filter add minerals to the water? 

Answers: To our knowledge, there has not been any research on the topic.

However, it is known that, for the first year at least, water that flows through the biosand filter increases in pH and total dissolved solids.  This is due to the water dissolving minerals from the sand (and concrete, in the case of a concrete filter). This effect wears off over time as the readily dissolvable minerals on the sand surface get used up.
 
Water that has had its minerals removed to the extent that the biosand filter could be considered to be beneficial in this way, such as with in the case of reverse osmosis or distillation, is probably not an ideal source water for biosand filtration as it would be low not only in minerals, but also in nutrients to feed the biolayer. 

 

Best, 

Catherine