New user?

high TDS and high fluoride levels in boreholes

Dear RedR Experts,

A friend of mine is reviewing some water boreholes drilled and equipped in Kenya. There are common threads emerging: high TDS and high fluoride levels.

What simple treatments are available to reduce these issues please?

I have heard of slow sand filters equipped with crushed cow bones being used to reduce fluoride levels but have no details. I am also wondering how much a slow sand filter reduces TDS levels ....but have nothing to hand on that topic.

Kind regards,


edit retag flag offensive close merge delete

3 Answers

Sort by » oldest newest most liked


There are very many methods of reducing fluoride levels, but it would be best to stick with a proven method that is already in use in Kenya, is simple and doesn’t require chemical dosing. Searching the IRC WASH library ( I found that the Catholic Diocese of Nakuru produce and re-activate bone char for fluoride removal, so that would seem to me to be the most appropriate line of enquiry ( There is a paper on the viability of the bone char operation here:

I hope this helps.



edit flag offensive delete publish link more


You may want to look at the WHO document also look at the paper in Sandec News 7 (2006) at



edit flag offensive delete publish link more


Just to add TDS is by definition dissolved and capable of passing through a 2 micron filter. Pretty much anything that will go through a 2 micron filter will go straight through a slow sand filter too, so I wouldn't bank on any decrease in TDS with slow sand or bone char.

You generally need desalination for TDS removal. Blending with a low TDS source may be more economical if one is available.

Kind regards


edit flag offensive delete publish link more
Login/Signup to Answer
Question Tools
1 follower
Public thread

This thread is public, all members of KnowledgePoint can read this page.

2014-01-27 05:16:12 -0500
1,303 times
Last updated:
Feb 04 '14