Search for "anaerobic limestone drain". It's commonly used to reduce acid
mine drainage (AMD) but has the same effects on nitrates. You need
"anaerobic" and not "aerobic." Check out the page below for a picture. Your
situation would be the wetlands and the pond on the right.

http://www.ctcnet.net/scrip/solution.htm

Sam

"Ali" wrote in message
...

"Sam Hopkins" wrote in message
.. .
There's no way to filter nitrate unless you have the water go through a
wetland first. The anerobic bacteria in the wetland will remove the
nitrate.
You could build one by digging a hole 18 inches deep. Line the bottom
with
a
return pipe and 6" of gravel. On the top place 12 inches of organics
(topsoil). Pump the water ontop of the dirt and as it flows down through
the
soil it'll be stripped of O2 and the anerobic bacteria will convert the
nitrate. To keep a constant supply of organics plant cattails.

Sorry yes my mistake with the nitrate. Any ideas where I can read up on
this
please.

Thanks

A