DIY Coil Denitrator Questions

I have been looking at different DIY plan for Coil Denitrators and I was
wondering if anyone has had any luck building one of these things. I am
really curious what kind of pump and flow rate did you use. Can anyone make
any recomendations or give me specific directions on how to build one? Any
information will be apprecitated.

From what I have heard you should get a some PVC pipe 3-4" diameter and run
75-100ft of 1/4in clear tubing around and fill the middle of the tube with
bio-balls. Then you should let the output drip at 1 drop/sec until the unit
has cycled then you can open it up to flow at full speed once the unit has
cycled. I have heard of cycle time between 6-8 weeks. Does this sound about
right? Thanks

"Kveill" wrote in message
...
I have been looking at different DIY plan for Coil Denitrators and I was
wondering if anyone has had any luck building one of these things. I am
really curious what kind of pump and flow rate did you use. Can anyone
make
any recomendations or give me specific directions on how to build one? Any
information will be apprecitated.

From what I have heard you should get a some PVC pipe 3-4" diameter and
run
75-100ft of 1/4in clear tubing around and fill the middle of the tube with
bio-balls. Then you should let the output drip at 1 drop/sec until the
unit
has cycled then you can open it up to flow at full speed once the unit has
cycled. I have heard of cycle time between 6-8 weeks. Does this sound
about
right? Thanks


You are on the right lines. I looked at building one but eventually bought
one of these....

http://www.shopsolution.nl/shop/home...nitrateragrade

The way all nitrate filters work is to encourage an oxygen free environment
in which Anaerobic bacteria will grow & live - they feed off the Nitrate.
You get this by passing water through them very slowly. The reason I went
for the Sulphur based filter was that there is a school of thought that says
that you need to feed "normal" de-nitrators with Methanol for them to work
properly. The sulphur is an alternative to this in that the bactreria will
feed of it instead - or so the story goes. I also decided that for the price
it was not worth messing about trying to build something with all the risks
of leaking cannisters etc.

As far as commissioning it is concerned it helps to give it water that is as
clean as possible and as oxygen depleted as possible. That means that you
(ideally) take a feed from the output side of a cannister filter. The water
goes through the cannister and the Aerobic bacteria in there deal with the
ammonia & nitrites as normal & in so doing deplete the water of oxygen.

You then run a bypass off the output of the cannister with a valve of some
kind so you can control the flow through the denitrator - the remainder just
goes straight back to the tank.

The instructions with mine say to run it at 1 drop /second for a week or so
(or until the water coming out of it is Nitrite and Nitrate free), then
increase to 2 drops a second till its clear again and then 4 drops a second
& then gradually on upwards to a maximum of about 10 litres an hour. The
final amount you can get to will depend on the size of the filter you have.

What actually happens (I think) is that in the first part of the filter you
get an Aerobic bacteria colony (as you would in any filter) and then
gradually the Anaerobic colony builds up in the last part of the filter. If
you increase the flow rate too quickly the first colony is not big enough to
fully deplete the water of oxygen and so the second colony doesn't take hold
properly, the thing breaks down and you have to start again.

The answer to your question is that you need to build the flow up gradually
over a number of weeks - you can not commission it at 1 drop a second and
then crank it up to full flow.

You also need to be aware of a few other things

1) The filter seems to strip the buffer out of the water causing the Kh (and
therefore Ph) to drop. Eventually this could cause a Ph crash in your tank
if left unchecked so I have been adding some sodium Bicarb to the tank a
couple of times a week to compensate (you could put a few marble chips in
your filter instead). If you have very soft (low Kh) water to start with
you'd need to watch this quite carefully.

2) As the filter builds up (and particularly in the first week or so) you
can find that the water coming out of it is VERY high in both Nitrites and
Nitrates - you need to keep an eye on this but it will pass soon enough. I
got this effect after I increased the flow rate for the first time - I went
too far. I stabilised the thing by slowing it down a bit.

3) If you run the thing too slowly (or let it stop for any period of time)
then it can go bad & you will get Hydrogen Sulphide (rotten eggs) out of
it - that would not do your tank any good at all! (I have detected a faint
whiff of this once or twice & when I did just increased the flow a tiny
bit).

All sounds a bit daunting but actually its not and mine is now beginning to
kick in nicely. I am upto 4 or 5 drops a second. As you increase the rate &
it starts to establish it seems to be less fiddly & sensisitive - I would
guess because the bacterial colony is becoming well established if that
makes sense.

In total you do not need a very high flow rate to keep nitrates under
control. WHen its working it absolutely strips the nitrates from the water -
they are simply not detectable at all. My tank is about 70 UK gallons (
85-90 USG) & I think that a flow rate of under 1 Gallon per hour will be
more than enough to ultimately reduce my nitrates to zero - which I don't
actually want to do because I have plants in the tank!

Hope that helps - come back if you have any more questions & I'll try to
answer them

rgds

I.