i need feedback about my Denitrate Tower, so I thought I would provide a thread with a few details.
The ?Denitrate Tower? is a monstrosity of an eye soar that only the most hardcore of hobbyist are likely to attempt. Yes, it?s ugly, but the tank this is on has been running for the last couple of months with zero nitrate creep. It?s on a 100 gallon tank. Stocking is an adult Oscar, an adult male convict, and three adult silver dollars.
As a starter, here is a pic of the current ?Denitrate Tower? (as I was setting it up).
Construction is very simple. It is a 7? tall (or thereabouts) tower made of 4? PVC and necessary fittings, powered by a Quite One 4000 that is throttled back to a flow rate of about 30gph (as measured from the outflow of the filter). The filter is filled with a mix of SeaChem Denitrate and Eheim EhfiLav (about 5 parts Denitrate and 1 part Ehfilav). Sorry, I cannot specify how much Denitrate media is involved as I?ve been through multiple stages with this, but it contains somewhere in the neighborhood of 9-12 liters of media.
This is NOT a classic anaerobic denitrification filter. It is what I call a ?Safe Denitrification? filter as no anaerobic areas are established inside the filter. Water exiting the filter tests out a 7ppm oxygen (the main tank is 9ppm). The only anaerobic conditions exist within the internal pore structure of the media. A basic diagram of the filter?s plumbing is detailed below:
Another important aspect of the filter is that I am using a 20 Micron ?Whole house sediment filter? (bought at Wal-Mart for $25) as a prefilter to the denitrate tower. This is important. I was never able to achieve zero nitrate creep until this 20 Micron Filter was added. What purpose does this Micron filter serve and how did adding it contribute to achieving zero nitrate creep? The short answer is I?m not sure. One of three things occurred. The micron filter itself is made of cellulose, cellulose is an organic carbon source. Perhaps there is enough break down of the micron filter material that it is serving as an organic carbon source for the denitrifying bacteria. Another possibility, this one is at least a certainty, is that the micron filter is removing all detritus (even microscopic) which allows the pores of the media inside the filter to remain open, enhancing denitrification efficiency. The final possibility is that it is serving no (or limited) purpose?. that the filter was going to achieve zero nitrate creep and adding the Micron filter was only a coincidence. The only certainty is that the Micron filter limits maintenance requirements of the denitrate tower as absolutely no ?gunk? makes it into the tower itself.
It has been my experience that the Micron filter cartridge needs to be replaced every two weeks to prevent a drop in flow rates. A two pack of replacement cartridges is about $7, so ongoing cost has not been an issue ($7 per month).
So?. I?ve been asked, how does this work? The theory is that the media within the filter possesses a pore structure that extends into the interior of the media. As water is forced (forced is an important concept here) into the media, nitrifying bacteria oxidize ammonia and nitrite, stripping oxygen from the water, allowing the internal pores of the media to become anaerobic, allowing these internal pores to support denitrifying bacteria. At least that is the theory. This much I can testify too, I am running zero nitrates on this tank and water exiting the filter had less oxygen than the main tank but is no where near anoxic. Hence the term ?Safe Denitrification?. There is no risk of incomplete denitrification (where nitrates are converted back into ammonia or nitrite) or of hydrogen sulfide production.
Flow rate is critical. Over the last couple of years I?ve been through many stages with this thing, some very complex, attempting to use various flow rates. Above 50gph and you basically have a very tall canister filter performing standard nitrification. Below 30gph and you wind up with reduced denitrification and the potential of establishing a classic anaerobic filter (and all of the risks that entails). The simple ?tall tower?, prefiltered by a 20 Micron filter, with a flow rate of 30gph, has produced the best results.
Finally, I am constructing a new tower and have a few photos that may help anyone else wishing to attempt this. Below is a pic of the individual components and where they were purchased:
Finally, what my daughter calls ?King Kong?s Bong? and my wife calls ?the big ugly green thing?.
I intend to run ?King Kong?s Bong? in conjunction (but not in series), with the existing filter. It?s only a matter of time before the existing filter is rendered infective by bacterial slime filling in the internal pores of the media. By running two of these (each with it?s own pump and plumbing), I can break one down and retain denitrification while the other is cleaned, added back to the system, and allowed to re-colonize with denitrifying bacteria. Once I learn ?how long? this thing remains effective, I will time the filter maintenance so that one is cleaned and replaced ? of the way through that time frame, so that I will always have at least one cycled and functional filter in place
and one of sub-adults broke back in
1/4/2010, 11:33 pm
