Ammonia Scrubbers

[iggy]

I recently reviewed ammonia scrubbers commercially and thought about applications from aquariums. It caught my interest when TOTM on Reefcentral had a non-photosynthetic coral display with frequent water changes, biopellets, and skimmer and still had 25+ nitrates. That could mean any value over 25! I questioned if a more efficient way to remove ammonia would be practical as a typical ATS would have very large screen and lighting requirements.

I have read reports that ammonia scrubbers have been used in large public aquariums. There does not exist a great incentive to perform this type of filtration because algae is an effective biological scrubber in small tanks with low bioloads, and there does not exist much valuable information in general.

The idea of ammonia scrubber is to degas the ammonia nitrogen. The ammonia gas NH3 is the only fraction that can be mechanically removed. The ammonium ion NH4+ can not be removed by degassing. Industrial applications raise temperature or raise pH to make NH3 removal much more efficient at very high concentrations. Temperature may be remotely possible in small aquariums but both parameters are not advised to be altered. This to take load off effluent systems.

I did academic exercise of calculating amount of available ammonia available to degas under typical reef tank conditions based on Clegg, S. and Whitfield, M., 1995. His equations is stated as effective from -2 to 40C and 0ppt salinity to 40 ppt salinity.

I solved equation using T=79F, Salinity = 35ppt. Results were pK'[NH4+] = ~9.3.
Using [NH3]/[NH4+] = [K-NH4+]/[H+] at pH 8.4, I got ratio of only 1:9 as ammonia gas. If pH goes to 7.8 I got 1:30.
Under industrial conditions on pH 11, conditions go to 100:1 of ammonia-nitogen existing as NH3.

It would be difficult to quantify if ammonia scrubber is working unlike ATS that produces algae. I would think the NPS tanks should look at denitrators and not ammonia scrubbers to keep up with excessive liquid feedings. Your welcome to my spreadsheet if you like. Xls is not a supported attachment here.

http://www.branchenv.com/air_strippers/Ammonia%20Stripping.pdf
http://www.geo.uu.nl/Research/Geochemistry/kb/Knowledgebook/NH4_dissociation.pdf

[34cygni]

I have read reports that ammonia scrubbers have been used in large public aquariums.

From looking at the PDF from Branch Environmental that you linked to, I'd venture to guess that in an aquarium setting, their air stripper design (page 5 of the PDF) facilitates aeration and gas exchange in general -- including offgassing some amount of ammonia, it would seem -- and also functions as a giant remote canister filter. Or am I the only one who sees bioballs when looking at the pics on page 7...?

[iggy]

Bioballs you see are referred to as packing material to help gas exchange as upward air flows against water trickling over large surface area. Idea would be to strip trace amount as it is generated. Not really necessary in managed tanks with light feeding but moster fish tanks and NPS tanks might benefit.

Likely energy intensive if it can be effective.My conclusion without trying it is that denitrators would be a better choice for a heavily fed NPS tank only because the nitrates can be easily measured as they decrease, and would be far less energy intensive.

Ammonia scrubbers are sometimes seen as process before primary effluent discharge on large farms with pigs, to take brunt of bioload of ponds or biofilters.