New Biodenitrator

[Delphinus]

Thanks, that's what I thought too. If you read the "DIY" instructions that Caribsea puts out though, they just have it as a single-pass basis and it sort of sounded like that's how Pansy-Paws does it too (I could be reading it wrong?). I guess that way works too, but to me anything that requires contact time is always better to have it on a recirculating basis.

Well sounds like I'm set then .. I just need some media. I'm gonna have this online within a couple of days (just as soon as I can get my hands on some media!).

[Psyire]

I believe it is this recirculating that helps remove the oxygen from the water to create the anerobic zone. (more effective)

[Delphinus]

Yes I agree that makes more sense. Like I said though the DIY instructions Carib-Sea talks about looks like single-pass to me, .. you can easily replicate the anoxic zone with a slow enough flow without the recirculation, but I agree it seems easier to do so with recirculation. If the channel was long enough I guess you could get away with it. But anything I would want to build I would want to make it as recirculation because anything that increases contact time cannot help but help.. whether it's a skimmer, reactor, heck even my Phosban reactor I'd like to modify and make recirc.. it just makes sense to me.

[Pansy-Paws]

Given the height of my design (36"), I only have a single water flow thru path, no recirculation.

As indicated, with a slow enough water flow, the anerobic zone can be established.

[Delphinus]

So I got to the point where I was on the phone to my LFS, asking them to bring in some LSM, and again, the topic came up.. "You realize there's a risk of H2S right?" Aaannnnnd..... arrrrrggggh, there we go, once again, I thought I had made a decision and was going to follow through on it, and here I am, second guessing myself all over again.

Here's my thought ... when I was a summer student I had it absolutely drilled into me how bad H2S is. You can smell it at 1ppm, at 10ppm you can only be exposed safely for 10 minutes at a time (I forget how long you have to wait in between) and I think it's instant-loss-of-consciousness at 100 ppm (it may not be 100ppm, I don't remember. At some point though, you can be dropped instantly with one breath).

Soooooo ... seriously, what are people's thoughts on this? I've even posted this question in Randy Holmes-Farley's forum on RC (although he's not online this week). Keep the tank area well-ventilated?

I may be overly paranoid but one thing I remember is that H2S is heavier than air, meaning anyone closer to the ground is at higher risk (think: pets and small children). Although I need to reduce my nitrates I can't do it if I'm risking the wellbeing of family and pets (or the tank itself).

Maybe Zeovit's the way to go after all ... I don't know ... argh, there I go, second-guessing myself again.

[ed99]

I don't have any experience with the biodenitrator but can I do know a little bit about H2S from the job. 10 ppm is the maximum concentration you can be exposed to during an 8 hour work day, so H2S is not a great risk at that level, but with the smell at that level your wife and family may be! 100 ppm will cause watery eyes, respiratory problems and nausea, and 200 ppm gets you close to the death range within hours. Above 500 ppm your life span is minutes and at 700ppm death is almost immediate. It is nasty stuff and kills a few people in the oil industry every year.

As you mention, H2S is detectable at very low levels but is very toxic and will collect in low spots so for me personally it's a piece of equipment that I would only use if the worst case H2S production rate is low, the area is well ventilated to the outside and you can check up on the equipment frequently.

[Delphinus]

Ok those numbers are a lot higher than what I thought they were. I was an oilfield worker as a summer student but those days are long behind me so my memory was clouded. I would think 700ppm would be hard to do, even playing with elemental sulfur, i.e., one would notice the smell @1ppm long, long, long before.

[Pansy-Paws]

Having used a denitrator with 4 gallons of LSM, I'm not really concerned on the toxic front. For one thing, if this was an issue for this application we would be seeing warning labels up the ying yang, and would have confirmed lawsuits from the US. If that was the case, I doubt that Caribsea and Korallin would still be marketing their products ... too much liability given our litigious nature (ever notice how many warning labels are on ladders these days ).

I'll definately concede that for industrial settings, this can be serious stuff. However, Delbeek and Sprung devote 7 pages to sulphur denitrification, and only a couple sentence mentions of hydrogen sulfide smell as an issue, mainly around the ambience impact of a smelly living room. The chemical reaction from Holmes-Farley shows:

2 H2O + 5 S + 6 NO3- ---> 3 N2 (gas) + 5 SO42- (sulphate) + 4 H+ (hence slightly acidic effluent and the reason for calcareous material after the sulphur)

so no H2S is emitted in the primary reaction, unless the flow is too slow and secondary chemical reactions occur. As you mention Tony, the 1 ppm level will provide ample nasal warning before the level can rise to dangerous levels (which I doubt is even possible ... as this application has been used in Europe for over 10 years on some massive aquariums).

Also, with a recircuation system, the volume of sulphur would be much less than even I'm using.