Hydrogen Sulfide

A background on how H[sub]2[/sub]S is produced:
In summer some relatively shallow estuaries may have no oxygen below the layer of no net motion. In the absence of oxygen, anaerobic organisms (those that can live in the absence of free oxygen) break down nitrates (NO[sub]3[/sub][sup]-[/sup]) or sulfates (SO[sub]4[/sub][sup]2-[/sup]) to obtain oxygen for metabolic processes, giving off NH[sub]4[/sub][sup]+[/sup], N[sub]2[/sub], and H[sub]2[/sub]S (hydrogen sulfide) as by-products.

When organic matter is digested, dissolved oxygen is used as well. Where oxygenated water is re-supplied slowly relative to the rate at which organic matter is being deposited, dissolved oxygen in the bottom water may be markedly depleted. When this happens, oxygen-using organisms, including most bacteria, can no longer live in or on the bottom. Only certain anaerobic bacteria can survive by decomposing sulfate from seawater and releasing hydrogen sulfide as a metabolic by-product. To most organisms, hydrogen sulfide is a poison, and the presence of these bacteria makes the bottom uninhabitable to virtually all other forms of life . . . In addition, decomposition of organic matter proceeds at greatly reduced rates under anoxic conditions. Sediments accumulating in these basins are usually rich in carbon as a result of this.

Information above was gathered from and is copyrighted by: Oceanography: a view of the earth. M. Grant Gross. 1972, Prentice-Hall

This is more geared toward drinking water contamination by H2S.
Although many impurities are regulated by Primary or Secondary Drinking Water Standards set by the EPA, hydrogen sulfide is not regulated because a concentration high enough to be a drinking water health hazard also makes the water unpalatable.

The odor of water with as little as 0.5 ppm of hydrogen sulfide concentration is detectable by most people. Concentrations less than 1 ppm give the water a "musty" or "swampy" odor. A 1-2 ppm hydrogen sulfide concentration gives water a "rotten egg" odor and makes the water very corrosive to plumbing.

Generally, hydrogen sulfide levels are less than 10 ppm but, occasionally, amounts of 50 to 75 ppm are found.

Have a look at this page: http://www.atsdr.cdc.gov/tfacts114.html

Information above was gathered from and is copyrighted by the Center for Disease Control - ATSDR website: http://www.atsdr.cdc.gov/tfacts114.html

Lets get a discussion going about this. Maybe someone can comment on DSBs and it's process with regards to H[sub]2[/sub]S.

DuhJeepster 8)

 

DJ- This is a great topic. When I am not at work I will give this some more thought. (You got PM. )

 

Hey Tony,

I was asked by the German site of which I am a member (www.meerwasserforum.com) to put together an introductory article on DSBs for the forum. You see, Germans do NOT use DSBs, and are fascinated by our "obsession" with them. ;D

They didn't want a "thesis" on the subject, just a general impression by an American on the subject of DSBs to get the discussion started. Here is most of what I gave them:

------------------------------------------------------------------------
Americans believe that DSB's help de-nitrify aquariums just as live rock does. We believe that the same de-nitrifying bacteria that lives on the live rock lives also on the surface area of the sand, and the deeper the sand is on the bottom of the tank, the better the de-nitrification that can take place in your sand bed.

In a post taken recently on www.3reef.com , out of 19 votes, 100% kept their sand beds less than 5" (12.7cm), while 26.3% kept theirs at 4" (10.17cm), 31.5% kept theirs at 3" (7.62cm), and 42.1% kept theirs at 2" (5cm) or less. I find this very interesting since some argue that the most benefit is gained by sand beds 6" (15.24cm) or more! This is because at this level, the so-called anaerobic level, the anoxic bacteria grow, and they are the MOST effecient, it is believed, in turning nitrates into nitrogen gas.

But, two of the members can attest to tank crashes attributed to crashes of sand beds of 6" (15.24cm) or more, caused by a major disturbance to the sand in the bed (by the aquarist or some other means). This released Hydrogen Sulfide into the tank, and killed everything in the system.

I have been keeping saltwater tanks for over 20yrs, and I have seen aquarists try just about everything to facilitate the keeping of fish and corals in an artificial environment. I have known many, many people who feel strongly that the DSB is the most efficient system for filtration. The small numbers in my poll do reflect the general feelings of the "larger community" of American aquarists. The majority of Americans are keeping a DSB of one type or another.

Having said that, I have found that the majority of the people that I know using DSB's are keeping their sand beds 4" or less. This still gives the aquarist the benefit of many square inches of surface area covered by de-nitrifying bacteria, but without the dangerous anoxic layers which form below 5" (12.7cm).
------------------------------------------------------------------------
I have printed it out here because I think it is relevant to the discussion of Hydrogen Sulfide. From what I have observed in the past couple of years, most Americans have dealt with the issue of hydrogen sulfide by limiting the depth of their sand beds to 4" or less.

What do you think of this argument? Do you think that we could find data that could refute this or back this up? Is it just a perceived trend on my part? Or, is it something that can be statistically shown to be true?

On a side note, the Germans find our "obsession" with DSBs to be peculiar, yet they have very complicated and very expensive de-nitrifying devices for sale in their country which operate using vodka!!! To each, his own, I guess... [smiley=freak3.gif] [smiley=grin3.gif] [smiley=laugh4.gif]