DIY Sulfur Denitrator
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Interesting artikels about Sulpur
Interesting artikels about Sulpur
Those who are not satisfied with a simple explanation can start here. But I think this wood be better handled as a topic in the chemics chapter. If it was not already.
Nitrate reduction through sulfur
http://books.google.be/books?id=xHC...ge&q=nitrate reduction through sulfur&f=false
Thiobacillus
http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Thiobacillus.html
From the forum:
Sulfate/sulfide transformations
Submitted by wetman on Mon, 03/21/2011 - 07:17
Sulfur is another element required for animal life. After carbon, hydrogen, oxygen and nitrogen, the next most common element found in organic molecules is sulfur. Sulfur is a component of some essential amino acids that are part of proteins and of humic substances. You won't be surprised to find a limited arc of the planetary "sulfur cycle," even in the aquarium's limited ecosystem, because all the elements essential to life must be recycled, or else biological processes would have exhausted the planet's supply, after a couple of billion years.
Sulfate and sulfide. In the sulfate ion (SO4), a sulfur atom is surrounded by four oxygen atoms: oxidized, in other words. Sulfates are harmless to fish, odorless and quite stable. By contrast, in sulfides, such as hydrogen sulfide (H2S), the sulfur atom is reduced, stripped of its oxygen and joined to another atom. Sulfides are reactive, and they can be quite toxic.
As with phosphate, inorganic sulfur is unavailable to animals; it must be assimilated by bacteria to form organic sulfur compounds before animals can use it in assembling essential proteins and co-enzymes and other necessary biochemicals.
So, like other elemental cycles represented in the aquarium, sulfur transformations are driven by bacterial processes. Some bacterial metabolisms can reduce sulfate, stripping it of its oxygen atoms, while others oxidize the sulfide that's produced. The various sulfur-metabolizing bacteria aren't all genetically related. They form a co-dependent community, passing sulfur back and forth between sulfate and sulfide states, even sometimes excreting a little elemental sulfur. In undisturbed regions of mature biofilm and the substrate, the aerobic sulfur bacteria help use up the last of diminishing supplies of oxygen, so they keep their anaerobic neighbors safe from the dangerous, reactive O2.
Where is the aquarium's sulfur? At any given moment, most of the sulfur in the aquarium is in the form of sulfates (SO4). Though most of the organic sulfur is in the form of sulfates, not all sulfates are built into organic compounds: sulfates can also be mineralized. Gypsum, for one example, is calcium sulfate, CaSO4: when ground fine it makes plaster-of-Paris, the major component of sheetrock and those weekend "feeder blocks" embedding food flakes. Sodium sulfate, the salt of sulfuric acid, is another widely distributed mineral sulfate. Potassium sulfate is only moderately soluble, but you might be adding it as a plant fertilizer. Magnesium sulfate is Epsom salts. Aluminum sulfate is the alum you might occasionally use to clarify water.
Sulfate is the form of sulfur plants can use, and like phosphate it can only re-enter the food web through algae and plants. They take it up and convert it into their characteristic proteins, which may be consumed by animals, who can't use sulfates directly; instead they convert these plant-produced amino acids into their own animal proteins.
The death of plants or animals begins the process of decomposition, communal processes that involve cooperating fungi and bacteria. The decomposers break down animal and plant proteins, releasing amino acids that animals can use or "mineralizing" the amino acids, that is, breaking them down all the way to release the sulfates, which plants take up once more. Within the aquarium there are sulfur transformations rather than a true cycle, as with phosphate.
Sulfide (SO), stripped of oxygen, is the other form of sulfur normally involved in biological processes. (Thiosulfates"” SO3"” are a less common form of sulfur. You know them most likely from sodium thiosulfate, the active ingredient in de-chlorinator. Thiosulfates don't last in the aquarium, because bacterial communities metabolize them.)
Sulfur bacteria in the substrate. Sulfur is much less common in freshwater sediments than it is in marine environments. Typical habitats for sulfur bacteria are freshwater lake sediments and intertidal mudflats. In such sediments sulfur bacteria communities form densely-populated mats (denser than cyanobacterial mats) that are confined to the narrow layers where the oxygen and sulfide gradients overlap. In the undisturbed substrate there are communities of sulfur bacteria, playing various metabolic roles. Their combined effect is to oxidize sulfides to sulfate.
Sediment banding. Distinct layers form in sandy sediments"” which are more like most aquarium substrates than mud sediments are. Bands in an undisturbed substrate form in reaction to four chemical gradients: light, oxygen, sulfate and sulfide. On the interface between water and substrate, diatoms coat most surfaces, mixing with cyanobacteria. The diatom layer protects the cyanobacteria beneath from the corrosive effects of oxygen. On a mud substrate this community might form a thin dense, somewhat slimy mat: a biofilm. Just below, purple bacteria (with bacterial chlorophyll a), lie in a layer just above green sulfur bacteria (with bacterial chlorophyll b). Purple and green bacteria are the phototrophic "non-sulfur" bacteria of freshwater sediments, especially in alkaline environments . In the layer where silica sand transmits some light, especially in the infrared range, "blind" but motile sulfur bacteria exist in permanent symbiotic relations with phototrophic green sulfur bacteria that cover them. Phototrophic sulfur bacteria require the simultaneous presence of reduced inorganic sulfur compounds"” diffusing upwards from anoxic layers"” and light coming from above. They get their carbon from CO2. Green sulfur bacteria have two distinguishing colors, bright grass green and chocolate-brown, arising from phototrophic pigments.
Link. I'm getting some of this information from Jörg Overmann's rather technical but perfectly readable document, "Diversity and ecology of phototrophic sulfur bacteria" in Microbiology Today, Aug 2001, archived at the Society for General Microbiology's site. If it might be more than you want to know, check the abstract.
In a nutrient-rich sediment, heterotrophic bacteria may overwhelm the slower-growing phototrophs.
Photosynthesizing sulfur bacteria. Anaerobic photosynthesizing sulfur bacteria sometimes form distinct dark layers in the substrate next to the tank glass, where daylight hits it. The bacteria involved are purple sulfur bacteria (with red, brown, purple and orange photosynthetic pigments) and, usually beneath them, the olive-green to brown green sulfur bacteria. In anoxic environments, these bacteria are able to metabolize sulfide or elemental sulfur, using a primitive and ancient kind of archaic photosynthesis that doesn't produce any oxygen. Very low levels of light will suffice for them.
On one of my tanks (and yet not on others), beginning a half-inch below the substrate surface, there's a clear-edged area that is black-green, perhaps dense with these sulfur bacteria probably mixed with cyanobacteria. My hunch is that these particular photosynthesizers are discouraged by the oxygen in the topmost gravel layer. What has been mysterious to me was, why does this photosynthesizing zone appear equally strongly in gravel that's not exposed to daylight from a window? Then RTR explained this phenomenon well in an AC post, 3 Dec 2002: "A significant part of this may well be only on those sand grains or the glass itself exposed to internally relected light. Light from the tank's lighting entering the glass at certain angles passes through the interior glass surface, but is reflected back from the exterior and comes back out within the tank just below the substrate surface"” the glass itself acts a light pipe for a short distance. In one small area, pull back or siphon up the sand. If the algae is still there in the glass with a bit on the sand removed, it is just internal reflection promoting growth, and it may be removed at will. If the patch extends into the tank away from the glass a completely different process is occuring."
Hydrogen sulfide. For generations hydrogen sulfide has been a bugaboo to aquarists, who have sniffed their tanks for the tell-tale whiff of rotten eggs that would confirm their dark fears. Hydrogen sulfide can be produced by two kinds of bacteria. Surprisingly, one kind are aerobic bacteria: H2S can be formed in the normal process of aerobic bacterial decomposing of plant and animal remains. Atoms of sulfur form part of the molecules in living tissues, notably in proteins. When tissues are broken down, the sulfur is first released as sulfides, contributing to the stink of putrefaction. In the decay process, where organic substances from cells are being decomposed, a group of "sulfur bacteria" scavenge oxygen from the organic sulfate and use it to oxidize carbon.
Minute quantities of sulfur are released throughout the aquarium, some of it as infinitesimal amounts of H2S. Other bacteria, however, are right at hand to oxidize the sulfides to sulfates; they are a wide-ranging group of aerobic bacteria, including thiobacilli. This sulfide/sulphate regeneration is a normal component of the mature community of the biofilm. But at points in the cycle where oxygen is locally scarce, such as microzones deep in a well-developed biofilm, sulfur-reducing bacteria can short-circuit the cycle by reducing free elemental sulfur or SO4 directly back to sulfides, by-passing plants and animals.
Obligate anaerobes and the dreaded hydrogen sulfide. But, pretty rarely in most aquaria, pockets of hydrogen sulfide can also form in deep substrate layers that are never touched by oxygen. In entirely oxygen-free zones of the substrate, de-nitrating bacteria can thrive, stripping the oxygen from nitrate and nitrite. Their activities produce a nitrate gradient. In sufficiently deep substrates, nitrates may become entirely used up. Below the de-nitrating zone, where there is neither nitrate to work on, nor oxygen to interfere, sulfate (SO4) can become the next-best electron receptor for obligate anaerobes, those bacteria who can't handle oxygen at all. This metabolic process is much less efficient as a source of energy, but as long as they are utterly protected from the deadly oxygen, a range of anaerobic sulfate-reducing bacteria strip the oxygen from sulfate and use it to get carbon from carbon dioxide. Their waste products include H2S. Hydrogen sulfide (H2S) is deadly to all aerobic organisms, so the noxious gassy byproduct can help stabilize a safely anoxic environment for the sulfate-reducing bacteria that produce it, surrounding themselves with a "killing zone" called a sulfuretum.
Hydrogen sulfide is highly reactive, part of what makes it toxic at the nanomolar (µM) level, according to a 1997 California Academy of Sciences BioForum lecture "Living with toxic sulfide" given by Dr Alissa Arp, who has been exploring marine H2S metabolisms in deep oceanic thermal vents and methane seeps and the black mud of tidal estuaries. Now, of course they are getting a long way from the freshwater aquarium, but these are good places to study sulfur metabolisms. For instance, Dr. Arp relates, H2S reacts with iron to make black iron sulfide. In the substrate, iron in the ferric state, Fe(III), will oxidize H2S, turn it to thiosulfate.
This useful reaction of Fe(III) and H2S has been harnessed by a curious California mudflat worm, Urechis, which lives in an excavated burrow where water is stagnant at low tide. There is a lot of bacterial activity in the mud, which is highly enriched organically, so the oxygen gradient is very steep. The bacteria in anoxic mud produce sulfide, and if you walk on the mudflat at low tide, you smell the hydrogen sulfide. So the worm Urechis is faced with environmental challenges, which it meets by detoxifying the H2S in its coelomic fluid, which is rich in heme compounds, though not associated with a protein as in our hemoglobin. The iron in the heme group is in the ferric state. Its extra positive charge oxidizes the sulfide to non-toxic forms, principally thiosulfate.
These sulfate-reducing bacteria giving off H2S are "obligate anaerobes," the kind of primitive bacteria that are poisoned by a breath of oxygen. There is another group of specialized anaerobic sulfur bacteria that can also metabolize sulfate for energy, converting it to sulfide. These bacteria also require a strictly anoxic environment to work in. Oxygen doesn't kill them outright, but in the presence of oxygen these sulfate reducers can't grow and multiply. They need an organic substrate, such as acids generated by the fermentative activities of other anaerobic bacteria. Nitrate also retards their action. Only in deep, richly organic substrates that are disturbed at long intervals could they become a problem.
Sulfate-reducing bacteria tend to create a blackened layer in the substrate, because iron reacts with some of the the sulphide they produce to form dark-colored iron sulfide (FeS).
Sulfate reduction in biofilms. Though the sulfate reducers are obligate anaerobes, suitable oxygen-free microzone environments aren't necessarily buried in the deeper layers of the substrate. Sulfate-reducing bacteria tend to multiply in undisturbed matured biofilms as well. A sulfuretum doesn't get established there because neighboring bacteria are waiting to oxidize the hydrogen sulfide to harmless sulfate.
Sulfate-oxidizing bacteria. So, if H2S has formed in a deeper anoxic layer in substrate or a thick biofilm, various aerobic bacteria are waiting to scavenge any available hydrogen sulfide and oxidize it to harmless sulfate. In an undisturbed substrate, bacteria like these would tend to congregate in a thin layer at the limits of diffused oxygen, subsisting on any H2S that might diffuse up from a deeper anoxic layer. If you found that the roots of plants are blackened (they should be white) you might suspect hydrogen sulfide poisoning. But healthy active plant roots have a natural defense against H2S; they release some oxygen, which creates a protective microzone surrounding each rootlet, where these H2S-oxydizing bacteria can thrive. In an undisturbed substrate, as H2S rises up to the rootzone, it is increasingly unlikely to avoid getting oxidized to sulfate. Diana Walstad notes that H2S was found to be negligible in oxygenated swamp water, even when it was present in the underlying sediment.
My H2S conclusions. In sum, hydrogen sulfide could only be an issue in a substrate that was too deep (over 4 inches, say), one that was also entirely anoxic, was also depleted in nitrate and was enriched with decaying organics and sulfate, perhaps from fertilizer. Then, to get the H2S up into the water column, though, you'd have to get in there at long intervals and vigorously stir up the deepest layers of substrate with a gravel cleaner. My point is that several poor aquaristic practices would have to be combined.
I did once have an unpleasant brush with H2S. An Aponogeton bulb had died back but never renewed itself. After some months I went to root it out. It was reduced to a shell- the heart was rotten and softer than a French cheese. When I managed to get it to the surface in one piece, the notorious stink of H2S greeted my nose. I figure that the resistant rind of the bulb had protected the interior from the destructive powers of oxygen. Inside it, an isolated community of stinky anaerobic decomposers had uninhibited free play, and H2S could accumulate, safe from the substrate bacteria that would otherwise have oxidized it to harmless sulfate.
...Other fishkeepers have had similar experiences. Apparently the fleshy tubers of a Banana Lily (Nymphoides aquatica) can provide a similar oxygen-free haven for sulphur-reducing anaerobes. G.S. Mollin posted at Tom'sPlace 10 Jan 2002: "Actually it took a dead banana plant to get the anaerobic pocket started. It smelled pretty bad and was jet black wastewater when vacuumed." But on the whole, I think aquarists tend to mistake the funky odors of thiols for the legendary rotten-egg fumes of hydrogen sulfide.
Thiobacilli. Among the varied community known as colorless (i.e. non-photosynthesizing) sulfur bacteria are the small tribe of thiobacilli. Microbiologists have identified five or so species. Some thiobacilli are definitely exotic: two live in sulfurous hot springs, and a couple more live in waters so acid that nothing else can survive. In fact, one thiobacillus is the most acid-tolerant organism known. Most need oxygen, but at least one, Thiobacillus denitrificans, is a facultative anaerobe: provided some nitrate is available, it can reduce nitrate to dinitrogen gas, then oxidize sulfide to sulfate, using the freed oxygen.
Because of these few highly-specialized thiobacilli, it is misleadingly easy to associate thiobacilli only with extreme environments. In oxygen-rich water, thiobacilli utilize various forms of sulfur as a source of energy, just as we use various forms of carbon. They burn sulfur with oxygen"” oxidize it"” to obtain energy, forming stable sulfate. As the metabolizing of carbon produces carbon dioxide, metabolizing sulfur produces sulfur dioxide, which thiobacilli can further use to produce sulfuric acid. Many thiobacilli can also use hydrogen sulfide, which is much more common in healthy aquaria than we imagine, as I've suggested.
Thiobacilli multiply in narrow zones and gradients where some sulfide is diffusing upwards from anoxic zones below and where some oxygen is fitfully available, diffusing down from the interface between water and substrate or biofilm surface. Rivers and estuaries support vast natural populations of thiobacilli, a very desirable inhabitant of the deeper strata of the aquarium substrate. Thiobacilli and a few other bacteria oxidize H2S (and elemental sulfur if they can get it) to sulfate (SO4). In the presence of some oxygen, on the outer fringes of a sulfate-reduction zone, thiobacilli and various other aerobic bacteria congregate to feast on hydrogen sulfide, oxidizing it to harmless sulfate. Some specialized photosynthetic anaerobes can also metabolize H2S. The only place in your aquarium where they could operate is where a deep, anoxic substrate is exposed to sunlight against a glass pane.
Thiobacilli links you might be curious to work through, because these bacteria are distinctly underrated in the aquarium: Erik Wentzel's brief (and pretty technical) lecture outline treatment of Thiobacilli in the context of his soil microbiology course at Virginia Tech might help. A very technical chapter on Thiobacilli excerpted from A. Balows et al, The Prokaryotes 1992, chapter 139, vol. iii.
Interesting artikels about Sulpur
Those who are not satisfied with a simple explanation can start here. But I think this wood be better handled as a topic in the chemics chapter. If it was not already.
Nitrate reduction through sulfur
http://books.google.be/books?id=xHC...ge&q=nitrate reduction through sulfur&f=false
Thiobacillus
http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/Thiobacillus.html
From the forum:
Sulfate/sulfide transformations
Submitted by wetman on Mon, 03/21/2011 - 07:17
Sulfur is another element required for animal life. After carbon, hydrogen, oxygen and nitrogen, the next most common element found in organic molecules is sulfur. Sulfur is a component of some essential amino acids that are part of proteins and of humic substances. You won't be surprised to find a limited arc of the planetary "sulfur cycle," even in the aquarium's limited ecosystem, because all the elements essential to life must be recycled, or else biological processes would have exhausted the planet's supply, after a couple of billion years.
Sulfate and sulfide. In the sulfate ion (SO4), a sulfur atom is surrounded by four oxygen atoms: oxidized, in other words. Sulfates are harmless to fish, odorless and quite stable. By contrast, in sulfides, such as hydrogen sulfide (H2S), the sulfur atom is reduced, stripped of its oxygen and joined to another atom. Sulfides are reactive, and they can be quite toxic.
As with phosphate, inorganic sulfur is unavailable to animals; it must be assimilated by bacteria to form organic sulfur compounds before animals can use it in assembling essential proteins and co-enzymes and other necessary biochemicals.
So, like other elemental cycles represented in the aquarium, sulfur transformations are driven by bacterial processes. Some bacterial metabolisms can reduce sulfate, stripping it of its oxygen atoms, while others oxidize the sulfide that's produced. The various sulfur-metabolizing bacteria aren't all genetically related. They form a co-dependent community, passing sulfur back and forth between sulfate and sulfide states, even sometimes excreting a little elemental sulfur. In undisturbed regions of mature biofilm and the substrate, the aerobic sulfur bacteria help use up the last of diminishing supplies of oxygen, so they keep their anaerobic neighbors safe from the dangerous, reactive O2.
Where is the aquarium's sulfur? At any given moment, most of the sulfur in the aquarium is in the form of sulfates (SO4). Though most of the organic sulfur is in the form of sulfates, not all sulfates are built into organic compounds: sulfates can also be mineralized. Gypsum, for one example, is calcium sulfate, CaSO4: when ground fine it makes plaster-of-Paris, the major component of sheetrock and those weekend "feeder blocks" embedding food flakes. Sodium sulfate, the salt of sulfuric acid, is another widely distributed mineral sulfate. Potassium sulfate is only moderately soluble, but you might be adding it as a plant fertilizer. Magnesium sulfate is Epsom salts. Aluminum sulfate is the alum you might occasionally use to clarify water.
Sulfate is the form of sulfur plants can use, and like phosphate it can only re-enter the food web through algae and plants. They take it up and convert it into their characteristic proteins, which may be consumed by animals, who can't use sulfates directly; instead they convert these plant-produced amino acids into their own animal proteins.
The death of plants or animals begins the process of decomposition, communal processes that involve cooperating fungi and bacteria. The decomposers break down animal and plant proteins, releasing amino acids that animals can use or "mineralizing" the amino acids, that is, breaking them down all the way to release the sulfates, which plants take up once more. Within the aquarium there are sulfur transformations rather than a true cycle, as with phosphate.
Sulfide (SO), stripped of oxygen, is the other form of sulfur normally involved in biological processes. (Thiosulfates"” SO3"” are a less common form of sulfur. You know them most likely from sodium thiosulfate, the active ingredient in de-chlorinator. Thiosulfates don't last in the aquarium, because bacterial communities metabolize them.)
Sulfur bacteria in the substrate. Sulfur is much less common in freshwater sediments than it is in marine environments. Typical habitats for sulfur bacteria are freshwater lake sediments and intertidal mudflats. In such sediments sulfur bacteria communities form densely-populated mats (denser than cyanobacterial mats) that are confined to the narrow layers where the oxygen and sulfide gradients overlap. In the undisturbed substrate there are communities of sulfur bacteria, playing various metabolic roles. Their combined effect is to oxidize sulfides to sulfate.
Sediment banding. Distinct layers form in sandy sediments"” which are more like most aquarium substrates than mud sediments are. Bands in an undisturbed substrate form in reaction to four chemical gradients: light, oxygen, sulfate and sulfide. On the interface between water and substrate, diatoms coat most surfaces, mixing with cyanobacteria. The diatom layer protects the cyanobacteria beneath from the corrosive effects of oxygen. On a mud substrate this community might form a thin dense, somewhat slimy mat: a biofilm. Just below, purple bacteria (with bacterial chlorophyll a), lie in a layer just above green sulfur bacteria (with bacterial chlorophyll b). Purple and green bacteria are the phototrophic "non-sulfur" bacteria of freshwater sediments, especially in alkaline environments . In the layer where silica sand transmits some light, especially in the infrared range, "blind" but motile sulfur bacteria exist in permanent symbiotic relations with phototrophic green sulfur bacteria that cover them. Phototrophic sulfur bacteria require the simultaneous presence of reduced inorganic sulfur compounds"” diffusing upwards from anoxic layers"” and light coming from above. They get their carbon from CO2. Green sulfur bacteria have two distinguishing colors, bright grass green and chocolate-brown, arising from phototrophic pigments.
Link. I'm getting some of this information from Jörg Overmann's rather technical but perfectly readable document, "Diversity and ecology of phototrophic sulfur bacteria" in Microbiology Today, Aug 2001, archived at the Society for General Microbiology's site. If it might be more than you want to know, check the abstract.
In a nutrient-rich sediment, heterotrophic bacteria may overwhelm the slower-growing phototrophs.
Photosynthesizing sulfur bacteria. Anaerobic photosynthesizing sulfur bacteria sometimes form distinct dark layers in the substrate next to the tank glass, where daylight hits it. The bacteria involved are purple sulfur bacteria (with red, brown, purple and orange photosynthetic pigments) and, usually beneath them, the olive-green to brown green sulfur bacteria. In anoxic environments, these bacteria are able to metabolize sulfide or elemental sulfur, using a primitive and ancient kind of archaic photosynthesis that doesn't produce any oxygen. Very low levels of light will suffice for them.
On one of my tanks (and yet not on others), beginning a half-inch below the substrate surface, there's a clear-edged area that is black-green, perhaps dense with these sulfur bacteria probably mixed with cyanobacteria. My hunch is that these particular photosynthesizers are discouraged by the oxygen in the topmost gravel layer. What has been mysterious to me was, why does this photosynthesizing zone appear equally strongly in gravel that's not exposed to daylight from a window? Then RTR explained this phenomenon well in an AC post, 3 Dec 2002: "A significant part of this may well be only on those sand grains or the glass itself exposed to internally relected light. Light from the tank's lighting entering the glass at certain angles passes through the interior glass surface, but is reflected back from the exterior and comes back out within the tank just below the substrate surface"” the glass itself acts a light pipe for a short distance. In one small area, pull back or siphon up the sand. If the algae is still there in the glass with a bit on the sand removed, it is just internal reflection promoting growth, and it may be removed at will. If the patch extends into the tank away from the glass a completely different process is occuring."
Hydrogen sulfide. For generations hydrogen sulfide has been a bugaboo to aquarists, who have sniffed their tanks for the tell-tale whiff of rotten eggs that would confirm their dark fears. Hydrogen sulfide can be produced by two kinds of bacteria. Surprisingly, one kind are aerobic bacteria: H2S can be formed in the normal process of aerobic bacterial decomposing of plant and animal remains. Atoms of sulfur form part of the molecules in living tissues, notably in proteins. When tissues are broken down, the sulfur is first released as sulfides, contributing to the stink of putrefaction. In the decay process, where organic substances from cells are being decomposed, a group of "sulfur bacteria" scavenge oxygen from the organic sulfate and use it to oxidize carbon.
Minute quantities of sulfur are released throughout the aquarium, some of it as infinitesimal amounts of H2S. Other bacteria, however, are right at hand to oxidize the sulfides to sulfates; they are a wide-ranging group of aerobic bacteria, including thiobacilli. This sulfide/sulphate regeneration is a normal component of the mature community of the biofilm. But at points in the cycle where oxygen is locally scarce, such as microzones deep in a well-developed biofilm, sulfur-reducing bacteria can short-circuit the cycle by reducing free elemental sulfur or SO4 directly back to sulfides, by-passing plants and animals.
Obligate anaerobes and the dreaded hydrogen sulfide. But, pretty rarely in most aquaria, pockets of hydrogen sulfide can also form in deep substrate layers that are never touched by oxygen. In entirely oxygen-free zones of the substrate, de-nitrating bacteria can thrive, stripping the oxygen from nitrate and nitrite. Their activities produce a nitrate gradient. In sufficiently deep substrates, nitrates may become entirely used up. Below the de-nitrating zone, where there is neither nitrate to work on, nor oxygen to interfere, sulfate (SO4) can become the next-best electron receptor for obligate anaerobes, those bacteria who can't handle oxygen at all. This metabolic process is much less efficient as a source of energy, but as long as they are utterly protected from the deadly oxygen, a range of anaerobic sulfate-reducing bacteria strip the oxygen from sulfate and use it to get carbon from carbon dioxide. Their waste products include H2S. Hydrogen sulfide (H2S) is deadly to all aerobic organisms, so the noxious gassy byproduct can help stabilize a safely anoxic environment for the sulfate-reducing bacteria that produce it, surrounding themselves with a "killing zone" called a sulfuretum.
Hydrogen sulfide is highly reactive, part of what makes it toxic at the nanomolar (µM) level, according to a 1997 California Academy of Sciences BioForum lecture "Living with toxic sulfide" given by Dr Alissa Arp, who has been exploring marine H2S metabolisms in deep oceanic thermal vents and methane seeps and the black mud of tidal estuaries. Now, of course they are getting a long way from the freshwater aquarium, but these are good places to study sulfur metabolisms. For instance, Dr. Arp relates, H2S reacts with iron to make black iron sulfide. In the substrate, iron in the ferric state, Fe(III), will oxidize H2S, turn it to thiosulfate.
This useful reaction of Fe(III) and H2S has been harnessed by a curious California mudflat worm, Urechis, which lives in an excavated burrow where water is stagnant at low tide. There is a lot of bacterial activity in the mud, which is highly enriched organically, so the oxygen gradient is very steep. The bacteria in anoxic mud produce sulfide, and if you walk on the mudflat at low tide, you smell the hydrogen sulfide. So the worm Urechis is faced with environmental challenges, which it meets by detoxifying the H2S in its coelomic fluid, which is rich in heme compounds, though not associated with a protein as in our hemoglobin. The iron in the heme group is in the ferric state. Its extra positive charge oxidizes the sulfide to non-toxic forms, principally thiosulfate.
These sulfate-reducing bacteria giving off H2S are "obligate anaerobes," the kind of primitive bacteria that are poisoned by a breath of oxygen. There is another group of specialized anaerobic sulfur bacteria that can also metabolize sulfate for energy, converting it to sulfide. These bacteria also require a strictly anoxic environment to work in. Oxygen doesn't kill them outright, but in the presence of oxygen these sulfate reducers can't grow and multiply. They need an organic substrate, such as acids generated by the fermentative activities of other anaerobic bacteria. Nitrate also retards their action. Only in deep, richly organic substrates that are disturbed at long intervals could they become a problem.
Sulfate-reducing bacteria tend to create a blackened layer in the substrate, because iron reacts with some of the the sulphide they produce to form dark-colored iron sulfide (FeS).
Sulfate reduction in biofilms. Though the sulfate reducers are obligate anaerobes, suitable oxygen-free microzone environments aren't necessarily buried in the deeper layers of the substrate. Sulfate-reducing bacteria tend to multiply in undisturbed matured biofilms as well. A sulfuretum doesn't get established there because neighboring bacteria are waiting to oxidize the hydrogen sulfide to harmless sulfate.
Sulfate-oxidizing bacteria. So, if H2S has formed in a deeper anoxic layer in substrate or a thick biofilm, various aerobic bacteria are waiting to scavenge any available hydrogen sulfide and oxidize it to harmless sulfate. In an undisturbed substrate, bacteria like these would tend to congregate in a thin layer at the limits of diffused oxygen, subsisting on any H2S that might diffuse up from a deeper anoxic layer. If you found that the roots of plants are blackened (they should be white) you might suspect hydrogen sulfide poisoning. But healthy active plant roots have a natural defense against H2S; they release some oxygen, which creates a protective microzone surrounding each rootlet, where these H2S-oxydizing bacteria can thrive. In an undisturbed substrate, as H2S rises up to the rootzone, it is increasingly unlikely to avoid getting oxidized to sulfate. Diana Walstad notes that H2S was found to be negligible in oxygenated swamp water, even when it was present in the underlying sediment.
My H2S conclusions. In sum, hydrogen sulfide could only be an issue in a substrate that was too deep (over 4 inches, say), one that was also entirely anoxic, was also depleted in nitrate and was enriched with decaying organics and sulfate, perhaps from fertilizer. Then, to get the H2S up into the water column, though, you'd have to get in there at long intervals and vigorously stir up the deepest layers of substrate with a gravel cleaner. My point is that several poor aquaristic practices would have to be combined.
I did once have an unpleasant brush with H2S. An Aponogeton bulb had died back but never renewed itself. After some months I went to root it out. It was reduced to a shell- the heart was rotten and softer than a French cheese. When I managed to get it to the surface in one piece, the notorious stink of H2S greeted my nose. I figure that the resistant rind of the bulb had protected the interior from the destructive powers of oxygen. Inside it, an isolated community of stinky anaerobic decomposers had uninhibited free play, and H2S could accumulate, safe from the substrate bacteria that would otherwise have oxidized it to harmless sulfate.
...Other fishkeepers have had similar experiences. Apparently the fleshy tubers of a Banana Lily (Nymphoides aquatica) can provide a similar oxygen-free haven for sulphur-reducing anaerobes. G.S. Mollin posted at Tom'sPlace 10 Jan 2002: "Actually it took a dead banana plant to get the anaerobic pocket started. It smelled pretty bad and was jet black wastewater when vacuumed." But on the whole, I think aquarists tend to mistake the funky odors of thiols for the legendary rotten-egg fumes of hydrogen sulfide.
Thiobacilli. Among the varied community known as colorless (i.e. non-photosynthesizing) sulfur bacteria are the small tribe of thiobacilli. Microbiologists have identified five or so species. Some thiobacilli are definitely exotic: two live in sulfurous hot springs, and a couple more live in waters so acid that nothing else can survive. In fact, one thiobacillus is the most acid-tolerant organism known. Most need oxygen, but at least one, Thiobacillus denitrificans, is a facultative anaerobe: provided some nitrate is available, it can reduce nitrate to dinitrogen gas, then oxidize sulfide to sulfate, using the freed oxygen.
Because of these few highly-specialized thiobacilli, it is misleadingly easy to associate thiobacilli only with extreme environments. In oxygen-rich water, thiobacilli utilize various forms of sulfur as a source of energy, just as we use various forms of carbon. They burn sulfur with oxygen"” oxidize it"” to obtain energy, forming stable sulfate. As the metabolizing of carbon produces carbon dioxide, metabolizing sulfur produces sulfur dioxide, which thiobacilli can further use to produce sulfuric acid. Many thiobacilli can also use hydrogen sulfide, which is much more common in healthy aquaria than we imagine, as I've suggested.
Thiobacilli multiply in narrow zones and gradients where some sulfide is diffusing upwards from anoxic zones below and where some oxygen is fitfully available, diffusing down from the interface between water and substrate or biofilm surface. Rivers and estuaries support vast natural populations of thiobacilli, a very desirable inhabitant of the deeper strata of the aquarium substrate. Thiobacilli and a few other bacteria oxidize H2S (and elemental sulfur if they can get it) to sulfate (SO4). In the presence of some oxygen, on the outer fringes of a sulfate-reduction zone, thiobacilli and various other aerobic bacteria congregate to feast on hydrogen sulfide, oxidizing it to harmless sulfate. Some specialized photosynthetic anaerobes can also metabolize H2S. The only place in your aquarium where they could operate is where a deep, anoxic substrate is exposed to sunlight against a glass pane.
Thiobacilli links you might be curious to work through, because these bacteria are distinctly underrated in the aquarium: Erik Wentzel's brief (and pretty technical) lecture outline treatment of Thiobacilli in the context of his soil microbiology course at Virginia Tech might help. A very technical chapter on Thiobacilli excerpted from A. Balows et al, The Prokaryotes 1992, chapter 139, vol. iii.
Belgian Anthias
New member
I thought it was a rhetorical question .Didn't think you wanted to play a game . Anyway you've left at least a half dozen questrons unanswered throughout the course of the thread.
I use 2 liters. for 20ppm.and manage the flow accordingly.
I can multi task and see the realtionship between the flow and volume of bacteria engaged in anaerobic vs aerobic activity .
Ok,to be sure I understand and don't misrepresent :
you'd use :
5 liters of sufur for 5ppm ,
10liters for 50ppm, even though the paper you cite recommends 5 liters for 50 and below.Why don't you follow the recommended amount in the paper you cited,.btw?
The same 10liters for 80ppm. Why not 8 or 16 ?
What do you do when your denitrator is shut down for relpensihment, power outage etc.? Let's say you were using 10liters for 500 liters of water volume with 80 ppm initially but on restart the nitrate in the aquarium is only 5 or 10ppm ,Do you still use the same 10 liters?
Do you see it yet?
Belgian Anthias
New member
Relation between amount sulfur and alkalinity?
Relation between amount sulfur and alkalinity?
The effect on sulfate and alkalinity has nothing to do with the amount of sulfur used.Why is the amount of sulphur a concern? Influence at the alkalinity is in relation to the aerobic, anaerobic and auto-tropic activity of the bacteria which is mainly regulated by the flow and the water quality.
Relation between amount sulfur and alkalinity?
The effect on sulfate and alkalinity has nothing to do with the amount of sulfur used.Why is the amount of sulphur a concern? Influence at the alkalinity is in relation to the aerobic, anaerobic and auto-tropic activity of the bacteria which is mainly regulated by the flow and the water quality.
The effect on sulfate and alkalinity has nothing to do with the amount of sulfur used.Why is the amount of sulphur a concern? Influence at the alkalinity is in relation to the aerobic, anaerobic and auto-tropic activity of the bacteria which is mainly regulated by the flow and the water quality.
I've been over this several times. One more try.
More bacterial activity including more aerobic activity by sulfur bacteria equals more sulfate production and alkainity use and some organic production as well. More sulfur supports more sulfur bacteria If it didn't there would be no need to vary the amount of sulfur which you and I both do.
The aerobic activity by facultative chemolithoautotrophic sulfur bacteria has no benfit in tems of nitrate reductionbut does add more sulfate ,uses alkainity and produces some organic material . It's not needed and can be managed.
I've been over this several times. One more try.
More bacterial activity including more aerobic activity by sulfur bacteria equals more sulfate production and alkainity use and some organic production as well. More sulfur supports more sulfur bacteria If it didn't there would be no need to vary the amount of sulfur which you and I both do.
The aerobic activity by facultative chemolithoautotrophic sulfur bacteria has no benfit in tems of nitrate reductionbut does add more sulfate ,uses alkainity and produces some organic material . It's not needed and can be managed.
CHSUB
"Certified Hobby Expert"
I will clear it up for you guys: the 1% rule is a good starting point for Sulfur Denitrator(imo & ime). most of the reactors in this post are undersized and imo this is why people fail with sulfur. if and when no3 becomes very low one can remove some sulfur and/or increase the flow. i found that using a dosing pump and an ORP controller makes Sulfur Denitrators foolproof and failsafe.
Belgian Anthias
New member
Only a small part of the sulfur is colonized bij autotropic bacteria. it does not matter how many sulfur you use. In the same aquarium system the same amount of bacteria will do the job. If your system is balanced at 2ppm en the aqua produces 1/2 ppm a day than you have to remove 1/2ppm/day. The same amount of bactaria is needed. That 5l or 10l of sulfur is used, it does not matter. Only the flow will be different. it is the amount of oxygen and nitrate that enters the reactor which will define how much of the sulfur will be colonized by autotropic bacteria The effect on alkalinity and sulfate will be about the same. And sulfate? I really do not care.
In the reactor not only autotropic bacteria are responsible for reducing the nitrate.
Bacteria will colonize whatever space and sufur energy souice is available .that's what bacteria do ,They use energy sources and space . Sulfur bacteria like all bacteria are very effective at it. More sulfur and more surface area equal more bacteria. The oxygen level determines the amount of anaerobic activity vs aerobic activity by these bacteria. More flow means more oxygen ;more oxygen means less nitrate reduction. Only the anaerobic activity reduces nitrate to nitrogen gas. Simple really .
Don't know why you don't care about sulfate or lost alkalinity,I do; but that's your choice. I disagree with it and so do the authors of some of the papers you cited : ""The quantity of sulfur to use depends on the initial nitrate level at startup and on the amount of food added" but if it makes you happy to think of it the way you do ,it's ok. Running 5 liters of sulfur to reduce 0.5ppm of nitrate while using the same 5 l for 50ppm nitrate doesn't make sense to me and I wouldn't recommend it .
Don't know why you don't care about sulfate or lost alkalinity,I do; but that's your choice. I disagree with it and so do the authors of some of the papers you cited : ""The quantity of sulfur to use depends on the initial nitrate level at startup and on the amount of food added" but if it makes you happy to think of it the way you do ,it's ok. Running 5 liters of sulfur to reduce 0.5ppm of nitrate while using the same 5 l for 50ppm nitrate doesn't make sense to me and I wouldn't recommend it .
Belgian Anthias
New member
I do not agree, there should never be a reason to remove sulfur. Why should you? There is only a part of the sulfur that is used by autotropic bacteria. Also the free oxygen reducing bacteria need space. Once the system and the reactor has found its balance it is not a good idea to remove sulfur. Sulfur de-nitrators should be used as a permanent part of the system, not as a problem solver. The effect on alkalinty will be minimal except when real overfeeding is a habit.
A 1% reactor which is managed correctly is very reliable. A failed pump should not be dramatic.
ORP and/or PH readings of the effluent are not needed to manage a sulpfur de-nitrator but it can help.
Most problems with sulhur de-nitrators occur when users decrease the flow instead of increasing when nitrate gets low. Everything will look fine till the moment the critical point of the reactor is reached. ORP will show you that this point is reached but than it is to late. Not that it would be dramatic because effluent flow will be low and is aerated before entering the system. Increasing the flow will solve the problem and remove the dead biomass. It will take some time for the bacteria to recover. In the case, please wait some time before to re-start with the start up procedure.
ORP can help to manage the reactor but can not avoid mismanagement.
You use a dosing pump? Can you tell me more?
Belgian Anthias
New member
Ok discussion closed.
I still did not get an answer from you how many sulfur you are going to use for a simple question: a 500l aquarium with 20 ppm. How many sulhpur to use based on the nitrate?
Next question: how many sulhpur do you use in a 500l aquarium system with a daily over production of 1ppm.
Next geustion: how many sulphur do you need in a 500l aquarium system with 20 ppm, a known daily over production of 1ppm and you want reduce the 20ppm to 2 ppm in a month.
My answer on all questions: 5l; when 50ppm or more in the system 10 l
Based on the nitrate in the system you would use how many sulphur?
Belgian Anthias
New member
I just wanted you to help and fix this. You have made yourself a possible H2S factory because this situation is not possible if flow is increased when nitrate drops, as I have explained. You have mismanaged your reactor the way I explained and your reactor was working close to its critical point. That is why you are afraid for H2S production and use GFO.
You do not have to accept my explanation, but you should do something to solve this.
Belgian Anthias
New member
Why so much sulpur?
Why so much sulpur?
The big advantage of a big enough reactor is the fact that it is easily managed. When nitrate is low flow will be high and only a small part of the reactor will be anaerobic. When the situation occurs that nitrate rises due to overfeeding , growing animals or dead biomass the flow is easily managed and reduced. The risk to reach the critical point is nihil. When a small reactor is used one may NOT reduce the flow because because the critical point is not known. Just leave it as it is. When the reactor is really to small the point may be reached that there is not enough room in the reactor for the bacteria needed to brake down the available nitrate and the process may not be completed and nitrite may be formed. This should not be a problem if the effluent is aerated before entering the system but nitrite will become nitrate again and nothing will be removed. As the nitrate reading of the effluent may be 0 and the nitrate readings of the water do not decrease conclusions will be made that the reactor thus not remove enough. Reducing the flow at this point will be critical. Less flow, less oxygen, less nitrate, max anaerobic activity. All available oxygen my be depleted.
This is also why removing sulfur from a reactor at low nitrate levels is not my advise.
Most reactors in this topic are to small. When managed the right way there should not be a problem. I have also noticed that reactors are mismanaged and this way they function close to there critical point. This is also the reason I think a lot of people are afraid to use one.
Why so much sulpur?
The big advantage of a big enough reactor is the fact that it is easily managed. When nitrate is low flow will be high and only a small part of the reactor will be anaerobic. When the situation occurs that nitrate rises due to overfeeding , growing animals or dead biomass the flow is easily managed and reduced. The risk to reach the critical point is nihil. When a small reactor is used one may NOT reduce the flow because because the critical point is not known. Just leave it as it is. When the reactor is really to small the point may be reached that there is not enough room in the reactor for the bacteria needed to brake down the available nitrate and the process may not be completed and nitrite may be formed. This should not be a problem if the effluent is aerated before entering the system but nitrite will become nitrate again and nothing will be removed. As the nitrate reading of the effluent may be 0 and the nitrate readings of the water do not decrease conclusions will be made that the reactor thus not remove enough. Reducing the flow at this point will be critical. Less flow, less oxygen, less nitrate, max anaerobic activity. All available oxygen my be depleted.
This is also why removing sulfur from a reactor at low nitrate levels is not my advise.
Most reactors in this topic are to small. When managed the right way there should not be a problem. I have also noticed that reactors are mismanaged and this way they function close to there critical point. This is also the reason I think a lot of people are afraid to use one.
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Belgian Anthias
New member
Why?
Why?
Of coarse the 1% reactor is only a guide line. It is advised to use a 2% reactor when 50ppm and more has to be removed. This is also a guide line. Following this guidelines will result in an easy manageable reactor.
Off coarse it the amount of sulphur can be less; If the situation in the system is known, the amount to remove daily is known, there should be no problem in using for example a 1/2% reactor as long as it is big enough.
If a sulpur de-nitrator is installed at start up of the aquarium system a 1/2% reactor will do the job satisfactory but the range in which it can work will be smaller.
A 1% reactor will work satisfactory in all circumstances without any headache.
At the end , only the over production has to be removed. A smaller reactor should be able to handle this, as long as it is big enough. And to avoid all calculations and worries, it is known that a 1% reactor is big enough.
The most important, less nitrate in the water, more flow. When nitrate builds up less flow.
Why?
Of coarse the 1% reactor is only a guide line. It is advised to use a 2% reactor when 50ppm and more has to be removed. This is also a guide line. Following this guidelines will result in an easy manageable reactor.
Off coarse it the amount of sulphur can be less; If the situation in the system is known, the amount to remove daily is known, there should be no problem in using for example a 1/2% reactor as long as it is big enough.
If a sulpur de-nitrator is installed at start up of the aquarium system a 1/2% reactor will do the job satisfactory but the range in which it can work will be smaller.
A 1% reactor will work satisfactory in all circumstances without any headache.
At the end , only the over production has to be removed. A smaller reactor should be able to handle this, as long as it is big enough. And to avoid all calculations and worries, it is known that a 1% reactor is big enough.
The most important, less nitrate in the water, more flow. When nitrate builds up less flow.
uncleof6
Active member
If someone is going to take the time to do this sort of write up (no reflection on the person that included the write up in their post,) one should at least get the information right. I read for less than a minute; I did not bother reading the rest...
Sulpher is one of the 17 "required for life" elements. However, when it comes to the most common elements in organic molecules, there is an acronym: CHNOPS. It stands for Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, and lastly Sulphur. In order...so after oxygen, the next most common element found in organic molecules is phosphorous...not sulfur. Easy enough mistake to make, but in an article concerning Sulphur denitrators, it is not a good mistake to make...
If we look at the cellular level composition of animal life, Sulphur drops down a bit. ~99% of the mass of a living animal is made up of 6 elements: Oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorous. The next 0.75% is comprised of the next 5 elements of the 17: Potassium (0.2%,) Sulphur (0.2%,) Chlorine (0.2%,) Sodium (0.1%,) Magnesium (0.05%.)
I read another article length post concerning carbon-dosing. I read for less than a minute, and noted that the author considered Ammonia (NH<sub>4</sub>) an organic compound...it isn't, it is an inorganic byproduct of decomposition. I did not bother reading the rest...
Not interested in getting into the topic of sulphur denitrators, just pointing something out...
Belgian Anthias
New member
All I know from sulphur is what one can find in Wikipedia.
I am not qualified to discus this matter. I just showed some articles I have red and found interesting.
Belgian Anthias
New member
Why installing a sulpur de-nitrator at start up of the aquarium system
Why installing a sulpur de-nitrator at start up of the aquarium system
Using a sulfur de-nitrator at start-up has the advantage that it will become a part of the biological system. It gives the possibility to manage the Nitrate as needed. One does not have to starve the animals or use a big skimmer that strips the water completely. One does not need expensive living stone to build a reef. Old or self made stone will do. One can provide food for non photosynthetic animal live.
When used at start up only the daily produced amount of nitrate has to be removed limiting the effect on alkalinity. System water should pass the reactor once or twice a day to prevent nitrate build up in the aquarium when something happens. Animals die. This means the flow must be high enough which means a big enough reactor has to be used. We know that a 1% reactor is big enough.
As nitrate nitrogen can be measured by electronic devices, flow regulation can be automated for bigger systems.
Why installing a sulpur de-nitrator at start up of the aquarium system
Using a sulfur de-nitrator at start-up has the advantage that it will become a part of the biological system. It gives the possibility to manage the Nitrate as needed. One does not have to starve the animals or use a big skimmer that strips the water completely. One does not need expensive living stone to build a reef. Old or self made stone will do. One can provide food for non photosynthetic animal live.
When used at start up only the daily produced amount of nitrate has to be removed limiting the effect on alkalinity. System water should pass the reactor once or twice a day to prevent nitrate build up in the aquarium when something happens. Animals die. This means the flow must be high enough which means a big enough reactor has to be used. We know that a 1% reactor is big enough.
As nitrate nitrogen can be measured by electronic devices, flow regulation can be automated for bigger systems.
I know how to manage denitrators. H2S occurred years ago (near the time when the thread started) when the nitrate dropped . Increasing the flow and reducing the amount of sulfur took away the odor in the effluent . I had to modify the diy reactor to allow more flow as part of that fix.Reducing the sulfur along with increasing the flow enabled an acceptable balance in the hypoxic range( nitrate but low oxygen). More oxidation reduces H2S faster and can be accelerated by passing through gfo. It's a simple safety device or add on when and if H2S production becomes an issue for users.
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