Rare Event Mystery of Exploding Massive Municipal Water Tanks

[John Cuthber]

"By the way, there is no 'my chemistry' here, as I have given, for the most part, peer reviewed published work."

In the real world, you don't get ammonia and nitrous acid in the same solution.

 

If the sun heats the vessel enough to initiate an explosion then the expansion / vapour pressure of water is going to be putting a serious strain on the tank without any chemistry.

 

Points 3 and 4 are almost contradictory. If the water has been chlorinated there won't be bugs or H2S

As I said, you need to look at the chemistry.

 

point 6 is likely to be significant. Old tanks fail.

Re. point 7 gases that don't dissolve well in water may accumulate.

You may note that I have already pointed out methane and hydrogen as potential contributors.

 

Now, could you please explain what you thought you meant by

"Personally attacking me, based on how I have, on many occasions embarassed a super moderator at SC who thinks, because he has a longer career as a practicing organic (not inorganic) chemist isn't a basis for a scientific assessment of my arguments."

and

"but claiming that all the incidents and investigations thereof, are all nonsense is really closed minded,"

Edited June 9, 2013 by John Cuthber

[ajkoer]

In my opinion, Points 3 and 4 are did not necessarily contradict. Timing is important, as Chlorine, per a source cited above, to quote: " Chloramine does not dissipate easily compared to chlorine." My take, although Cl2 can kill nearly all kinds of bugs, it dissipiates and the water can be subsequently contaminated with organic matter and bacteria (forming NH3). Hence, the argument for Chloramine, although a much weaker disinfectant, having greater longevity. You may be aware of some arguments about chlorine cleansers, that they can create super bugs in your home, well, at least, that is the assertion. No one has mentioned drinking water, but perhaps a biochemist will confirm with some words of comfort.

 

On point 7, I would add NO pending exposure to sufficient oxygen (form newly added fresh water) at which point the highly soluble NO2 is formed and HNO2 transported from an earlier tank composition. While temporary, this may actually play a role at times (my speculation) in a nitrite concentration mechanism as an answer to valid dilution arguments.

 

Also, NH3 and HNO2 can co-exist, at least until they react, as my reference provided previously cites the creation of ammonium nitrite by the action of ammonia on Nitrous acid:

 

HNO2 + NH3•H2O --> NH4NO2 + H2O

 

The other comment is more directed toward active followers of that other chemical forum.

Edited June 9, 2013 by ajkoer

[John Cuthber]

"On point 7, I would add NO pending exposure to sufficient oxygen"

I wouldn't.

That's because I looked up the solubility of nitric oxide.

 

"Also, NH3 and HNO2 can co-exist, at least until they react, as my reference provided previously cites the creation of ammonium nitrite by the action of ammonia on Nitrous acid:

HNO2 + NH3•H2O --> NH4NO2 + H2O"

 

It's precisely because they react that they can't co exist.

[ajkoer]

To quote a source (see http://cgmp.blauplanet.com/adv/nomol.html ):

 

"At room temperature and at atmospheric pressure Nitric oxide is a colorless gas with low solubility in water".

 

See also Wikipedia solubility table results at (http://en.wikipedia.org/wiki/Solubility_table#N ), low solubility indeed, .0056 g/100g water at 20 C. Now as NO molar mass is 30 g which would occupy 22.4 liters, the dissolved amount of gas of .0056 g equates to 4.2 ml.

 

Now, add O2 to the water and things change as, to quote Wikipedia (http://en.wikipedia.org/wiki/Nitric_oxide ):

 

"In water, NO reacts with oxygen and water to form HNO2 or nitrous acid. The reaction is thought to proceed via the following stoichiometry:

 

4 NO + O₂ + 2 H₂O → 4 HNO₂

 

So, in oxygen poor water, Nitric oxide can accumulate per low solubility, but undergoes a chemical reaction in fresh oxygen rich water.

 

An important point is that one accept the formation (and decomposition) of HNO2 and NH4NO2. The gaseous decomposition/explosive nature of NH4NO2 alone could account for the tank ruptures.

Edited June 9, 2013 by ajkoer

[John Cuthber]

The typical amount of nitrogen present as nitrite is less than 1 ppm.

http://water.epa.gov/drink/contaminants/basicinformation/nitrite.cfm

So, call it 0.5ppm, just to have a figure to work with.

 

You give the solubility of NO as 0.0056 g/100 ml, whic is 0.056 g/l

which is 56 ppm

So, all the gas that might be produced will dissolve.

So would ten times more

So would a hundred times more.

 

Now, can you please stop being silly.

[arc]

"If anyone has new theories, please present them,"

I did: hydrogen, unburned fuel gas from the torch , bacterially produced methane.

John, I think you are correct;

Years ago in my line of work, some workmen prepared to cut down a large electric advertising sign on top of a very tall steel pole. One of the workmen dropped the acetylene torch next to the pole and then broke for lunch. As they ate the pole was filled from the bottom below grade with acetylene from an open valve on the torch, the electrical access opening at the bottom of the column provided a slow air flow up inside the solar heated steel pylon to the large sign above. When the torch was applied to the base after lunch the gas exploded like a cannon, blowing the sign on top to pieces. The guys almost had heart attacks as debris shot out in all directions.

[ajkoer]

John:

 

I actually came up with something that supports your zinc-copper couple hydrogen based model (opened minded in spite of my critics). The argument goes, assume there is only a small amount of copper salt around (this has been one of main points of concern), but a double replacement reaction with Zn will deposit the copper on the tank's lining over time. So, with sufficient time and some copper presence, it could accumulate. Then, upon sufficient warming of the water, the reaction:

 

Zn + 2 H2O ---Copper & Heat--> Zn(OH)2 + H2 (g)

 

and more rapid generation of hydrogen could occur. I am still not confident, however, why pressure release valves could not address (relieve) this pressure buildup over time.

----------------------------------------------------------------------------------------------

 

On the nitrite argument, I was reading that ammonia contamination of the water table is a problem is increasing common in agriculture settings from ammonia based fertilizers and a movement in the water table attributed to a drought. Also, septic tanks can be a contributing factor. Here is one source (http://www.google.com/url?url=http://scholar.google.com/scholar_url%3Fhl%3Den%26q%3Dhttps://info.ngwa.org/GWOL/pdf/750600769.PDF%26sa%3DX%26scisig%3DAAGBfm3aEthCEvtudr9v10x6q9dduq6EuA%26oi%3Dscholarr&rct=j&sa=X&ei=1pW3UcHCCZXA4APa7oDYDQ&ved=0CDYQgAMoAjAA&q=ammonia+contamination+in+groundwater&usg=AFQjCNHAxw6vBvSYKGG2jZTNycURei1eUA ) where the nitrate presence based on 230 water samples was 250 mg per liter of water. One word, incredible, but even more shocking is the range from less than 1 mg/Liter to 3,100 mg/Liter. Not surprising, some cattle actually were documented as having died of anoxia (excess nitrate poisoning).

 

Perhaps my nitrite hypothesis isn't a mystery after all, it is just an unpleasant truth reflective of a much larger problem that governments have been unwilling or unable to address, as I have been hearing more talk (case in point, Bloomberg News June 10, 2013 ) of a worldwide water problem. The first symptoms, of course, would be water quality, and an exploding tank may simply be an obvious indication of that reality. Someone tell me I am wrong, I will sleep better.

Edited June 11, 2013 by ajkoer

[ajkoer]

If one accepts the presence of nitrates in the drinking water, then in the presence of the following metals Fe and Pb in neutral solutions, and Zn, Cd, Cu, Mg and Al also appear active (see "American journal of science", Volume 112, page 188 at http://books.google.com/books?id=MvcQAAAAIAAJ&pg=PA188&lpg=PA188&dq=zinc+reduces+nitrates+to+nitrites&source=bl&ots=Dq9GZDHiTU&sig=sVyXwq5mDYxfUJzj51enKIVdpjg&hl=en&sa=X&ei=K1K4UcXCGOji4AOJ0oDYBA&ved=0CFIQ6AEwCDge#v=onepage&q=zinc%20reduces%20nitrates%20to%20nitrites&f=false in reducing nitrates to nitrites. In fact, Zinc powder is widely used in test for nitrate reducing bacteria (see, for example, http://www.mesacc.edu/~johnson/labtools/Dbiochem/nit.html via a sensitive nitrite based test.

 

Bottomline, if there is a water quality issue associated with nitrates and nitrites in the presence of select metals, reduction reaction can occur forming N2 gas. In fact, this is pretty much common knowledge as to quote from the last source:

 

"However, it is possible that the nitrate was reduced to nitrite but has been
further reduced to ammonia or nitrogen gas."

[John Cuthber]

You are still ignoring the fact that you could get nitric oxide- if there were enough nitrate and there usually isn't. We know that there isn't because we would have heard about the poisonings.

http://www.who.int/water_sanitation_health/diseases/methaemoglob/en/

That data is from the WHO a group paid for by the governments that you say are not dealing with the problem.

"Someone tell me I am wrong, I will sleep better."

I already have, repeatedly. the only effect was that you came up with more outlandish suggestions.

 

Production of nitrogen isn't much of an issue either- it's also slightly soluble in water and most water couldn't (even if the reactions went to completion) produce much nitrogen because there's not much nitrite or ammonia.

 

And, just to make this clear. There's no way that your fantasy of ammonium nitrite explosions can happen.

You can't get nitric oxide and ammonia from the same water because they would react, and you also seem to be ignoring the fact that the stuff would be hygroscopic in the conditions concerned (i.e. 100% RH) so it would dissolve and run back into the rest of the tank forming such a dilute solution that nobody would care about it.

 

Why are you still going on about this?

 

Do you realise that normal people would think "the tank corrodes and so it fails"

but you think

"the tank corrodes and due to some obscure chemistry this creates an impossible set of conditions that creates an acid and a base at the same time by either oxidation or reduction of something which probably isn't actually there, but they don't react in solution, They bubble out into the gas phase- even though neither of them could be present at anything like their solubility limits- unless there's an international government conspiracy going on which would lead to an epidemic which we don't see.- and they create a salt which, for some reason doesn't just pick up water from the saturated water vapour that it's in and dissolve, but crystallises out and explodes- so the tank fails."?

 

"Bottomline, if there is a water quality issue associated with nitrates and nitrites in the presence of select metals, reduction reaction can occur forming N2 gas. In fact, this is pretty much common knowledge as to quote from the last source:"

And if there isn't (which we know to be the case) then the reaction won't happen.

 

 

Alternatively, bottom line, the tanks corrode and fail.

Edited June 12, 2013 by John Cuthber

[Moontanman]

If there really is a problem with exploding water towers the most likely route would seem to be methane dissolved in the water out gassing into the tank. It's not unusual for ground water to contain methane, in some areas water from the tap will appear to ignite if exposed to a flame. A water tank containing a significant amount of methane gas could ignite, I can see it exploding under the right conditions...

[ajkoer]

John:

 

One of the pictures I posted clearly shows that the top of the tank has been blow off as if by a pressure eruption. This observation is not consisent of a failure by corrosion (there is no solution contact on the top of the tank).

 

Also, the corrosion argument can be used to support a pressure reaction before a mechanical failure. Galvanic corrosion, like for example, with the Zn-Cu couple, does consume Zn forming some Zn(OH)2 which can eventually lead to a failure. But the other product is a whole lot of H2 gas:

 

Zn + 2 H2O ---Cu & Heat--> Zn(OH)2 + H2

 

in fact, for each mole of Zn(OH)2 formed by evenly dissolving of the lining forms 22.4 liters of Hydroen gas forms!

-----------------------------------------

 

Now, with respect to Nitric oxide formation per the decomposition of HNO2, assuming it hasn't formed the very problematic NH4NO2, it presence would be insignificant in comparison to amount of possible N2 formation from the metal induced decomposition of nitrates and nitrities in significant concentrations.

 

Read my quote above, this isn't 'obscure chemistry', very common in testing for the presence of bacteria for nitrate determination (many google hits), but the field is perhaps more biochemistry. Also, my dated reference is perhaps a 100 years old that notes the breakdown of nitrates by various metals in neutral and other conditons forming nitrogen as one of the gaseous products.

 

The fact that it is new to many (including chemists) may be related to the fact that only in the last 50 years has the underlying chemistry been examined and explained.

 

In essence, bad water with high nitrates and nitrities could behave (meaning explode, erupt, burns,..) more and more like chemical plants waste water for which such reactions are common place.

 

In my opinion, it may all be a question of water quality. Mechanical failure (like of the aquarium) by miscalculating the required thickness of the glass (no corrosion there) for the expected weight of water, fish and the like just does not happen as much in the computer age. In fact, the likelihood of someone trying to break the glass may have been anticipiated by requiring the glass to be even thicker than needed.

Edited June 12, 2013 by ajkoer

[John Cuthber]

Have you forgotten that I was the first to suggest hydrogen as a cause?

I said "There are, on the other hand, sensible explanations of the tank failures you cite. A zinc coated tank will generate hydrogen which is known to be explosively flammable when mixed with air." about a week ago.

The chemistry isn't obscure because of its age, it's obscure because the circumstances in which it happens to any significant extent are rare.

 

"In essence, bad water with high nitrates and nitrities could behave (meaning explode, erupt, burns,..)"

No it could not. It is far too dilute.

Stop being silly.

[ajkoer]

Now, to quote Wikipedia again:

"In anything other than very dilute, cold solutions, nitrous acid rapidly decomposes into nitrogen dioxide, nitric oxide, and water:

 

2 HNO₂ → NO₂ + NO + H₂O "

So, assuming some very dilute aqueous HNO2 (or NH4NO2) is formed, it is stable, until the water temperature rises, or the solution becomes acidic. So, correct me, but dilution itself, is not a negative as it contributes to Nitrous acid's stability, and more interestingly, per this source, HNO2 has limited solubility (see http://pubs.acs.org/doi/abs/10.1021/j100333a025 ). The severity of pressure eruption is most likely a function of the quantity of nitrite present, and the change in conditions that trigger its decomposition (temperature, concentration and pH).

Edited June 13, 2013 by ajkoer

[Bromo_DragonFly]

here in my country (IR) in, they add little amounts of CuSO₄ to water storage tanks to kill microorganisms.

though it's not fully harm-less, but that's just what they do. there have been reports of people getting sick, and it got found out that CuSO₄ could be the reason, but organizations just don't care. and keep adding it without any approval or something. maybe because it's less-costing compound than others.

I am NOT saying this is the case in USA or Canada, it's just what is happening here. maybe you can consider it.

[John Cuthber]

Now, to quote Wikipedia again:

 

"In anything other than very dilute, cold solutions, nitrous acid rapidly decomposes into nitrogen dioxide, nitric oxide, and water:

 

2 HNO₂ → NO₂ + NO + H₂O "

 

So, assuming some very dilute aqueous HNO2 (or NH4NO2) is formed, it is stable, until the water temperature rises, or the solution becomes acidic. So, correct me, but dilution itself, is not a negative as it contributes to Nitrous acid's stability, and more interestingly, per this source, HNO2 has limited solubility (see http://pubs.acs.org/doi/abs/10.1021/j100333a025 ). The severity of pressure eruption is most likely a function of the quantity of nitrite present, and the change in conditions that trigger its decomposition (temperature, concentration and pH).

Did you read the article you cited?

Did you understand it?

That article says that the Henry's law constant for the solubility of HNO2 is 49M/atm

So, at one atmosphere pressure the theoretical solubility of HNO2 is 49 molar.

That's notionally 2.3 kilos of acid in each litre of water (obviously the linearity of Henry's law will have broken down at this point, but the fact remains that HNO2 is very very soluble in water.)

Sure it's limited but when the realistic concentrations are in parts per million, a theoretical solubility of 2,300,00 parts per million isn't much of a limit.

 

Why don't you just drop this silly idea?

[ajkoer]

I like the concept of why it was felt necessary to add a cupric salt to the water storage tank to kill (Copper is highly toxic to lower organisms) micro-organisms. If they are present, some micro-organisms are reputedly capable of breaking the otherwise stable nitrates into nitrites (see, for example, page 527 at http://books.google.com/books?id=8aw4ZWLABQkC&pg=PA527&lpg=PA527&dq=bacteria+convert+gaseous+nitrogen+into+ammonia+nitrates+and+nitrites&source=bl&ots=SQWZ3JcRrc&sig=Of3QJShC3vIQrrFR_1Ah4-URVSY&hl=en&sa=X&ei=T-PIUYf-IeTx0wHvxIHYAQ&ved=0CDQQ6AEwAjgK#v=onepage&q=bacteria%20convert%20gaseous%20nitrogen%20into%20ammonia%20nitrates%20and%20nitrites&f=false and the role of denitrifying bacteria), and the associated problems caused therein that I had speculated on (namely, possible massive rapid gas evolution events). I can undertstand the logic, albeit drastic, in my opinion.

 

I would list this as another possible route as it avoids the necessity of the presence of a significant amount of a heavy metal (like Zn, Cu, Pb,...), even if acting in the role of a catalysis. However, it still requires one to accept that nitrate levels may be rising and impacting water quality.

 

Another path, for those firmly believing in the ability and willingness of goverments to keep water standards high, is to focus on Iron consuming bacteria. Apparently (see http://en.wikipedia.org/wiki/Iron_bacteria ), it is possible for certain bacteria to attack ferrous Iron salts (like Iron bicarbonate) and gradually (or rapidly?) release massives amount of CO2. Another related path, Chlorine treated Iron rich water could form FeCl2. On standing in a water tank, upon warming and in the presence of O2:

 

4 FeCl2 + O2 + H2O ---> 2 Fe2O3 (s) + 8 HCl

 

Or, Iron bicarbonate on standing with exposure to oxygen or Iron bacteria:

 

4 Fe(HCO3)2 + O2 + 2 H2O --> 4 Fe(OH)3↓ + 8 CO2↑

 

so that Iron oxide accumulates at the bottom of the tank and in the presence of the right microbes, could further generate gas. Per Wikipedia (http://en.wikipedia.org/wiki/Iron_bacteria ) a reaction in low oxygen conditions, to quote:

 

" H₂O + Fe₂O₃ → 2 Fe(OH)₂ + O2 "

 

which is, unfortunately, not balanced with respect to Hydrogen, but does gives an idea of what is occurring.

 

A parallel argument could go for water orginally rich in H2S and treated with Chlorine:

 

H2S + Cl2 --> 2 HCl + S (s)

 

where the free Sulfur could also accumulate in the water tanks. In the presence of the right bacteria, metals, pH and water temperature, gas generation is also possible. For example, Sulfur can be converted into sulfites and sulfates by either bacteria or available hypochlorous acid:

 

Cl2 + H2O <--> HOCl + HCl

2 HOCl + S --> 2 HCl + SO2

SO2 + H2O <--> H2SO3

H2SO3 + HOCl --> H2SO4 + HCl

 

and to quote Wikipedia source above:

"Corrosion of of pipes is another source of soluble iron for the first reaction above and the sulfurous smell of rot or decay results from enzymatic conversion of soil sulfates to volatile hydrogen sulfide as an alternative source of oxygen in anaerobic environments.^[5]"

 

So the bottom line in this microbe assisted scenario, is that bacteria may serve a catalytic role in a changing oxygen content environment in the water tank, along with the presence of any nitrates, Iron or Sulfur compounds, to form problematic gaseous accumulations.

Edited June 25, 2013 by ajkoer

[hypervalent_iodine]

!

Moderator Note

Moved to speculations.

[John Cuthber]

Ajkoer,

The bottom line is that, since the water is usually quite pure, there isn't much in it.

So it can't make much gas.

 

This reaction

" H2O + Fe2O3 → 2 Fe(OH)2 + O2 "

(or, rather the properly balanced version)

goes the other way

 

4 Fe(OH) 2 + O2 + 2 H2O--> 4 Fe(OH)3)

 

or if you prefer

4 Fe(OH)2 +O2 --> 2 Fe2O3 +4 H2O

 

If you try to prepare Fe(OH)2 it goes brown as soon as the air gets to it.

(The reaction in wiki is a bookkeeping simplification it doesn't produce free O2, the reaction is coupled to the oxidation of some organic material. It would have been better if you had understood what you were citing)

And in the case of

"4 Fe(HCO3)2 + O2 + 2 H2O --> 4 Fe(OH)3↓ + 8 CO2↑" you have forgotten that CO2 is rather soluble in water (like a few other spurious suggestions you have invoked)

 

In essence, the only valid comment you have made is that tanks rust.

[ajkoer]

Yes, I agree if the water is pure it shouldn't make gas. Or, one could state, if it makes gas, the water is impure. So, are there rare instances in varying locales where the water could be impure? I claim the reported incidents indicate a possible yes as well as potentially newly implemented solutions in some countries (like adding CuSO4 to the water supply).

 

Now, on the solubility of the CO2 in the context of the specifics of the water tank, there are several parameters to examine. First, solubility is a function of temperature. Also the presence of other dissolved gases (like O2), and I would suspect, in the case for the formation of Carbonic acid, the pH of the water is a factor (see http://ion.chem.usu.edu/~sbialkow/Classes/3650/CO2%20Solubility/DissolvedCO2.html and more advanced discussion at http://www.pwtag.org/researchdocs/Used%20Ref%20docs/52%20Carbondioxide%20in%20water%20equilibrium.pdf ). Next, the available surface area at the top of the tank (to permit a rapid re-absorption if needed to avoid a pressure situation) and the flux between CO2 and the water (see http://en.wikipedia.org/wiki/Solubility_pump ).

 

On the biochemistry, my reading is that the reaction is normally reversible in nature as decaying vegetation consumes oxygen. In the current context, with O2 accumulating at the top of the tank, no vegetation, limited air/surface contact, and the Fe2O3 at the bottom of a large water tank, there may be the possibility of different dynamics.

 

Finally, I do not claim rust as structural failure mechanism to explain a pressure explosion. I do agree that in the presence of certain metals (Zn, Cu,..) a galvanic corrosion reaction is possibility as this leads to both corrosion and, more importantly, in my opinion, the possibility of large gas generation.

Edited June 26, 2013 by ajkoer

[John Cuthber]

"On the biochemistry, my reading is that the reaction is normally reversible"

Well read it again, and keep reading it until you realise that the reaction goes practically to completion. Fe(OH)2 will remove oxygen very effectively.

Oxygen simply is not produced by Fe(OH)3 in water.

 

If you have a tank full of water there are only two thing present in macroscopic quantities, the metal of the tank, and the water.

In some circumstances those can react and produce hydrogen.

 

There's also a reasonable chance of production of methane from organic stuff in the water.

 

So, there are two mechanisms that might produce a build up of flammable gases.

Air can generally get into tanks too.

Either as bubbles or by dissolving where the pressure is high and then coming out of solution where the pressure is low.

 

So, you can fairly easily get an explosive mixture it a tank my mechanisms that are sensible and plausible.

 

Now, why in the name of all that's holy do you insist on coming up with absurd schemes to produce impossibly hygroscopic explosives like ammonium nitrite?

 

Incidentally, adding copper ions to the water is a bit of a red herring.

If the pipes are made from any metal more reactive than copper then the copper ions will be reduced to the metallic copper.

If the pipe is copper then the metal of the pipe is likely to dissolve and give traces of copper ions, whether any is added or not.

If the pipe is concrete then the copper is likely to be precipitated as silicate.

In hard water areas the copper is likely to get trapped in the limescale.

Basically, unless the pipes are plastic the addition of copper won't make much difference.

[ajkoer]

John:

 

Thanks for raising questions.

 

I think we can forget the point on whether any more gas (meaning O2) is generated via iron bacteria as I do not feel it alone is the answer, but would explain, on testing the gas mixture, any increased in the amount of oxygen. The important point is that Fe(HCO3)2, all by itself, on standing with exposure to air breaks down releasing CO2 and deposits Fe2O3.xH2O and consumes O2. Absence oxygen, Iron bacteria could attack ferrous salts (including Fe(HCO3)2) depositing more iron oxide and,in the case of this bicarbonate, releasing CO2, Now, the hypothesis is that depending on several factors (like temperature, pH, surface area, water air flux, dissolved gases, carbonates,..) this may lead/contribute to a pressure event.

 

Similarly, there are denitrifying bacteria that will breakdown nitrates in O2 deficient water releasing N2. Now, for those who still believe that nitrates in drinking water is not a growing problem exacerbated by droughts (global warming a possible contributing factor) with associated change in water tables, non-optimal farming practices and septic tank leakage,... please explain why typing the following into google "reduce nitrates in drinking water" returns so many US states issuing nitrate related public health material. Strange for a non-existing problem.

 

Absent bacteria, I have presented some chemistry on how certain heavy metals (like Fe coated with Zn or Sn) can act to break down ammonia, nitrites and nitrates ultimately to N2. One does not have to accept the formation of either HNO2 or NH4NO2, just the final product Nitrogen gas which is infrequently released in laboratory situations in an explosive manner. So called laboratory preparation of Nitrogen gas employing NH4NO2 from NaNO2 + NH4Cl, at the proper pH and concentration level, requires 'careful' boiling or 'gentle heating' (for example, see page 2 at http://www.edudigm.in/downloads/Grp%2015.pdf ) as perhaps a rapid heating can precipitated an unwanted explosion. Interestingly, the dry mixture of NaNO2 + NH4Cl + a Stabilizer is employed commercially for 'safe' blasting, to quote one source (see page 240 at https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=29&ved=0CHAQFjAIOBQ&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.137.1104%26rep%3Drep1%26type%3Dpdf&ei=i_jKUc-kA-7e4APUyIGoCQ&usg=AFQjCNH_R1tjaiZ34fYeyHWF9gX-BbQqBw&sig2=Jy1020D3J7a1_xsgIeZn6A ):

 

"The dry reaction [ NaNO2 + NH4Cl] proceeds briskly with 0.42
kcal heat developed per gram of mixture and has been used with a
stabilizing additive in a mixture called "Hydrox" for safe blasting in
coal mines, the explosive effect being caused only by pressure from
expansion of the gases.[6] Such nitrogen is, however, not pure and
contains some ammonia and oxides of nitrogen."

 

You mention of Copper is interesting as, per the chemistry I have documented, the latest research suggests it is actively engaged in the reaction mechanism by forming a cuprous and then a cupric salt which, in the presence of Copper, reforms the cuprous salt. The Zinc (and Tin) metal may behave in a similar fashion.

Edited June 26, 2013 by ajkoer

[THX-1138]

One of the pictures I posted clearly shows that the top of the tank has been blow off as if by a pressure eruption. This observation is not consisent of a failure by corrosion (there is no solution contact on the top of the tank).

 

Correct me if I'm wrong, but in a water tank there is likely to be water vapour. And maybe even condensation. And possibly gasses going into solution in drops of condensation. And some of that might touch the top of the tank.

 

Or am I all wet?

[John Cuthber]

" I think we can forget the point on whether any more gas (meaning O2) is generated via iron bacteria as I do not feel it alone is the answer,"

Stop ignoring reality.

We can forget it because it simply never happens.

It's not that it isn't part of the answer; it can't be any of the answer.

 

 

" but would explain, on testing the gas mixture, any increased in the amount of oxygen."

Or the relatively high solubility of oxygen in water (compared to nitrogen) might explain it .

This has the advantage that it's known to happen and doesn't require fairy tale bacterial production.

 

"please explain why typing the following into google "reduce nitrates in drinking water" returns so many US states issuing nitrate related public health material. Strange for a non-existing problem."

Sure, there's no difficulty explaining that (did you think there might be?)

Nitrites are toxic (potentially carcinogenic) at rather low levels so a few ppm is a real problem (not, as you put it a non-existent one)

However a few ppm of nitrite won't generate more than a few ppm of nitrogen oxides and, at that level they are soluble in water so they don't blow the tank up.

 

I already explained that.

Why didn't you believe me?

[ajkoer]

OK, lets assume there is not ever a high concentration of any compounds to form a gaseous eruption. Also, your proposal of the action of Zn and water to form H2 is not likely given the water temperature. However, I believe your idea is close.

 

I was recently exploring (seemingly unrelated to this topic) a hypochlorite based Aluminum and Copper battery. Here is the chemistry per my research. To quote (see http://www.exo.net/~pauld/saltwater/ and http://sci-toys.com/scitoys/scitoys/echem/batteries/batteries.html ):

 

"In the bleach battery, sodium hypochorite (NaOCl), the major constituent in bleach, and hypochorous acid (HOCl), a minor constituent, are reduced, according to equations 6 and 7:

(6) ClO- + H2O + 2 e- --> Cl- + 2 OH- Eo = 0.89V

(7) HOCl + H+ + e --> 1/2 Cl2(g) + H2O Eo = 1.3V

 

The possible reactions involving aluminum are given by equations 8 and 9:

(8) 3 ClO- + 2 Al + 2 OH- + 3 H2O --> 2 Al(OH)4- + 3 Cl- Eo net = 3.21 V
(9) 3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V "

 

The author also notes that "Even though there is relatively little HOCl in bleach, the latter reaction is more favored because of its large potential of 3.93 volts. Over time, you will see both green cupric hydroxide (Cu(OH)2) and black cupric oxide (CuO). Black CuO is formed from green Cu(OH)2 by the loss of water, which happens over time."

 

The implied reactions at anode:

Al + 3OH- ⇒ Al(OH)3 + 3e-

 

given reaction at cathode (copper);

3 HOCl + 3 H3O+ + 3 e- --> 3/2 Cl2(g) + 3 H2O

 

for an implied net of:
3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V "

 

More, fully, I would express the reactions with respect to HOCl powered cell as follows:

H2O <--> H3O+ + OH-

 

with the implied reactions at the anode:

Al + 3OH- ⇒ Al(OH)3 + 3e-

 

and the reaction at cathode (copper);

3 HOCl + 3 H3O+ + 3 e- --> 3/2 Cl2(g) + 3 H2O

 

for an implied net reaction of:

3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) where Eo net = 3.93 V

 

A very important comment by the author above is "Even though there is relatively little HOCl in bleach", implying that the above reactions proceed even at low concentrations.

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So, how does this apply potentially to water tank problems (ruptures, explosions, etc.)?

 

Consider an Aluminum alloy tank with at least one copper pipe in contact with an ionic (mineral rich) water containing hypochlorite or HOCl (from the reaction of H2CO3 on NaOCl added during purification, for example).

 

Bottom line, with time the Aluminum tank will corrode (forming Al(OH)3 more precisely) causing it to weaken. In addition, the protective Al2O3 will be removed allowing the side reaction:

2 Al + 3 H2O --> Al(OH)3 + 3 H2 (g)

 

to proceed. As such, an explosive combination of H2, O2 and Cl2 may potentially form over time in the tank. The actual air concentration of Cl2, given its solubility, may vary with water temperature and the presence of dissolved CO2.

 

Note, this explanation requires no high concentration of any compound, just a persistent use of chlorination in an Aluminum tank with continuous (or periodic with change in water levels) exposure to copper fittings. Also, in the case of a Zinc plated tank, similar chemistry follows.

 

I have performed the above reaction as follows:

 

Combined bleach (NaOCl) and vinegar (which contains Acetic acid HAc) in the volume ratio 1.4 parts of 5% vinegar to one part of 8.25% extra strength chlorine bleach. Then, add a piece of copper metal which will function as the cathode and an Aluminum source to act as the anode (finely cut up Al foil, for example, will do). Finally, add a touch of sea salt (better than NaCl) to act as the electrolyte to get things started. An interesting aspect of the reaction, performed in a closed vessel with shaking, is how long its takes to completely dissolve the Aluminum (a couple of hours) and a warming of the reaction mixture. No heating is required.

 

As expected, using an excess of Aluminum slowly over a course of days, does form hydrogen gas. I tested it by exposing it to a flame and did observe a loud retort (caution: it is know that H2 and Cl2, and/or O2, can produce a kinetically powerful explosion).

Edited August 28, 2013 by ajkoer

[Humblemun]

While this rare event of massive sized water tanks rupturing occurs rarely, it is oftened accompanied by some loss of life and large property loss. I have put together some chemical based theories on how some of the evidently pressure detonations could be occurring. Those more familar with these large water tanks may be able to supply more insights (like what metal is employed, ventilation/pressure release valves, is the water stored pre or post aeration and/or chlorination,.etc). If a coherent list of possible causes can be produced, I will forward to OSHA, which apparently review these incidents, for considerations. As to why I am presenting on this forum is a net search reveals little insight and I can understand why a very respected scientist may feel reluctant to be associated with a topic on water tank pressure explosions.

 

First, some history of the events to ascertain some possible patterns. Here is a report of a large explosion from Fox News reported on April 07, 2011 "Two Killed From 300,000 Gallon Water Tank Explosion" (see http://www.foxnews.com/us/2011/04/07/killed-300000-gallon-wa... ). To quote:

 

"Two men died Thursday when a 300,000 gallon water tank exploded in Florida, unleashing a flood and causing an adjacent building to collapse.

The victims were in the midst of repairing a pump that filled the tank inside an adjacent concrete block building. The force of the water from the explosion caused the building to collapse, MyFoxTampaBay.com reported."

 

Here is another incident in Tomball, Texas where a worker was killed after a water storage tank exploded..

Hi ajkoer, I found the topic of this thread very relevant to some of my own research. It reminded me of other kinds of disasters which were attributed to sudden inexplicable increases of fluid pressure. There's been train disasters, most recently the Canadian tragedy, where "fail-safe brakes" have failed. A loss of fluid pressure would actually apply the brakes, so only a mystery increase in pressure could release them. The other issue is a multitude of hydraulic fluid pressure loss on aircraft landing gear. On some occasions, the landing gear has suddenly dropped under the influence of gravity whilst inflight.

 

I have an alternative hypothesis: an intermittent geo-force which acts on fluids but not solids. It sounds a strange idea, I know. I have deduced that this mystery force is from fluid exotic matter around the 360 mile diameter innermost core of the Earth. This deduced intermittent force is also a good candidate for the Earth flyby anomaly. What do you think to this left field way of thinking?

Edited August 29, 2013 by Humblemun