Biology / Chemistry Challenge or: Should We Really Blame the Dead Frog?

We often say we operate in Leonardo da Vinci Renaissance Mode – given our odd ‘portfolio of diverse services’. But as much as the Chief Engineer does not like to work with mortar, cement, or any other slimy substances I tried to avoid pondering about the intricacies of living beings and chemicals so far.

But slimy, smelly species were to strike back.

For two years we could confirm with confidence that the water in our underground water tank / heat sink does never smell. Until two weeks ago when the water appeared a bit turbid and there was the signature ‘rotten eggs’ smell of hydrogen sulfide.

Water in ponds can ‘die’ – due to eutrophication: Algae bloom due to too much nutrients, die, and their decomposition by bacteria consumes all the oxygen in the water. This can kill fish and other species who need the oxygen.

Since the tank is dark there are no algae but there might be other biomass, subject to decomposition. The most recent rebuilding of the solar collector and brine piping has probably invited some curious or suicidal life-forms.

Dead frog or toad

Researching cisterns in a German forum (‘The water in our cistern stinks’) I learned the following:

“Clean your gutters and check your filters.”

“Install an air pump to supply the bacteria in the water with oxygen. Otherwise there will be anaerobic decomposition, such as turning sulfate into sulfide. The pump resolved this issue within two days.”

“Use chlorine, as for swimming pools.”

“Absolutely don’t use chlorine – cisterns are designed to work without intervention. We use a cistern for twenty years and never had to use chemicals.”

“If the black layer of mud at the bottom of the cistern gets too thick there will be anaerobic decomposition.”

“The black layer of mud at the bottom of the cistern is like a natural sewage plant.”

“Our cistern smelled, too, and we found six dead birds at its bottom.”

Insights are somewhat contradictory but there were more accounts of people advocating the additional supply of oxygen and otherwise letting the bacteria do their work. Proper filters and sealings should prevent the invasion of animals of course.

We still wondered about the coincidence of the H2S accident and recent repairs – was it only due to a sudden invasion of (more) worms, snails, and frogs because of some pipes that were open for a short period of time?

But several users reported that a small amount of brine from their solar collectors had trickled into their cisterns and gave rise to the rotten eggs smellWith cisterns brine could be collected by the gutters, from leaky collectors mounted at the rooftop.

And yes – we had a leak in the new part of the brine piping. The Chief Engineer had heroically cleaned the emptied tank and used the ‘synergy effects’ of being able to do some other maintenance.

Chief Engineer in the Tank

A few days after having refilled the tank the water showed turbid streaks again – and we finally spotted the leak in the new part of the brine piping. Now it is leakproof again!

The good thing finally is:

  • It all boils down to simply following ‘cistern best practices’.
  • The smell provides for a sensitive early warning systems that signals a leak in brine piping.

And we have a new gadget now:

Air Pump

Why is brine so detrimental? Brine used for solar collectors contains about 40% ethylene glycol – frost protection. This provides a feast for bacteria – like sugar. On airports the fluid used for de-icing airplanes is collected and then decomposed by bacteria in a biological sewage plant. It seems that in a tank bacteria reproduce like hell, die, and are finally decomposed anaerobically when there is no more oxygen left.

Tiny amounts of brine alone seem to be suffcient to trigger that chain reaction within days – whereas the occasional earth worm did not do any harm in the past years. But blowing oxygen into the tank with this tiny air pump obviously made the chemical reaction (and the smell) stop.

We hope we will be able to keep the right variety of bacteria happy in the future rather than fight them!


Edit: As I have asked about the treatment systems on airports: Treating glycol runoff from airport deicing operations

11 Comments Add yours

  1. M. Hatzel says:

    I agree with Maurice’s comment on forums! Having recent needs to know how long a deer can be shot dead by a hunter and left without butchering, and still be safely consumed as meat, I encountered several dead ends in North American hunter forums. Sadly, this appears to perpetuate the stereotype that people who own guns don’t consider the benefits of education/scientific knowledge as relevant to their daily lives. After reading your comments, I will now reconsider how to reword my Google search to land at a different sort of forum.

    I appreciate your notes on bacteria. I’ve noticed that in areas where farming heavily relies on chemical fertilizers the surface water can become putrid by the end of summer. In more recent years in our area of the world, heavy rains have reduced this type of farming by making less land available for cropping(and thus less chemical has been used), but have also “flushed” the chemicals out of local water systems and sent them elsewhere. I am expecting there to be some international tensions arising from this, as environmental impact studies are already hinting at the problems this is causing. For us locally, right now, the water is clear and there has been a huge resurgence in local frog populations. My husband and I noticed the same on our small farm years ago. We changed land management practices and about five to six years later the surface water could sustain the egg/tadpole life cycles of frogs. It was a good indicator that we were safe to use the water for livestock and our mini ecosystem had regained its balance. I agree… reject the “FIGHT BAC” campaigns of the past and forge ahead!

    1. elkement says:

      Probably there are some topics that are typically covered by better managed forums? I found that many of the major IT forums are very well moderated and really useful (in the way Dave describes). I have also found some forums where doctors, lawyers, or tax consultants respond to questions very useful.

      The more “ideology-based” a topic is the less useful forums are and the more they are invaded by experts who are only self-proclaimed ones or people who rather want to vent than to help and respond to questions. Having said this I realize that I believe forums should explicitly state (in “codes of conduct”) how questions should be asked, that the main purpose is to respond to questions etc. In those well-managed forums any opinionated off-topic comments will be deleted or threads would be closed.

      As for frogs: We had an incredible population last year – sometimes in the evening when it got colder the sudden appearance of frogs or toads looked like a scene right taken out of a Hitchcock movie :-) I wonder where they come from as they is no pond or creek nearby (We had lots of them before we flooded the cellar).
      I am not at all an expert on trends in our local agriculture but things (and laws) have changed tremendously in the past 30 years or so. “Bio” as organic, pesticide-free crop is called here is a big thing .. and I think for many smaller farms this is a chance to maintain somewhat competitive.

  2. Blaming the dead frog could become synonymous with beating the dead horse

    1. elkement says:

      It would be really cool to be the creator of a proverb :-)

  3. I too had assumed that brine meant salt brine and also wondered about corrosion. Like Maurice, I am glad that this mystery is now solved. You should worry just a bit about your local cat population however, apparently a little as teaspoon of fill-in-the-blank-glycol can be fatal. The Chief Engineer must be watchful of future leaks. Is there very much pressure in the system? If so, perhaps that could be a way to monitor for leaks. In the end, there’s nothing like a little oxygen to keep your bacterial population happy. Those that claim their cisterns have been self-sufficient for years must be unaware of the oxygen source that is keeping their little ecosystems happy and smelling ‘bright’ and ‘fresh’ (sounds like a detergent commercial). As far as forums go … perhaps it is a matter of experience. Given my lack of experience with coding, I have found several forums on this topic helpful. If I were either you or Maurice, however, given the monumental experiences there … I am sure that forums are of little value. D

    1. elkement says:

      Thanks, Dave! So I really need to do my ‘cultural’ research – as it seems brine used in terms of glycol is more common in Europe (I find mainly UK links when searching for brine-water heat pumps but this might als be due to Google’s localization logic).
      We have finally spotted the leak by our monitoring system (the gadget connected to all the sensors and to the computer network) as the pressure was actually decreasing. The (excess) pressure is typically about 0,5 – 1bar. The first ‘batch’ of brine was released during rebuilding the collector – noticed directly but underestimated re impact :-)

      I find forums very useful – the better moderated and focused on specific topics they are, the more useful. As I said to Maurice, I am a regular contributor to IT security forums as I had found so much useful advice myself in the past and I believe in the ‘open source’ idea of giving and taking advice on public forums.

      I think if you are not familiar with a topic forums can be a good starting point but – as with Wikipedia – you should be critical. You also find many ‘philosophical’ discussions, people discussing their pet peeves (e.g. their opinions on heaters and renewable energies or if Windows or Linux or Mac is better…) that are off-topic and even misleading. But on the other hand such discussions can even provide some background information. But forums on programming (as stackoverflow) are typically very well managed so that you don’t find off-topic ramblings.

      1. Yes. And, I find it encouraging that there are a number of folks out there willing to put up with newbies like me … when it comes to HTML anyway. They are always very patient. D

  4. An interesting piece of essential troubleshooting. For me it’s sparked two different kinds of comments:
    1–Forums. I have almost given up on them as I cannot recall one single instance of the content on any of them being at all useful. Most of what I find whenever I look is of a general nature; comments anyone with even a glancing understanding of the subject matter could have put there. You know–“maybe it’s the rotors” or “First check the user manual” … stuff like that.
    2–brine. I had noticed you using the term and meant to ask about it as I had assumed it was salt brine. I’d assumed it was that way to guard against frost but was concerned of the long-term effects of such a potentially caustic material. Mystery solved!

    1. elkement says:

      Thanks, Maurice!

      1–With forums I am a bit partial as I am myself an (excessive) contributor to Microsoft’s public security forums. Actually I had resumed answering questions there as such forums have been an invaluable ressource for myself in the past. I think it depends on how tightly they are moderated and thus on the bandwidth of knowledge (or ignorance) those forums attract. Unmoderated physics forums are a worst case in my opinion and a playground for ‘outsider scientists’ (to put it politely – I mean ‘quantum healers’ and ‘free energy enthusiasts’).The forum I quoted is perhaps the leading German forum on domestic engineering – it is not extremely specialized or tightly moderated but it is still dominated by experts so usually the quality of the threads is quite good.

      2–Yes, with heat pumps ‘brine’ always refers to polypropylene glycol or ethylene glycol. I wonder if the term ‘brine-to-water heat pump’ is then more common in Europe? I should probably do some comparison of ‘heat pump culture’ or ‘heating culture’ in different countries and add a ‘glossary’. For example I suppose that air-to-air heat pumps are more common in North America as heat pumps are combined with AC (?)
      Glycol had become infamous here as it had been mixed with wine (illegally) in the 1980s – a dark period in Austria’s winemaking history:

  5. Mike Howe says:

    I’m glad you found the problem Elke. I like your new air pump too, it looks like a smart toaster :)

    1. elkement says:

      You’re right, Mike – it definitely should have a smart interface and allow control over the internet :-)

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