Temperature needed to destory bacterial spores

[capybara]

TL;DR Summary

What is the minimum temperature required to kill any highly resistant bacterial spore?

What is the minimum temperature required to kill any highly resistant bacterial spore?

 

[pinball1970]

Summary: What is the minimum temperature required to kill any highly resistant bacterial spore?

What is the minimum temperature required to kill any highly resistant bacterial spore?

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[jim mcnamara]

For sterile conditions to be created in a bacterial test medium, there is an autoclave "protocol" if you will. This depends depends on the fact that water boils at higher temperatures as air pressure increases.
Effectiveness also changes depending on the target items. So, at an elevation of 7000 feet you have to set an autoclave differently from the sea level setting. And use different temperatures and times and pressures.

The short answer you want is 250 °F or 270 °F and vary the duration of autoclaving. You have to alter pressure to compensate for elevation in ordfer to get the temperature. FWIW - an Instapot pressure cooker at sea level runs pretty close to the lower value. Once you open it you pretty much undo sterility.

And you should try to do a little legwork on questions beforehand. Granted, this is not simple number kind of problem:
https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/steam.html

 

[capybara]

Thanks I appreciate your reply. It does coincide temperature-wise with what I've seen online. I'm probably not entitled to use this forum as I'm not a student, but rather a desperate wildlife pond keeper who ill-advisedly used a sporeforming commercial bacterial agent to kill off lemna/duckweed, but which had the unfortunate consequence of killing all plantlife in the pond, aquatic and marginal.

The edging rocks and stones were also infected, and although I heated them in batches in a domestic oven, set at 220C (420f) for about an hour apiece, I think that the water in the material meant that they did not all achieve 270F (and obviously not under pressure).

I discovered this by testing some of the heated edging stones in a test pool with elodea canadensis, which died in exactly the same way as before. I can't believe that it's not possible to kill off any residual spores in these rocks, and hence casting about for advice and specialist knowledge of microbiological resistance. Again, I'm sorry if this all breaches what this forum is intended to cover, though I would imagine it's a fairly vivid if offbeat instance of microbial resistance. It is hard to find suitable forums for this, particularly any specialising in microbiology. Thanks, Nigel

 

[jim mcnamara]

You can dry sterilize at higher temperatures and longer times. Plus, rock surfaces are generally great places for spores to survive adverse conditions. But, yes you can sterilize them. I do not believe that simply sterilizing rocks will get rid of your problem.
Edit: Try commercial bleach - wear protective gear

I would guess the pond would have spores everywhere -- like in any sediments.

Consider going to internet places like Pond Medic and getting bacteriacide. Garden supply places may also stock these types of compounds. It would help to know what you used.

Can you tell us the the name of the bacterial agent you used to kill the duckweed?

FWIW: It sounds to me like you attacked a pond going into eutrophication. And this approach had basic issues.

Eutrophication indicates excess nutrient input, usually from runoff. Analogy: Killing the plants is like putting calamine lotion on itchy spots you get every time you do some gardening -- instead of removing plants that cause the itchy spots to start with.

 

[BillTre]

Once infected, a pond will be difficult to uninfect.

As @jim mcnamara said, sterilizing the rocks but leaving the water alone will probably not do much.
Depending on details like: the size of the pond, what might be in it worth preserving, and how you treated it, I would consider starting over.

Even smaller more controlled situations like aquaculture water system are difficult to uninfect.
Ponds or water systems can be fitted with UV "Sterilizers" or treated with ozone (O₃) generators to treat pumped water, but there will still be unaffected microbes in the water since it is not pumped all at once. Removing the water or bleaching the water in the pond may kill the unwanted microbes (if other debris that might react with the chemicals are removed), but would also kill possibly desired occupants.

Another approach often taken with (large) ponds is to drain them and let them dry out for an extended period of time. This kills some stuff and also promotes oxidation of organics in the bottom muck (more oxygen in air than in water). Treatments like this are used periodically to ward-off eutrophication.
Less extreme treatments could be using iodine or potassium permanganate.

You might try contacting the source of your treatment to see what they recommend. An aquaculture extension service might also be of help. There may also be aquaculture societies of various kinds around in your area.

 

[Laroxe]

Yes, really it would be useful to know what the product details were, the only biological agents I'm aware of are designed to improve the breakdown of organic matter and reduce toxic nitrates. As duckweed thrives in nutrient rich environments adding this does make some sense but to kill the duckweed a product would have to contain a herbicide and many are designed to last for a full season.

I suspect attempting to sterilize the pond is pointless and quite likely impossible. You need to carry out several significant water changes, don't rely on rain, you need to take water out of the pond to dilute the chemicals. You could try adding a filter with plenty of activated charcoal to speed things up and try removing sediment where some of the chemicals might settle, adding some aeration can also be useful.
I agree with people who have suggested a problem with the build up of the nutrients to toxic levels, killing the plants would have made this worse. Avoid using fertilizers anywhere near the pond but again the solution is in water changes, I don't know how big the pond is but it shouldn't be necessary to drain it, though this might be quickest.

If this was simply bacteria the pond would rapidly be colonised by other bacteria that would use these as a food source, nature doesn't approve of single occupant ponds. :)
This all means some work but it shouldn't take to long to put right.