[Q] Do microwaves kill bacteria? All? How long is needed to kill?

[Michaelangelica]

I am tired (have taken my pills0 so acup of tea was called for.

turned on the jug, put the tea bag, honey, milk in, pored the water in to find it was cold. jug turned off at power point

So out to the microwave- zap 30 secs, not quite hot enough --zap another 10secs- about right to drink

Then I thought are microwaves as effective is killing bacteria in water as boiling seems to be?

Maybe, in my microwave tea ,lurked a few Ray Resistant Bugs!?

 

You wouldn't think anything would live bombarded with microwaves, but then bacteria seem to keep surprising everyone

 

So what do you reckon?

Is there already a colonising colony of Microwave Resistant Bugs already mutating, swapping genes & T-shirts, silently socialising in my Microwave?:phones::hihi::naughty:

[freeztar]

Microwaves will destroy most any living cells given enough time. I think I remember reading that one minute is sufficient, but I'll have to check up on that. I do know that cysts of cryptosporidium can survive past most treatments. If you have a suspect water source, boiling or microwaving is likely not sufficient!

 

I purchased this nifty wand last year that uses UV to purify water. It's really cool imho! :naughty:

It takes about 1:30 minutes to purify 1 liter (litre) of filtered water. I used it in Mexico and had no ill-effects other than bad tasting water.

[CraigD]

To answer this question, a brief primer on sterilization is needed.

 

Most harmful living pathogens – mainly bacteria, but also plant and fungus spores, and arguably non-living viruses – can’t survive high temperature, so an effective way to sterilize mostly-water liquids or the surfaces of non-porous stuff immersed in liquid or steamed is to boil the liquid. However, many pathogens can survive boiling water at typical atmospheric pressure (expecially if you’re well above sea level, where the boiling point of water is well under 100 C), for a long time, so the rule-of-thumb is that the boiling water must excede 120 C for 15 minutes for effective sterilization. To get water this hot, the container in which it’s boiled must be pressurized to about 1 atmosphere (100 kPa or 15 PSI).

 

There’s no technical reason you couldn’t do this in a microwave container, using, say, a silicone gasket-sealed Pyrex glass container, but such rigs aren’t common, while steel stove-top pressure cookers are. Just bringing an open container to a boil in a microwave for under a minute isn’t effective sterilization.

 

You can get more info by reading articles with titles like “autoclave”, like wikipedia’s.

 

Primer complete, we need to step back and ask just how sterile something you intend to put in your mouth – a veritable cesspool of bacteria and other wee beasties – needs to be. The answer, unless your immune system is weakened by drugs (eg: immunosuppressants following transplant surgery) or disease (eg: HIV/AIDS), is “not very”. So, unless you’re drawing your water from downstream of a raw sewer outlet, something likely these days only in the third world or communities with infrastructures broken by war or abandonment, or some failure or accident has temporarily contaminated your water, you don’t need to boil it before drinking, so microwaving your tea to a comfortable temperature is fine.

 

There’s even some sense to arguments that it’s healthier – especially for young children with still-developing immune systems – to eat and drink food and water as contaminated as possible without being outright toxic, than food and water that’s been somewhat or fully sterilized. So a bit of gunk in your tea gear may be good for you.

[maikeru]

Microwaves are very good for sterilizing things like wet sponges. Note that I mentioned WET sponges. Putting a dry sponge in the microwave for a minute or more will cause it to catch on fire. It should be reasonably damp if you want to disinfect it. The microwave will cause the water to begin to heat up, boil and steam, and it fries the little suckers quickly, safely, and cleanly. 2 mins recommended for 99% kill of microbes. Make sure sponge does not dry out during microwaving. Do not touch sponge immediately after its done. Hot!

 

Microwave Kills Germs in Sponges

[Michaelangelica]

I purchased this nifty wand last year that uses UV to purify water. It's really cool imho! :confused:

It takes about 1:30 minutes to purify 1 liter (litre) of filtered water. I used it in Mexico and had no ill-effects other than bad tasting water.

Niffty yes, but how does the SteriPEN® JourneyLCD Handheld Water Purifier work?

 

A married friend sent me a postcard from S. America, saying she had caught "Montezuma's Curse". I was a very surprised and shocked:eek2: as i always thought that was VD.

But that is not what she meant at all, I later discovered. :shrug:

 

It is interesting that even in Countries with good clean potable water (USA, Oz, bits of Europe) many still complain about "the change of water" effecting their insides.:confused: One of life's little mysteries?

[freeztar]

Niffty yes, but how does the SteriPEN® JourneyLCD Handheld Water Purifier work?

 

It uses UV to sterilize the water. The UV-B actually kills anything living in the water. It also can penetrate and destroy cell membranes which is particularly useful for stubborn contaminants such as cryptosporidium cysts. :confused:

 

A married friend sent me a postcard from S. America, saying she had caught "Montezuma's Curse". I was a very surprised and shocked:eek2: as i always thought that was VD.

But that is not what she meant at all, I later discovered. :shrug:

 

I'm gussing she is referring to "Montezuma's revenge", also called traveler's diarrhea.

 

It is interesting that even in Countries with good clean potable water (USA, Oz, bits of Europe) many still complain about "the change of water" effecting their insides.:confused: One of life's little mysteries?

 

Change of water? Well, all water (aside from distilled) contains trace amounts of minerals and dissolved elements (as well as bacteria, viruses, spores, etc.).

[Michaelangelica]

I stumbled (not literally) across this today. (But I may put it on stumble :phones: )

http://www.tommeetippee.com.au/pdfs/ctn-micro-steri-leaflet-feb08.pdf

 

How big a nifty pen would it take to change the colour of my pool from the now bright green?

Should I just give up, contemplate my navel, and grow sacred lotus ( and eat/drink some too?)

[CraigD]

How big a nifty pen would it take to change the colour of my pool from the now bright green?

Should I just give up, contemplate my navel, and grow sacred lotus ( and eat/drink some too?)

I’ll offer no practical solution (having no acquaintance, professional or personal experience with pool maintenance or owning, I don’t think any from me would be very valuable) to you algae growing where you don’t want it problem.

 

Instead, I’ll just note out an “eco-philosophical” point: you don’t actually want to kill all of the organisms in your pool – sterilize it – but rather have it dominated by ones that don’t offend you. Fully or partially sterilizing a medium exposed to the world is likely one of the worst thing you can do to achieve this, as in doing so you’d be creating conditions favoring the fastest-spreading, most aggressively control-seizing organism, in a way effectively similar to when a water ecosystem die-off due to, for example, low dissolved oxygen, results in a spectacular algae bloom.

 

In short, sterilizing a pool makes it into a giant Petri dish ready to receive a sample.

 

So, whatever you do, don’t seal and superheat your pool! ;)

I stumbled (not literally) across this today. (But I may put it on stumble :) )

http://www.tommeetippee.com.au/pdfs/ctn-micro-steri-leaflet-feb08.pdf

This product, a special container intended for use in sterilizing infant feeding bottles, is, I suspect, an example of an unwise biological practice, not as in the previous example, where sterilization can lead to aggressive, unwanted organisms thriving, but because medical science suggests that it’s bad for babies not to put dirty things in their mouths, because this may result in malformation of their immune systems, leading to disorders randing from skin rashes to allergies to, possibly, MS to diabetes (a recent article about this: Mama Knows Breast: Dirty Babies-- Stronger Immune System).

 

In short, don’t keep babies in a sterile environment!

[Michaelangelica]

Yes i understand where you are coming from Craig.

All those adds on TV about kitchen/bathroom cleaners when all is happening is natural selection for super bugs.

 

The same thing upsets me about automatic pesticide misters or the lights they sell that attract and kill all bugs in the garden (and probably not the mosquitoes!).

 

I was surprised when recently in Hospital that the cleaner had a lot of mop heads.

She explained to me that after one use on one bathroom they were thrown out.!

 

I did manage to catch staf infection anyway!

[enorbet2]

OT Just a note on purifying water w/ UV. Efficiency goes up several orders of magnitude if pure Oxygen is bubbled through the water while UV passes through. UV alone is pretty weak.

[freeztar]

OT Just a note on purifying water w/ UV. Efficiency goes up several orders of magnitude if pure Oxygen is bubbled through the water while UV passes through. UV alone is pretty weak.

 

Interesting. Do you have a source for this?

[enorbet2]

I doubt I can find my original source since I discovered it while researching for a means to purify my spring water when I lived in the mountains of Colorado over 15 years ago. The reason I remember the device itself is that I built my own and ruined several before I gave up and swirched to staged filters since sand was a problem. At the time, besides subscribing to numerous Science magazines I was also working for a Solar company that employed several Master Plumbers so I could have gotten the info anywhere. However Google does give lots of hits and here's a patent Drinking water purifier - Patent 4902411 There are also units that use Ozone now.

[freeztar]

I doubt I can find my original source since I discovered it while researching for a means to purify my spring water when I lived in the mountains of Colorado over 15 years ago. The reason I remember the device itself is that I built my own and ruined several before I gave up and swirched to staged filters since sand was a problem. At the time, besides subscribing to numerous Science magazines I was also working for a Solar company that employed several Master Plumbers so I could have gotten the info anywhere. However Google does give lots of hits and here's a patent Drinking water purifier - Patent 4902411 There are also units that use Ozone now.

 

Well, I was asking mainly for the claim that "UV alone is pretty weak". It's well known (well, at least among water ecologists) that increasing DO (dissolved oxygen) is very effective at being very inhospitable for most life forms. If you have to drink from a river, drink from the bottom of a waterfall.

 

So, I can intuitively see where O2 would increase efficiency, but I doubt the claim that "UV alone is weak". Until shown otherwise, I remain skeptical.

[Moontanman]

Freezy, I think the main reason oxygen and UV are so effective is that UV makes ozone out of the oxygen. I used to build UV sterilizers for my aquariums, they operated at 257 nanometers (i think, it's been a long time) I think the ozone developing UV is most efficient at another wave length but a 257 nanometers light should still produce some ozone. If I remember correctly 257 nanometers is the wave length that is absorbed best by organic material

[freeztar]

Freezy, I think the main reason oxygen and UV are so effective is that UV makes ozone out of the oxygen. I used to build UV sterilizers for my aquariums, they operated at 257 nanometers (i think, it's been a long time) I think the ozone developing UV is most efficient at another wave length but a 257 nanometers light should still produce some ozone. If I remember correctly 257 nanometers is the wave length that is absorbed best by organic material

 

Interesting. So would you say that UV is weak by itself, without the ozone?

Or is it a tit for tat kind of thing?

 

Also, wouldn't excess DO kill the fish? Perhaps the 257nm wavelength is customized for optimal conditions for fish?

 

Even after all my studies in water ecology, I'm unaware of ozone production or the correlation between ozone and UV. Any info you could provide me would be much appreciated! :hyper:

[Moontanman]

The water has to be circulated around an UV source in a separate tube away from the aquarium 257nm light would kill the fish the plants and you too if you exposed yourself to it long enough, it will blind you and burn your skin. A strong UV source is used by some commercial ionizers to produce ozone for various purposes. UV light produceds the ozone in our atmosphere.

[freeztar]

The water has to be circulated around an UV source in a separate tube away from the aquarium 257nm light would kill the fish the plants and you too if you exposed yourself to it long enough, it will blind you and burn your skin.

 

That makes perfect sense. Cool stuff!

 

A strong UV source is used by some commercial ionizers to produce ozone for various purposes. UV light produceds the ozone in our atmosphere.

 

Indeed. The sun does quite a number of amazing things to our atmosphere.

Surface water is different though and I'm curious about the mechanisms involved in producing ozone in water. Is it the same principle as what produces ozone in our atmosphere?