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

[Moontanman]

I'm not sure if UV can produce ozone from water, I was referring to the extra oxygen you added to the water being converted to ozone. But yes the mechanism of a UV light producing ozone is basically the same as what the sun does to the top of our atmosphere.

[enorbet2]

My apologies. I should have been more clear instead of worrying about OT hijacking the thread :) I did not mean to imply that UV purification of water was weak on any absolute scale. I only meant to display the considerable increase when O2 is added, so I meant "weak" in a relative sense.

[Moontanman]

Enorbit, I have to agree that UV is not a very "strong" way to sterilize anything. I helped design UV sterilizers at the DuPont plant where i worked. We used them to sterilize a liquid we used to lubricate and influence the properties of the Polyester fibers we manufactured. It was almost impossible to insure 100% sterilization under even the most ideal conditions. Ozone or heat would have been far more effective but would not have been possible under the conditions we had to operate under.

 

 

I do have to say i see no reason for microwaves to be any more or less effective than heating the water with a flame or any other method for sterilization

[MajorHeadrush]

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?

I hate to burst all of your uv illuminated oxygen bubbles but microwaves do indeed kill bacteria in as little of 60 seconds without boiling....

 

https://www.cdc.gov/hicpac/Disinfection_Sterilization/13_10otherSterilizationMethods.html

 

Microwave. Microwaves are used in medicine for disinfection of soft contact lenses, dental instruments, dentures, milk, and urinary catheters for intermittent self-catheterization925-931. However, microwaves must only be used with products that are compatible (e.g., do not melt)931. Microwaves are radio-frequency waves, which are usually used at a frequency of 2450 MHz. The microwaves produce friction of water molecules in an alternating electrical field. The intermolecular friction derived from the vibrations generates heat and some authors believe that the effect of microwaves depends on the heat produced while others postulate a nonthermal lethal effect932-934. The initial reports showed microwaves to be an effective microbicide. The microwaves produced by a "home-type" microwave oven (2.45 GHz) completely inactivate bacterial cultures, mycobacteria, viruses, and G. stearothermophilus spores within 60 seconds to 5 minutes depending on the challenge organism933, 935-937. Another study confirmed these resuIts but also found that higher power microwaves in the presence of water may be needed for sterilization932. Complete destruction of Mycobacterium bovis was obtained with 4 minutes of microwave exposure (600W, 2450 MHz)937. The effectiveness of microwave ovens for different sterilization and disinfection purposes should be tested and demonstrated as test conditions affect the results (e.g., presence of water, microwave power). Sterilization of metal instruments can be accomplished but requires certain precautions926. Of concern is that home-type microwave ovens may not have even distribution of microwave energy over the entire dry device (there may be hot and cold spots on solid medical devices); hence there may be areas that are not sterilized or disinfected. The use of microwave ovens to disinfect intermittent-use catheters also has been suggested. Researchers found that test bacteria (e.g., E. coli, Klebsiella pneumoniae, Candida albicans) were eliminated from red rubber catheters within 5 minutes 931. Microwaves used for sterilization of medical devices have not been FDA cleared.

[fahrquad]

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?

This discussion regarding water purification and aquariums has been interesting, but getting back to the original question, it is not the microwaves that kill the bacteria, but the heat generated by the microwaves exciting the molecules of whatever is being heated.  My microwave is an 1100 watt unit and it takes a minute to heat up a mug of water to brew a cup of tea.  You might want to make that a minute and a-half for a 700 watt microwave oven.

[fahrquad]

This discussion regarding water purification and aquariums has been interesting, but getting back to the original question, it is not the microwaves that kill the bacteria, but the heat generated by the microwaves exciting the molecules of whatever is being heated.  My microwave is an 1100 watt unit and it takes a minute to heat up a mug of water to brew a cup of tea.  You might want to make that a minute and a-half for a 700 watt microwave oven.

BTW, I like a nice cup of Twinings Earl Gray or Formosa Oolong in the winter.  I rarely drink tea except for Iced Tea for the rest of the year.  I need to track down some blackberry tea.  I can't remember who made it, but it was very nice on a chilly Sunday morning. 

Edited November 9, 2016 by fahrquad

[fahrquad]

On the our three trips to the out-Islands (or Family Islands) of the Bahamas (specifically Eleuthera), I thought about snorkeling in some of the large fresh-water coral lagoons that dot the island.  The coral was deposited long before the oceans receded in the modern era, and the likelihood of finding some nice marine fossils was good.  Fortunately I did not have time, before I found out about Schistosomiasis.

 

https://en.wikipedia.org/wiki/Schistosoma_haematobium

https://en.wikipedia.org/wiki/Schistosomiasis

[fahrquad]

BTW, the fresh-water was rain water, not ground-water welling up from sub-surface deposits.  Many homes on Eleuthera relied on rain-water collection in roof gutters to holding cisterns, a pump, and a filtration system.  Still not a bad idea to boil the water before drinking it, or to just drink Kalick Beer (brewed in Nassau, i.e. boiled) or coffee (i.e boiled) or wine (i.e. sterilized during the fermentation process).

[fahrquad]

A glass of iced tea involves boiling at some boint, and I will not get into the measures that Coke-A-Cola goes through to get water out of the Chattanooga river.

[inductance]

This discussion regarding water purification and aquariums has been interesting, but getting back to the original question, it is not the microwaves that kill the bacteria, but the heat generated by the microwaves exciting the molecules of whatever is being heated.  My microwave is an 1100 watt unit and it takes a minute to heat up a mug of water to brew a cup of tea.  You might want to make that a minute and a-half for a 700 watt microwave oven.

 

Good point.

 

The wavelength of a microwave oven is about 12cm (5 inches), so any object of length or diameter less than about 3cm will not be sufficiently large enough to convert much of the 1100W EMR into heat.  

 

That's why it's not good for the microwave oven to be operated without anything inside. All of that available 1100W is dissipated as heat within the magnetron.    

Edited November 15, 2016 by inductance