When people want to kill germs on their plates, spoons, forks, bowls, ladles, and so forth, they typically depend on their dishwasher to do the job since that machine uses hot water to wash all of your dishes in a more effective manner than regular hand washing of dishes.
Or they could end up boiling items in water to sterilize them, reaching up to 273.2°F to 278.6°F (134°C to 137°C) in temperature to complete the sterilization process. However, what about water? Can you kill bacteria in water by microwaving it as you would boil it?
Does Microwave Kill Bacteria in Water?
Yes, particularly when it microwaves the water for 2 minutes or so. If it’s a particularly powerful 2-kilowatt heavy-duty microwave, it could halve that time. The rate your microwave boils water usually serves as the mark when it kills all bacterial life within your water, freeing it from contamination.
In particular, you should microwave the water for however long (preferably 2 minutes on most microwaves) until you reach the autoclave temperature sweet spot of 273.2°F to 278.6°F. Long story short, to sterilize water to a bacteria-free state, boil it using the microwave.
Boiling water can only do so much in cleaning it but at least you’ve assumed most if not all the bacteria ends up dead after the water reaches the ideal sterilization temperature.
Err on the Side of Caution
Most Americans own microwaves and don’t own autoclaves—a medical device specifically designed to sterilize items along with water—so why not use the microwave you probably own in order to boil all your tap water or even your mineral water in order to eliminate bacterial contamination risk?
You can also use your microwave to sterilize items in your kitchen or medicine cabinet like gauze, cotton balls, mugs, flasks, glasses, dishes, bowls, utensils (preferably not metal though), and more. Just put them in water, microwave them, and let the hot steam kill all the rest of the bacteria.
The Partial Sterilization Method by Microwave
Using this partial sterilization method—an autoclave still provides 100 percent sterilization compared to heating in the microwave—you can make your drinking or washing water as bacteria-free as possible, killing all sorts of microbes.
Kill E. Coli, salmonella, and all sorts of viruses, germs, and microorganisms in your water and in your kitchen before they can spread to your food and drink. This is especially true during the Covid-19 pandemic.
Kill Most Bacteria by Microwaving for Two Minutes
Since you can kill most bacteria by boiling water for 6-8 minutes (gas stove) or 9-10 minutes (electric stove) and letting it boil for about 1 minute, the same principle applies to microwaves. It takes microwaves about less than 2 minutes to make water boil at full power.
Just microwave the water for about 2 minutes to kill most if not all bacteria. If you can measure the temperature, let the water boil at about 273.2°F to 278.6°F for a minute to kill all bacteria then you’re golden. The 2-minute mark is based on 1-kilowatt microwaves.
It takes a little over 3 minutes for 700-watt microwaves and a little over 1 minute for 2-kilowatt microwaves.
Boiling Water and Sterilizing Scrubbers and Sponges
Aside from sterilizing water by boiling it inside your microwave, you can use the water in your sponges and scrubbers to sterilize them as well. Sure, you can also use the dishwasher and its boiling waters to sterilize the filthiest items in your home, but the microwave proves more effective and autoclave-like.
The heat of the dishwasher doesn’t fully reach the sponge since it’s more concerned about washing the filth and grime in your dishes (what it’s designed for). Ultimately, the medical autoclave remains the safest bet when it comes to sterilizing objects and items, but most don’t have access to one.
You can microwave damp sponges and scrubbers to the point of boiling for two minutes like you would when sterilizing a glass, cup, mug, or bowl of water.
Approximately Like the Autoclave
The autoclave offers pressurized heat in order to consistently sterilize medical items like gauzes and flasks. In contrast, heating up food serves as the microwave’s main and true purpose. With it, you can decontaminate water by boiling and sterilize items by boiling their water content.
Indeed, the part where you can set its timer to heat up objects in oven format for sterilization purposes approximates the performance of an autoclave. This allows you to sterilize dishes and jars in steamy hot water and within two minutes.
Similar to the autoclave, the microwave can reach high temperatures at relatively high speeds, thus making it the perfect and more accessible autoclave alternative.
Research on Microwave Sterilization
According to the findings of an anesthesiology professor, a biomedical engineering doctoral student, and wastewater microbiology expert, two minutes can effectively kill bacteria in water in all shapes and sizes even when absorbed by a filthy cleaning dish sponge.
They conducted their experiment by soaking scrubbing pads and sponges with sewage water filled with (fecal) bacteria, viruses, and microbes such as Bacillus spores, protozoan parasites, and so forth.
Two Minutes to Reach 278.6°F or 137°C
It takes the average 1-kilowatt microwave 2 minutes to reach the autoclave temperatures of 278.6°F or 137°C for sterilization purposes. This is in accordance with the wastewater or sewage water research conducted above. Heat at that magnitude can kill even wastewater bacteria in 2 minutes.
You can also heat up the sponge in 30-second increments to allow the heat to build up gradually yet reach the same conclusion of bacterial death similar to that of antibacterial soaps with a 99.9 percent killing rate.
This should save you from the risk of food poisoning and contamination as well as Covid-19. Just imagine the savings you’ll get on your medical bill.
Factors to Consider
In order to kill bacteria in water, you need to boil water. It takes more than boiling to treat sewage water for obvious reasons—the presence of fecal matter, dirt, sand, and other solids suspended in the water—but for ordinary water like tap water or mineral water, microwave boiling should suffice.
You can also boil water using a stove or an oven as well as other heating apparatuses (maybe a Bunsen burner or a charcoal grill) to get the same results. With microwaves, however quickly it boils the water to about 273.2°F (134°C) determines how fast it can kill bacteria, viruses, or microbes.
- “Researchers: Microwave oven can sterilize sponges, scrub pads“, UFL.edu, January 22, 2007
- “Can I use a microwave to sterilize clothes in place of an autoclave?“, Quora.com, November 27, 2019