Dear Omotayo Erejuwa,

First of all, I'd like to point out that "invisible microbes" is a meaningless phrase, since microbes are -by definition- not visible to the naked eye.

Secondly, as mention before, destilation should remove most "bigger" particles but smaller ones can be transported in the vapor stream (it will also kill most living microorganisms, though not all spores and the like).

So filtering is the best way to remove any particle from water. I'm not an expert on filtering devices, so google about it. It will depend on what you want to filter and the amount of liquid that need filtering.

As mention by Satyendra Mondal , a 0,22 uM filter will remove any microbial contamination, producing sterile water. For smaller particles you could try 0.05uM or 0.02 uM filters. They aren't cheap and are a pain to work with, so I would only suggest it for small volumes.

Hope this helps. Cheers

Distillation will remove dust (and microbes), however, you may get new dust into the distillate unless you prevent its access, for example with a filter in the air inlet. Of course, the inside of the entire apparatus also needs to be dust free.

Dear Omotayo Erejuwa

For the purpose of removing microbial contamination, you can use membrane filter techniques. If the sample volume is not huge, 0.22-0.45 micron membrane filters are well sufficient to filter out the microbial contamination.

Best wishes.

A general obvious response: Boiling, filtering of vapour and condensation, with proper devices. Is there some hidden sense in this question?

Dear Omotayo Erejuwa,

First of all, I'd like to point out that "invisible microbes" is a meaningless phrase, since microbes are -by definition- not visible to the naked eye.

Secondly, as mention before, destilation should remove most "bigger" particles but smaller ones can be transported in the vapor stream (it will also kill most living microorganisms, though not all spores and the like).

So filtering is the best way to remove any particle from water. I'm not an expert on filtering devices, so google about it. It will depend on what you want to filter and the amount of liquid that need filtering.

As mention by Satyendra Mondal , a 0,22 uM filter will remove any microbial contamination, producing sterile water. For smaller particles you could try 0.05uM or 0.02 uM filters. They aren't cheap and are a pain to work with, so I would only suggest it for small volumes.

Hope this helps. Cheers

https://www.freshwatersystems.com/blogs/blog/how-many-microns-should-your-water-filter-be

need to know whats in your water, but this link is a good summary

Filter with 0.22 u filter.

One of my companies sells water filters with known reduction. Paper filters are short lived and leave you guessing at the results. The spec sheet for my filters is located here you can see if they meet your needs. The issue with obtaining pure water also involves removing chemical contaminants which my filters also remove. Distillation has issues in that the dust can be carried in the vapor and also any volatiles that have a lower boiling point than water will be in your distillate. Here is the web page with spec sheet link also. This is not an advertisement it is just something I happen to deal with every day. If you want email and we can send you some for free. Happy to help.

spec sheet ... https://www.jmccanneyscience.com/FilterElementSpecSheet.HTM

sales page ... https://www.jmccanneyscience.com/SecWebOrderPg.htm

Dear ALL. I appreciate your various responses and comments. I am trying to work with what I have available (Whatman filter paper - 110 mm). It seems the mentioned filters are different from Whatman filter papers, am I correct? I need a lot of distilled water like 10 Litres. The distilled water is primarily for biochemical reactions and washing of lab tools such as test tubes, beakers and so on.

Tomás Brito Devoto Kindly excuse my use of 'invisible'. You said distillation can kill 'most' living microorganisms. I am wondering how accurate or correct could that statement be?

Joaquin Diaz-alonso What are the proper devices? I am sure I don't have any at my disposal. I don't understand what you meant by this your statement ' Is there some hidden sense in this question? '. I need distilled water and I want to be sure that the distilled water from AC is free from contaminants including microbes. That's the essence of asking the question. There is nothing hidden.

James McCanney Thanks. I will contact you

Thanks. I'm sorry. Now I understand the sense of your question.

I agree with Mr. Tomás Brito Devoto and distillation of water is done using the heat with which the micro-organisms and large suspended particles are eliminated and the filtering with Whatman paper ensures this, but we are in the laboratory work to obtain sterile distilled water we use Autoclave.

Dear Omotayo Erejuwa ,

Boiling water kills most microorganisms because of many phenomenons occurring at the same time. Basically, at 100°C most proteins, plasma membranes and nucleic acids lose their structure and generally can't re-fold properly, effectively disabling their functions. Only some microorganisms are able to live/survive such extreme conditions. That being said, some bacterial spores and fungal conidia may be able to survive; since their main function is to survive extreme conditions until the time/ambient conditions are right to activate and grow. In this sense, as Meison Abdulbary suggests, an autoclave will effectively kill even B. subtillis spores; which are among the most resistant spores known.

All in all, it will depend on the starting quality of your water. It seems to me, that for your purpose, assuming that is just water and has no other chemical contaminants, filtering with Whatman filters, followed by one-two destilation processes and finally autoclave, should be enough for biochemical reactions. Mili-Q grade water would be preferred, but you won't get it by destilation.

For washing lab equipment such as test tubes and the like, don't even bother to autoclave. Simple distilled water is enough for most laboratories and practices.

P.S: For more information on the "why"s, I'd recommend you to read more about extremophiles, mili-q and other quality grades of water, and the autoclave process.

Eddited for typos. Sorry in advance for any other gramatical mistake :)

Meison Abdulbary and Tomás Brito Devoto Thanks for the additional clarifications. It is interesting to know that I can still use Whatman filter papers and combined with other processes including autoclaving.

Where do microbes and dust come from in distilled water. Nobody would call such water distilled. If, however, the distilled water has become contaminated, it can be purified by distillation or by using suitable membranes.

Thank you Prof. Mirosław Grzesik for your comments. The distilled water is being obtained from air conditioners. Hence, there is a high possibility of presence of microbes and dust in the distilled water.

filtration is simple inexpensive effective with known end results using real filters (not paper filters but multi layer filters in clean containers)

Redistill it properly or use sterile filter-syringe (with suitable filter of about 0.1 micron or less than that size, if available) if the quantity of distilled water to be used for your experiment is less. There are also centrifugal filters to remove small particles that can be used based on your necessity. These are only alternatives but the contamination-free distilled water preparation always lies with your expertise. Use "glass double distillation system" to prepare distilled water with an initial source of potable water i.e., water with permissible levels of TDS. Be careful to avoid contamination with air while collecting distilled water from your unit by proper protection.