Sciencemadness Discussion Board

Disinfection of rainwater

SnailsAttack - 3-11-2023 at 14:43

Our tapwater is saturated with lime, which has proven to be an issue for some of my chemistry experiments (e.g. recrystallizing soluble phosphate salts), but since it rains a lot where I live I've taken to collecting rainwater as a convenient source of distilled water.

Unfortunately, through the miracle of nature, my rainwater (which I store in large sealed plastic jars) tends to grow filamentous mats of bacteria, most likely cyanobacteria due to the smell of what I presume to be geosmin and 2-methylisoborneol. It essentially smells like a fish tank or a creek filled with stagnant water.

What I want to do is find a way to sterilize rainwater without adding anti-bacterial contaminants.

Boiling it may be the most effective option, but is a bit of a waste of energy since I use about a gallon of distilled water a month.

Bleach seems to be an effective disinfectant using as little as 10 drops per gallon, but it's still more salt than I'd like to have in my distilled water.

I've considered using a volatile non-reactive solvent such as alcohol, isopropanol or acetone, but I believe these may actually nourish some of the hardier germs I'm trying to eliminate.

Other sterilization ideas I've considered (but haven't researched) are ultraviolet light, hydrogen peroxide (how effective is this?), or highly mass-efficient anti-microbial agents. Tell me if you guys have ideas or experience with a similar issue.

[Edited on 11/3/2023 by SnailsAttack]

Deathunter88 - 3-11-2023 at 17:06

Get yourself one of these: https://www.amazon.com/uv-lights-aquarium/s?k=uv+lights+for+...

Neal - 3-11-2023 at 22:59

Quote: Originally posted by SnailsAttack  
hydrogen peroxide (how effective is this?),
[Edited on 11/3/2023 by SnailsAttack]

You can buy hydrogen peroxide at 12% concentration, like at these beauty supply stores, Sally Beauty Salon. It contains a little amount of phosphoric acid.

Sulaiman - 4-11-2023 at 00:46

I think that without light most things die or go into hybernation,
So store your water in a dark place or container.
I'd try hydrogen peroxide as it seems to be a mild contaminant yet effective.

PS I read recently (may have been here on SM)
that east and west German chemist's often had different results
due to one side using distilled water, and the other tap water.

Fery - 4-11-2023 at 04:56

Alternatives like solar distillation or passing tap water through ion exchange resins (making deionized water instead of distilled water) ?

Tsjerk - 4-11-2023 at 06:43

Mats of bacteria in rainwater? Are you sure your collection vessel was clean? Maybe sterilise everything you use to collect with copiuos amounts of bleach and try again? Unless there is some big poluter nearby rainwater should be effectively distilled water with some CO2 dissolved.

Neal - 4-11-2023 at 07:22

Quote: Originally posted by Neal  
Quote: Originally posted by SnailsAttack  
hydrogen peroxide (how effective is this?),
[Edited on 11/3/2023 by SnailsAttack]

You can buy hydrogen peroxide at 12% concentration, like at these beauty supply stores, Sally Beauty Salon. It contains a little amount of phosphoric acid.

And since hydrogen peroxide decomposes to water and oxygen. How long does it take for H2O2 to fully decompose? Well, looks like you can always take a small sample and do some indicator test, where the H2O2 would have reacted with something for a color change.

unionised - 4-11-2023 at 11:43

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

Benj-NH2 - 5-11-2023 at 10:38

You could consider using UV sterilization for your water. Thereby you would avoid having to buy additional Hydrogen peroxide or ion exchange resin.

[Edited on 5-11-2023 by Benj-NH2]

Twospoons - 5-11-2023 at 13:59

Do you have a dehumidifier or a condensing clothes dryer? I collect the water from mine for watering chlorine sensitive house plants. The most likely contaminant in that would be fabric fibers, which can be filtered out.
With rain water I would go with the UV route - you can get bulbs with no filter for 180nm, so they generate ozone as well.

Rainwater - 5-11-2023 at 16:55

Removing all the O2 and CO2 makes it more difficult for organisms to grow. Degassing is an easy process and doesn't contaminate the solution.

Neal - 6-11-2023 at 17:07

Quote: Originally posted by Rainwater  
Removing all the O2 and CO2 makes it more difficult for organisms to grow. Degassing is an easy process and doesn't contaminate the solution.

You know most degassing is heating the solution, which is what the topic started stated not to do. What do you recommend for something other than heating, for degassing?

Also, as a separate question, do you know if rain water has much bacteria in it? Before it hits the ground?

SnailsAttack - 6-11-2023 at 17:21

Quote: Originally posted by Deathunter88  
Get yourself one of these: https://www.amazon.com/uv-lights-aquarium/s?k=uv+lights+for+...
Interesting, looks like these lights are all 255 nanometers. The UV flashlights I have are 365 nm or higher.
Quote: Originally posted by Neal  
You can buy hydrogen peroxide at 12% concentration, like at these beauty supply stores, Sally Beauty Salon. It contains a little amount of phosphoric acid.
Quote: Originally posted by Sulaiman  
I'd try hydrogen peroxide as it seems to be a mild contaminant yet effective.
Sounds like a good option.
Quote: Originally posted by Sulaiman  
I think that without light most things die or go into hybernation, so store your water in a dark place or container.
Fungi most likely don't care about light, but it seems like my rainwater actually grew cyanobacteria, which are photosynthetic, so that's a good suggestion.
Quote: Originally posted by Tsjerk  
Mats of bacteria in rainwater? Are you sure your collection vessel was clean? Maybe sterilise everything you use to collect with copiuos amounts of bleach and try again? Unless there is some big poluter nearby rainwater should be effectively distilled water with some CO2 dissolved.
They weren't huge mats I guess. There were maybe 3 leaves in the rainwater collection bucket that I removed within an hour, and I filtered the whole thing before putting it away. The container I used was clean, but maybe pre-sterilizing it with bleach is a good idea anyways.
Quote: Originally posted by unionised  
https://en.wikipedia.org/wiki/Solar_water_disinfection
Could work, but could also make things worse by feeding phototrophic germs. The water will have to either get really hot or a lot of short-wave UV exposure.
Quote: Originally posted by Twospoons  
Do you have a dehumidifier or a condensing clothes dryer? I collect the water from mine for watering chlorine sensitive house plants. The most likely contaminant in that would be fabric fibers, which can be filtered out.
Yes, we do actually have a humidifier running in the basement. Its hose pours into a set tub but maybe the water is clean enough to be worth saving.
Quote: Originally posted by Twospoons  
With rain water I would go with the UV route - you can get bulbs with no filter for 180nm, so they generate ozone as well.
Interesting.
Quote: Originally posted by Rainwater  
Removing all the O2 and CO2 makes it more difficult for organisms to grow. Degassing is an easy process and doesn't contaminate the solution.
Quote: Originally posted by Neal  
You know most degassing is heating the solution, which is what the topic started stated not to do. What do you recommend for something other than heating, for degassing?
It might be possible to freeze out the gases in the refrigerator? Not sure how much energy that takes, but it's gotta be cheaper than boiling it.
Quote: Originally posted by Neal  
Also, as a separate question, do you know if rain water has much bacteria in it? Before it hits the ground?
My rainwater had very little macroscopic contaminents (leaves, bugs, whatever) and it still got a bit nasty so I would say that rainwater could very well grab bacteria directly from the air on its way down.

[Edited on 11/7/2023 by SnailsAttack]

Rainwater - 7-11-2023 at 02:14

Quote: Originally posted by Neal  

What do you recommend for something other than heating, for degassing?

Also, as a separate question, do you know if rain water has much bacteria in it? Before it hits the ground?


Put the liquid under reduced pressure(vacuum) until the bubbles stop
Cheap, easy, energy-efficient.

Edit: preview/post error
No clue how much bacteria is in it. I know some will be present. Seams like a lot of variables would effect this. Area, season, weather, etc.

Attachment: srf97c27.pdf (88kB)
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Here is a reference cern published in regards to how they treat their water
They use a membrane to extract 99% of O2 in a continuous process for about 3.5x10⁶ cubic meters of water.
Thats not the important bit.
You can use a much simpler appratus.

Once O2 is removed, the bacteria per volume decreased with time.

[Edited on 7-11-2023 by Rainwater]

Neal - 7-11-2023 at 08:07

Quote: Originally posted by Rainwater  
the bacteria per volume decreased with time.

Okay good post, except for this part where you obviously meant living bacteria, as living bacteria die, the amount of dead bacteria increase over time.

So is it safe to drink a cup of water with dead bacteria in it?

The answer is mostly yes, so, it depends. If bacteria slowly die, they can secrete something called exotoxins which can worsen the situation. Bacteria release it when they're stressed, so weak concentrations of bleach and slow heating will cause them to release it, but I don't know where to draw the line with fast-heating.

And to confuse more people, exotoxins are separate from endospores, and endotoxins. Not all bacteria produce endospores, only Gram-negative bacteria can shed endotoxins, and not all bacteria produce exotoxins. In face mostly Gram-positive bacteria produce exotoxins.

So now, you got me to do a new research. Which is find out if degassing bacteria, can causes them to secrete exotoxins.

And then a 2nd issue. Is however, not all bacteria are aerobic. Some are anaerobes so they hate oxygen. So now that raises a 2nd question for me, is does degassing water actually increase anaerobes.



[Edited on 7-11-2023 by Neal]

Texium - 7-11-2023 at 10:27

The house I grew up in had a whole-home rainwater collection system because the local water utility was unreliable and supplied really poor quality water. All the water from the gutters flowed through underground pipes and into large holding tanks. The tanks were made of opaque black plastic. There would be some very minor algal growth in the tanks, but nothing significant since it was a dark environment. After being pumped into the house, the water went through a woven filter, carbon filter, and finally UV sterilization (by means of a “Sanitron” unit, which uses a 254 nm germicidal lamp).

So overall, I think collecting in a dark, opaque container followed by UV sterilization would be most effective. You can use one of those aquarium lights, no need to buy a super fancy germicidal lamp. Only issue with any of these methods is that you’ll still have dead bacteria junk in your water without physically filtering or distilling it, but as long as you sterilize it before they have a chance to grow, it should be pretty minor.

pneumatician - 7-11-2023 at 16:55

You need to know a lot about rain water. Not all is the same, the season of the year, if the storm have lighting...

get water in a calm rain without thunder in winter, etc. get the last water of the rain, after the first clean the air, put in scalded blue glass jars...

do not put your rainwater in used plastic containers, this end, sure, in troubled water...

if you collect the water falling in a roof... full of birds excrement... :-)

if you see "chem trails" from "jumbos" avoid it? "megaultracrazy" people say is full of heavy metals... or if you live in a dirty city, industrial zone...

anyway if you have eyes and you can collect crystal clear water bubble sodium chlorite in it, first the water get a amber color but after some days return to crystal clear again.

or rot the water and a lot of shit fall to bottom, then you have crystal clear water...

but hey! what is WATER??? any idiot say: H2O but apart from this WATER is a MATRIX, the question is how many things can you support is this MATRIX before you call it "pure WATER".

yes oh no! horror, water are composed of 4x4 elements! oh no, shit! :-D Fire, Air, Water & Earth.

good luck my captain.

Texium - 7-11-2023 at 18:14

Leave it to pneumo to show up with an absolutely unhinged reply… good for a nervous laugh, at least

j_sum1 - 7-11-2023 at 18:33

In my lab I use rainwater straight from the tap for most things. I know it has crap in it but levels are low and there is little ionic content.
When i need something better than that I use water that I buy from the supermarket. It is purified via RO and comes in 10L containers. It is dirt cheap. If I had rainwater as dirty as the OP sounds, I would be using this exclusively.
In other words, I am not really seeing a problem that requires a time-intensive or equipment intensive solution. Just buy what you need.

Neal - 7-11-2023 at 20:06

Quote: Originally posted by j_sum1  
In my lab I use rainwater straight from the tap for most things. I know it has crap in it but levels are low and there is little ionic content.
When i need something better than that I use water that I buy from the supermarket. It is purified via RO and comes in 10L containers. It is dirt cheap. If I had rainwater as dirty as the OP sounds, I would be using this exclusively.
In other words, I am not really seeing a problem that requires a time-intensive or equipment intensive solution. Just buy what you need.

Would also save a bit to buy a filter system and keep dumping in the rainwater continuously. But to check and change the filter.

SnailsAttack - 11-11-2023 at 17:50

Quote: Originally posted by Neal  
And then a 2nd issue. Is however, not all bacteria are aerobic. Some are anaerobes so they hate oxygen. So now that raises a 2nd question for me, is does degassing water actually increase anaerobes.
It's worth noting that anaerobic respiration is a lot less efficient, so anaerobic bacteria will have a harder time. Also, most anaerobes still rely on gases other than oxygen.
Quote: Originally posted by Texium  
The house I grew up in had a whole-home rainwater collection system ... All the water from the gutters flowed through underground pipes and into large holding tanks.
haha you drank gutter water
Quote: Originally posted by Texium  
Only issue with any of these methods is that you’ll still have dead bacteria junk in your water without physically filtering or distilling it, but as long as you sterilize it before they have a chance to grow, it should be pretty minor.
Yeah, as long as there isn't secondary growth the remains of any dead bacteria won't be an issue.

clearly_not_atara - 11-11-2023 at 20:06

No carbon, no life. If there's stuff living in your rainwater, that's because there's carbon in it. And guess what? That's normal:

https://analusis.edpsciences.org/articles/analusis/pdf/1999/...

Now how do you get crap out of water? Well, the ancients discovered this crazy stuff called "alum"... and would you believe, we still use it today! :D

If you just want to kill bacteria, unfortunately all living cells produce an enzyme called "catalase" that gives resistance to hydrogen peroxide, so this isn't preferred... that's why halogenated oxidants are more common, although you could use ozone. But I think your typical water disinfection kit is primarily sodium chlorite, which produces a very dilute solution of chlorine dioxide, a very effective disinfectant.

Neal - 11-11-2023 at 22:39

Quote: Originally posted by clearly_not_atara  
No carbon, no life. If there's stuff living in your rainwater, that's because there's carbon in it. And guess what? That's normal:

https://analusis.edpsciences.org/articles/analusis/pdf/1999/...

Now how do you get crap out of water? Well, the ancients discovered this crazy stuff called "alum"... and would you believe, we still use it today! :D

If you just want to kill bacteria, unfortunately all living cells produce an enzyme called "catalase" that gives resistance to hydrogen peroxide, so this isn't preferred... that's why halogenated oxidants are more common, although you could use ozone. But I think your typical water disinfection kit is primarily sodium chlorite, which produces a very dilute solution of chlorine dioxide, a very effective disinfectant.

Yes, I heard this is true, at least for 3% hydrogen peroxide. Bacteria can get immune to it fast. Which is why I go to beauty hair salons to get 6, 9, or 12% hydrogen peroxide.

Keras - 12-11-2023 at 03:05

If you really want pure water, you have no other option than boiling it and collecting the vapour. But frankly, I’m not sure it’s even worth the effort, given the price of a 5 l distilled water tank (€ 3.80 over here, that’s much less than the same amount of mineral water!).

unionised - 12-11-2023 at 04:12

Quote: Originally posted by clearly_not_atara  


unfortunately all living cells produce an enzyme called "catalase"

No, they don't.
It's a useful part of classic identification of bacterial.
https://learn.chm.msu.edu/vibl/content/catalase.html

Sulaiman - 12-11-2023 at 08:23

There is a big difference between drinkable water
(Rainwater or glacial melt water, rivers, lakes, aqueducts, reservoirs, cisterns, tanks, pipes.......
which contain variable types and quantities of 'contaminants' that are generally considered to be acceptable or desirable,
and 'distilled' water for analytical chemistry,
the type that I buy is distilled then 'polished' with ion exchange resins,
which is cheaper than diy.

A great deal of chemistry can be done with rainwater or municipal tap water,
the main contaminant for Rainwater is CO2, with some airborne dust, bacteria etc. but negligible dissolved solids.
Municipal water has chlorides and/or fluorides, iron, and much more.
eg here is a water quality report for my UK home
https://www.south-staffs-water.co.uk/household/my-water-supp...

In Malaysia (my other home) biological contamination of municipal water is significant due to the temperature, it is reduced by chlorination, but water is boiled (or treated with filtration) before drinking.

At the moment I'm in Morocco, most cities and towns have private or municipal water supplies,
but like much of North Africa and the middle East, older homes were designed to catch rainwater and store it in a cistern... protected from daylight.
Seems to have been successful for centuries or millenia ;)

If you have space you could consider a solar still https://en.wikipedia.org/wiki/Solar_still

For cheap distillation maybe use a metal pot over a fire made from whatever you can find to burn
(wood, paper, used cooking oil......)


SnailsAttack - 3-1-2024 at 23:38

Some new findings:

Fresh snowfall is a nice way to gather a lot of rainwater without having to lay out a big fancy collection system. I just skim the top layer off our cars into a big bucket.

As it melts you can pick out any little bits of organic debris before they have a chance to leach impurities into the water.

However, I still had issues. Firstly, the filter (a simple paper towel pinned against a mesh) somehow kept getting completely jammed on an extremely small amount of impurity, which was strange.

Secondly, with no added disinfectants, the dirty-water smell manifested within just over a week; even hours-old snow is a vector for germs, apparently, which raises some interesting questions about why the entire Earth isn't choked in dirty-water smell.

Sulaiman - 4-1-2024 at 01:53

Quote: Originally posted by SnailsAttack  
... which raises some interesting questions about why the entire Earth isn't choked in dirty-water smell.

Food chain?

SnailsAttack - 4-1-2024 at 03:58

Quote: Originally posted by SnailsAttack  
...with no added disinfectants, the dirty-water smell manifested within just over a week

Also, shoutout to the 12 and a half atoms of cobalt that sustain their entire ecosystem. The devil works hard, but chelating proteins work harder.

unionised - 4-1-2024 at 05:13

Quote: Originally posted by SnailsAttack  



...

Secondly, with no added disinfectants, the dirty-water smell manifested within just over a week; even hours-old snow is a vector for germs, apparently, which raises some interesting questions about why the entire Earth isn't choked in dirty-water smell.


UV light and oxygen

EF2000 - 7-1-2024 at 00:41

The problem with snow is that snowflakes form around aerosol particles. Supercooled water droplets wait for something to freeze on. Those particles are what jams a filter.
Ice self-nucleation occurs only in pretty cold clouds, so if you live not somewhere in Oymyakon, your local snowfall is most likely from a warmer cloud.
Studies of snow samples show that biological particles are pretty widespread nuclei for snow. So, snow doesn't get colonised by bacteria after snowfall, it carries its germs with itself.

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pneumatician - 7-1-2024 at 11:41

boiling the water don't disintegrates the chaos in the air dissolved and carried by rain water when the rain drops fall...

make a cultivation and see what type of shit grow in agar... then use a disinfectant tolerable for the use you want for the rain water.

Else use a wide spectrum disinfectant and good luck! because now you have water full of shit and disinfectant! :-)

snow?? this is the worse "water" you can use, layer over layer of shit!