# Best post filter after bacteria/virus filtration



## DavidJH (Jul 27, 2020)

I have a LifePlan Family that can filter a large amount of water, which filters down to the virus level. We also have a stream near our house which I plan on using if needed. My problem is that this filter type is not good at removing a lot of the chemicals that could end up in the water supply, not to mention radiological contamination. What is a good post filter for a filter like this that would work for filtering my families water supply in an extended disaster?


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## SOCOM42 (Nov 9, 2012)

There two methods depending on what you are trying to remove, reverse osmosis and distillation.

There is no one size fits all.

Myself I have opted for mechanical filtration, chem purification and distillation.

That is if the need ever arises for the last two, I use a Big Berkey everyday here at home, not really needed but it does pull out some crap.

I check for bacterial content with samples under one of my microscopes, staining the samples, before and after filtration.

I have three sources of water, town supply, my shallow well and the river and lake out front.

The are/would be used in the order listed.

Radioactive contaminants are easy to remove because of their size.

Some chemistry is impossible to remove without million dollar systems.

The two I listed are very efficient and relatively cheap, best to pre-filter any water run through the reverse osmosis as a stand alone.

A sand filter will do for it. you will require a pump of sorts to use the process as it does not work on gravity.

Distillation will take any crap you throw in it, but temps are critical to remove some chemistry such as alcohol from the final product.

The process would depend on what you local supply has suspended in it.

Some stuff would need reagents for each known chemical and the equipment for titration for the levels.

I am not chemist, just a trained monkey, just what I need to know,

@Mad Trapper is the chemist, he will bring you up to speed.


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## DavidJH (Jul 27, 2020)

So correct me if I am wrong here, but after going to the ultra fine filter of the LifeStraw Family filter which is designed to take absolutely filthy water, wouldn't some kind of activated carbon filter be able to take out most contaminates that are left? I am thinking of pesticides, fertilizers, coal tar run off from the road and other stream contamination. I realize this does not work for radiological contamination (or at least I don't think so), but I have seen a few pitchers filters that do. I had not thought of distillation but that is an interesting idea. I would need a way to re-mineralize the water after that though right?


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## Camel923 (Aug 13, 2014)

I have a Berkey and lifesaver jerry can. Another idea is to have a cistern to cache rain water. You will need to run it though a filter system or perhaps sand and then chlorine.


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## Mad Trapper (Feb 12, 2014)

Start out with best water available. Deep wells (tested prior) will be safe a long time even after a nuke event, shallow wells rain water will contaminate them, same as rain water. Otherwise, rainwater is a good start but you'll have bird poop and any other atmospheric debris you collect. A deep spring is good resource

A 55-gal slow sand filter with a layer of charcoal might be a good starting place for treatment.

It will remove particles and once the bio-layer sets up kill most all bacteria/virus. Charcoal below that would help with organics/fuels/pesticides. Charcoal will reach a limit of adsorption. I'd refilter or retreat that for drinking

Inorganic stuff is harder to remove by filtration, need some sort of ion exchange. Most won't have a problem with that pollution anyway.

Distillation will remove all pathogens and most other contaminants that are non-volitile, some organics even high boiling will co-distill (think grain alcohol , clove oil ). Contaminates will concentrate in the still pot, which will need cleaning. It's energy intensive, so best have a supply of firewood.

Reverse osmosis will also produce very pure water but will easily clog unless pre-treated. I'd worry about upkeep/parts needed. And need a good head for inflow or some sort of pump.

Nuked? I'd want a gieger counter to see what I'm trying to purify.


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