Post by Keith. on Dec 2, 2017 14:05:10 GMT 10
Continuing with the bacteria & viruses, I believe it is not necessary to provide a description of all of them.
We will list them by name (only those that might be ingested with untreated water) and if applicable we will group them by size (filtration) and reactivity to either chlorine or iodine treatments, or both.
Boiling is generally effective with all of them (those causing potential infection through water ingestion).
*Some bacteria are “thermophile” (e.g. they like and thrive in hot water environment) some in temperatures exceeding water boiling point. We can see them in some hot water springs; they create, sometime, a bright coloration of the rocks. But these are of no concern to us.
Some of the names are very familiar to us, some a little less know. What is important to know is that they almost omnipresent.
It has to be noted that there are many sub-species of a single type of these crawlies. Bacteria, especially, could be good (we use them in many industrial processes, food production and even in medicine for some experimental cancer treatment) and some, those we are concerned with, less amenable.
Concerning the viruses, bear in mind that when it comes to claim of this or that filter to remove them, you must be in the position of reading and understanding the product specifications and do not take anything for granted when it comes to stated tests or standards.
One of the common mentioned standards for filters is the US EPA (Environmental Protection Agency), many manufacturers uses EPA standard for their own testing. EPA doesn’t test, approve or endorse mechanical filters (those where no chemicals are used and that rely exclusively on mechanical removal of the micro organisms), it merely assigns registration numbers.
During EPA regulated “laboratory” testing the pass requirements are as follows:
a) 3 log reduction for cysts
b) 4 log reduction for viruses (99.99%)
c) 5-6 log reduction for bacteria (99.999 – 99.9999%)
To be called a “microbiological water purifier” a device must eliminate all of water borne disease causing micro organism from the water.
We have seen when talking about the SODIS method, that the “load” (the amount) of micro organisms in the water might vary considerably thus changing the end result of a given log filtration performance in terms of left over crawlies.
In highly contaminated water where sewage or human feces are suspected, filtration only is a bet if not accompanied by heat or chemical treatment.
So be aware of a claim that says that all the viruses have been eliminated according to EPA standards. It has some latitude for uncertainty.
Having read few microbiology articles in which viruses’ average size or range of sizes have been mentioned. Rarely, they coincide.
Here are few examples:
a) 0.004 – 0.06 microns (a textbook)
b) 0.03 microns average size (a microbiology paper)
c) 0.02 – 0.09 microns (a microbiology paper)
d) 0.004 – 0.1 microns (a microbiology article on the web)
Since when it comes to human life I don’t really like approximations I have listed all the sizes I have found for each specific virus in an effort to sort of cut the chase. This gives me a pretty good feeling of the worst case scenario in the event I have to go for filtration albeit as much as i can search the data will always have some latitude for the reasons stated above.
I benchmark these sizes with 0.1 microns filter (Sawyer Point One®) as not everyone can afford to spend 150 dollars on a piece of equipment for a Point Zero Two® device.
To provide another useful benchmarking consider that a coffee filter or a microfiber cloth filtering performance is in the range of 100 microns. That is as far as it can go without taking unnecessary chances.
Doubling or tripling the layers does not increase filtering performance in terms of size catching capability; it increases only the likely hood of catching anything that might have slipped through one layer due to variability in the texture of the material.
Let’s see the bacteria and viruses listing:
Bacteria (dimensions in parenthesis)
Clostridium Botulimum* (0.6 x 3 – 7)
Campylobacter Jenuni (0.5 x 2.0 approx.)
Vibrio (including V. Cholerae)* (0.5 x 1.5 – 3.0)
Escherichia Coli (0.5 x 3 – 8 microns)
Shigella (1.5 x 3.0 microns)
Salmonella** (0.5 x 2.0 microns)
Legionella (0.5 – 1.0 x 1.0 – 3.0 microns)
Leptospira (0.2 – 0.3 x 6.0 – 30.0 microns)
*Several subspecies exist, including the one responsible for Tetanus
**Several subspecies exist causing more than one disease
Some of these bacteria are highly infective (very small number required to start doing damages), heat resistant (will see to what extent), acid resistant and thrive in absence of oxygen.
Given the smaller size of the diameter (we don’t know if the bug comes though standing or laying) we can see that a 0.1 micron ABSOLUTE POROSITY FILTER should do the work.
Let’s look at chemicals.
As stated earlier, Chlorine treatment is subject to a lot of variables including temperature, concentration, time and PH. To cover all the variables would require considerable time and would go beyond the scope of this paper as well as the objective of providing an easy, immediate way of water disinfection in the wilderness.
As stated before I would not recommend chlorine solutions (bleach) in the wilderness, but rather chlorine dioxide in tablets when it comes to bacteria.
Iodine is effective at killing bacteria at the concentrations and holding times indicated earlier and therefore recommended in the wilderness. As a matter of fact lower concentrations are sufficient to eliminate a variety of bacteria, however in the wilderness we have to go rough and simple.
Boiling is 100% effective.
Viruses (dimensions in parenthesis)
Adenovirus* (0.06/0.07 – 0.09 microns)
Astrovirus (0.028 – 0.03 microns)
Calicivirus (0.03 – 0.04 microns)
Parvovirus (0.03 microns)
Coronavirus (0.08 – 0.016 microns)
Hepatitis Virus (0.042 – 0.047 microns)
Poliovirus (0.03 microns)
Polyomavirus (JC and BK strains) (0.04 – 0.05 microns)
*Present in more than one sub specie
As we can see benchmarking against a filter with absolute pore size of 0.1 microns, it is obvious that it won’t do the job.
A 0.02 microns absolute pore size on paper will perform quite well but it expensive.
If the filter is tested under EPA standards some viruses’ presence is tolerated, this means that the indicated sizes sometime have a degree of latitude in the measurement (after all, albeit very tiny, within a species each one might not be a copy of the other).
It also indicates that borderline performance (0.02 micron filter to catch a 0.03 microns virus) might be affected by any degrading in filter performance in terms of enlargement of pores’ size due to prolonged utilization over time.
If you want to go for an expensive filter, by all mean feel free to go; I recommend, when it comes to “border line performance” to familiarize yourself THOROUGHLY with the factors that might cause DEGRADATION OF SUCH PERFORMANCES (lack of regular backwashing, pore enlargement, mechanical factor due to the filter construction, anything you can think about), always with the objective in mind of being able to make informed judgment calls.
When it comes to borderline performance I use double treatment (filtration + iodine). Of course boiling clears all of the above.
*Some testing indicated that Hepatitis virus gets inactivated at temperatures above 98°C in 2 minutes so it appears quite heat resistant when it comes to alternative methods of heat disinfections like SODIS. Other papers indicated a much lower temperature for complete killing. As usual we have to cut the chase and go for a sure kill. BOIL IT. Iodine treatment in the concentration indicated in the saturated solution description and at the prescribed holding times, is an effective virus killer. If you want to be 200% sure, especially at lower temperatures, throw in the entire content of the 1oz bottle (EXCLUDING THE CRYSTALLS) and wait for one full hour.
That’s pretty much all about bacteria and viruses. Next we will look at the “facts and myths” about iodine toxicity.
We will follow with industrial pollutant and a bit about carbon filters principles.
After all these, I’ll leave you in peace and thank you for your patience.
It goes without saying that since the objective is improving and expanding on existing knowledge, any question, comment or additional information is always welcomed.
Paolo
(To be continued.....)
We will list them by name (only those that might be ingested with untreated water) and if applicable we will group them by size (filtration) and reactivity to either chlorine or iodine treatments, or both.
Boiling is generally effective with all of them (those causing potential infection through water ingestion).
*Some bacteria are “thermophile” (e.g. they like and thrive in hot water environment) some in temperatures exceeding water boiling point. We can see them in some hot water springs; they create, sometime, a bright coloration of the rocks. But these are of no concern to us.
Some of the names are very familiar to us, some a little less know. What is important to know is that they almost omnipresent.
It has to be noted that there are many sub-species of a single type of these crawlies. Bacteria, especially, could be good (we use them in many industrial processes, food production and even in medicine for some experimental cancer treatment) and some, those we are concerned with, less amenable.
Concerning the viruses, bear in mind that when it comes to claim of this or that filter to remove them, you must be in the position of reading and understanding the product specifications and do not take anything for granted when it comes to stated tests or standards.
One of the common mentioned standards for filters is the US EPA (Environmental Protection Agency), many manufacturers uses EPA standard for their own testing. EPA doesn’t test, approve or endorse mechanical filters (those where no chemicals are used and that rely exclusively on mechanical removal of the micro organisms), it merely assigns registration numbers.
During EPA regulated “laboratory” testing the pass requirements are as follows:
a) 3 log reduction for cysts
b) 4 log reduction for viruses (99.99%)
c) 5-6 log reduction for bacteria (99.999 – 99.9999%)
To be called a “microbiological water purifier” a device must eliminate all of water borne disease causing micro organism from the water.
We have seen when talking about the SODIS method, that the “load” (the amount) of micro organisms in the water might vary considerably thus changing the end result of a given log filtration performance in terms of left over crawlies.
In highly contaminated water where sewage or human feces are suspected, filtration only is a bet if not accompanied by heat or chemical treatment.
So be aware of a claim that says that all the viruses have been eliminated according to EPA standards. It has some latitude for uncertainty.
Having read few microbiology articles in which viruses’ average size or range of sizes have been mentioned. Rarely, they coincide.
Here are few examples:
a) 0.004 – 0.06 microns (a textbook)
b) 0.03 microns average size (a microbiology paper)
c) 0.02 – 0.09 microns (a microbiology paper)
d) 0.004 – 0.1 microns (a microbiology article on the web)
Since when it comes to human life I don’t really like approximations I have listed all the sizes I have found for each specific virus in an effort to sort of cut the chase. This gives me a pretty good feeling of the worst case scenario in the event I have to go for filtration albeit as much as i can search the data will always have some latitude for the reasons stated above.
I benchmark these sizes with 0.1 microns filter (Sawyer Point One®) as not everyone can afford to spend 150 dollars on a piece of equipment for a Point Zero Two® device.
To provide another useful benchmarking consider that a coffee filter or a microfiber cloth filtering performance is in the range of 100 microns. That is as far as it can go without taking unnecessary chances.
Doubling or tripling the layers does not increase filtering performance in terms of size catching capability; it increases only the likely hood of catching anything that might have slipped through one layer due to variability in the texture of the material.
Let’s see the bacteria and viruses listing:
Bacteria (dimensions in parenthesis)
Clostridium Botulimum* (0.6 x 3 – 7)
Campylobacter Jenuni (0.5 x 2.0 approx.)
Vibrio (including V. Cholerae)* (0.5 x 1.5 – 3.0)
Escherichia Coli (0.5 x 3 – 8 microns)
Shigella (1.5 x 3.0 microns)
Salmonella** (0.5 x 2.0 microns)
Legionella (0.5 – 1.0 x 1.0 – 3.0 microns)
Leptospira (0.2 – 0.3 x 6.0 – 30.0 microns)
*Several subspecies exist, including the one responsible for Tetanus
**Several subspecies exist causing more than one disease
Some of these bacteria are highly infective (very small number required to start doing damages), heat resistant (will see to what extent), acid resistant and thrive in absence of oxygen.
Given the smaller size of the diameter (we don’t know if the bug comes though standing or laying) we can see that a 0.1 micron ABSOLUTE POROSITY FILTER should do the work.
Let’s look at chemicals.
As stated earlier, Chlorine treatment is subject to a lot of variables including temperature, concentration, time and PH. To cover all the variables would require considerable time and would go beyond the scope of this paper as well as the objective of providing an easy, immediate way of water disinfection in the wilderness.
As stated before I would not recommend chlorine solutions (bleach) in the wilderness, but rather chlorine dioxide in tablets when it comes to bacteria.
Iodine is effective at killing bacteria at the concentrations and holding times indicated earlier and therefore recommended in the wilderness. As a matter of fact lower concentrations are sufficient to eliminate a variety of bacteria, however in the wilderness we have to go rough and simple.
Boiling is 100% effective.
Viruses (dimensions in parenthesis)
Adenovirus* (0.06/0.07 – 0.09 microns)
Astrovirus (0.028 – 0.03 microns)
Calicivirus (0.03 – 0.04 microns)
Parvovirus (0.03 microns)
Coronavirus (0.08 – 0.016 microns)
Hepatitis Virus (0.042 – 0.047 microns)
Poliovirus (0.03 microns)
Polyomavirus (JC and BK strains) (0.04 – 0.05 microns)
*Present in more than one sub specie
As we can see benchmarking against a filter with absolute pore size of 0.1 microns, it is obvious that it won’t do the job.
A 0.02 microns absolute pore size on paper will perform quite well but it expensive.
If the filter is tested under EPA standards some viruses’ presence is tolerated, this means that the indicated sizes sometime have a degree of latitude in the measurement (after all, albeit very tiny, within a species each one might not be a copy of the other).
It also indicates that borderline performance (0.02 micron filter to catch a 0.03 microns virus) might be affected by any degrading in filter performance in terms of enlargement of pores’ size due to prolonged utilization over time.
If you want to go for an expensive filter, by all mean feel free to go; I recommend, when it comes to “border line performance” to familiarize yourself THOROUGHLY with the factors that might cause DEGRADATION OF SUCH PERFORMANCES (lack of regular backwashing, pore enlargement, mechanical factor due to the filter construction, anything you can think about), always with the objective in mind of being able to make informed judgment calls.
When it comes to borderline performance I use double treatment (filtration + iodine). Of course boiling clears all of the above.
*Some testing indicated that Hepatitis virus gets inactivated at temperatures above 98°C in 2 minutes so it appears quite heat resistant when it comes to alternative methods of heat disinfections like SODIS. Other papers indicated a much lower temperature for complete killing. As usual we have to cut the chase and go for a sure kill. BOIL IT. Iodine treatment in the concentration indicated in the saturated solution description and at the prescribed holding times, is an effective virus killer. If you want to be 200% sure, especially at lower temperatures, throw in the entire content of the 1oz bottle (EXCLUDING THE CRYSTALLS) and wait for one full hour.
That’s pretty much all about bacteria and viruses. Next we will look at the “facts and myths” about iodine toxicity.
We will follow with industrial pollutant and a bit about carbon filters principles.
After all these, I’ll leave you in peace and thank you for your patience.
It goes without saying that since the objective is improving and expanding on existing knowledge, any question, comment or additional information is always welcomed.
Paolo
(To be continued.....)