1. I thought that to have a filter with pores fine enough to remove viruses,
there should be frequent clogging problems. Is that why some used a bacteria
size pore and a secondary disinfectant step (e.g., iodine resin) to kill
viruses.
The proprietary filter formulation used in
Black Berkey™ purification elements makes up for
the incredibly small pore size by utilizing an exponentially greater
number of micro pores in each purification element than that found in
other filter elements. This is the reason
Black Berkey™ purification elements produce
approximately 8 times more water per hour than do other elements.
Therefore, while some of the surface pores will clog up from
contaminates, it is difficult for such contamination to overwhelm all of
the pores and so clog up the filter. Eventually the majority of surface
pores may clog up slowing down the flow rate of the
Black Berkey™ purification elements. When this happens the filter can be refreshed by simply
brushing the outside of the element with a ScotchBrite® pad or
toothbrush. This will remove the surface pores that have become clogged.
Therefore, in answer to your question, even though the filters have such
small micro fine pores, the element will not clog up prematurely.
2. How does your filter in the
Berkey® system deal with viruses? Possibly with a
series of filters with graded pore sizes.? Or is the virus filtration
due to the tendency of viruses to clump with bacteria and debris in the
water?
The micro fine pores are so small that they prevent micro fine
particulate such as bacteria, virus and even food coloring particulate
from passing through the tortuous path that water is able to pass
through. These contaminates are trapped in the microfine pores while the
much smaller H20 molecules are not. Therefore, in answer to your
question, this method separates the contaminates from the purified
water.
3. Is the MS2 - Fr Coliphage still known to be a good indicator of virus
filtration? At least one article suggests that it might not be. Do you have
tests on any other viruses?
MS2 and Fr Coliphage are two separate virus with two different removal
characteristics. That is why they are used as surrogates for other types
of virus. These virus were selected, by both the EPA and the Military,
because of their small size relative to other virus strains and the
difficulty in removing both strains. They each are approximates 24-26 nanometers in size which makes them among the smallest of virus. To see
their relative size we would suggest that you visit The
University of Utah Cell Size and Scale Chart. These
virus are comparable in size on that chart to the Rhonivirus.
Therefore, in answer to your question, yes MS2 and Fr Coliphage are the
ideal virus for use as indicators of a purification systems ability to
remove virus.
Special Notes:
To understand the difference between the
size of path bacteria and viruses, we suggest the following web link as
it will give you a great visual of the difference: The
University of Utah Cell Size and Scale Chart.
Slide the scale at the bottom to see the size of virus vs bacteria vs
other potential contaminates and magnify to greater levels.
The fact that
Black Berkey™ purification elements have been tested to remove viruses to
greater than the EPA purification standards suggests that contaminates
larger in size, such as bacteria, should also be removed.
The MS-2 virus is 24-26 nm in size.
The Fr Coliphage virus is 25nm in size.
In other words, they are smaller than the hepatitis virus at 45mn and the rhinovirus at 30nm both referenced on the chart.
For more information on the MS-2 virus: MS-2 - Wikipedia
For more information on Bacteriophages in general: Bacteriophages:
Update on application as models for viruses in water
