Improved Virus Removal
in Ceramic Depth Filters Modified
with MgO
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Abstract
Ceramic filters, working on the depth filtration principle,
are
known to improve drinking water quality by removing human pathogenic
microorganisms from contaminated water. However, these microfilters
show no sufficient barrier for viruses having diameters down to 20
nm. Recently, it was shown that the addition of positively charged
materials, for example, iron oxyhydroxide, can improve virus removal
by adsorption mechanisms. In this work, we modified a common ceramic
filter based on diatomaceous earth by introducing a novel virus adsorbent
material, magnesium oxyhydroxide, into the filter matrix. Such filters
showed an improved removal of about 4-log in regard to bacteriophages
MS2 and PhiX174. This is explained with the electrostatic enhanced
adsorption approach that is the favorable adsorption of negatively
charged viruses onto positively charged patches in an otherwise negatively
charged filter matrix. Furthermore, we provide theoretical evidence
applying calculations according to Derjaguin–Landau–Verwey–Overbeek
theory to strengthen our experimental results. However, modified filters
showed a significant variance in virus removal efficiency over the
course of long-term filtration experiments with virus removal increasing
with filter operation time (or filter aging). This is explained by
transformational changes of MgO in the filter upon contact with water.
It also demonstrates that filter history is of great concern when
filters working on the adsorption principles are evaluated in regard
to their retention performance as their surface characteristics may
alter with use