Sample Processing - Waterborne Pathogens: Detection Methods and Applications - page 63

different approaches to this are discussed. The chapter concludes with a
summary identifying what has thus far been achieved in the area of sample
processing, what has so far been neglected, and what needs to be done. This
summary will discuss the challenges and limitations, timescales for adoption
of new technology, and—in addition to suggesting what improvements are
most needed—will consider how likely they are.
4.1. BACKGROUND
In this section we will first present different methods of sampling
and give an overview of sample processing, as applied to the differ-
ent categories of pathogen. More detailed information on the tech-
niques, including emerging research-stage methods, as they are applied
to waterborne pathogens is given in subsequent sections. The basics of
the physical and chemical processes underlying the techniques are also
described in the various sections, with suggestions for more detailed
reading.
To enable detection of low amounts of microbial pathogens in water,
large volumes (40-100 L) need to be analyzed. This can be achieved by
various filtration techniques that reduce the water volume while retaining
the microorganisms. Available filtration methods (USEPA, 2001, 2005) to
concentrate waterborne pathogens have many disadvantages; they are either
too costly for studies requiring large numbers of samples, limited to small
sample volumes, or not very portable for routine field applications.
Glass wool filtration is a cost-effective and easy-to-use method mainly
used to retain viruses, though one recent study reports application to bacte-
ria and protozoa, 1 but its efficiency and reliability are not adequately under-
stood. 2-4 NanoCeram are cost-effective newly developed electropositive
pleated microporous filters composed of microglass filaments coated with
nanoalumina fibers. Most bacteria are large enough to be mechanically fil-
tered or retained by e.g. adsorption of Bacillus spores 5 while smaller particles
such as viruses are retained principally by electroadhesion, which has proven
useful for the isolation of viruses from water. 6,7 Hollow-fiber ultrafilters
normally have a cut-off of ∼30 kDa and will retain parasites, bacteria, and
viruses. They are disposable thus avoiding the risk of cross contamination,
and filtration can either be achieved by coupling the filter directly to a tap
or pumping an environmental water sample through the filter. They have
mainly been used for filtration of tap water 8,9 but have also been used for
surface waters. 10,11