Conclusions - Waterborne Pathogens: Detection Methods and Applications - page 368

procedures for the recovery of viruses, bacteria, and parasites from water
exist, each with their own advantages and disadvantages. Many factors mak-
ing up the physico-chemical quality of the water, including but not limited
to the pH, conductivity, turbidity, presence of particulate matter, and organic
acids can all affect the efficiency of recovery of microorganisms. There is no
single universally superior method; the choice of the appropriate approach
depends upon the type of microorganism, the type of monitoring to be
undertaken, and the eventual detection method as well as factors such as
efficiency, constancy of performance, robustness, cost, and complexity. For
example, in operational monitoring, rapid and simple-to-use methods are
preferable, in investigative monitoring, the key focus is most likely to be effi-
cient removal of interferents to enable species level determination whereas
in surveillance monitoring, recovery rates are essential to identify pathogens
at extremely low concentrations.
Techniques for the recovery and concentration of viruses include ultra-
filtration, adsorption-elution using filters or membranes, NanoCeram
filters, glass wool or glass powder, two-phase separation with polymers, floc-
culation, the use of monolithic chromatographic columns, ultrafilter cen-
trifugation, immunomagnetic separation, and polyethylene glycol (PEG)
precipitation. The recovery rates generally do not exceed 60%.
Bacteria are commonly processed using ultrafiltration, centrifugation,
and membrane filtration although flocculation, immunomagnetic separa-
tion, and density gradient centrifugation are also used and initial studies have
explored the potential of NanoCeram and glass wool. The use of membrane
filtration is popular as the membranes can be immediately employed in
traditional culture based detection techniques. In general, recovery rates for
bacteria appear to be higher than for viruses, though there is a high degree
of variability observed depending upon factors such as water quality, opera-
tor skill, secondary concentration efficiency, etc.
Parasites can be concentrated using ultrafiltration, flocculation, centrifu-
gation, and membrane filtration; they can also be isolated using immuno-
magnetic separation. Recovery rates are often comparable to those achieved
for bacteria.
Section 3 of the topic has presented a range of developing and emerging
technologies for waterborne pathogen detection, giving an overview of the
latest research advances. Chapter 5 discussed optical detection technolo-
gies. Fluorescent based techniques are well-established, and there have been
developments toward automation and commercialization of existing fluo-
rescent approaches, e.g. TECTA™ and the Shaw Water systems. Although