Sample Processing - Waterborne Pathogens: Detection Methods and Applications - page 83

and “Method 1623: Cryptosporidium and Giardia in Water by Filtration/
IMS/FA”. 45 The methods consist of concentration by capsule filtration fol-
lowed by a secondary concentration step, isolation using IMS, and detection
by microscopy (see Section 4.4 ). The ISO-method also describes alterna-
tive concentration methods that can be used for small volumes of water
(<10 L); carbonate flocculation, iron (II) sulfate flocculation, and membrane
filtration.
Three different filters are included in the protocols ( Table 4.2 ), all of
which typically recover >70% of the target organisms according to the
manufacturers.
The main difference between the two Envirochek™ capsules is the max-
imum operating pressure tolerated, 2.1 bar for Envirochek™ and 4.2 bar for
Envirochek™ HV which affects the flow rate and the water volumes that
can be filtered. It is recommended that a pressure gauge is included in the
filtration setup to ensure that the recommended pressure is not exceeded.
After filtration is completed, the filter is emptied by draining. Parasites and
particular matter are eluted in two steps with a Tris/EDTA/Laureth-12/
Antifoam A buffer using a wrist shaker. For Envirochek™ HV filters, a
pretreatment step with NaPP and a rinse with deionized water precede the
elution. The eluate normally exceeds 200 mL, and centrifugation is required
for further concentration.
The compressed Filta-Max ® foam filter module is inserted into a reus-
able housing and connected to a water supply. After filtration, the filter is
removed from the housing and washed twice in 600 mL PBS/Tween20
using either a manual or an automatic wash station. During this procedure,
the filter is decompressed and the parasites/particulate matter is released.

Table 4.2 Overview of parasite filters
Filter Capacity (L) Filter media

Pall Envirochek™ Supor ® membrane, hydro-

philic polyethersulfone,
1300 cm 2 , pore size 1 µm

Pall Envirochek™ HV Up to 1000 L or more

of treated water or
up to 50 L of source
water

Polyester, hydrophilic
membrane,
1300 cm 2 , pore size 1 µm

IDEXX Filta-Max ®

Up to 1000 L or more
finished water or up
to 50 L raw water

Compressed open-cell foam
discs that gives a nominal
porosity of 1 µm