POLYMERS FOR USE IN THE MONITORING AND TREATMENT OF WATERBORNE PROTOZOA - Biomaterial Applications: Macro to Nanoscales - page 51

cur each year, playing a significant role in high childhood mortality and
morbidity [55]. Prevalence of giardiosis is around 20-30% in the develop-
ing world, with up to 100% of children acquiring the infection before the
age of 3 [46]. In the developed world, where water treatment is better and
more wide-spread, the prevalence is lower but outbreaks do occur. For
Cryptosporidium one of the most serious outbreaks was in Milawaukee
in 1993, and there were several recent cases in the UK, Australia and in
Sweden [5]. In the US Giardia was the most common intestinal protozoan
infection in the early 2000s with infections reported in Norway in 2004.
Understanding the behavior and fate of protozoa in water treatment
systems is essential to assess risk at existing plants and appropriately de-
sign future systems. Although it is known that the nature of the coagula-
tion pretreatment is very important for the efficiency of the subsequent
water treatment processes, the exact adhesion and removal mechanisms
have not been elucidated. Few field studies of protozoa in water treatment
systems have been undertaken, due to limitations in assay techniques for
determining a mass balance for (oo)cysts and lack of understanding of the
mechanisms of interaction with chemicals or surfaces within the process.
Instead, laboratory studies have concentrated on the adhesion characteris-
tics, to a range of materials, and measurement of interaction forces.
While various studies of Cryptosporidium adhesion have been under-
taken, with materials ranging from metal oxides, quartz, silanes, natural
organic matter, biofilms, clays and natural suspended sediments, little
work, apart from a paper by Dai et al who have investigated polymeric
materials [13]. Additionally, the majority of studies investigating Giardia
interactions with surfaces have focused on the postingestion trophozoite
stage and its attachment through an adhesive disk. There has been limited
investigation of the cyst stage, where the adhesive disk is internalized and
fragmented, apart from that reported by Dai [13].
There are several reasons why understanding the interactions of these
protozoa with polymers is potentially very useful. Firstly, the membranes
employed in filtration methods of water treatment, and monitoring, are
made out of polymeric materials; secondly, polymers could easily be used
as coatings in water treatment systems or sensing applications; thirdly, it
is easy to systematically vary polymer properties to facilitate studies to
elucidate structure-activity relationships [6].
In this chapter, we review our latest work investigating the interaction
of the protozoa, Cryptosporidium and Giardia , with a wide range of poly-