Sample Processing - Waterborne Pathogens: Detection Methods and Applications - page 82

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Figure 4.5 Schematic of flocculation process by polymers. Source: From Figure 8 from
Ref. 96 . Reprinted with permission.
The use of nonmetal coagulants has been attracting increasing atten-
tion over the last few years. Polymers and natural compounds have
been the main focus of attention, and a schematic of the process of
polymer flocculation is shown in Fig. 4.5 . One example is the natural
compound extracted from the Opuntia ficus-indica cactus as a floccula-
tion and concentration agent for bacteria suspended in water. 46 Another
example, presented in 2012, is the use of Moringa oleifera seeds to floc-
culate Giardia and Cryptosporidium , although the focus of the study
was water treatment. 47 Alternatively, the reader is referred to the 2009
review by Renault et al. for more information on the uses of chitosan
as a coagulant. 48
Polysaccharide polymers of microbial origin offer a unique and interest-
ing class due to their structural plasticity, stability, and functionality. More-
over, by using metabolic engineering, the turnover of such extracellular
polymers from producer bacterial strains may be increased significantly.
Ghosh and co-workers have applied such polymers for the flocculation of
bacteria 49 and protozoan pathogens. 50,51
4.3.5. Filtration specific for parasites
Concentration and detection of Cryptosporidium oocysts and Giardia cysts
are standardized and described in for example “ISO 15553 Water quality—
Isolation and identification of Cryptosporidium and Giardia cysts from water”