Environmental Engineering Reference
In-Depth Information
microorganism in water. The removal of pathogenic species from water is important
due to their ability to generate immediate adverse health effects on the population
forced to consume non-safe water. Just to have an idea of the problem's magnitude,
it has been estimated that in Africa, Latin America and the Caribbean alone, nearly
one billion people no not have access to safe water supplies (WHO/UNICEF, 2000).
As a result of this situation, waterborne diseases result in the death of 1.5 million
children every year (Montgomery and Elimelech, 2007). Besides health concerns, lack
of access to safe drinking water is also associated with poverty and limits sustainable
development (Bandala et al., 2011a).
13.3.2.1 Bacteria
Solar water disinfection (SODIS) has been identified in the past decade as a simple,
environmentally friendly, and low cost point-of-use treatment technology for drinking
water purification capable to use the bacteriostatic effect of the UV-A part of the solar
spectrum (320-400 nm) and dissolved oxygen in water to inactivate pathogenic species
through the production of reactive forms of oxygen (ROS). According to previous
systematic studies, the best bacteria inactivation effect is reached on sunny days when
heat and UV radiation combine synergistically (EWAG, 2002; Schmid et al., 2008).
Application of advanced oxidation processes to water disinfection using solar
radiation, coined as enhanced photocatalytic solar disinfection (ENPHOSODIS) by
Bandala et al. (2011a), has improved SODIS disinfection efficiency, solved some
disadvantages identified previously with SODIS, and allows the efficient inactivation
of not only common waterborne bacteria but other highly resistant microorganisms
(Guisar et al., 2007). In this regard, SDPAF processes have been tested for the inac-
tivation of bacterial strains commonly infecting water such as
Escherichia coli
and
Pseudomonas aeruginosa
with very satisfactory results (Bandala et al., 2011a,c).
13.3.2.2 Helminth egg
Species with the ability to resist adverse conditions may survive conventional disin-
fection processes even after long periods of treatment. One example of these kinds
of undesirable species is helminth eggs. The WHO has estimated that about 1 billion
people in developing countries are infected by Ascaris and that 25-33% of this popu-
lation is affected by helminthiasis alone. These diseases are importantly related to poor
physical growth and development, as well as retardation of intellectual and cognitive
development in children less than 15 years of age (Bandala et al., 2012).
Inactivation of helminth eggs in water is not an easy task mainly because their basic
structure makes them resistant to external agents. Conventional sanitary engineering
processes have been applied to the removal of helminth eggs from wastewater. For these
cases, 80-100% helminth egg removal within 20-35 h of treatment has been achieved.
Presence of these microorganisms, however, is not exclusive to wastewater. Several
studies have reported the presence of helminth eggs in surface and even ground water
and it is well documented that they possess high resistance to disinfection, resisting
conventional drinking water treatment and emerging live from domestic taps (Bandala
et al., 2012).
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