Environmental Engineering Reference
In-Depth Information
13.4.1.3 Surfactant degradation
Use of SDHPC for surfactant removal in aqueous media has been also widely reported
for many different surfactant structures. Among the most recently reported are non-
ionic (Du et al., 2008; Eng et al., 2010) and cationic (Han et al., 2009; Naldoni et al.,
2009; Natoli et al., 2012) surfactants; relatively few reports are available dealing with
anionic surfactants.
13.4.2 Microorganisms inactivation by solar driven
heterogeneous photocatalysis
TiO
2
semiconductor photocatalyst is widely reported, as suspended powder or thin
film, to inactivate different organisms such as viruses, vegetative cells, and spores of
organisms with a high resistance to desiccation and radiation (i.e.
Escherichia coli
,
Lactobacillus acidophilus
,
Saccharomyces cerevisiae
,
Bacillus atrophaeus
,
Aspergillus
niger
, and
Kocuria rhizophila
) with very interesting results (Castillo et al., 2011;
Muranyi et al., 2009). Some other specific strains have been tested for SDHPC disinfec-
tion, for example Fernandez-Ibañez et al. (2008) tested the inactivation of
Fusarium
solani
and
Fusarium sp
spores, a pathogen infecting food crops using slurry TiO
2
and a solar CPC photorreactor. They found that these pathogens are susceptible to
solar photocatalytic disinfection with TiO
2
in distilled water not only at the labora-
tory scale but also at the pilot plant scale (Fernandez-Ibañez et al., 2008; Polo-Lopez
et al., 2010). The effect of some water quality parameters on disinfection processes
has been estimated at pilot plant scale and some authors have proposed that natu-
ral organic matter (NOM) and hardness may inhibit the SDHPC process due to the
hydroxyl radical scavenging effect of NOM (Bandala et al., 2011b), the formation of
calcium carbonate film adhering to the internal glass wall of the photoreactor which is
in contact with the liquid being treated, and to the presence of calcium carbonate pre-
cipitates on catalyst surface (Acevedo et al., 2012). In a very recent work, Byrne et al.
(2011) reviewed the available literature of SDHPC enhancement for solar disinfection
of water, including an analysis of parameters affecting the process and a comparison
with the widely known solar disinfection (SODIS) technology.
13.5 CHALLENGES AND PERSPECTIVES
Solar driven water disinfection technologies hold great promise as low cost, effective
replacements for conventional water treatments, potentially bringing clean drinking
water to a large number of people. However, before widespread adoption is realized,
several significant technological hurdles must be overcome.
13.5.1 Photorreactor design
UV at ground level includes both direct beam and diffuse radiation at almost similar
portions. During cloudy days, this proportion in solar UVA spectrum may change to
60% diffuse and 40% direct. Since direct beam radiation may represent as little as
40% of the total radiation available, non-imaging solar collecting systems capable to
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