448
S. Das et al.
were superior than reports from post-chlorination disinfection in another WWTP
where survivability of adenovirus was 75%.
Therefore, UV Irradiation and chlorination might be ineffective in producing considerable effect over MDR and ARG in wastewater, with unclear reasons. Although
evidence of a selection process for MDR and ARG produced by these treatments
are probable, but this is not a conclusive fact; it typically depends on the antibiotic,
mechanism of resistance achieved and the bacteria.
1.4 Wastewater Disinfection by Nonconventional Process like
Heterogenous Photocatalysis
Above mentioned inadequacies in conventional water treatment process have led to
the rapid development in AOPs as an inventive water treatment method. The AOPs
involve in situ generations of ROS like OH•, H 2 O 2 , and O 2 •
− . These ROS were
reported as the chief arsenal for photocatalysis of refractory organic molecules and
disinfection of microorganisms (Esplugas et al. 2002). Among these AOPs, heterogeneous photocatalysis employing semiconductor metal oxide catalysts mainly TiO 2 ,
ZnO, Fe 2 O 3 , CdS, GaP, and ZnS has confirmed its competence in mineralization of a
wide range of refractory and POPs into readily less harmful intermediates, and their
eventual mineralization into harmless carbon dioxide and water. Among the semiconductor metal oxide photocatalysts, TiO 2 , and ZnO have received tremendous attention
owing to their UV light and visible light-mediated activation properties, respectively.
Both of them were reported to have high thermal, chemical, and mechanical stability
making them ideal candidates for photocatalytic treatment applications (Chong et al.
2010).
Heterogeneous photocatalysis possesses certain important features that promote
its applicability in water treatment; they are (1) operation under ambient pressure
and temperature and, (2) total mineralization of refractory and persistent organics
minus generating secondary pollutants, and (3) low operational costs. The ROS produced as a result of the photo-induced charge separation on semiconductor metal
oxide surface has been well-documented for microbial disinfection and POP mineralization without generating secondary pollutants. Being so, versatile semiconductor metal oxide photocatalysts possess some technical challenges. This may include
post-reaction separability of the semiconductor photocatalyst after water treatment,
which is pausing their practicality as an industrial process. The fine particle size of
semiconductor metal oxides, together with their large surface area and surface energy
creates a resilient inclination for catalyst agglomeration during application. This is
vastly adverse in terms of particles size maintenance, decreasing surface area, and
its reusability. Further technical confrontations involve designing catalysts which
will be active for a wider spectrum of light, keeping in mind the photoperiods of
12 h sunlight and 12 h dark for real-time photocatalytic applications (Chong et al.
S. Das et al.
were superior than reports from post-chlorination disinfection in another WWTP
where survivability of adenovirus was 75%.
Therefore, UV Irradiation and chlorination might be ineffective in producing considerable effect over MDR and ARG in wastewater, with unclear reasons. Although
evidence of a selection process for MDR and ARG produced by these treatments
are probable, but this is not a conclusive fact; it typically depends on the antibiotic,
mechanism of resistance achieved and the bacteria.
1.4 Wastewater Disinfection by Nonconventional Process like
Heterogenous Photocatalysis
Above mentioned inadequacies in conventional water treatment process have led to
the rapid development in AOPs as an inventive water treatment method. The AOPs
involve in situ generations of ROS like OH•, H 2 O 2 , and O 2 •
− . These ROS were
reported as the chief arsenal for photocatalysis of refractory organic molecules and
disinfection of microorganisms (Esplugas et al. 2002). Among these AOPs, heterogeneous photocatalysis employing semiconductor metal oxide catalysts mainly TiO 2 ,
ZnO, Fe 2 O 3 , CdS, GaP, and ZnS has confirmed its competence in mineralization of a
wide range of refractory and POPs into readily less harmful intermediates, and their
eventual mineralization into harmless carbon dioxide and water. Among the semiconductor metal oxide photocatalysts, TiO 2 , and ZnO have received tremendous attention
owing to their UV light and visible light-mediated activation properties, respectively.
Both of them were reported to have high thermal, chemical, and mechanical stability
making them ideal candidates for photocatalytic treatment applications (Chong et al.
2010).
Heterogeneous photocatalysis possesses certain important features that promote
its applicability in water treatment; they are (1) operation under ambient pressure
and temperature and, (2) total mineralization of refractory and persistent organics
minus generating secondary pollutants, and (3) low operational costs. The ROS produced as a result of the photo-induced charge separation on semiconductor metal
oxide surface has been well-documented for microbial disinfection and POP mineralization without generating secondary pollutants. Being so, versatile semiconductor metal oxide photocatalysts possess some technical challenges. This may include
post-reaction separability of the semiconductor photocatalyst after water treatment,
which is pausing their practicality as an industrial process. The fine particle size of
semiconductor metal oxides, together with their large surface area and surface energy
creates a resilient inclination for catalyst agglomeration during application. This is
vastly adverse in terms of particles size maintenance, decreasing surface area, and
its reusability. Further technical confrontations involve designing catalysts which
will be active for a wider spectrum of light, keeping in mind the photoperiods of
12 h sunlight and 12 h dark for real-time photocatalytic applications (Chong et al.