1 3
Topics in Current Chemistry (2020) 378:7
with more expensive processes such as AOP, and particularly HPC. The treatment
of industrial wastewater is a more complex matter, and process efficiency strongly
depends on the specific industrial process. In such a case, wastewater characteristics
can change substantially in terms of organic loading (from tens of milligrams to tens
of grams per liter of COD) and in quantity of toxic/refractory contaminants. As high
organic loads in wastewater are of concern, HPC is less effective than more consolidated processes (namely ozonation and Fenton) as a pre-oxidation step to improve
wastewater biodegradability before a less expensive biological treatment step. Nevertheless, HPC could become competitive provided that certain technological limitations are resolved (e.g., reactor design, synthesis, and development of effective
supported photocatalysts), as an advanced treatment of industrial wastewater (after
biological treatment) to remove specific contaminants not effectively removed by
biological processes (e.g., phenols in olive oil wastewater treatment).
5 Conclusions
Although HPC has been widely investigated in recent decades for the removal of
several contaminants from aqueous matrices, due to the several issues outlined
herein, its application in real wastewater treatment at full scale is still far from
becoming a consolidated technology. However, (1) continuing technological developments in terms of increasingly effective photocatalysts (even under visible light)
and easily scalable synthesis methods, along with the design of new reactors and
the identification of specific applications in wastewater treatment where HPC can be
competitive with consolidated technologies, may promote its application at full scale
in the mid- to long term. A contribution in that direction can come from an increasing number of investigations under real conditions, developing more reactors at a
pilot scale to better investigate their feasibility, and possible scale-up conditions to
successfully address specific challenges in wastewater treatment.
Acknowledgements This work is part of a project that has received funding from the European Union’s
Horizon 2020 under the Innovative Training Networks (ITN-ETN) programme Marie Skłodowska-Curie
Grant (ANtibioticS and mobile resistance elements in WastEwater Reuse applications: risks and innovative solutions) agreement no. 675530.
References
1. Esplugas S, Gimenez J Contreras S, Pascual E, Rodrı́ guez M (2002) Comparison of different
advanced oxidation processes for phenol degradation. Water Res 36:1034–1042
2. Bhatkhande DS, Pangarkar VG, Beenackers AACM (2002) Photocatalytic degradation for environmental applications–a review. J Chem Technol Biotechnol Int Res Process Environ Clean Technol
77:102–116
3. Ohno T, Sarukawa K, Tokieda K, Matsumura M (2001) Morphology of a TiO 2 photocatalyst
(Degussa, P-25) consisting of anatase and rutile crystalline phases. J Catal 203:82–86
4. Bekbölet M, Boyacioglu Z, Özkaraova B (1998) The influence of solution matrix on the photocatalytic removal of color from natural waters. Water Sci Technol 38:155–162
255
Reprinted from the journal
Topics in Current Chemistry (2020) 378:7
with more expensive processes such as AOP, and particularly HPC. The treatment
of industrial wastewater is a more complex matter, and process efficiency strongly
depends on the specific industrial process. In such a case, wastewater characteristics
can change substantially in terms of organic loading (from tens of milligrams to tens
of grams per liter of COD) and in quantity of toxic/refractory contaminants. As high
organic loads in wastewater are of concern, HPC is less effective than more consolidated processes (namely ozonation and Fenton) as a pre-oxidation step to improve
wastewater biodegradability before a less expensive biological treatment step. Nevertheless, HPC could become competitive provided that certain technological limitations are resolved (e.g., reactor design, synthesis, and development of effective
supported photocatalysts), as an advanced treatment of industrial wastewater (after
biological treatment) to remove specific contaminants not effectively removed by
biological processes (e.g., phenols in olive oil wastewater treatment).
5 Conclusions
Although HPC has been widely investigated in recent decades for the removal of
several contaminants from aqueous matrices, due to the several issues outlined
herein, its application in real wastewater treatment at full scale is still far from
becoming a consolidated technology. However, (1) continuing technological developments in terms of increasingly effective photocatalysts (even under visible light)
and easily scalable synthesis methods, along with the design of new reactors and
the identification of specific applications in wastewater treatment where HPC can be
competitive with consolidated technologies, may promote its application at full scale
in the mid- to long term. A contribution in that direction can come from an increasing number of investigations under real conditions, developing more reactors at a
pilot scale to better investigate their feasibility, and possible scale-up conditions to
successfully address specific challenges in wastewater treatment.
Acknowledgements This work is part of a project that has received funding from the European Union’s
Horizon 2020 under the Innovative Training Networks (ITN-ETN) programme Marie Skłodowska-Curie
Grant (ANtibioticS and mobile resistance elements in WastEwater Reuse applications: risks and innovative solutions) agreement no. 675530.
References
1. Esplugas S, Gimenez J Contreras S, Pascual E, Rodrı́ guez M (2002) Comparison of different
advanced oxidation processes for phenol degradation. Water Res 36:1034–1042
2. Bhatkhande DS, Pangarkar VG, Beenackers AACM (2002) Photocatalytic degradation for environmental applications–a review. J Chem Technol Biotechnol Int Res Process Environ Clean Technol
77:102–116
3. Ohno T, Sarukawa K, Tokieda K, Matsumura M (2001) Morphology of a TiO 2 photocatalyst
(Degussa, P-25) consisting of anatase and rutile crystalline phases. J Catal 203:82–86
4. Bekbölet M, Boyacioglu Z, Özkaraova B (1998) The influence of solution matrix on the photocatalytic removal of color from natural waters. Water Sci Technol 38:155–162
255
Reprinted from the journal