**1. Introduction**

Reliable access to clean and safe water remains a major worldwide challenge for the twenty-first century, in a global climate change context. In recent years, the classic problems associated with the presence in the ecosystems of priority pollutants have been extended to the detection of increasing amounts of micropollutants commonly called emerging. These, due to their

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toxicity and persistence in the environment (water column and sediments), have brought new challenges to existing water treatment systems (WTS) aiming to protect public health and the preservation of drinking water sources.

The Directive 2008/105/EC (PSD) lays down environmental quality standards (EQS) and presents the List of Priority Substances as afforded on the Article 16 and Annex X of the Water Framework Directive 2000/60/EC (WFD). However, the pharmaceuticals are not yet included among those compounds to be monitored, despite the increase in its occurrence reported in many European countries [1]. For urban water monitoring, possible priority pharmaceutical compounds (PhCs) should be the mainly analgesics, antidepressants, antibiotics, antineoplastics [2], synthetic estrogens, and hormones [3]. The inclusion of target PhCs in the EU List of Priority Substances implies the definition of their corresponding EQSs and the necessity to subject to monitoring EU aquatic ecosystems.

Recent advances in nanotechnology offer opportunities to develop next generation of WTS, as sustainable and safe alternative to current water treatment practices relied on centralized systems. The highly efficient and multifunctional processes, enabled by nanotechnological solutions, can also provide new capabilities allowing economic utilization of unconventional water sources on water-stressed regions [4]. Future water treatment systems in developing countries will most likely opt for nanotechnology-based water monitoring, treatment and reuse systems that can efficiently immobilize a wide variety of water emergent pollutants (for which existing technologies are inefficient or ineffective) coupled with affordability and ease of operation [5].

Advanced oxidation processes (AOPs) have been widelly studied because of their potential as a complementary or alternative process to conventional wastewater treatment. These AOPs have proven to be particularly efective in the degradation of many toxic pollutants [6–8] when nanomaterials are applied as photocatalyst. Photocatalytic oxidation with TiO<sup>2</sup> has been used in the removal of micropollutants (like antibiotics) and microbial pathogens from waters, as a useful pre-treatment and/or a polishing step to oxidize hazardous and recalcitrant organic compounds.

This chapter presents the development and results of several pilot-scale studies aiming to assess the effects of TiO<sup>2</sup> nanoparticles on antibiotic removal efficiency and to define its photo-oxidation kinetics, using different low-cost photocatalytic water treatment systems.

The antibiotic tested in this work was oxytetracycline (OTC) is a widely used broad spectrum antibiotic, especially employed in veterinary medicine [9, 10] and for human therapy [11]. It can be found not only in raw and treated wastewaters but also in surface water sources [12]. The catalyst used is Degussa (*Evonik*) P25 TiO<sup>2</sup> , which was applied as suspended and immobilized nanoparticles exposed to UV and solar radiation in two photocatalytic reactors: water columns and columns filters with a granular porous medium coated by immobilized TiO<sup>2</sup> nanoparticles using a sol-gel method.

For both photo-oxidation reactors, different test scenarios are defined in order to assess the effect on OTC removal efficiency of the major abiotic parameters, such as hydraulic conditions, OTC initial concentration, pH, cumulate solar energy, and media granulometry.

The experimental results were very promising, because removal efficiencies in both reactors achieved the maximum value of 96% for water columns with suspended TiO<sup>2</sup> nanoparticles [13] and 98% for the photocatalytic filtration performed by the porous medium coated with TiO<sup>2</sup> [14].

toxicity and persistence in the environment (water column and sediments), have brought new challenges to existing water treatment systems (WTS) aiming to protect public health

The Directive 2008/105/EC (PSD) lays down environmental quality standards (EQS) and presents the List of Priority Substances as afforded on the Article 16 and Annex X of the Water Framework Directive 2000/60/EC (WFD). However, the pharmaceuticals are not yet included among those compounds to be monitored, despite the increase in its occurrence reported in many European countries [1]. For urban water monitoring, possible priority pharmaceutical compounds (PhCs) should be the mainly analgesics, antidepressants, antibiotics, antineoplastics [2], synthetic estrogens, and hormones [3]. The inclusion of target PhCs in the EU List of Priority Substances implies the definition of their corresponding EQSs and the necessity to

Recent advances in nanotechnology offer opportunities to develop next generation of WTS, as sustainable and safe alternative to current water treatment practices relied on centralized systems. The highly efficient and multifunctional processes, enabled by nanotechnological solutions, can also provide new capabilities allowing economic utilization of unconventional water sources on water-stressed regions [4]. Future water treatment systems in developing countries will most likely opt for nanotechnology-based water monitoring, treatment and reuse systems that can efficiently immobilize a wide variety of water emergent pollutants (for which existing technologies are inefficient or ineffective) coupled with affordability and ease of operation [5]. Advanced oxidation processes (AOPs) have been widelly studied because of their potential as a complementary or alternative process to conventional wastewater treatment. These AOPs have proven to be particularly efective in the degradation of many toxic pollutants [6–8] when nano-

removal of micropollutants (like antibiotics) and microbial pathogens from waters, as a useful pre-treatment and/or a polishing step to oxidize hazardous and recalcitrant organic compounds. This chapter presents the development and results of several pilot-scale studies aiming to assess

The antibiotic tested in this work was oxytetracycline (OTC) is a widely used broad spectrum antibiotic, especially employed in veterinary medicine [9, 10] and for human therapy [11]. It can be found not only in raw and treated wastewaters but also in surface water sources [12].

bilized nanoparticles exposed to UV and solar radiation in two photocatalytic reactors: water columns and columns filters with a granular porous medium coated by immobilized TiO<sup>2</sup>

For both photo-oxidation reactors, different test scenarios are defined in order to assess the effect on OTC removal efficiency of the major abiotic parameters, such as hydraulic conditions,

The experimental results were very promising, because removal efficiencies in both reactors

OTC initial concentration, pH, cumulate solar energy, and media granulometry.

achieved the maximum value of 96% for water columns with suspended TiO<sup>2</sup>

nanoparticles on antibiotic removal efficiency and to define its photo-oxidation

, which was applied as suspended and immo-

has been used in the

nanoparticles

materials are applied as photocatalyst. Photocatalytic oxidation with TiO<sup>2</sup>

kinetics, using different low-cost photocatalytic water treatment systems.

The catalyst used is Degussa (*Evonik*) P25 TiO<sup>2</sup>

nanoparticles using a sol-gel method.

and the preservation of drinking water sources.

126 Application of Titanium Dioxide

subject to monitoring EU aquatic ecosystems.

the effects of TiO<sup>2</sup>

It must be also highlighted that the surprising regeneration ability showed by the developed photocatalytic porous media can completely recover its oxidative properties after a simple sun exposure [15], allowing a truly sustainable use of the developed photocatalytic filter.
