Pilot plant use of two types of TiO₂ thin-films as a sustainable alternative for reuse of kitchen greywater

The accelerated growth of the world's population generates large volumes of domestic wastewater, therefore the objective of this research was to perform the photocatalytic treatment and reuse of kitchen greywater by using a laboratory scale and pilot plant, TiO₂ films, deposited on commercial glass substrates and laminar biochar of Guadua, through peroxo sol-gel (PSG), atomic layer deposition (ALD) and magnetron sputtering (MS) methods; laboratory-scale tests involved films deposited by peroxo sol-gel (PSG), atomic layer depositions (ALD), and magnetron sputtering (MS); later the two less expensive with best results were evaluated in the pilot plant, composed of a homogenisation tank, a filtration system and the photocatalysis reactor. Laboratory results showed that all three kinds of TiO₂ films inactivated >70 % of Escherichia coli after 120 min of K-GW treatment and were successfully reusable for five cycles with an inactivation efficiency >48 %. Pilot plant results with the PSG and MS deposited films, an overall efficiency for E. coli inactivation of 93 ± 6 and 88 ± 4 %, respectively, was obtained at 140 min, as well as an efficiency above 90 % for chemical oxygen demand and nitrite removal. In addition, the treated greywater favoured the “in vitro” germination of Lactuca sativa L. and Lolium perenne seeds and complied with 95 % of the U.S. standards for water reuse. The pilot plant with TiO₂ films offered an effective solution to inactivate Escherichia coli and remove contaminants.